Patent Publication Number: US-2020289722-A1

Title: Systems and methods for aspiration and monitoring

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/440,955, filed on Jun. 13, 2019, which claims the benefit of priority to U.S. Provisional Patent Application No. 62/685,659, filed on Jun. 15, 2018, U.S. Provisional Patent Application No. 62/733,618, filed on Sep. 19, 2018, U.S. Provisional Patent Application No. 62/744,576, filed on Oct. 11, 2018, U.S. Provisional Patent Application No. 62/749,647, filed on Oct. 23, 2018, U.S. Provisional Patent Application No. 62/755,475, filed on Nov. 3, 2018, and U.S. Provisional Patent Application No. 62/769,527, filed on Nov. 19, 2018, all of which are herein incorporated by reference in their entirety for all purposes. Priority is claimed pursuant to 35 U.S.C. § 120 and 35 U.S.C. § 119. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The field of the invention generally relates to an aspiration system for removing, by aspiration, undesired matter such as a thrombus from a fluid carrying cavity, duct, sinus, or lumen of the body, such as a blood vessel, including a vessel in the brain, or in any space in the body, whether intended to carry fluid or not. 
     Description of the Related Art 
     A treatment method for removing undesired matter such as thrombus from a blood vessel of a patient involves use of an aspiration catheter having elongate shaft formed with an aspiration lumen extending therein. An aspiration catheter may also include a guidewire lumen for placement of a guidewire, which is used to guide the aspiration catheter to a target site in the body. By applying a vacuum or negative pressure to a proximal end of the aspiration lumen, for example, with a syringe having a hub that is connected to the proximal end of the aspiration catheter, the matter can be aspirated into an aspiration port at the distal end of the aspiration catheter, into the aspiration lumen, and thus be removed from the patient. 
     SUMMARY OF THE INVENTION 
     In one embodiment of the present disclosure, a system for catheter-based aspiration includes an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft including an aspiration lumen having a proximal end and an open distal end, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the lumen of the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, a peristaltic pump configured for driving fluid through the extension tube and including a pump base having a pressure shoe, and a rotatable head, the rotatable head including two or more compression elements arrayed therearound, a compressible tubular portion disposed between the distal end and the proximal end of the extension tube, the compressible tubular portion configured to be coupled to the pressure shoe and the rotatable head of the peristaltic pump, such that operation of the peristaltic pump causes the rotatable head to rotate such that the two or more compression elements drive fluid from the aspiration lumen of the aspiration catheter through the extension tube from the distal end of the extension tube to the proximal end of the extension tube, a first sensor configured to measure a characteristic of flow through at least one of the aspiration lumen or the lumen of the extension tube, and a controller configured to receive a first signal from the first sensor and configured to vary the operation of the peristaltic pump based at least in part on the first signal received from the first sensor related to a change in the characteristic of flow. A “characteristic of flow” may include a pressure, a flow rate, a flow velocity, or a variation or disturbance in any of these. A “characteristic of flow” may even be a laminar or turbulent condition, or a change between them. 
     In another embodiment of the present disclosure a method for performing a thrombectomy procedure includes providing an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen and an injection lumen, the aspiration lumen having an open distal end and a proximal end, the injection lumen extending within the aspiration lumen and having a distal end and a proximal end, the distal end of the injection lumen located within the aspiration lumen near the open distal end of the aspiration lumen, the aspiration catheter further including an orifice at the distal end of the injection lumen configured to create one or more jets when pressurized fluid is injected through the injection lumen, placing at least a distal portion of the elongate shaft into a blood vessel of the subject, placing an extension tube having a distal end and a proximal end and a lumen extending therebetween, the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, within a roller pump such that a compressible portion of the extension tube disposed between the distal end and the proximal end of the extension tube is engageable by two or more rollers of a rotatable head of the roller pump, injecting pressurized fluid through the injection lumen of the aspiration catheter from the proximal end to the distal end such that it passes through the orifice into the aspiration lumen, thereby causing some body fluid to enter into the aspiration lumen of the aspiration catheter, and operating the roller pump such that body fluid forced into the aspiration lumen of the aspiration catheter is caused to transit through the extension tube from the distal end of the extension tube to the proximal end of the extension tube. 
     In still another embodiment of the present disclosure, a system for catheter aspiration includes an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen and an injection lumen, the aspiration lumen having an open distal end and a proximal end, the injection lumen extending within the aspiration lumen and having a distal end and a proximal end, the distal end of the injection lumen located within the aspiration lumen near the open distal end of the aspiration lumen, an orifice at the distal end of the injection lumen configured to create one or more jets when pressurized fluid is injected through the injection lumen, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the distal end of the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, the extension tube further having a compressible portion disposed between the distal end and the proximal end of the extension tube, the compressible portion configured for placement within a peristaltic pump, such that operation of the peristaltic pump causes fluid from the aspiration lumen of the aspiration catheter to transit through the extension tube from the distal end of the extension tube to the proximal end of the extension tube, and a return conduit hydraulically coupled to the extension tube and configured to return to the vasculature of the subject fluid that has passed through the extension tube from distal to proximal. 
     In yet another embodiment of the present disclosure, a system for catheter aspiration includes a peristaltic pump, an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen and an injection lumen, the aspiration lumen having an open distal end and a proximal end, the injection lumen extending within the aspiration lumen and having a distal end and a proximal end, the distal end of the injection lumen located within the aspiration lumen near the open distal end of the aspiration lumen, an orifice at the distal end of the injection lumen configured to create one or more jets when pressurized fluid is injected through the injection lumen, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the distal end of the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, the extension tube further having a compressible portion disposed between the distal end and the proximal end of the extension tube, the compressible portion configured for placement within the peristaltic pump, such that operation of the peristaltic pump causes fluid from the aspiration lumen of the aspiration catheter to transit through the extension tube from the distal end of the extension tube to the proximal end of the extension tube, and a filter located within a conduit that includes the aspiration lumen of the aspiration catheter and the lumen of the extension tube, the filter located between the orifice and the compressible portion of the extension tube. 
     In still another embodiment of the present disclosure a system for catheter aspiration includes an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen and an injection lumen, the aspiration lumen having an open distal end and a proximal end, the injection lumen extending within the aspiration lumen and having a distal end and a proximal end, the distal end of the injection lumen located within the aspiration lumen near the open distal end of the aspiration lumen, an orifice at the distal end of the injection lumen configured to create one or more jets when pressurized fluid is injected through the injection lumen, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the distal end of the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, the extension tube further having a compressible portion disposed between the distal end and the proximal end of the extension tube, the compressible portion configured for placement within a peristaltic pump, such that operation of the peristaltic pump causes fluid from the aspiration lumen of the aspiration catheter to transit through the extension tube from the distal end of the extension tube to the proximal end of the extension tube, a controller configured to operate a piston pump configured to pressurize fluid through the injection lumen, and a sensor configured to sense the presence of air within pressurized fluid injected into or through the injection lumen, the sensor configured to output a signal to the controller. 
     In yet another embodiment of the present disclosure, a system for catheter aspiration includes an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen having an open distal end and a proximal end, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the distal end of the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, the extension tube further having a compressible portion disposed between the distal end and the proximal end of the extension tube, the compressible portion configured for placement within a roller pump, such that operation of the roller pump causes fluid from the aspiration lumen of the aspiration catheter to transit through the extension tube from the distal end of the extension tube to the proximal end of the extension tube, a pressure sensor configured for placement in fluid communication with a conduit that includes the lumen of the extension tube and the aspiration lumen of the catheter, a measurement device coupled to the pressure sensor and configured for measuring deviations in fluid pressure, and a communication device coupled to the measurement device and configured to generate a signal related to the deviations in fluid pressure. 
     In still another embodiment of the present disclosure, a system for catheter aspiration includes an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen having an open distal end and a proximal end, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the distal end of the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, the extension tube further having a compressible portion disposed between the distal end and the proximal end of the extension tube, the compressible portion configured for placement within a peristaltic pump, such that operation of the peristaltic pump causes fluid from the aspiration lumen of the aspiration catheter to transit through the extension tube from the distal end of the extension tube to the proximal end of the extension tube, a pressure sensor configured for placement in fluid communication with a conduit that includes the lumen of the extension tube and the aspiration lumen of the catheter, a measurement device coupled to the pressure sensor and configured for measuring deviations in fluid pressure, and a communication device coupled to the measurement device and configured to generate a signal related to the deviations in fluid pressure. 
     In yet another embodiment of the present disclosure, a method for performing a thrombectomy procedure includes providing an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen having an open distal end and a proximal end, placing at least a distal portion of the elongate shaft into a blood vessel of the subject, placing an extension tube having a distal end and a proximal end and a lumen extending therebetween, the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, within a roller pump such that a compressible portion of the extension tube disposed between the distal end and the proximal end of the extension tube is engageable by two or more rollers of a rotatable head of the roller pump, and operating the roller pump such that body fluid forced into the aspiration lumen of the aspiration catheter is caused to transit through the extension tube from the distal end of the extension tube to the proximal end of the extension tube. 
     In still another embodiment of the present disclosure, a system for catheter aspiration includes an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen having an open distal end and a proximal end, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the distal end of the extension tube configured to be hydraulically coupled to the aspiration lumen of the aspiration catheter, the extension tube further having a compressible portion disposed between the distal end and the proximal end of the extension tube, the compressible portion configured for placement within a peristaltic pump, such that operation of the peristaltic pump causes fluid from the aspiration lumen of the aspiration catheter to transit through the extension tube from the distal end of the extension tube to the proximal end of the extension tube, and a return conduit hydraulically coupled to the extension tube and configured to return to the vasculature of the subject fluid that has passed through the extension tube from distal to proximal. 
     In yet another embodiment of the present disclosure, a system for catheter aspiration includes a centrifugal pump, an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen having an open distal end and a proximal end, and a controller configured to operate the centrifugal pump. 
     In still another embodiment of the present disclosure, a system for real time monitoring of catheter aspiration includes an ultrasound sensor configured for placement in fluid communication with a lumen which at least partially includes an aspiration lumen of a catheter, the aspiration lumen configured to couple to a negative pressure source, the ultrasound sensor configured to output a signal, a measurement device coupled to the ultrasound sensor and configured to count the number of times N during a predetermined time period P that the signal output by the ultrasound sensor surpasses a predetermined threshold amplitude A, the measurement device further configured to determine whether the number of times N is less than or less than or equal to a predetermined value V or whether the number of times N is greater than or greater than or equal to the predetermined value V, and a communication device coupled to the measurement device and configured to be in a first communication mode if the number of times N is less than or less than or equal to the predetermined value V and to be in a second communication mode if the number of times N is greater than or greater than or equal to the predetermined value V. 
     In yet another embodiment of the present disclosure, a system for catheter aspiration includes an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft including an aspiration lumen having an open distal end and a proximal end, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the distal end of the extension tube configured to be hydraulically coupled to the proximal end of the aspiration lumen of the aspiration catheter, a receptacle having an interior volume, wherein the proximal end of the extension tube is configured to deliver material flowing from the lumen of the extension tube into the interior volume of the receptacle, a scale configured to weigh at least the material contained within the receptacle, and a communication element configured to demonstrate changes in the mass of the material contained within the receptacle over time to a user. 
     In still another embodiment of the present disclosure, a method for performing a thrombectomy procedure includes providing a system for aspiration including an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen having an open distal end and a proximal end, an extension tube having a distal end and a proximal end and a lumen extending therebetween, the distal end of the extension tube configured to be hydraulically coupled to the proximal end of the aspiration lumen of the aspiration catheter, a receptacle having an interior volume, wherein the proximal end of the extension tube is configured to deliver material flowing from the lumen of the extension tube into the interior volume of the receptacle, and a scale configured to weigh at least the material contained within the receptacle, placing at least a distal portion of the elongate shaft into a blood vessel of the subject, causing at least some thrombus to be aspirated from the blood vessel of the subject through the aspiration lumen of the aspiration catheter and through the lumen of the extension tube, and into the interior volume of the receptacle, and monitoring a change in the mass of material within the receptacle over time. 
     In yet another embodiment of the present disclosure, a system for catheter aspiration includes an aspiration catheter including an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen, the aspiration lumen having an open distal end and a proximal end, an injection tube having an injection lumen extending therein, the injection tube configured to extend within the aspiration lumen and having a distal end and a proximal end, the distal end of the injection tube configured to be located within the aspiration lumen near the open distal end of the aspiration lumen, a microfabricated cap externally covering and providing a seal around an external perimeter of the distal end of the injection tube, and an orifice in at least one of the microfabricated cap or the injection tube proximal to the microfabricated cap, the orifice configured to create one or more jets into the aspiration lumen when pressurized fluid is injected through the injection lumen. 
     In still another embodiment of the present disclosure, a method for aspirating a thrombus includes providing an aspiration catheter having an elongate shaft having an aspiration lumen having a proximal end and an open distal end and an injection tube extending within the aspiration lumen and having an injection lumen having a proximal end, a closed distal end, and an orifice at or adjacent the close distal end, attaching a pressurizable fluid source to the proximal end of the injection lumen, coupling a pump to the proximal end of the aspiration lumen configured to aspirate fluid through the aspiration lumen in a distal to proximal direction, inserting a distal region of the shaft of the aspiration catheter into the vasculature of a patient such that the open distal end of the aspiration lumen is in or adjacent a thrombus, determining that the combination of the injection of the pressurized fluid through the injection lumen and the aspiration by the pump through the aspiration lumen is not sufficient to cause aspiration of the thrombus, advancing the aspiration catheter until the open distal end of the aspiration lumen is distal to the thrombus, injecting pressurized fluid through the injection lumen without operating the pump on the aspiration lumen, such that the pressurized fluid passes through the injection lumen, into the aspiration lumen and out of the open distal end of the aspiration lumen into a space distal to the thrombus, and aspirating at least some of the thrombus by injecting the pressurized fluid while also operating the pump on the aspiration lumen. 
     In yet another embodiment of the present disclosure, a system for catheter aspiration includes, an aspiration catheter comprising an elongate shaft configured for placement within a blood vessel of a subject, the shaft having an aspiration lumen, the aspiration lumen having an open distal end and a proximal end, an injection tube having an injection lumen extending therein, the injection tube extending within the aspiration lumen and longitudinally adjustable in relation to the elongate shaft, the injection lumen having an open distal end and a proximal end, the open distal end of the injection lumen configured to extend distally from the open distal end of the aspiration lumen, and an orifice through a wall of the injection tube proximal to the open distal end of the injection lumen, the orifice configured to create one or more jets into the aspiration lumen when pressurized fluid is injected through the injection lumen, and when the injection lumen of the injection tube is occluded distally of the orifice through the wall of the injection tube. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a system for aspiration according to an embodiment of the present disclosure. 
         FIG. 2A  is a view of an aspiration monitoring system according to a first embodiment of the present disclosure. 
         FIG. 2B  is a view of an aspiration monitoring system according to a second embodiment of the present disclosure. 
         FIG. 3  is a view of an aspiration monitoring system according to a third embodiment of the present disclosure. 
         FIG. 4A  is a sectional view of an aspiration catheter in a blood vessel prior to contact with a thrombus. 
         FIG. 4B  is a sectional view of an aspiration catheter in a blood vessel upon contact with a thrombus. 
         FIG. 4C  is a sectional view of an aspiration catheter during a loss of aspiration. 
         FIG. 4D  is a sectional view of thrombi being aspirated through an aspiration catheter. 
         FIG. 5A  is a graphic representation of pressure vs. time for the condition of  FIG. 4A . 
         FIG. 5B  is a graphic representation of pressure vs. time for the condition of  FIG. 4B . 
         FIG. 5C  is a graphic representation of pressure vs. time for the condition of  FIG. 4C . 
         FIG. 5D  is a graphic representation of pressure vs. time for the condition of  FIG. 4D . 
         FIG. 6  is a graphic representation of pressure and an output sound amplitude vs. time for an embodiment of an aspiration monitoring system. 
         FIG. 7  is a graphic representation of pressure and an output sound amplitude vs. time for an embodiment of an aspiration monitoring system. 
         FIG. 8  is a graphic representation of pressure and an output sound frequency vs. time for an embodiment of an aspiration monitoring system. 
         FIG. 9  is a graphic representation of pressure and an output of sound frequency vs. time for an embodiment of an aspiration monitoring system. 
         FIG. 10  is a plan view of a system for aspiration according to another embodiment of the present disclosure. 
         FIG. 11  is a plan view of a system for aspiration according to another embodiment of the present disclosure. 
         FIG. 12  is a detailed view of an aspiration monitoring system of the system for aspiration of  FIG. 11 . 
         FIG. 13  is a plan view of a system for aspiration according to another embodiment of the present disclosure. 
         FIG. 14  is a detailed view of an aspiration monitoring system of the system for aspiration of  FIG. 13 . 
         FIG. 15  is a diagrammatic view of a system for aspirating thrombus according to an embodiment of the present disclosure. 
         FIG. 16  is a diagrammatic view showing more detail of the proximal portion of the system for aspirating thrombus of  FIG. 15 . 
         FIG. 17  is a diagrammatic view of the distal end portion of the system for aspirating thrombus of  FIG. 15 . 
         FIG. 18  is a plan view of a portion of a multi-purpose system according to an embodiment of the present disclosure. 
         FIG. 19  is a perspective view of a proximal portion of the multi-purpose system of  FIG. 18 . 
         FIG. 20  is a plan view of a portion of a multi-purpose system according to an embodiment of the present disclosure. 
         FIG. 21  is a detail view of the distal end of a multi-purpose catheter of the multi-purpose system of  FIG. 20 . 
         FIG. 22  is a perspective view of a proximal portion of the multi-purpose system of  FIG. 20 . 
         FIG. 23  is a plan view of a proximal portion of the multi-purpose system of  FIG. 20 . 
         FIG. 24  is a perspective view of a portion of the multi-purpose system of  FIG. 20 . 
         FIG. 25  is a plan view of an aspiration catheter according to an embodiment of the present disclosure. 
         FIG. 26  is a plan view of a tubing set according to an embodiment of the present disclosure. 
         FIG. 27  is a plan view of a stopcock according to an embodiment of the present disclosure. 
         FIG. 28  is a plan view of a stopcock according to an embodiment of the present disclosure. 
         FIG. 29  is a plan view of a vacuum source according to an embodiment of the present disclosure. 
         FIG. 30  is a plan view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 31  is a plan view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 32  is a plan view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 33  is a plan view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 34  is a partial sectional view of an embodiment of a saline injection aspiration (thrombectomy) catheter according to an embodiment of the present disclosure, with a guidewire in place. 
         FIG. 35  is a plan view of the proximal end of a guiding catheter with an aspiration catheter placed therein. 
         FIG. 36  is a perspective view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 37  is a perspective view of a subject being reinjected with blood, according to an embodiment of the present disclosure. 
         FIG. 38  is a perspective view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 39  is a perspective view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 40  is a perspective view of an ultrasonic sensor for use with an aspiration system, according to an embodiment of the present disclosure. 
         FIG. 41  is a plan view of an aspiration system comprising a y-connector having the ultrasonic sensor of  FIG. 40  placed therein. 
         FIG. 42  is a perspective view of a console of the aspiration system of  FIG. 41 . 
         FIG. 43  is a plan view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 44  is a detail view of the weight-based aspiration monitoring system of the system of  FIG. 43 . 
         FIG. 45  is a perspective view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 46  is a detail view of an alternative weight-based aspiration monitoring system of the system. 
         FIG. 47  is a plan view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 48  is a perspective view of an aspiration system, according to an embodiment of the present disclosure. 
         FIG. 49  is a sectional view of the distal end of an aspiration catheter, according to an embodiment of the present disclosure. 
         FIG. 50  is a sectional view of the distal end of an aspiration catheter, according to an embodiment of the present disclosure. 
         FIG. 51  is a sectional view of the distal end of an aspiration catheter, according to an embodiment of the present disclosure. 
         FIG. 52  is a sectional view of the distal end of an aspiration catheter, according to an embodiment of the present disclosure. 
         FIG. 53  is a plan view of a microcatheter being tracked over a guidewire, in a first step. 
         FIG. 54  is a plan view of the insertion of an insertable injection tube and cap being inserted into a microcatheter, in a second step according to an embodiment of the present disclosure. 
         FIG. 55  is a plan view of the insertable injection tube and cap being advanced through a lumen of the microcatheter, in a third step. 
         FIG. 56  is a plan view of the insertable injection tube and cap in a fully inserted position within the microcatheter, in a fourth step. 
         FIG. 57  is a perspective cut-away view of a distal end of an insertable injection tube and cap with a spline inserted within a microcatheter, according to an embodiment of the present disclosure. 
         FIG. 58  is a perspective view of the insertable injection tube and cap with spline of  FIG. 57 . 
         FIG. 59  is a perspective cut-away view of a distal end of an insertable injection tube and cap with a spline inserted within a microcatheter, according to an embodiment of the present disclosure. 
         FIGS. 60-63  illustrate a method for treating a patient using an aspiration catheter and system, according to an embodiment of the present disclosure. 
         FIGS. 64-65  illustrate a method for treating a patient using an aspiration catheter and system, according to an embodiment of the present disclosure. 
         FIGS. 66-69  illustrate a method for treating a patient using an aspiration catheter and system, according to an embodiment of the present disclosure. 
         FIG. 70  is a sectional view of a translatable occluder of the aspiration system of  FIGS. 66-69  in a first position, according to an embodiment of the present disclosure. 
         FIG. 71  is a sectional view of the translatable occluder of the aspiration system of  FIGS. 66-69  in a second position. 
         FIG. 72  illustrates an optional blocking step in the method of  FIGS. 66-69 , according to an embodiment of the present disclosure. 
         FIG. 73  is a perspective view of an aspiration system according to an embodiment of the present disclosure. 
         FIG. 74  is a perspective view of an aspiration system according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The present disclosure relates to aspiration catheter systems and monitoring, warning and communication systems for aspiration catheter systems, including aspiration systems for removing thrombus from the vasculature of patients. Such vasculature can include veins and arteries, including coronary arteries, carotid arteries, cerebral arteries, and other arteries of the head and neck. Clogging of aspiration catheters, for example by large pieces of thrombus, is a common concern for users. Techniques to avoid clogging/choking of material within the catheter often involve rapidly, aggressively advancing the aspiration catheter or gently plucking at edges of a thrombus to insure only small pieces or portions are introduced at a time, pieces which are small enough to not clog or occlude the aspiration lumen. When a device becomes clogged during use, the potential for inadvertent dislodgment of thrombus downstream increases; this is referred to as distal embolism. As aspiration procedures of this type are often used in highly technical emergent settings, early clog detection of the aspiration catheter for the user during aspiration can contribute to the success of the procedure and clinical outcome. Some sources have reported that up to 50% of aspiration catheters used get clogged during use. 
     The user may have difficulty determining whether there is a vacuum or negative pressure in the system or not. For example, the user may have difficulty determining whether the vacuum or negative pressure has been applied or not (e.g., the vacuum source has been turned on or off). Additionally, the user may have difficulty determining whether there has been a loss of vacuum in the system, for example because of the syringe (or other vacuum source) being full of fluid or because of a leak in the system. Blood is relatively opaque and can coat the wall of the syringe, thus making it difficult to determine when the syringe becomes full. This makes it difficult to determine whether sufficient vacuum or negative pressure is being applied to the aspiration catheter. The negative pressure gradient may change to an unacceptable level even before the syringe becomes full. Extension tubing or other tubing may also cause a loss in vacuum or negative pressure in the system. Certain tubing kinks may be difficult for a user to see or identify. It is also difficult to determine whether there is an air leak in the system, which can be another cause for a loss of vacuum or negative pressure even before the syringe becomes full of the aspirated fluid. 
     During the aspiration of thrombus with an aspiration catheter, it is difficult to identify when thrombus is actively being aspirated, or when only blood is being aspirated. Typically, it is desired to not aspirate sizable quantities of normal blood from blood vessels, because of the importance of maintaining normal blood volume and blood pressure. However, when tracking the tip of an aspiration catheter in proximity to a thrombus, it is difficult to know whether the aspiration catheter has actively engaged a thrombus, whether it has aspirated at least a portion of the thrombus, or whether it is not engaged with the thrombus, and is only aspirating blood. Though some aspiration catheters, such as those used in the peripheral blood vessels or in an arterio-venous fistula, may be around 50 cm or even less, the tip of an aspiration catheter may in same cases be more than 90 cm from the hands of the user, or as much as 135 cm from the hands of the user, or in some cases as much as 150 cm, and the particular status of aspiration capability at the tip of the catheter is often not known by the user. A user may thus be essentially plunging a catheter blindly without significant, usable sensory feedback. The catheter may have an outer diameter up to or even greater than 6 French, and may be as high as 10 French or greater. The increased catheter outer diameter can cause some concern of potential trauma inside a blood vessel. The use of aspiration catheters can therefore be inefficient, and cause more blood removal than desired, causing a user to minimize the length of the therapy and in severe cases necessitating blood transfusion. An increased volume of normal blood being aspirated also means that the vacuum source (e.g. syringe) will fill in a shorter amount of time, thus requiring more frequent replacement of the vacuum source. Distal embolism may occur if the negative pressure gradient is not sufficient, and yet the user is not aware. 
     In some cases, a syringe that is completely or mostly full or blood and/or thrombus may continue to be used, though in this state, there is not sufficient pressure to effectively aspirate thrombus or unwanted material, thus causing inefficient use of time, and lengthening the procedure. In some cases, the user may not realize the plunger of the syringe has mistakenly not been pulled back (to evacuate the syringe). In some cases, the syringe itself may be defective, and a sufficient negative pressure may not be achieved, without the user being aware. In some cases, kinked tubing, lines, or catheters may go unnoticed, because of bad visibility in a procedural laboratory, or simply from the extent of concurrent activities being performed. In many cases, the user&#39;s eyes are oriented or focused on a monitor, for example a fluoroscopic monitor or other imaging monitor, or a monitor with patient vital data. Though the user may be able to view flow through transparent or partially transparent lumens (such as extension tubing), in dim lighting with intermittent viewing, it is difficult for the user&#39;s mind to process flow of an opaque liquid (such as blood/thrombus). Even in good lighting with a focused eye, the movement of fluid through extension tubing may not present an accurate picture of the aspiration status, as the visual flow effect may be delayed in relation to the applied vacuum or negative pressure. More than one medical device personnel may be sharing sensory information with each other to attempt to build a current status in each other&#39;s minds of the aspiration procedure. When a user relies on another&#39;s interpretation, especially when either are multitasking, a false sense of the status may occur. A syringe attached to the aspiration catheter may cause kinking, for example, if placed on an uneven surface. The distal opening in an aspiration lumen of an aspiration catheter may be prone to aspirating directly against the wall of a blood vessel, thus being temporarily stuck against the vessel wall, and stopping flow throughout the aspiration lumen. In some cases, a negative pressure gradient that is too large may be accidentally or inappropriately applied to the aspiration lumen of the aspiration catheter, limiting effectiveness (for example, if it causes the walls surrounding the aspiration lumen to collapse and thus, cut off the significantly decrease the flow through the aspiration lumen). The syringes which are sometimes used as a vacuum source to connect to an aspiration lumen of an aspiration catheter may malfunction, and not be fully actuated/evacuated. But, even when the syringe is functioning correctly, it will tend to fill up at difficult to predict moments, and thus commonly have periods with no applied negative pressure gradient. In the cases wherein a portion of clot/thrombus is being aspirated through the aspiration lumen, a significant pressure drop may occur at the current position of the thrombus, and thus, a sufficient negative pressure may only exist from the proximal end of the aspiration lumen and distally up to the point of the thrombus. Thus, an insufficient negative pressure may exist, causing insufficient aspiration at the distal end of the aspiration lumen, e.g., at the distal end of the aspiration catheter. The same situation may occur if there is an actual clog at some intermediate point within the aspiration lumen. In either of these conditions, because of the insufficient aspiration at the distal end of the aspiration lumen, there may be a risk of thrombus or emboli being sent distally in the vasculature, which may cause occlusion, stroke, pulmonary embolism, or other disorders, depending upon the location of the intervention or procedure being performed. With current apparatus and techniques, these situations are very difficult to detect when they occur. It has been estimated that in as many as 50% of thrombus aspiration procedures, some sort of failure occurs. 
     An aspiration system  2  is illustrated in  FIG. 1  and is configured to allow real time monitoring of catheter aspiration. The aspiration system  2  comprises an aspiration catheter  4 , a vacuum source  6 , a valve  8 , extension tubing  10 , and an aspiration monitoring system  48  including an in-line pressure transducer  12 . The aspiration catheter  4  has a proximal end  14  and a distal end  16  and an aspiration lumen  18  extending from the proximal end  14  to the distal end  16 . The aspiration lumen  18  may be sized for aspiration of thrombus, and in some embodiments may have an inner diameter of between about 0.38 millimeter (0.015 inches) and about 2.54 millimeters (0.100 inches). The aspiration catheter  4  includes a hub  20  at its proximal end which may include a female luer connector  22 . The aspiration lumen  18  at the distal end  16  of the aspiration catheter  4  may include an angled orifice  24 , which aids in the tracking through tortuous or occluded vasculature. In some embodiments, a guidewire lumen  26  is coupled to the distal end  16  of the aspiration catheter  4 , and is configured to track over a guidewire  28 . The vacuum source  6  may comprise a syringe, and may be sized between 5 ml and 100 ml, or between 20 ml and 60. The vacuum source  6  may comprise a VacLok® syringe, made by Merit Medical, South Jordan, Utah. The vacuum source  6  may include a barrel  30  and plunger  32 , with a lock  34  which is configured to retain the plunger  32  in position in relation to the barrel  30 , for example, when the plunger  32  is pulled back in direction D to create a negative pressure (vacuum) inside the barrel  30 . In some embodiments, the vacuum source  6  may comprise any other type of evacuatable reservoir, or may comprise a vacuum pump. The vacuum source  6  is connected to the aspiration lumen  18  of the aspiration catheter  4  via the extension tubing  10  and the valve  8 . In some embodiments, the vacuum source  6  may be connected directly to the aspiration lumen  18  of the aspiration catheter  4 . Male luer connectors  36  and female luer connectors  38  are indicated in  FIG. 1 . The valve  8  may be a standard two-way stopcock, as illustrated. 
     The pressure transducer  12  of the aspiration monitoring system  48  is configured to be fluidly coupled between the vacuum source  6  and the aspiration catheter  4 . In  FIG. 2A , the aspiration monitoring system  48  is illustrated as a self-contained device of a first embodiment. The pressure transducer  12  comprises a housing  40  having a cavity  42  extending between a first port  44  and a second port  46 . In some embodiments, the first port  44  comprises a female luer and the second port  46  comprises a male luer. In some embodiments, the first port  44  comprises a female luer lock and the second port  46  comprises a male luer lock, each of which is attachable to and detachable from a corresponding luer lock of the opposite gender. The first port  44  is configured to be coupled to the vacuum source  6 , either directly, or with the valve  8  and/or extension tubing  10  connected in between. The second port  46  is configured to be coupled to the aspiration lumen  18  of the aspiration catheter  4 , for example, by coupling the second port  46  directly or indirectly to the hub  20  of the aspiration catheter  4 . When the aspiration system  2  is used to aspirate body fluids and/or materials, for example blood and/or thrombus, the body fluids and/or materials are aspirated through the aspiration lumen  18  of the aspiration catheter from the angled orifice  24  at the distal end  16  to the female luer connector  22  at the proximal end  14 , then pass through the second port  46  of the pressure transducer  12  first, through the cavity  42 , and then through the first port  44 . Depending on the amount of amount of vacuum or negative pressure applied by the vacuum source  6 , and the amount of flow resistance and resulting pressure drop along the aspiration system  2 , the pressure within the cavity  42  will vary. For example, a more viscous fluid like blood, or a fluid having solid, semi-solid, or gel-like particles or portions, will cause more flow resistance through the relatively small aspiration lumen  18  of the aspiration catheter  4  than would water or normal saline solution. Thus, the pressure within the cavity  42  of the pressure transducer  12  will decrease (the negative pressure gradient will increase) as the flow resistance in the aspiration lumen  18  increases. 
     For definition purposes, when speaking of the amount of “vacuum,” a pressure of, for example, −15,000 pascal (−2.18 pounds per square inch, or psi) is a “larger vacuum” than −10,000 pascal (−1.45 psi). Actually, a true vacuum, where no molecules are present within the volume is extremely difficult. Additionally, −15,000 pascal is a “lower pressure” than −10,000 pascal. Furthermore, −15,000 pascal has a larger “absolute vacuum pressure” than does −10,000 pascal, because the absolute value of −15,000 is larger than the absolute value of −10,000. In  FIG. 2A , a vacuum sensor  50  is disposed within the cavity  42  of the housing  40  and is in fluid communication with fluid that passes through the cavity  42 . The vacuum sensor  50  may be a standard pressure sensor or transducer, including a pressure sensor designed primarily for measuring positive pressure. It may use any type of pressure sensing technology known in the art, including MEMS Technology. In some embodiments, the vacuum sensor  50  is configured for highest accuracy and/or precision within the range of pressures between about 0 pascal to about −101,325 pascal (−14.70 psi), or between about −45,000 pascal (−6.53 psi) and about −90,000 pascal (−13.05 psi), or between about −83,737 pascal (−12 psi) and about −96,527 pascal (−14 psi). In some embodiments, the power requirement for the vacuum sensor may range from 2.5 volts DC to 10 volts DC. In some embodiments, the vacuum sensor  50  may be an analog gauge with an output voltage. In the self-contained embodiment of the  FIG. 2A , the vacuum sensor  50  is powered by one or more battery  52 . Based on the power requirements of the vacuum sensor  50 , and the power requirements of other components of the aspiration monitoring system  48  described herein, in some embodiments the one or more battery  52  may range between 1.5 volts and nine volts. Also contained within the housing is a measurement device  54 , which in some embodiments may comprise a microprocessor. The measurement device  54  is coupled to the vacuum sensor  50  and receives signals from the vacuum sensor  50  indicative of real time measured pressure. In some embodiments, the measurement device  54  includes a memory module  56  in which information is stored that may be used by the measurement device  54 , for example, in calculations. Information may include, for example, an array of one or more pressure values. In some embodiments, the array of one or more pressure values may be correlated with one or more different corresponding system models or catheter models. The vacuum sensor  50  may be used in some cases for detecting the presence or amount of vacuum or negative pressure alone, for the purpose of monitoring whether the vacuum source  6  (e.g., syringe) is significantly full, and thus needs to be changed. The vacuum sensor  50  may be used in some cases for detecting whether there is a vacuum or negative pressure in the system of not. For example, whether the vacuum or negative pressure has been applied or not (e.g., the vacuum source has been turned on or off). 
     One or more communication devices  58   a ,  58   b ,  58   c  are included within the aspiration monitoring system  48  and are coupled to the measurement device  54 . Each of the one or more communication devices  58   a - c  are configured to generate a type of alert comprising an alert signal  60   a - c , in response at least in part to activity and output of the measurement device  54 . In some embodiments, the communication device  58   a  may include one or more LEDs (light emitting diodes) configured to generate a visible alert via a visible alert signal  60   a , such as light that is continuously illuminated, or is illuminated in a blinking pattern. In some embodiments, the LEDs may be oriented on multiple sides of the communication device  58   a , so that they may be easily seen from a variety of different locations. In some embodiments, lights other than LEDs may be used. Light pipes or other lighting conduits may also be incorporated in embodiments, to further place visual indicators at multiple locations and/or orientations. In some embodiments, the communication device  58   b  may include one or more vibration generators configured to generate a tactile alert via a tactile alert signal  60   b , which may include, but is not limited to, vibration or heat. In some embodiments, the vibration device may be similar to a video game controller. In some embodiments, the vibration generator may comprise a piezoelectric device which is configured to vibrate when a voltage is applied. In some embodiments, the communication device  58   c  may include one or more sound generating devices configured to generate an audible alert via an audible alert signal  60   c , such as a continuous noise, or a repeating noise. The communication device  58   c  in some embodiments may comprise a loudspeaker for generation of any variety of sounds, at any variety of frequencies (Hz) or sound pressures (dB) within the human audible range and/or human tolerance range. The communication device  58   c  may even be configured to generate sounds that are outside the human audible range in embodiments wherein the signal is intended to be felt as a vibration or other tactile sensation, instead of an audible sensation. In some embodiments, the sound generating device may comprise a buzzer which is configured to sound one or more audible pitches when a voltage is applied. In some embodiments a piezoelectric device, such as that described in relation to the communication device  58   b  may also serve as a sound generating device, included as communication device  58   c . The alert signal  60   a - c  can at times serve as a “wake up” alarm for the user, in cases where the user has become too focused on other factors during the procedure. 
     A user of an aspiration system  2  may desire to be notified of several conditions which may occur during use of the aspiration system  2 . These potential conditions include, but are not limited to clogging, a loss of vacuum or negative pressure due to filling of the vacuum source  6  and or a breach, break or puncture in the aspiration system  2 , and the engagement or aspiration of non-fluid, solid or semi-solid material such as thrombus. The aspiration monitoring system  48  of  FIG. 2A  is configured to alert users of an aspiration system  2  about real time status of the aspiration system  2 , including operational conditions, which include: whether vacuum or negative pressure is being applied or not; flow conditions, which include whether a thrombus is engaged, whether a thrombus is being actively aspirated, whether the system is leaking air, whether the system is clogged, whether the vacuum source  6  is full and/or needs to be changed; or other potential set up issues. The real time feedback provided frees a user or operator from the need of excessive personal monitoring of the vacuum source  6 , extension tubing  10 , or other portions of the aspiration system  2 , for improper or undesired flow or operation conditions, and thus allows the user to focus more attention on the patient being treated. The user is kept aware of whether a clot is being aspirated or has been aspirated, or whether there is a clog. Additionally, the user is kept aware of whether there is too large an amount of blood being removed from the patient, or whether there are fault conditions like system leak or tubing kink. A tubing kink distal to the vacuum sensor  50  may be identified (for example by an increase in measured negative pressure) and a tubing kink proximal to the vacuum sensor  50  may be identified (for example, by a loss or degradation of the negative pressure gradient). In some cases, the user may attempt to operate the catheter with a vacuum source  6  that is already full (and thus has no significant negative pressure gradient). In some cases, a user may even forget to open the valve  8  to begin aspiration, but the aspiration monitoring system,  48  can also identify that the system is not yet functioning, and communicate a list of potential errors or specific errors (for the particular pressure waveform measured). By having the real-time awareness of the many factors related to the operating status, the procedure is made safer, the time of the procedure may be reduced, and blood loss may be reduced. 
     The pressure transducer  12  of the aspiration monitoring system  48  is configured to continuously measure and monitor the absolute pressure amplitude within the closed system of the aspiration system  2 , and also is configured to measure and monitor the relative pressure over time to detect noteworthy flow changes within the flow circuit of the aspiration system  2 . Some changes are discernible via absolute pressure measurement, while more subtle pressure deflections may be compared to a stored library in memory. Noteworthy conditions may be signaled to the user when appropriate. In some embodiments, the unfiltered signal may be amplified by an amplifier and filtered by a filter, for example, to increase the signal-to-noise ratio. Examples of the (background) noise  57  in an unfiltered signal can be seen in  FIGS. 5A-5D  (labeled in  FIG. 5A ). In some embodiments, one or more algorithms may be used, as described herein, to identify particular conditions of interest. 
       FIG. 2B  illustrates a second embodiment of an aspiration monitoring system  62  having a pressure transducer  12  having a vacuum sensor  50  disposed within the cavity  42  of a housing  40 . The vacuum sensor  50  may be powered by at least one battery  52 . In some embodiments, the pressure transducer  12  may be reusable, and may be configured to allow charging of the battery  52 , or of a capacitor (not shown) by direct charging methods, or by inductive power transfer methods and devices known in the art. Unlike the aspiration monitoring system  48  of  FIG. 2A , the aspiration monitoring system  62  of  FIG. 2B  comprises a measurement device  64 , memory module  66 , and communication device  68  which are external to the pressure transducer  12 . A power module  72 , also external, may be used to power any of the measurement device  64 , memory module  66 , or communication device  68 . The communication device  68  may be any of the communication device  58   a ,  58   b ,  58   c  described in relation to the aspiration monitoring system  48  of  FIG. 2A , and are configured to product an alert via an alert signal  70 . The communication device  68  may be portable so that it may be positioned close to the user. 
     In some embodiments, the communication device  68  may be wearable by the user.  FIG. 3  illustrates an aspiration monitoring system  78  which includes an antenna  80  coupled to a measurement device  76 . The measurement device  76  is similar to the measurement device  54  of prior embodiments, except that it wirelessly sends a communication signal  84  via the antenna  80  to a corresponding antenna  82  of a communication device  74 . In some embodiments, the communication device  74  comprises a wristband which the user wears, and which may include a vibration generator or heat generator. In some embodiments, the communication device  74  comprises an audio speaker which may be attached to equipment or even to the patient or user. In some embodiments, the communication device  74  comprises an audio speaker on an earpiece or earbud that the user may wear. In some embodiments, Bluetooth® communication technology may be used. The real time feedback supplied by the aspiration monitoring system  62  may decrease the time that the aspiration system  2  is actively aspirating without being engaged with a thrombus, thus minimizing the amount of non-thrombotic blood lost by aspiration. This may be particularly beneficial in larger bore catheters, for example in catheters having a diameter of 7 French or larger. The real time feedback may also minimize the amount of total time that catheters are tracked back-and-forth through the blood vessels, minimizing potential damage to the intima of the blood vessels, dissection of the blood vessels, or distal embolization. By lowering the risk of the aspiration catheter tip getting caught (via suction) against the blood vessel wall, the distal end of the aspiration lumen may be more aggressively designed for optimized aspiration characteristics. The technique of using the aspiration catheter may additionally be able to be performed in a more sophisticated manner, with continual or continuous knowledge of the aspiration status or negative pressure gradient sufficiency. For example, a piece of thrombus may be aspirated, followed by a “chaser” of blood aspiration, followed by another piece of thrombus, etc. 
       FIG. 4A  illustrates the distal end  16  of an aspiration catheter  4  within a blood vessel  86  having at least one thrombus  88 . The aspiration catheter  4  is being advanced in a forward direction F, but the distal end  16  of the aspiration catheter  4  has not yet reached the proximal extremity  94  of the thrombus  88 . A vacuum source  6  ( FIG. 1 ) has been coupled to the aspiration lumen  18  of the aspiration catheter  4  and activated (i.e. the valve  8  is open) causing blood  96  to be aspirated into the aspiration lumen  18  (arrows A). Turning to  FIG. 5A , a corresponding curve  98  is represented for the normal fluid (e.g. blood) vacuum or negative pressure over time for the condition of  FIG. 4A . The curve  98  represents vacuum or negative pressure over time sensed by the vacuum sensor  50  of any of the embodiments presented. No leaks are present and no thrombus is being evacuated, and therefore the curve  98  includes a downward slope  99  when the vacuum source  6  lowers the pressure within the cavity  42  of the pressure transducer  12  to a relatively steady state. The steady pressure curve  97  continues while blood  96  is being aspirated. As the vacuum source  6  is decoupled from the aspiration lumen  18 , for example by closing the valve  8  or by detaching any two of the ports (e.g. luers), or if the vacuum source  6  fills completely with blood  96 , then an upward slope  95  is measured. 
     The measurement device  54 ,  64  is configured to compare the curve  97  with information stored in the memory module  56 ,  66  to identify this condition. In some embodiments, the measurement device  54 ,  64  uses an algorithm to make the comparison. In some embodiments, the measurement device  54 ,  64  then sends a signal to the communication device  58   a - c ,  74 , and the communication device  58   a - c ,  74  generates an appropriate alert. Communication device  58   a , for example a particular color LED, may be illuminated, or an LED may flash in a particular pattern or number of flashes. Communication device  58   b  may create a characteristic sound, or may generate an audio message in a number of languages. For example, the audio message may state, “Thrombus encountered,” or “No thrombus encountered.” A different type of sound may be used for each of a plurality of “modes”: “Thrombus encountered,” “Actively flowing,” and “No Vacuum.” For example, a buzzing sound for “Thrombus encountered,” a beep for “No vacuum,” etc. The various characteristics of sound that may be varied include, but are not limited to timbre, or sound quality, spectrum, envelope, duration, phase, pitch (frequency), number of sounds (repetition). Communication device  58   c  may vibrate or heat in a characteristic pattern, for example, a certain number of repetitions or a certain frequency between repetitions. The user may determine that an additional fluoroscopic image (e.g. angiography) or other imaging modalities may be necessary to better identify the location of the thrombus  88 . 
       FIG. 4B  illustrates the distal end  16  of an aspiration catheter  4  advanced to a position such that the distal end  16  of the aspiration catheter  4  contacts the proximal extremity  94  of the thrombus  88 . The corresponding curve  93  in  FIG. 5B  represents vacuum or negative pressure over time sensed by the vacuum sensor  50  of any of the embodiments presented. The curve  93  initially has a downward slope  99  followed by a steady pressure curve  97 , as in the condition of  FIG. 4A , graphed in  FIG. 5A , however, when the distal end  16  of the aspiration catheter  4  contacts the proximal extremity  94  of the thrombus  88 , if the aspiration causes a portion of the thrombus  88  (for example a large or relatively hard portion) to enter and become trapped in the aspiration lumen  18 , then a clog condition occurs. A similar condition occurs if the distal end  16  of the aspiration catheter  4  is caught on the thrombus  88  by a suction effect, with virtually nothing flowing through the aspiration lumen  18 . In either condition, the curve  93  includes a deviation (or disturbance) in fluid pressure  91 . If the clog (or stuck condition) continues, then a flat, depressed pressure  89  is measured. 
     The measurement device  54 ,  64  is configured to compare the curve  93  with information stored in the memory module  56 ,  66  to identify this condition. In some embodiments, the measurement device  54 ,  64  uses an algorithm to make the comparison. In some embodiments, a pre-set pressure differential ΔP 1  may be stored in the memory module  56 ,  66  as a threshold, whereby the measurement of a pressure difference  81  less than this threshold does not result in the measurement device  54 ,  64  commanding the communication device  58   a - c ,  74  to send an alert signal  60   a - c ,  70 . In some embodiments, when the pressure difference  81  is greater than (or greater than or equal to) the pre-set pressure differential ΔP 1 , the measurement device  54 ,  64  then sends a signal to the communication device  58   a - c ,  74 , and the communication device  58   a - c ,  74  generates an appropriate alert. Communication device  58   a , for example a particular color LED, may be illuminated, or an LED may flash in a particular pattern or number of flashes. Communication device  58   b  may create a characteristic sound, or may generate an audio message in a number of languages. For example, the audio message may state, “Clog Condition.” Communication device  58   c  may vibrate or heat in a characteristic pattern, for example, a certain number of repetitions or a certain frequency between repetitions. When the user realizes that the clog condition is present, the user may pull on the aspiration catheter  4  and readvance it, in an attempt to contact a portion of the thrombus  88  that can be aspirated. If a portion of the thrombus is clogged in the aspiration lumen  18 , and repositioning of the aspiration catheter  4  does not produce good results, the aspiration catheter  4  can be removed and the aspiration system  2  can be repurged, for example by a positive pressurization. 
       FIG. 4C  illustrates the distal end  16  of the aspiration catheter  4  in a general situation during which a breach in the aspiration system  2  has occurred. For example, a break, leak, puncture, pinhole, loosening, or disconnection may cause air to be pulled into the aspiration lumen  18  of the aspiration catheter  4 , the cavity  42  of the pressure transducer  12 , of the interior of the extension tubing  10 , valve  8 , or vacuum source  6 . As graphed in the curve  85  of  FIG. 5C , a downward slope  99  and a subsequent steady pressure curve  97  are measured, but at the point in time of the breach 87 an upward slope  83  begins. 
     The measurement device  54 ,  64  is configured to compare the curve  85  with information stored in the memory module  56 ,  66  to identify this condition. In some embodiments, the measurement device  54 ,  64  uses an algorithm to make the comparison. In some embodiments, the measurement device  54 ,  64  then sends a signal to the communication device  58   a - c ,  74 , and the communication device  58   a - c ,  74  generates an appropriate alert. Communication device  58   a , for example a particular color LED, may be illuminated, or an LED may flash in a particular pattern or number of flashes. Communication device  58   b  may create a characteristic sound, or may generate an audio message in a number of languages. For example, the audio message may state, “System Leak.” Communication device  58   c  may vibrate or heat in a characteristic pattern, for example, a certain number of repetitions or a certain frequency between repetitions. Upon receiving the alert, the user will check the components of the aspiration system  2  and either fix the breach or replace one or more of the components of the aspiration system  2 . For example, in some cases, the communication device  58   a - c ,  74  may alert the user when the measurement device  54 ,  64  confirms a loss of applied vacuum or negative pressure, allowing the user to change or recharge the vacuum source  6 , which has become depleted (e.g. by filling with blood and/or thrombus). 
       FIG. 4D  illustrates the distal end  16  of the aspiration catheter  4  during the successful aspiration of pieces or portions  90  of the thrombus  88 . In some cases, the pieces or portions  90  may follow a tortuous path  92 , due to disturbances or collisions with the inner wall of the aspiration lumen  18  while being pulled through the aspiration lumen  18 . In some cases, the pieces or portions  90  may catch and slip within the inner wall of the aspiration lumen  18 , for example, do to variance of the inner diameter of the aspiration lumen  18  along the length. Either of these situations can cause a corresponding series of increases and decreases in the pressure being sensed by the pressure transducer  12 , while the pieces or portions  90  are traveling through the aspiration lumen  18 . As graphed in the curve  79  of  FIG. 5D , a downward slope  99  and a subsequent steady pressure curve  97  are measured, but as the pieces or portions  90  of thrombus  88  travel down the aspiration lumen  18  of the aspiration catheter  4 , a deviation  77  of fluid pressure comprising a one or more decreases and increases in pressure (increases and decreases in vacuum or negative pressure) is measured. As the pieces or portions  90  of thrombus  88  exit the proximal end of the aspiration lumen  18  of the aspiration catheter  4 , a second steady pressure curve  75  is measured. The duration 67 of the deviation  77  is the amount of transit of the particular significant pieces or portions  90  of thrombus  88 . The duration 67 can range quite a bit, but in some cases may be less than a second or up to about 30 seconds. A single thrombus being aspirated may cause a single decrease in pressure (a blip) which is identified by the measurement device  54 ,  64 . Subsequently, this occurrence may be communicated to the user by the communication device  58   a - c ,  74 . When again additional pieces or portions  90  of thrombus  88  are aspirated into and travel down the aspiration lumen  18  of the aspiration catheter  4 , another deviation  73  of fluid pressure comprising a one or more decreases and increases in pressure (increases and decreases in vacuum or negative pressure) is measured. At the end of the curve  79 , the vacuum source  6  is shown filling completely with blood  96  and the pieces or portions  90  of thrombus  88 , and so an upward slope  95  is measured. 
     The measurement device  54 ,  64  is configured to compare the curve  79  with information stored in the memory module  56 ,  66  to identify when the pieces or portions  90  of thrombus  88  are actively being aspirated, as in deviation  77  and deviation  73 , and when the pieces or portions of thrombus  88  are not being actively, or substantially, aspirated, as in steady pressure curve  97 , the steady pressure curve  75 , and the steady pressure curve  71 . In some embodiments, the measurement device  54 ,  64  uses an algorithm to make the comparison. In some embodiments, a pre-set pressure differential ΔP 2  may be stored in the memory module  56 ,  66  as a threshold, whereby the measurement of a pressure difference  69  less than this threshold does not result in the measurement device  54 ,  64  commanding the communication device  58   a - c ,  74  to send a first type of alert via an alert signal  60   a - c ,  70 . In some embodiments, when the pressure difference  69  is greater than (or greater than or equal to) the pre-set pressure differential ΔP 2 , the measurement device  54 ,  64  then sends a signal to the communication device  58   a - c ,  74 , and the communication device  58   a - c ,  74  generates an appropriate alert. Communication device  58   a , for example a particular color LED, may be illuminated, or an LED may flash in a particular pattern or number of flashes. In some embodiments, the communication device  58   a  may comprise a light whose intensity increases proportionally with the pressure. Communication device  58   b  may create a characteristic sound, or may generate an audio message in a number of languages. For example, the audio message may state, “Thrombus being aspirated.” In some embodiments, communication device  58   b  may comprise one or more noises or beeps. In some embodiments, the communication device  58   b  may comprise a particular series of beeps corresponding to each different condition. For example, three short beeps may correspond to no thrombus being aspirated, while five long, loud beeps may correspond to a system leak. In some embodiments, a plurality of different tones (pitches) may be used to alert a user about different conditions. As an example, a low pitch sound may be used for a first condition (e.g. no thrombus being aspirated) and a second, higher pitch sound may be used for a second condition (e.g. a system leak). In some embodiments, a plurality of different tones may be used to alert a user about a first condition and a second plurality (e.g. in a different combination, or with additional tones) may be used to alert a user about a second condition. Communication device  58   c  may vibrate or heat in a characteristic pattern, for example, a certain number of repetitions or a certain frequency between repetitions. When the user realizes that the thrombus is being aspirated, the user may choose to advance (or retract) the aspiration catheter  4 , for example with fluoroscopic visualization, along the length of the thrombus  88 , in an attempt to continue the aspiration of the thrombus  88 . In some cases, the user may choose to stop the advancement or retraction of the aspiration catheter  4  at a certain amount of time after the alert is generated, in order to allow the pieces or portions  90  of thrombus  88  to completely exit the aspiration lumen  18 . When the measurement device  54 ,  64  identifies a subsequent steady pressure curve  75 ,  71  that follows a deviation  77 ,  73 , the measurement device  54 ,  64  in some embodiments sends a signal that causes the communication device  58   a - c ,  74  to generate a second type of alert via an alert signal  60   a - c ,  70 . For example, in some embodiments, communication device  58   b  may send an audio message that states, “Thrombus no longer being aspirated.” When the user realizes that the thrombus is no longer being aspirated, the user may advance or retract the aspiration catheter, in an attempt to contact another portion of the thrombus  88  that can be aspirated. In some embodiments, the deviation  77  may be positively identified as a true deviation indicating thrombus being actively aspirated, pressure difference  69  is between about 700 pascal and about 1700 pascal. In some embodiments, the deviation  77  may be positively identified as a true deviation indicating thrombus being actively aspirated, pressure difference  69  is between about 1000 pascal and about 1300 pascal. In some embodiments, the deviation  77  may be positively identified as a true deviation indicating thrombus being actively aspirated, pressure difference  69  is about 1138 pascal. The pressure difference  69  may be measured by determining a baseline pressure  63  and a peak pressure  61  and determining the absolute value difference. For example: 
       Absolute value difference (AVD)=|(−89,631 pascal)−(−90,769 pascal)|=1138 pascal
 
       Or for example: 
       Absolute value difference (AVD)=|(−43,710 pascal)−(−45,102 pascal)|=1281 pascal
 
     The pressure difference  81  ( FIG. 5B ) may also represent a deviation that may be identified in a similar manner, after which the communication device  58   a - c ,  74  generates an appropriate alert, such as, “Clog condition.” 
     Because vacuum or negative pressure has a nominal value less than zero, the peak pressure  61 , as shown in  FIG. 5D , is actually a lower number than the baseline pressure  63 . In some embodiments, the measurement device  54 ,  64  may also be configured to make a comparison, for example by using an algorithm, between a stored differential time ti and a duration 65 of a single one of the more or more decreases and increases in pressure in the deviation  77 . For example, in some embodiments, the deviation may be positively identified as a true deviation indicating thrombus being actively aspirated, if the duration is between about 0.001 seconds and about 0.50 seconds. In some embodiments, the deviation may be positively identified as a true deviation indicating thrombus being actively aspirated, if the duration is between about 0.005 seconds and about 0.10 seconds. In some embodiments, the deviation may be positively identified as a true deviation indicating thrombus being actively aspirated if the duration is between about 0.05 seconds and about 0.20 seconds. In some embodiments, the measurement device  54 ,  64  is configured to recognize deviation  77  after two or more decreases and increases in pressure are measured. In some embodiments, the measurement device  54 ,  64  is configured to recognize deviation  77  after five or more decreases and increases in pressure are measured. In some embodiments, the measurement device  54 ,  64  is configured to recognize deviation  77  after ten or more decreases and increases in pressure are measured. 
     The baseline pressure  63  may in some embodiments be predetermined and may be stored in the memory module  56 ,  66 . In some embodiments, the baseline pressure  63  may be stored in the memory module  56 ,  66  during the manufacture of the aspiration monitoring system  48 ,  62 ,  78 , but the baseline pressure  63  may also be input by the user prior to or during a particular procedure. In some embodiments, the baseline pressure  63  may be determined or otherwise defined by the measurement device  54 ,  64 ,  76  based on averaging of a particular number of samples of measured pressure. The baseline pressure  63  may be constructed as a moving average, such as a running average or rolling average. Several types of moving average may be used, including a simple moving average, a cumulative moving average, a weighted moving average, or an exponential moving average. In any of these cases, a threshold may be determined by the measurement device  54 ,  64 ,  76  based on the determined baseline pressure  63  and a known pressure differential ΔP. In some case, a pressure differential ΔP may even be calculated by the measurement device  54 ,  64 ,  76  based on the determined baseline pressure  63  and a known threshold. 
     Insertion of the pressure transducer  12  in line in either the embodiment of  FIG. 2A  or the embodiment of  FIG. 2B  does not measurably change performance characteristics of the aspiration system  2 , because the cavity  42  is relatively short and has a relatively large inner diameter, and thus is not a significant source of fluid flow resistance. In some embodiments, the inner diameter may be between about 2.2 mm (0.086 inches) and about 3.2 mm (0.125 inches). In some embodiments, the measurement device  54 ,  64 ,  76  need not include a microprocessor, as pre-defined set points (e.g. for certain thresholds) may be included in firmware, microcontroller, or other locations. In some embodiments, including but not limited to the embodiment of  FIG. 2B , the pressure transducer  12  may be an off-the-shelf blood pressure monitor system, which is modified or augmented with other components. In some embodiments an off-the-shelf blood pressure monitor system may be used as the output of the aspiration monitoring system  48 ,  62 ,  78 . In some embodiments, an aspiration catheter  4  may have a pressure transducer in the distal end  16 . This pressure transducer may be used as the pressure transducer  12  of the aspiration monitoring system  48 ,  62 ,  78 . In some embodiments, a pressure sensor may be located within a Tuohy-Borst valve, and introducer sheath, a guiding catheter, or another component of the system through which is in fluid communication with the aspiration lumen  18 . In some embodiments, the pressure sensor may be located anywhere within the aspiration lumen of the aspiration catheter. 
     In some embodiments, instead of an LED, the visual alert is provided by a communication device  58   a  comprising a display which displays visual messages of text in a particular language, for example, “Thrombus encountered,” “No thrombus encountered,” “Clog condition,” “System leak,” “Loss of vacuum,” “Thrombus being aspirated,” or “Thrombus no longer being aspirated.” The visual messages may be combined with any of the other alert signals  60   a - c ,  70  described herein. The aspiration monitoring system  48 ,  62 ,  78  described herein give real time awareness to users performing aspiration procedures, such as the removal of thrombus via an aspiration system  2 . One skilled in the art will recognize that by knowing the real time condition of the aspiration system  2 , the user is able to immediately make changes to the procedure in order to optimize results, increase safety for the patient and/or medical personnel, reduce costs (e.g. number of vacuum sources  6  required), and reduce procedure time (also a cost benefit). Because the user is typically performing multiple tasks during an aspiration procedure, the sensory aid provided by the aspiration monitoring system  48 ,  62 ,  78  allows the user to focus on these tasks without having to continually attempt to monitor conditions which are often difficult to visually monitor. The user may also modify and control the aspiration monitoring system  48 ,  62 ,  78  via an input  59  ( FIG. 2B ), which may comprise a data entry module, keyboard, or a series of buttons with a display. The input  59  may in some embodiments comprise an auditory input which accepts voice commands. Alternatively, the user may input information and control the aspiration monitoring system,  48 ,  62 ,  78  remotely. Some of the alerts which the user may select or deselect in the aspiration monitoring system  48 ,  62 ,  78  include, but are not limited to: whether the aspiration system  2  is potentially blocked or clogged, or is flowing normally; whether thrombus has been contacted or not; whether a clog has occurred; whether the vacuum source  6  is adequate, or whether it has been depleted and requires replacement; whether there is a leak in the aspiration system  2 ; whether setup or connection of the components of the aspiration system  2  was done correctly or incorrectly; whether to advance the catheter distally; whether to retract the catheter; whether to continue moving the catheter at the same speed; whether to increase or decrease the speed of catheter advancement; whether thrombus is actively being aspirated; and whether thrombus stops being actively aspirated. As the user becomes familiar with the aspiration monitoring system  48 ,  62 ,  78 , the user may even begin to make certain responses to the system subconsciously. For example, a user may automatically pull back the catheter upon hearing a clot warning signal (e.g., three beeps), and may automatically begin advancing the catheter and/or start fluoroscopic visualization upon hearing a free blood flow signal (e.g., two beeps). By being “at one” with the aspiration monitoring system  48 ,  62 ,  78  and the catheter, the user optimizes reactions and actions. This may be helpful improving the skill of having the catheter take a small “bite” of thrombus, and following the “bite” with a “chaser” of some fast flowing blood, the clean/open the lumen. This would also help minimize the chance of clogging, and would in turn reduce maintenance or corrections of the system (removing the catheter, flushing the lumen outside of the patient, replacing the catheter). The overall experience for the user is improved, as the user receives instant gratification for good results, and is instantly notified of errors or instances for concern. 
     In some embodiments, alternate power sources may be used, for example, standard AC power with or without an AC/DC convertor; direct connection to existing equipment (e.g. vacuum pumps, etc.); solar power. The aspiration monitoring system  48 ,  62 ,  78  may be packaged sterile or may be resterilizable by techniques known by those skilled in the art. In some embodiments, flow or volume gauges may be used in conjunction with or instead of the pressure gauge  12 , in order to determine, for example, a clog, or a change in the amount of vacuum or negative pressure. In some embodiments, the input  59 , power module  72 , measurement device  64 , memory module  66 , and communication device  68  (e.g., of  FIG. 2B ) may all be incorporated into a single external device, which may in some cases be sold separately. In some embodiments, the external device may also have other functions, such as providing aspiration and/or injection (negative pressure and/or positive pressure) to a catheter. In other embodiments, the external device may comprise some, but not all of the input  59 , power module  72 , measurement device  64 , memory module  66 , and communication device  68 . For example, in some embodiments, a communication device  58  ( FIG. 2A ) may replace the external communication device  68 , and may be carried on the aspiration monitoring system  48 , while the input  59 , power module  72 , measurement device  64 , memory module  66  ( FIG. 2B ) are incorporated into a single external device. A number of combinations are possible, as described in more detail herein. 
     Though aspiration of thrombus has been described in detail, the aspiration monitoring system  48 ,  62 ,  78  has utility in any aspiration application wherein heterogeneous media is being aspirated. This may include the aspiration of emboli (including not thrombotic emboli) from ducts, vessels, or cavities of the body, or even from solid or semi-solid portions of the body, including, but not limited to, portions of fat, breasts, and cancerous tissue. 
     In some embodiments, the aspiration system  2  is be provided to the user as a kit with all or several of the components described, while in other embodiments, only the aspiration monitoring system  48  is provided. Though discussion herein includes embodiments for aspiration of thrombus and blood, the definition of the word “fluid” should be understood throughout to comprise liquids and gases. 
     In some embodiments, an additional or alternate sensor may be used to monitor flow conditions for the notification of the user, including, but not limited to: a Doppler sensor, an infrared sensor, or a laser flow detection device. In some embodiments, an externally-attached Doppler sensor may be employed. In some embodiments, an infrared sensor or a laser flow detection device may be employed around the extension tubing  10 . 
     Additional embodiments allow real time communication of the particular value of fluid pressure (for example the level of vacuum or negative pressure) measured by the sensor  50 . For example, as the negative pressure gradient increases, an audible sound may increase in sound intensity or in sound pressure level (dB) proportionally. Or, as the negative pressure gradient increases, the pitch (frequency) of an audible sound may made to rise, and as the negative pressure gradient decreases, the pitch may be made to fall (as does a siren). By controlling either the amplitude of a signal or the frequency of a signal by making them proportional to the fluid pressure, the system can give a user a real-time sense of whether the negative pressure gradient is increasing, decreasing, or staying the same, as well as whether the pressure is close to zero or quite different from zero. When an audible sound is used as the signal, the user&#39;s eyes can remain focused on the procedure, whether by viewing a monitor of fluoroscopic images, the patient, or a separate piece of equipment. 
       FIG. 6  illustrates a graph  800  of time (x-axis) and multiple variables (y-axis). A pressure curve  802  shows a vacuum or negative pressure being applied at a pressure drop  808 , and a maintenance of vacuum or negative pressure  810   a  with a decrease in vacuum or negative pressure  812  and an increase in vacuum or negative pressure  814 . A removal of vacuum or negative pressure  816  is shown at the end of the pressure curve  802 . In some cases, the decrease in vacuum or negative pressure  812  may be caused by a temporary or permanent leak or detachment within the system or by filling of the vacuum source (e.g., syringe). In  FIG. 6 , the decrease in vacuum or negative pressure  812  is shown as temporary, as a subsequent maintenance of vacuum or negative pressure  810   b  is illustrated. The increase in vacuum or negative pressure  814  may in some cases be caused by thrombus being sucked through the system and may occur for a short or long amount of time, and may be steady or intermittent. Though the amount of vacuum or negative pressure applied in the pressure curve  802  varies, in some embodiments, it may only be desirable to show to a user only whether the vacuum or negative pressure is generally being applied or not being applied. The measurement device  54 ,  64 ,  76  may be configured to apply an algorithm to the signal from the vacuum sensor  50  (pressure sensor) that calculates an inverse value, represented by the dashed curve  804 . The measurement device  54 ,  64 ,  76  further may apply an algorithm that increases, amplifies or otherwise augments the signal for ease of identification, for example within the human range of audible identification (hearing). For example, a modified signal curve  806  may be created that has the following general mathematical relationship with the signal from the vacuum sensor  50  represented by the pressure curve  802 . 
       Sound Pressure Level (dB)= A+B ×(1/fluid pressure)
 
     where A is a first constant, and 
     B is a second constant 
     In one particular example, a modified signal curve  806  may be created that has the following mathematical relationship with the signal from the vacuum sensor  50  represented by the pressure curve  802 . 
       Sound Pressure Level (dB)=70+20×(1/fluid pressure (kPa))
 
     where dB is units in decibels, and 
     kPa is units of kiloPascal 
     The modified signal curve  806  may be constructed of an algorithm such that the sound pressure level drops below the audible level of human hearing at relatively small amounts of vacuum or negative pressure, thus giving the user an “on/off” awareness of the vacuum or negative pressure being applied. 
       FIG. 7  illustrates a graph  820  of time (x-axis) and multiple variables (y-axis). A pressure curve  822  shows a vacuum or negative pressure being applied at a pressure drop  828 , and a maintenance of vacuum or negative pressure  830   a  with a decrease in vacuum or negative pressure  832  and an increase in vacuum or negative pressure  834 . A removal of vacuum or negative pressure  836  is shown at the end of the pressure curve  822 . In some cases, the decrease in vacuum or negative pressure  832  may be caused by a temporary or permanent leak or detachment within the system or by filling of the vacuum source (e.g., syringe). In  FIG. 7 , the decrease in vacuum or negative pressure  832  is shown as temporary, as a subsequent maintenance of vacuum or negative pressure  830   b  is illustrated. The increase in vacuum or negative pressure  834  may in some cases be caused by thrombus being sucked through the system and may occur for a short or long amount of time, and may be steady or intermittent. In some cases or configurations, it may be desirable for the user to have a very specific real-time or close to real-time characterization of the amount or level of vacuum (negative pressure gradient in general) being applied. The measurement device  54 ,  64 ,  76  may be configured to apply an algorithm to the signal from the vacuum sensor  50  (pressure sensor) that calculates an absolute value, represented by the dashed curve  824 . The measurement device  54 ,  64 ,  76  further may apply an algorithm that increases, amplifies or otherwise augments the signal for ease of identification, for example within the human range of audible identification (hearing). For example, a modified signal curve  826  may be created that has the following general mathematical relationship with the signal from the vacuum sensor  50  represented by the pressure curve  822 . 
       Sound Pressure Level (dB)= A+B ×|(fluid pressure)|
 
     where A is a first constant, and 
     B is a second constant 
     In one particular example, a modified signal curve  826  may be created that has the following mathematical relationship with the signal from the vacuum sensor  50  represented by the pressure curve  822 . 
       Sound Pressure Level (dB)=2×|(fluid pressure (kPa))|
 
     where dB is units in decibels and, 
     kPa is units of kiloPascal 
     The modified signal curve  826  may be constructed of an algorithm such that the sound pressure level seems to the user to follow the amount of vacuum or negative pressure being applied, thus becoming louder as the vacuum or negative pressure is increased. 
       FIG. 8  illustrates a graph  840  of time (x-axis) and multiple variables (y-axis). A pressure curve  842  shows a vacuum or negative pressure being applied at a pressure drop  848 , and a maintenance of vacuum or negative pressure  850   a  with a decrease in vacuum or negative pressure  852  and an increase in vacuum or negative pressure  854 . A removal of vacuum or negative pressure  856  is shown at the end of the pressure curve  842 . In some cases, the decrease in vacuum or negative pressure  852  may be caused by a temporary or permanent leak or detachment within the system or by filling of the vacuum source (e.g., syringe). In  FIG. 8 , the decrease in vacuum or negative pressure  852  is shown as temporary, as a subsequent maintenance of vacuum or negative pressure  850   b  is illustrated. The increase in vacuum or negative pressure  854  may in some cases be caused by thrombus being sucked through the system and may occur for a short or long amount of time, and may be steady or intermittent. As mentioned, in some cases or configurations, it may be desirable for the user to have a very specific real-time or close to real-time characterization of the amount or level of vacuum (negative pressure gradient in general) being applied. The measurement device  54 ,  64 ,  76  may be configured to apply an algorithm to the signal from the vacuum sensor  50  (pressure sensor) that calculates an absolute value, represented by the dashed curve  844 . The measurement device  54 ,  64 ,  76  further may apply an algorithm that determines a frequency of an audible sound (or pitch), for example within the human range of audible identification (hearing), that varies within the human range of audible frequencies. For example, a modified signal curve  846  may be created that has the following general mathematical relationship with the signal from the vacuum sensor  50  represented by the pressure curve  842 . 
       Sound Frequency (Hz)= A+B ×|(fluid pressure)|
 
     where A is a first constant, and 
     B is a second constant 
     In one particular example, a modified signal curve  846  may be created that has the following mathematical relationship with the signal from the vacuum sensor  50  represented by the pressure curve  842 . 
       Sound Frequency (Hz)=50×|(fluid pressure (kPa))|
 
     where Hz is Hertz (1/second), and 
     kPa is units of kiloPascal 
     The modified signal curve  846  may be constructed of an algorithm such that the sound frequency seems to the user to follow the amount of vacuum or negative pressure being applied. In this embodiment, the pitch of the sound becomes “higher” when vacuum is increased (fluid pressure decreases), and “lower” when the vacuum or negative pressure is decreased. Alternatively, the opposite may instead by chosen, wherein the pitch of the sound becomes lower when vacuum or negative pressure is increased. 
       FIG. 9  illustrates a graph  860  of time (x-axis) and multiple variables (y-axis). A pressure curve  862  shows a vacuum or negative pressure being applied at a pressure drop  868 , and a maintenance of vacuum or negative pressure  870  with a one or more decreases and increases in pressure  872 . These one or more decreases and increases in pressure  872  (or increases and decreases in vacuum or negative pressure) may represent, in some instances, clot being sucked through aspiration lumen of an aspiration catheter. In some cases, a single decrease in pressure  873  (increase in vacuum or negative pressure) may occur. The single decrease in pressure  873  may in some cases be extended in duration, as shown in  FIG. 9 , as may any one of the one or more decreases and increases in pressure  872 . In some cases or configurations, it may be desirable for the user to have a very specific real-time or close to real-time characterization of the instances when these small perturbations are occurring, as they may correspond to the catheter finding and aspirating a portion of thrombus. The measurement device  54 ,  64 ,  76  be configured to apply an algorithm that determines a frequency of an audible sound (or pitch), for example within the human range of audible identification (hearing), that varies within the human range of audible frequencies. For example, a modified signal curve  866  may be created that has the following general mathematical relationship with the signal from the vacuum sensor  50  represented by the pressure curve  862 . 
       Sound Frequency (Hz)= A+B ×(fluid pressure)
 
     where A is a first constant, and 
     B is a second constant 
     In one particular example, a modified signal curve  866  may be created that has the following mathematical relationship with the signal from the vacuum sensor  50  represented by the pressure curve  862 . 
       Sound Frequency (Hz)=40×(fluid pressure (kPa))
 
     where Hz is Hertz (1/second), and 
     kPa is units of kiloPascal 
     It should be noted that in this equation, no absolute value is used, but rather the actual value of fluid pressure. Or in some cases, an absolute (or negative) value may be used. 
     The modified signal curve  866  may be constructed of an algorithm such that the sound maintains a steady pitch until the clot is being sucked through the catheter, at which time the pitch changes slightly, but distinctly, away from a steady pitch. For example, in some embodiments, the pitch may change between about 20 Hz and about 2000 Hz to correspond to a pressure change of between about one kPa to about two kPa, or between about 40 Hz and about 80 Hz. 
     In any of the examples, the modification of signals may include any type of signal conditioning or signal modification that may be performed, including, but not limited to filtering, amplification, or isolation. The modified signal curve  806 ,  826 ,  846 ,  866  is used to determine the output signal to be generated by the communication device  58 ,  68 ,  74 . As mentioned, if the output signal of the communication device  58 ,  68 ,  74  is configured to be an audible sound, the sound pressure level may be varied, or the sound frequency may be varied. In some embodiments, the output signal of the communication device  58 ,  68 ,  74  may have both its sound pressure level and sound frequency varied. In one embodiment, the sound frequency varies continuously in proportion to fluid pressure, but at one or more particular thresholds of fluid pressure, the sound pressure level may be caused to vary quite suddenly and strikingly. Thus there is a two-part communication occurring, a continuous real-time status indicator, with an intermittent, alert indicator (failure, danger, etc.). In some cases, the continuous real-time status indicator may represent a first continuous signal and the alert indicator may represent a second alert signal. In other cases, the continuous real-time status indicator and the alert indicator may be combined or integrated into the same signal. In some embodiments, other characteristics of psychoacoustics may be varied using variable sound generation devices. In some embodiments, the spectral envelope may be varied. In some embodiments, timbre may be changed to varies levels between light and dark, warm and harsh, or different noise “colors” (pink, white, blue, black, etc.). 
     Though an audible output from the communication device  58 ,  68 ,  74  has been described with the examples from  FIGS. 6-9 , other communication signals may be used, including visual or tactile signals. Tactile signals may also include vibration devices or heat generation devices, either of which could be varied (as described) in relation to the measured fluid pressure. Either the amplitude of the frequency could analogously be varied in communication signals that include signals other than the audible signals already described. For example, the intensity of a light can be varied, or the frequency (e.g., color) of a light can be varied. The amplitude of displacement of a vibration device can be varied (or other techniques that vary the vibration intensity) or the frequency of the vibration can be varied. 
     In some cases, a pseudo-continuous analog may be used in place of a truly variable output. For example, instead of a single light whose intensity is continuously varied, an array of multiple lights, for example and array comprising multiple LEDs, may be used, with an increased number of LEDs being lit when the level of vacuum or negative pressure is increased, and a decreased number of LEDs being lit when the level of vacuum or negative pressure is decreased. The same may be possible with an array comprising multiple vibrating elements, wherein more elements begin vibrating upon an increase or decrease, depending on the application, of fluid pressure. 
     In any of the embodiments described in relation to  FIGS. 6-9 , the equations for sound pressure level or for sound frequency which depend on fluid pressure as a variable, may depend on actual measured fluid pressure, or an absolute value of actual measured fluid pressure, but may also use measured fluid pressure in an alternative manner. For example, with a baseline pressure  63  either pre-set, pre-determined, or determined or calculated by any other method (averaging, etc.), the differential between the measured pressure and the baseline pressure  63  may be used as the variable on which to base the particular dependency (e.g., proportionality). 
     Thus, a base mathematical relationship used with the proportionality described with respect to the embodiment of  FIG. 6  may be represented as: 
       Sound Pressure Level (dB)= A+B ×(1/Δ P )
 
     where A is a first constant, 
     B is a second constant, and 
     ΔP is a difference or differential between a baseline pressure and a measured fluid pressure. 
     Likewise, a base mathematical relationship used with the proportionality described with respect to the embodiment of  FIG. 7  may be represented as: 
       Sound Pressure Level (dB)= A+B ×|(Δ P )|
 
     where A is a first constant, 
     B is a second constant, and 
     ΔP is a difference or differential between a baseline pressure and a measured fluid pressure. 
     Likewise, a base mathematical relationship used with the proportionality described with respect to the embodiment of  FIG. 8  may be represented as: 
       Sound Frequency (Hz)= A+B ×|(Δ P )|
 
     where A is a first constant, 
     B is a second constant, and 
     ΔP is a difference or differential between a baseline pressure and a measured fluid pressure. 
     Likewise, a base mathematical relationship used with the proportionality described with respect to the embodiment of  FIG. 9  may be represented as: 
       Sound Frequency (Hz)= A+B ×(Δ P )
 
     where A is a first constant, 
     B is a second constant, and 
     ΔP is a difference or differential between a baseline pressure and a measured fluid pressure. 
     A pressure transducer  912  of an aspiration monitoring system  900  is illustrated in  FIG. 10 , for coupling to an aspiration system including an aspiration catheter  4 . The pressure transducer  912  includes a housing  40 , a first port  44 , a second port  46  and a cable  902  for carrying a signal. The cable  902  includes an interface  904 , or plug, which is configured to connect to a port  906  of a console  908  of the aspiration monitoring system  900 . The housing  40  of the pressure transducer  912  includes a cavity  42  extending between the first port  44  and the second port  46 . The console  908  is powered by a power module  972 , which is connected to the console  908 , and may comprise a source of AC or DC power. The console  908  may include a measurement device  964 , a memory module  966  and a communication device  968 , which may be coupled to each other as described in the prior embodiments and configured such that the communication device  968  is capable of creating a signal  970 , which may be an alert signal, a continuous signal, a combined signal, or other type of signal. The console  908  may also include wired or wireless connections to other interfaces or displays which may be found in health care sites, such as a monitor  931 . In some embodiments, the monitor  931  may be a monitor which also displays fluoroscopy or angiogram images, or a monitor which also displays electrocardiography or blood pressure graphics or other information. The monitor  931  may have a portion that maintains the status of the aspiration. For example, it may read “Thrombus being aspirated” or “No thrombus detected.” The pressure transducer  912  (housing  40 , ports  44 ,  46 , cable  902 , interface  904 ) may be sold sterile, and may be configured to output a signal that is received by the console  908 , for example the measurement device  964  of the console  908 . The pressure transducer  912  may have its own internal source of power (e.g., the battery  52  in  FIG. 2A ), or may be powered by its connection to the console  908 , or alternatively, by its connection to the aspiration catheter  4 , or even the extension tubing  10 . In some embodiments, the console  908  may be configured to identify and/or recognize the pressure transducer  912 , for example, to recognize the particular model of the pressure transducer  912 . In some embodiments, the console  908  may be configured to measure a resistance between two electrical contacts in the pressure transducer  912  in order to identify the type (e.g., model) of pressure transducer. In some embodiments, the console  908  may be configured to read an RFID chip on the pressure transducer  912 . The console  908  may also be configured to connect to two or more different models of pressure transducer. The port  906 , may comprise at least one port, which may comprise two or more ports, each port configured to allow connection of a different model of pressure transducer. 
     An aspiration system  1000  in  FIG. 11  includes an aspiration console  1001  having a connector  1002 , or hub, (e.g., male luer) for connecting to an aspiration catheter  4 , for example, to a connector  22  (e.g., female luer) of the aspiration catheter  4 . The aspiration console  1001  is powered by a power module  972 , which is connected to the aspiration console  1001 , and may comprise a source of AC or DC power. The aspiration console  1001  may include a canister  1006  for collecting the aspirated materials, and may include a vacuum pump  1004  for creating a vacuum or negative pressure with which to create the aspiration. Tubing  1008  may be connected between the canister  1006  and the connector  1002 . In some embodiments, the canister  1006  is removable or replaceable. An aspiration monitoring system  900  includes a pressure sensor  1010  (e.g., a vacuum sensor) in fluid communication with the tubing  1008 . The tubing  1008  may instead comprise a lumen formed inside fabricated parts. The aspiration monitoring system  900  is shown in more detail in  FIG. 12 , and may include some or all of the features described in relation to  FIG. 10 . The aspiration console  1001  may also include wired or wireless connections to other interfaces or displays which may be found in health care sites, such as a monitor  931 . In some embodiments, the monitor  931  may be a monitor which also displays fluoroscopy or angiogram images, or a monitor which also displays electrocardiography or blood pressure graphics or other information. By combining all communication related to the procedure on or at a single monitor or single monitor location, uninterrupted focus can be achieved by the user, who may be freely dedicated to the safe advancement and placement of the aspiration catheter in proximity to the thrombus. 
     A system for forced (or assisted) aspiration  1100  in  FIG. 13  includes an aspiration/injection console  1101  having a first connector  1016 , or hub, (e.g., male luer) for connecting to an injection lumen  1020  of a forced aspiration catheter  1013 , and a second connector  1012 , or hub (e.g., male luer) for connecting to an aspiration lumen  1018  of the forced aspiration catheter  1013 . The first connector  1016  is configured to connect to connector  1024  (e.g., female luer) of a y-connector  1022  and the second connector  1012  is configured to connect to connector  1026  of the y-connector  1022  at a proximal end  14  of the forced aspiration catheter  1013 . The aspiration/injection console  1101  is powered by a power module  972 , which is connected to the aspiration console  1101 , and may comprise a source of AC or DC power. The aspiration console  1101  may include a canister  1106  for collecting the aspirated materials, and may include a vacuum pump  1104  for creating a vacuum or negative pressure with which to create the aspiration. Tubing  1108  may be connected between the canister  1106  and the connector  1012 . A positive pressure pump  1014  is coupled to a fluid source  1032  (e.g., a saline bag) and is configured to inject infusate out the connector  1016  at a high pressure. An aspiration monitoring system  900  includes a pressure sensor  1110  (e.g., a vacuum sensor) in fluid communication with the tubing  1108 . The tubing  1108  may instead comprise a lumen formed inside fabricated parts. The aspiration monitoring system  900  is shown in more detail in  FIG. 14 , and may include some or all of the features described in relation to  FIG. 10 . At a distal end  16  of the forced aspiration catheter  1013 , the injection lumen  1020  terminates in an orifice  1028 , which is configured to create a jet  1030  formed from the high pressure infusate exiting the orifice  1028 . The jet  1030  enters the aspiration lumen  1018 , thus creating suction at the distal end  16  of the forced aspiration catheter  1013 , which forces materials (e.g., thrombus) into the aspiration lumen  1018 , and into the canister  1106 . The aspiration/injection console  1101  may also include wired or wireless connections to other interfaces or displays which may be found in health care sites, such as a monitor  931 . In some embodiments, the monitor  931  may be a monitor which also displays fluoroscopy or angiogram images, or a monitor which also displays electrocardiography or blood pressure graphics or other information. 
     In an alternative embodiment, the forced aspiration catheter  1013  of the aspiration catheter  4  may have an additional lumen or guide channel for placement of an additional device or tool. In some embodiments, the guidewire lumen  26  may be used as this additional lumen, and may extend the entire length or most of the length of the catheter, so that the lumen is accessible from the proximal end  14 . The additional device or tool may comprise a laser fiber, a mechanical screw, a vibrating wire or a variety of other modalities for disrupting thrombus or other material. 
     In any of the embodiments presented, the system may be configured so that most or all of the components are supplied together. For example, a catheter and an aspiration monitoring system that are permanently attached to each other. In some embodiments, the aspiration catheter and/or the aspiration monitoring system may include configurations that purposely make it difficult to reprocess (e.g., clean or resterilize) them, thus protecting from potential uses that are not recommended or warranted, and which may risk patient infection and/or device malfunction. For example, the sensor or the portion adjacent the sensor may be purposely difficult to access or clean. Alternatively, one or more batteries may be impossible to access or change. 
     In some embodiments, it may be desired to have other descriptive warnings that can be tied to pressure measurement or pressure measurement combined with another measured attribute. For example, if a sensor (accelerometer or temperature sensor) within the aspiration catheter is used to detect catheter movement, a change in this sensor may be tied to the pressure sensor. In this manner, a catheter that is engaged with a thrombus at its tip and is moved (e.g., begins to be pulled out of the patient) may then cause a warning: “Warning, do not move catheter; risk of thromboembolus.” 
       FIG. 15  is a diagrammatic figure depicting an assisted aspiration system  510 . The aspiration system  510  includes a remote hand piece  512  that contains a fluid pump  526  and an operator control interface  506 . In one contemplated embodiment, the system  510  is a single use disposable unit. The aspiration system  510  may also include extension tubing  514 , which contains a fluid irrigation lumen  502  and an aspiration lumen  504 , and which allows independent manipulation of a catheter  516  without requiring repositioning of the hand piece  512  during a procedure performed with the aspiration system  510 . Extension tubing  514  may also act as a pressure accumulator. High pressure fluid flow from the pump  526 , which may comprise a displacement pump, pulses with each stroke of the pump  526  creating a sinusoidal pressure map with distinct variations between the peaks and valleys of each sine wave. Extension tubing  514  may be matched to the pump  526  to expand and contract in unison with each pump pulse to reduce the variation in pressure caused by the pump pulses to produce a smooth or smoother fluid flow at tip of catheter  516 . Any tubing having suitable compliance characteristics may be used. The extension tubing  514  may be permanently attached to the pump  526  or it may be attached to the pump  526  by a connector  544 . The connector  544  is configured to ensure that the extension tubing  514  cannot be attached to the pump  526  incorrectly. 
     An interface connector  518  joins the extension tubing  514  and the catheter  516  together. In one contemplated embodiment, the interface connector  518  may contain a filter assembly  508  between high pressure fluid injection lumen  502  of the extension tubing  514  and a high pressure injection lumen  536  of the catheter  516  ( FIG. 17 ). The catheter  516  and the extension tubing  514  may be permanently joined by the interface connector  518 . Alternatively, the interface connector  518  may contain a standardized connection so that a selected catheter  516  may be attached to the extension tubing  514 . In some embodiments, the filter assembly  508  may be removably coupled to the extension tubing  514  by a quick disconnect connection. A pressure transducer of an embodiment of the aspiration monitoring system presented herein may be located at a point along the aspiration lumen  504  or any extension of the aspiration lumen  504 . 
     Attached to the hand piece  512  are a fluid source  520  and a vacuum source  522 . A standard hospital saline bag may be used as fluid source  520 ; such bags are readily available to the physician and provide the necessary volume to perform the procedure. Vacuum bottles may provide the vacuum source  522  or the vacuum source  522  may be provided by a syringe, a vacuum pump or other suitable vacuum source. The filter assembly  508  serves to filter particulate from the fluid source  520  to avoid clogging of the high pressure injection lumen  536  and an orifice  542  ( FIG. 17 ). As described herein, distal sections of the high pressure injection lumen  536  may be configured with small inner diameters, and to the filter assembly  508  serves to protect their continuing function. By incorporating one of a variety of catheters  516  into the assisted aspiration system  510 , for example with varying lumen configurations (inner diameter, length, etc.), a variety of aspiration qualities (aspiration rate, jet velocity, jet pressure) may be applied in one or more patients. These aspiration qualities can be further achieved by adjustment of the pump  526 , to modify pump characteristics (flow rate, pump pressure). In some embodiments, the catheter  516  may be used manually, for example, without the pump  526 , and controlled by hand injection. The manual use of the catheter  516  may be appropriate for certain patient conditions, and may serve to reduce the cost of the procedure. 
     In one contemplated embodiment, the catheter  516  has a variable stiffness ranging from stiffer at the proximal end to more flexible at the distal end. The variation in the stiffness of the catheter  516  may be achieved with a single tube with no radial bonds between two adjacent tubing pieces. For example, the shaft of the catheter  516  may be made from a single length of metal tube that has a spiral cut down the length of the tube to provide shaft flexibility. Variable stiffness may be created by varying the pitch of the spiral cut through different lengths of the metal tube. For example, the pitch of the spiral cut may be lower (where the turns of the spiral cut are closer together) at the distal end of the device to provide greater flexibility. Conversely, the pitch of the spiral cut at the proximal end may be greater (where the turns of the spiral cut are further apart) to provide increased stiffness. A single jacket covers the length of the metal tube to provide for a vacuum tight (air tight, outside to inside) catheter shaft. Other features of catheter  516  are described with reference to  FIG. 17 , below. 
       FIG. 16  is a diagrammatic view showing more detail of the hand piece  512  and the proximal portion of assisted catheter aspiration system  510 . The hand piece  512  includes a control box  524  where the power and control systems are disposed. The pump  526  may be a motor driven displacement pump that has a constant output. This pump displacement to catheter volume, along with the location of the orifice  542  (exit) of the catheter high pressure lumen  536  within the aspiration lumen  538  ( FIG. 17 ), ensures that no energy is transferred to the patient from the saline pump as all pressurized fluid is evacuated by the aspiration lumen. A prime button  528  is mechanically connected to a prime valve  530 . When preparing the device for use, it is advantageous to evacuate all air from the pressurized fluid system to reduce the possibility of air embolization. By depressing the prime button  528 , the user connects the fluid source  520  to the vacuum source  522  via the pump  526 . This forcefully pulls fluid (for example 0.9% NaCl solution, or “saline”, no “normal saline”, or heparinized saline) through the entire pump system, removing all air and positively priming the system for safe operation. A pressure/vacuum valve  532  is used to turn the vacuum or negative pressure on and off synchronously with the fluid pressure system. One contemplated valve  532  is a ported one-way valve. Such a valve is advantageous with respect to manual or electronic valve systems because it acts as a tamper proof safety feature by mechanically and automatically combining the operations of the two primary systems. By having pressure/vacuum valve  532 , the possibility of turning the vacuum or negative pressure on without activating the fluid system is eliminated. 
     The operator control interface  506  is powered by a power system  548  (such as a battery or an electrical line), and may comprise an electronic control board  550 , which may be operated by a user by use of one or more switches  552  and one or more indicator lamps  554 . The control board  550  also monitors and controls several device safety functions, which include over pressure and air bubble detection and vacuum or negative pressure charge. A pressure sensor  564  monitors pressure, and senses the presence of air bubbles. Alternatively, an optical device  566  may be used to sense air bubbles. In one contemplated embodiment, the pump pressure is proportional to the electric current needed to produce that pressure. Consequently, if the electric current required by pump  526  exceeds a preset limit, the control board will disable the pump by cutting power to it. Air bubble detection may also be monitored by monitoring the electrical current required to drive the pump at any particular moment. In order for a displacement pump  526  to reach high fluid pressures, there should be little or no air (which is highly compressible) present in the pump  526  or connecting system (including the catheter  516  and the extension tubing  514 ). The fluid volume is small enough that any air in the system will result in no pressure being generated at the pump head. The control board monitors the pump current for any abrupt downward change that may indicate that air has entered the system. If the rate of drop is faster than a preset limit, the control board will disable the pump by cutting power to it until the problem is corrected. Likewise, a block in the high pressure lumen  536 , which may be due to the entry of organized or fibrous thrombus, or a solid embolus, may be detected by monitoring the electrical current running the pump  526 . In normal use, the current fluxuations of the pump  526  are relatively high. For example, the pump may be configured so that there is a variation of 200 milliAmps or greater in the current during normal operation, so that when current fluxuations drop below 200 milliAmps, air is identified, and the system shuts down. Alternatively, current fluxuations in the range of, for example, 50 milliAmps to 75 milliAmps may be used to identify that air is in the system. Additionally, an increase in the current or current fluxuations may indicate the presence of clot or thrombus within the high pressure lumen  536 . For example, a current of greater than 600 milliAmps may indicate that thrombus it partially or completely blocking the high pressure lumen  536 , or even the aspiration lumen  538 . 
     A vacuum line  556 , connected to the vacuum source  522 , may be connected to a negative pressure sensor  558 . If the vacuum or negative pressure of the or negative pressure source  522  is low or if a leak is detected in the vacuum line  556 , the control board  550  disables the pump  526  until the problem is corrected. The negative pressure sensor  558  may also be part of a safety circuit  560  that will not allow the pump  526  to run if a vacuum is not present. Thereby a comprehensive safety system  562 , including the safety circuit  560 , the pressure sensor  564  and/or the optical device  566 , and the negative pressure sensor  558 , requires both pump pressure and vacuum or negative pressure for the system to run. If a problem exists (for example, if there is either a unacceptably low pump pressure or an absence of significant vacuum or negative pressure), the control board  550  will not allow the user to operate the aspiration system  510  until all problems are corrected. This will keep air from being injected into a patient, and will assure that the aspiration system  510  is not operated at incorrect parameters. 
       FIG. 17  is a diagrammatic view of the distal end portion  568  of the assisted catheter aspiration system  510 , showing more details of the catheter  516 . The catheter  516  is a single-operator exchange catheter and includes a short guidewire lumen  534  attached to the distal end of the device. The guidewire lumen  534  can be between about 1 and about 30 cm in length, or between about 5 and about 25 cm in length, or between about 5 and about 20 cm in length, or approximately 13.5 cm in length. An aspiration lumen  538  includes a distal opening  540  which allows a vacuum or negative pressure (for example, from vacuum source  522 ) to draw thrombotic material into the aspiration lumen  538 . A high pressure lumen  536  includes a distal orifice  542  that is set proximally of distal opening  540  by a set amount. For example, distal orifice  42  can be set proximally of distal opening  540  by about 0.0508 cm (0.020 inches), or by 0.0508 cm±0.00762 cm (0.020 inches±0.003 inches) or by another desired amount. The orifice  542  is configured to spray across the aspiration lumen to macerate and/or dilute the thrombotic material for transport to vacuum source  522 , for example, by lowering the effective viscosity of the thrombotic material. The axial placement of the fluid orifice  542  is such that the spray pattern interaction with the opposing lumen wall produces a spray mist and not a swirl pattern that could force embolic material out from the distal opening  540 . The system may be configured so that the irrigation fluid leaves the pump at a pressure of between about 3,447,378 pascal (500 psi) and about 10,342,135 pascal (1500 psi). In some embodiments, after a pressure head loss along the high pressure lumen  536 , the irrigation fluid leaves orifice  542  at between about 4,136,854 pascal (600 psi) and about 8,273,708 pascal (1200 psi), or between about 4,481,592 pascal (650 psi) and about 5,860,543 pascal (850 psi). In some cases, it may be possible (and even desired) to use the assisted catheter aspiration system  510  without operating the pump  526 , and thus use the catheter  516  while providing, for example, a hand saline injection via a syringe. Or, in some cases, the assisted catheter aspiration system  510  may be used without the pump  526  attached, with the saline injections done by hand using a syringe through the high pressure lumen  536 . If a clog occurs, the syringe may be removed and the pump  526  attached and initiated, for example, for the purpose of unclogging the high pressure lumen  536 . 
     When normal blood flow is achieved after unblocking occlusions or blockages from atherosclerotic lesions and/or thrombosis, there is sometimes a risk of reperfusion injury. This may be particularly significant following thrombectomy of vessels feeding the brain for treatment of thromboembolic stroke, or following thrombectomy of coronary vessels feeding the myocardium. In the case of the revascularization of myocardium following a coronary intervention (e.g. thrombectomy). Reperfusion injury and microvascular dysfunction may be mechanisms that limit significant or full recovery of revascularized myocardium. The sudden reperfusion of a section of myocardium that had previously been underperfused may trigger a range of physiological processes that stun or damage the myocardium. Distal coronary emboli, such as small portions of thrombus, platelets and atheroma, may also play a part. Controlled preconditioning of the myocardium at risk has been proposed to limit the effect of reperfusion injury and microvascular dysfunction. The embodiments of the thrombectomy systems  100 ,  300  presented herein may be combined with additional features aimed at allowing flow control, in order to limit the potential dangers due to reperfusion following thrombectomy. 
       FIG. 18  illustrates a multi-purpose system  1200  comprising a multi-purpose catheter  1202  having an infusion/injection port  1204  and an aspiration port  1206 . The infusion/injection port  1204  and the aspiration port  1206  may each comprise luer connectors, such as female luer lock connectors. A tubing set  1208  and a pressure sensor  1210  are connected in line with a vacuum source  1212 . A cable  1214  carries signals from the pressure sensor  1210  to an aspiration monitoring system  1216  ( FIG. 19 ), and connects to the aspiration monitoring system  1216  via an interface  1218 , or plug, which is configured to connect to a port  1220  of a console  1222  of the aspiration monitoring system  1216 . Apparatus and methods described herein may be used to monitor aspiration using the aspiration monitoring system  1216 . In one manner of use, a syringe  1224  ( FIG. 18 ) may be used to manually inject through the injection port  1204  and injection lumen  1225  (e.g., high pressure lumen) of the multi-purpose catheter  1202 . The syringe  1224  may have an injectable volume of about 5 ml or less, or in some embodiments about 1 ml or less. The injection lumen  1225  in some embodiments may be configured for injection of saline at a relatively high pressure, or at either high or low pressures. If the valve  1226  (e.g., stopcock) is closed, blocking the vacuum source  1212  from applying a vacuum or negative pressure to the aspiration lumen  1227  via the aspiration port  1206 , then injection through the injection lumen  1225  causes injectate to be delivered to a site in the blood vessel near the distal exit of the injection lumen  1225  (at the distal end of the multi-purpose catheter  1202 ). Or, if the vacuum source  1212  is removed from, or simply not coupled to, the aspiration lumen  1227 , then injection through the injection lumen  1225  may also cause injectate to be delivered to a site in the blood vessel near the distal exit of the injection lumen  1225 . Either of these techniques may be utilized to apply a medicant to a blood vessel wall, or to an atherosclerotic plaque, or to a thrombus. In some cases, a clot busting drug (tissue plasminogen activator-tPA, thrombokinase, urokinase, thrombin, plasmin) is infused into a clot or thrombus, allowing it to act over a period of time. One purpose may be to soften the thrombus over time. Lytics, glycoprotein inhibitors (GPIs), vasodilators, and other drugs may be used to dilate the blood vessel, or treat disease in the area. The controlled, precision, local delivery allows an efficient use of the drug, with the desired amount delivered to the tissue to be treated with minimal runoff or waste. As many of these drugs are quite expensive, this efficiency reduces procedural costs. Because of the precision diameter of the injection lumen  1225 , and its known length, the injection lumen  1225  contains a known volume, or dead space. This additionally allows a known, controlled, precision injection of medicant. A representative injection lumen  1225  may have a length of 150 cm and have an inner diameter of 0.038 cm (0.015 inches), and thus a total volume of only 0.17 ml. The injection lumen  1225  volume may be varied, by controlling the diameter of the inner diameter of the injection lumen  1225  and/or the length of the injection lumen  1225 . For example, the injection lumen  1225  volume may be between about 0.08 ml and about 0.26 ml, or between about 0.14 ml and about 0.20 ml. By injecting through the injection lumen  1225  with a small bore syringe (e.g., 1 ml) or with a precision pump, an accurate measurement of the medicant delivered can be made. If, however, the valve  1226 , or stopcock, is opened, connecting the vacuum source  1212  to the aspiration port  1206  and applying a vacuum or negative pressure on the aspiration lumen  1227 , a forced aspiration is commenced, as described herein. As described, the injection lumen  1225  may serve either a closed system (aspiration) or an open system (injection of infusate). At the beginning of a procedure, it is not always known what different actions will be required, thus the use of the multi-purpose catheter  1202  and multi-purpose system  1200  may eliminate the need to use multiple catheters (e.g., both a microcatheter and a single function aspiration catheter). 
       FIGS. 20-24  illustrate a multi-purpose system  1240  comprising a multi-purpose catheter  1242  having an infusion/injection port  1244  and an aspiration port  1246 . Cooled saline may be injected from a saline bag  1248  ( FIG. 23 ) through a tubing set  1250 , attached to the saline bag  1248  via a spike  1252 . A pump  1254  ( FIG. 24 ), which may include a displacement pump, such as a piston pump, includes an interface  1256  for attaching a cassette  1258  ( FIG. 20 ). In some embodiments, the pump  1254  has moving portions that connect to a moving piston  1255  in the cassette  1258  to inject controlled amounts of fluid. As described in relation to the multi-purpose system  1200  of  FIG. 18 , the injection may serve either a closed system (aspiration) or an open system (injection of infusate), depending on whether a valve  1260  which couples a vacuum source  1262  to the aspiration port  1246  via extension tubing  1264  is open or closed, or simply whether the vacuum source  1262  is attached or not attached. A pressure sensor  1266  communicates with the interior of the extension tubing  1264 , but may communicate with the interior of other parts of the flow path. A cable  1268  carries signals from the pressure sensor  1266  to an aspiration monitoring system  1270  ( FIG. 22 ), and connects to the aspiration monitoring system  1270  via an interface  1272 , or plug, which is configured to connect to a port  1274  of a console  1276  of the aspiration monitoring system  1270 . The utility of the multi-purpose systems  1200 ,  1240  in multiple modes is facilitated by the sterile fluid path combined with precision volume control (either by small syringe  1224 , or by the precision pump  1254 ). In addition, the aspiration monitoring system  1216 ,  1270  allows real-time feedback to the user, further facilitating controlled delivery and/or aspiration. 
     The multipurpose system  1200 ,  1240  optimizes interventional procedures, such as percutaneous coronary interventions (PCIs), for simplicity, case flow, and cost. Infusing drugs intracoronary prepares clot for aspiration by placing highly concentrated pharmaco agents directly at the lesion site, at a location which can be more distal (e.g., more superselective) than that which is typically accessible by the tip of a guiding catheter. This can minimize the volume of drug/medicant/agent used. By limiting the amount of certain medicants, systemic complications (bleeding, etc.) can be minimized or eliminated. The direct application of the medicant, for example at the thrombus itself, allows it to soften or disaggregate the thrombus. The maceration of the thrombus, for example by a saline jet  1278  ( FIG. 21 ) injected through the injection lumen  1257  of the multi-purpose catheter  1242 , keeps the catheter aspiration lumen  1259  patent at all times without interruption, and allows standardized catheter advancement technique, for example, moving the catheter slowly from a proximal location to a distal location in the vessel (in relation to the thrombus). The maceration also dilutes the proximally flowing aspirate for optimal aspiration efficiency. In certain situation, aspiration may be performed until the normal blood flow is restored (at least to a significant level), and then the vacuum source  1262  may be closed off via the valve  1260  and cooled injectate may be infused into the blood vessel. The resultant selective cooling of this area serves to reduce reperfusion injury by potentially slowing ischemic cell metabolism. The injection of cooled infusate may be used any time post-aspiration, pre-stenting, without having to remove an aspiration device, advance a new injection device. Because the multi-purpose catheter  1202 ,  1242  is already in place, this critical operation may be started immediately. By having these functionalities all on one catheter, there is also a cost saving to the user. 
     In aspiration mode, the aspiration monitoring system  1216 ,  1270  is able to monitor proper function of the aspiration circuit at all times. The user knows when warnings are communicated or when the system (e.g., motor) shuts down, that a key event has occurred, an event that needs attending. This knowledge helps the user avoid plunging the catheter distally, potentially causing distal embolism. In infusion/infusate cooling mode, the pump  1254  pumps at a predetermined constant volume or speed to deliver constant temperature cooling infusate. Core temperature feedback (e.g., via rectal, esophageal, ear or other temperature probes) may be used to indicate to the system that further cooling must stop. For example, a core body temperature below 35° C. or below 34° C. The feedback of a temperature below the threshold may be used to shut down the pump and/or to send a warning. The infusate path, which is precision and direct to the catheter tip and/or ischemic area, results in concentrated cooling, causing the least systemic hypothermic potential. By bypassing the aspiration lumen (e.g., with the valve  1260  closed), unintentional embolic debris is less likely to be infused back into the blood vessel, and less likely to thus be sent downstream to critical areas. This eliminates the need to exchange devices after flow has been restored. 
     In some cases, in infusion mode, infusate is injected into the fluid injection lumen  1225 ,  1257  with a relatively low pressure. In some cases, maceration is performed at a relatively high pressure. In some cases, the multi-purpose system  1240  may be used without the pump  1254  attached, with the saline injections done by hand using a syringe attached to the infusion/injection port  1244 . If a clog occurs, the syringe may be removed and the pump  1254  attached and initiated, for example, for the purpose of unclogging the injection lumen  1257 . In an exemplary procedure, a user places a catheter similar to the multi-purpose catheter  1202  of  FIG. 18  or multi-purpose catheter  1242  of  FIGS. 20-21  in the vasculature. Initially, the user may choose to have neither a pump  1254 , nor a syringe  1224  ( FIG. 18 ) attached to the multi-purpose catheter  1202 ,  1242 . The user may then commence aspiration through the aspiration lumen  1227 ,  1259  via a vacuum source  1212 ,  1262 , thus utilizing the multi-purpose catheter  1202 ,  1242  as a simple (vacuum or negative pressure only) aspiration catheter. If at any time, the user determines that additional positive pressure injection of saline and/or medicant is needed, for example, to overcome clogging, overcome slow aspiration, or to increase maceration or dilution of the thrombus, the user can attach the pump  1254  or the syringe  1224  to the infusion/injection port  1204 ,  1244  and begin injecting the saline and/or medicant. 
     In one embodiment, an aspiration system includes an elongate catheter having a proximal end and a distal end, the catheter including an aspiration lumen having a proximal end and a distal end and a high pressure injection lumen having a proximal end and a distal end and extending from a proximal end of the catheter to a location adjacent a distal end of the aspiration lumen, and at least one orifice at or near the distal end of the high pressure injection lumen and configured to allow high pressure liquid injected through the high pressure injection lumen to be released into the aspiration lumen, wherein the proximal end of the high pressure injection lumen is configured to be repeatably coupled to and uncoupled from one or more injection modules. In some embodiments, the one or more injection modules include a first injection module and a second injection module. In some embodiments, the first injection module comprises a pump and the second injection module comprises a syringe. In some embodiments, the second injection module comprises a syringe having a volume of about 5 ml or less. In some embodiments, the second injection module comprises a syringe having a volume of about 1 ml or less. In some embodiments, the second injection module comprises a syringe containing a drug. 
       FIGS. 25 through 33  illustrate several different embodiments of devices having a pressure sensor  1300 , which is configured to function as a component in an aspiration monitoring system sharing some or all of the functionality of any one of the aspiration monitoring systems  48 ,  62 ,  78 ,  900 ,  1216 ,  1270  presented herein.  FIG. 25  illustrates an aspiration catheter  1302  having a distal end  1304  and a proximal end  1306 , the proximal end  1306  comprising a female luer connector  1308 . The pressure sensor  1300  is in fluid communication with (e.g., fluidly coupled to) a lumen of the aspiration catheter  1302 .  FIG. 26  illustrates a tubing set  1310  having a male luer  1312  and a female luer  1314 , extension tubing  1316 , and a stopcock  1318 . The pressure sensor  1300  is in fluid communication with a lumen of the extension tubing  1316 .  FIG. 27  illustrates a stopcock  1320  having a male luer  1322 , a female luer  1324 , and a valve  1326 , the valve  1326  located proximally of the pressure sensor  1300 . The pressure sensor  1300  is in fluid communication with an internal cavity of the stopcock  1320 .  FIG. 28  illustrates a stopcock  1328  having a male luer  1330 , a female luer  1332 , and a valve  1334 , the valve  1334  located distally of the pressure sensor  1300 . The pressure sensor  1300  is in fluid communication with an internal cavity of the stopcock  1328 .  FIG. 29  illustrates a syringe  1336  having a male luer  1342 , a barrel  1338 , and a plunger  1340 . The syringe  1336  may include a locking feature  1344 , which allows the plunger  1340  to be locked in relation to the barrel  1338 , such as a VacLok® syringe. The pressure sensor  1300  is located distally of the barrel  1338  and is in fluid communication with an internal cavity of the barrel  1338 . 
       FIG. 30  illustrates a syringe  1346  having a male luer  1352  (i.e., luer connector, luer lock), a barrel  1348 , and a plunger  1350 . The syringe  1346  may include a locking feature  1344 . The pressure sensor  1300  is in fluid communication with an internal cavity of the barrel  1348 , and may be directly connected to either the barrel  1348  or the male luer  1352 , or a hollow transition  1351  between them.  FIG. 31  illustrates an aspiration system  1354  comprising a syringe  1356  having a male luer  1357 , a barrel  1358  and a plunger  1360 . The syringe  1356  may include a locking feature  1344 . The aspiration system  1354  also comprises a connector assembly  1361  comprising a male luer  1362 , a valve  1364 , and a female luer  1365  (connected under the male luer  1357  in  FIG. 31 ). The pressure sensor  1300  is in fluid communication with an internal lumen or cavity between the barrel  1358  of the syringe  1356  and the male luer  1362  of the connector assembly  1361 .  FIG. 32  illustrates an aspiration system  1366  comprising a syringe  1368  having a male luer  1369 , a barrel  1370  and a plunger  1372 . The syringe  1368  may include a locking feature  1344 . The aspiration system  1366  also comprises a connector assembly  1373  comprising a male luer  1374 , a valve  1376 , and a female luer  1377  (connected under the male luer  1369  in  FIG. 32 ). The pressure sensor  1300  is in fluid communication with an internal lumen or cavity between the barrel  1370  of the syringe  1368  and the male luer  1374  of the connector assembly  1373 .  FIG. 33  illustrates an aspiration system  1378  comprising a syringe  1380  having a male luer  1382 , a barrel  1384  and a plunger  1386 . The syringe  1380  may include a locking feature  1344 . The aspiration system  1378  further comprises a tubing set  1388  having a male luer  1390  and a female luer  1392 . A valve  1394  is located either proximal or distal to the pressure sensor  1300 . Extension tubing  1396  may be utilized to connect one or more of the components of the tubing set  1388 , but in some cases, the components may be connected directly. The pressure sensor  1300  is in fluid communication with an internal lumen of the tubing set  1388 . The stopcock or valve in any of these embodiments may be a one-way stopcock or a three-way stopcock or a one-way valve or a three-way valve. Other embodiments may exist which combine one or more elements of each of the embodiments presented herein. These embodiments are also included within the scope of this disclosure. In any of the embodiments in which a male luer is used, it may be replaced with a female luer or another liquid-tight connector. In any of the embodiments in which a female luer is used, it may be replaced with a male luer or another liquid-tight connector. As such, either of the connector assemblies  1361 ,  1373  may be connected in reverse manner to the syringes  1356 ,  1368 , i.e., wherein the distal end becomes the proximal end and is thus connected to the syringe  1356 ,  1368 , and wherein the proximal end becomes the distal end. 
       FIG. 34  illustrates a thrombectomy system  300  which incorporates the high pressure injection of a liquid, for example sterile saline solution, in order to macerate and aspirate thrombus  104 . A guiding catheter  108  has an inner lumen  110  extending between a proximal end  144  and a distal end  120 . A y-connector  148 , coupled to the proximal end  144  of the guiding catheter  108 , includes a proximal seal  150  and a sideport  152  and is configured to couple the inner lumen  110  of the guiding catheter  108  to a vacuum source  146 , as described in relation to the prior embodiments. A thrombectomy catheter  306  comprises a distal tube  314  having a distal end  316  and a proximal end  318 , the proximal end  318  incorporating one or more sealing members  324  for sealing off an annulus  342  between the guiding catheter  108  and the distal tube  314 , as described in relation to the prior embodiments. The distal tube  314  has an aspiration lumen  330 . A support/supply tube  368 , having a lumen  370 , is coupled to the distal tube  314 . The support/supply tube  368  serves as a support member for pushing and pulling the thrombectomy catheter  306 , but is also a conduit (via the lumen  370 ) for high pressure saline, which is injected from the proximal end  372  to the distal end  374 . The saline is supplied from a saline source  376  (e.g. saline bag, bottle) and pressurized by a pump  378 , through a supply tube  380  and through a luer connector  382  which is connected to a luer hub  384  coupled to the support/supply tube  368 . In some embodiments, the support/supply tube  368  comprises a hypo tube. In some embodiments, the support/supply tube  368  comprises stainless steel or nitinol. The distal end  316  of the distal tube  314  may include a skive  358 , which aids in the trackability of the distal tube  314  through vasculature of a patient. In some embodiments, the inner diameter of the aspiration lumen  330  of the distal tube  314  may be approximately one French size smaller than the inner diameter of the inner lumen  110  of the guiding catheter  108 . In some embodiments, the thrombectomy catheter  306  may include a support tube or support shaft to replace the support/supply tube, and not comprise a lumen  370 . Thus, aspiration is only controlled by evacuation of the inner lumen  110  of the guiding catheter  108  in combination of the aspiration lumen  330  of the distal tube  314 , and injection of a high pressure liquid is not necessary. Other embodiments of the thrombectomy catheter  306  are described in U.S. Pat. No. 9,433,427, issued Sep. 6, 2016, and entitled “Systems and Methods for Management of Thrombosis,” which is hereby incorporated by reference in its entirety for all purposes 
       FIG. 35  illustrates the proximal end of a guiding catheter  108  used with aspiration catheters, such as the thrombectomy catheter  306  of  FIG. 34 . A hemostasis valve  389  of y-connector  390  seals over both the support/supply tube  391  and the guidewire  28 . The hemostasis valve  389  (e.g., Touhy-Borst, longitudinally spring-loaded seal, etc.) must be adjusted to allow catheter and/or guidewire  28  movement (translation, rotation), but must keep air from being pulled into the lumens during aspiration. Because of the continual adjustment often required to the hemostasis valve  389 , for example, to aid movement of the catheter and/or guidewire, the hemostasis valve  389  may create significant variability in the amount of air that may leak. A leak (e.g., at location  393 ) may be fast, and may be unknown to the user. A pressure sensor  394  used in conjunction with any of the aspiration monitoring systems described herein allows the user to know immediately if the seal of the hemostasis valve  389  of the y-connector  390  is not correctly sealed. Additionally, any leaks between the distal luer  388  of the y-connector  390  and the luer hub  386  of the guiding catheter  108  can be detected by the aspiration monitoring system. Furthermore, any leaks between a luer  392  of the pressure sensor  394  and a sideport  395  of the y-connector  390  or between a luer connector  396  of the extension tube  387  and a luer fitting  397  of the pressure sensor  394  can be detected by the aspiration monitoring system. The aspiration monitoring system may be configured to be integral or attachable to any component of the aspiration circuit (e.g., aspiration catheter, syringe/vacuum source), or may be connected in series (at any point) between these components. In some embodiment, the aspiration monitoring system may comprise a flow or pressure sensor or detector that is in series or in parallel with the components, or is configured to be placed in series or in parallel with the components. In any of these configurations, a number of different leak locations may be assessed by the aspiration monitoring system of the embodiments disclosed herein. The aspiration monitoring system may be configured to detect: changes, relative changes, absolute changes, thresholds, absolute values, the presence of or the lack of pressure and/or flow. The aspiration monitoring system may be configured to determine the operation status of a system including a catheter having an aspiration lumen. In some cases, the aspiration monitoring system may be configured to provide information about the operation of the system that is not discernable from typical clues such as angiography, sound, feel, or other visual, auditory, tactile or other feedback from the system itself. 
       FIG. 36  illustrates an aspiration system  1400  comprising an aspiration catheter  1402  comprising an elongate shaft  1401  including an aspiration lumen  1404  having an open distal end  1405  and a proximal end  1406  configured to couple to a peristaltic pump  1408 . The peristaltic pump  1408  may be a roller pump having a base  1426 , a pressure shoe  1428  carried by the base  1426 , and a rotatable head  1430 , rotatably coupled to the base  1426 , and carrying two or more rollers  1432   a - d . The rollers  1432   a - d  are arrayed around a perimeter  1434  of the rotatable head  1430 . The rotatable head  1430  is configured to be rotatable in at least a first rotational direction  1436  with respect to a rotational axis  1499 . The rotatable head  1430  may be rotated by a motor  1497 , either directly, or with a gear train  1495 . The peristaltic pump  1408  may be battery powered, and the battery(ies) may be rechargeable by wired or wireless means. The peristaltic pump  1408  may alternatively, or additionally be powered by a power cord  1493  configured to connect to a power supply. An extension tube  1438  having a distal end  1440  and a proximal end  1442 , and having a lumen  1444  extending therethrough, is hydraulically coupled to the proximal end  1406  of the aspiration lumen  1404  via a connector  1424 . The extension tube  1438  may be supplied (e.g., sterile) with the aspiration catheter  1402 , or may be packaged and supplied separately. A Touhy-Borst seal  1446  carried on the connector  1424  is configured to be loosened/opened to allow the insertion of a guidewire  1448  through the connector  1424  and the aspiration lumen  1404 . The aspiration lumen  1404  may thus be used to track the aspiration catheter  1402  over the guidewire  1448  through a subject&#39;s vasculature. The Touhy-Borst  1446  can be tightened to seal over the guidewire  1448 , to maintain hemostasis. Other types of seals may be incorporated in place of the Touhy-Borst  1446 , including a spring-loaded, longitudinally compressible and actuatable seal. The extension tube  1438  includes a male luer  1450  at its distal end  1440 , for connecting to a female luer  1452  of the connector  1424 . The male luer  1450  may include a stopcock  1454 , which is configured to be turned to select between an open position (shown) or a closed position. The extension tube  1438  and its components may be supplied sterile as a single unit. Alternatively, the extension tube  1438  may be integral with the aspiration lumen  1404 , or may be permanently attached to the connector  1424 . In use, a compressible portion  1437  of the extension tube  1438  is placed within the pressure shoe  1428  of the peristaltic pump  1408  such that rotation of the rotatable head  1430  in the rotational direction  1436  causes fluid to be forced through the lumen  1444  of the extension tube  1438  from the distal end  1440  to the proximal end  1442 , via compression of the compressible portion  1437  by the rollers  1432 , one at a time. The single insertion step to couple the compressible portion  1437  to the peristaltic pump  1408  is simple, quick, reliable, and does not involve any connection that has to seal (e.g., luer, etc). It is also easier to visualize whether a peristaltic pump is successfully operating, vs. a vacuum pump or evacuated syringe. This may be because, under relatively high vacuum or negative pressure conditions, blood tends to cavitate, thus filling the space of a container (e.g., canister or syringe) at an accelerated rate due to the excess gaseous volume. The gaseous bubbles may also make it more difficult to see inside and visually inspect the condition. Optionally, an interface  1456  on the peristaltic pump  1408  is configured to allow a user to input information or commands to the peristaltic pump  1408  or other components of the system  1400 . Otherwise, hardware or firmware may be pre-programmed with specific run parameters (motor speed, rotation speed, etc.). In some embodiments, there are only two rollers  1432 . In other embodiments, there are three rollers  1432 . In still other embodiments, as shown, there are four rollers  1432 . In an alternative embodiment, instead of rollers, smooth, radiused bumps of a rigid material slide over the compressible portion  1437 , compressing it. In this alternative embodiment, the compressible portion  1437  and/or the bumps may be treated with a lubricious material or may be constructed from significantly lubricious materials to lover the sliding friction between the compressible portion  1437  and the bumps. Returning to the embodiment of  FIG. 36 , the compressible portion  1437  may comprise silicone tubing, polyurethane tubing, polyvinyl chloride tubing, or other compressible tubing. The compressible section  1437  may be a relatively short section that is attachable to and detachable from the peripheral ends of the extension tube  1438 , or in other embodiments, may comprise the entirety of the extension tube  1438  between the distal end  1440  and the proximal end  1442 . The proximal end  1442  of the extension tube  1438  may be coupled to a hub  1457  of a canister  1458  having an interior  1460 , to allow fluid  1459  passing through the extension tube  1438  to pass into the interior  1460 . An additional hub  1462  in the canister  1458  may be left open (as shown) to allow the unfilled interior  1460  to match atmospheric pressure. Alternatively, the canister  1458  may be replaced by another type of receptacle, such as a bag, or more specifically an empty infusion bag, configured for collecting aspirate therein. 
     The aspiration catheter  1402  additionally has a high pressure injection lumen  1410  for injecting saline from a fluid source  1479 , for example, via a high pressure pump  1412 . A tubing set  1464  may include a pump cartridge  1466  having a piston, or bellows, or other movable element that the pump  1412  may manipulate using an internal motor  1491 , thus pressurizing saline (or other fluid) from the fluid source  1479  with a significantly high pressure such that the saline is forced through the injection lumen  1410  of the aspiration catheter  1402 . The tubing set  1464  includes proximal end  1468  having a spike  1489 , or other connecting element, for hydraulically coupling the tubing set  1464  to the fluid source  1479 . The tubing set  1464  further has a distal end  1470 , which may comprise a male luer, and which is configured to hydraulically couple the tubing set  1464  to the injection lumen  1410  via a female luer  1472 . The tubing set  1464  may be supplied sterile as a single unit, or alternatively may be permanently attached to the aspiration catheter  1402 . In use, injected saline is forced through the injection lumen  1410  by the pump  1412  and exits an orifice  1474  at a distal end  1476  of the injection lumen  1410 . The injection lumen  1410  may extend within a separate tube  1478  (injection tube) that is substantially or entirely within the shaft  1401 . In some embodiments, the tube  1478  is attached to the internal wall of the shaft  1401  only at a distal end portion  1403 . Thus, the free-floating nature of the remainder of the tube  1478  within the aspiration lumen  1404  increases the flexibility and trackability of the shaft  1401 . There also a reduced chance of the tube  1478  being kinked because of flexing of the shaft  1401 , because the bending of the shaft  1401  is not directly applied to the tube  1478 . The high pressure saline is forced through the injection tube  1478  and out the orifice  1474 , causing a jet  1487 . The jet  1487  is within the aspiration lumen  1404 , just proximal the open distal end  1405  which can create a Venturi effect that forces blood or thrombus that is external and adjacent the open distal end  1405  into the aspiration lumen  1404 . The operation of the peristaltic pump  1408  with the rotatable head  1430  rotating in the first rotational direction  1436  moves fluid and thrombus from the open distal end  1405  of the aspiration lumen  1404  to the proximal end  1442  of the extension tube  1438  by continually and forceably moving the fluid column within the lumen  1444  of the extension tube  1438 , which pulls the fluid column within the aspiration lumen  1404  along with it. The combination of the operation of the peristaltic pump  1408  and the jet  1487  created by the high pressure saline cause the maceration of thrombus, and the movement/flow of material (saline/blood/macerated thrombus/small pieces of thrombus) through the aspiration lumen  1404  from the open distal end  1405  to the proximal end  1406 , through the interior  1485  of the connector  1424 , and through the lumen  1444  of the extension tube  1438  from its distal end  1440  to its proximal end  1442 , and finally into the interior  1460  of the canister  1458 . Thus, thrombus within a blood vessel of a subject may be macerated and removed by use of the system  1400 . Blood vessels may include peripheral blood vessels, coronary blood vessels, or blood vessels within the head or neck of the subject, including carotid arteries or cerebral arteries. 
     An aspiration monitoring system  1414  comprising a pressure transducer  1416  may be coupled, for example, between the distal end  1440  of the extension tube  1438  and the connector  1424  and/or the proximal end  1406  of the aspiration lumen  1404  of the aspiration catheter  1402 . The aspiration monitoring system  1414  can include any of the features described in relation to the other aspiration monitoring systems  48 ,  62 ,  78 ,  900 ,  1216 ,  1270  disclosed herein. Signals from the pressure transducer  1416  are carried on an electric cable  1480  to an input  1482  of the pump  1412 . A controller  1484  within the pump  1412  is configured to control the operation of the pump  1412 , including motor  1491 , but the controller  1484  may also be configured to control the operation of the peristaltic pump  1408 , with via a cable  1486 , or wirelessly. The controller  1484  may comprise a microcontroller. The controller  1484  may alternatively be located within the peristaltic pump  1408 , or may be located at another location. Control using signals of measured pressure from the pressure transducer  1416  adds an additional safety element to the system  1400 . Furthermore, a non-functional system  1400  or particular component of the system  1400  can be quickly identified. For example, a leak, incomplete connection, incomplete priming of one of the lumens, rupture, or breakage can cause changes in the signal from the pressure transducer  1416 , thus allowing their identification. Unallowably high pressures can also be quickly identified, and the controller  1484  is configured to automatically shut down the pump  1412 , thus protecting the motor  1491  of the pump  1412  from burnout or overheating, and the failure or danger associated therewith. The peristaltic pump  1408  may also be shut down by the controller  1484 . In some embodiments, the peristaltic pump  1408  is configured to be shut down by the controller  1484  after the pump  1412  is shut down (e.g., after a finite delay). The delay may be between about 0.01 second and about 1.00 second, or between about 0.10 second and about 0.25 second. The integrity of the tube  1478  is also protected, e.g., avoiding unnaturally high pressures that could lead to burst. In some embodiments, the peristaltic pump  1408  may be battery powered, and the controller  1484  may be located within the peristaltic pump  1408 , thus providing a self-contained peristaltic pump  1408  which may be easily moved from one location to another. In some embodiments, the peristaltic pump  1408  may even be easily cleanable and sterilizable, such that it may be placed within a sterile field, such as a sterile field in the vicinity of a patient. In some embodiments, the pump  1412  is configured to remain in a non-sterile area, while the peristaltic pump  1408  is configured for sterile use. A push button  1411  may be carried on the peristaltic pump  1408 , and may be configured for activation by a user, for example, a user who is scrubbed for contact of sterile articles only. The push button  1411  may be configured to start or stop the operation of the peristaltic pump  1408 . Additionally, the push button may be configured to start or stop the operation of the pump  1412  (e.g., via the cable  1486 ). In some embodiments, the peristaltic pump  1408  and the pump  1412  are combined into a single console. This allows for a smaller size that may be mounted on a standard IV pole. 
     In some embodiments, activation of the push button  1411  by a finger of a user starts the operation of the peristaltic pump  1408 , and then starts the operation of the pump  1412 , with a slight delay after the peristaltic pump  1408  is started. The delay is useful to assure that some aspiration, or a significant amount of aspiration, is being applied to the aspiration lumen  1404  prior to the injection of pressurized fluid (e.g., saline) through the injection lumen  1410 . Thus, blood vessels or other vasculature in the vicinity of the open distal end  1405  are spared any injection of fluid from a high pressure jet, as it is instead aspirated through the aspiration lumen  1404 , along with any aspirated thrombus or blood. In addition, in some embodiments, activation of the push button  1411  by a finger of a user during the operation of the pump  1412  and the peristaltic pump  1408  stops the operation of the pump  1412  and the operation of the peristaltic pump  1408  at the same time. In other embodiments, a delay may be applied, for example, such that the pump  1412  is stopped, and then the peristaltic pump  1408  is stopped slightly afterwards. The length of the delays described may be between about 0.01 second and about 1.00 second, or between about 0.10 second and about 0.25 second. In some embodiments, the controller  1484  is configured to change the rotational speed of the rotatable head  1430  of the peristaltic pump  1408 , for example, increase the speed or decrease the speed. In some embodiments, the controller  1484  is configured to change the flow rate (injection rate) of the pump  1412 , for example, increase the injection rate or decrease the injection rate. In some embodiments, the controller  1484  is configured to change the speed/rate of both pumps  1408 ,  1412  at the same time. In some embodiments, the controller  1484  is configured to change the speed/rate of one of the pumps  1408 ,  1412  and then change the speed/rate of the other of the pumps  1408 ,  1412  after a particular delay. Any of these commands from the controller  1484  may be in response to changes in the signal received from the pressure transducer  1416 , The peristaltic pump  1408  in its peak pulse (e.g., sinusoidal peak amplitude) provides a significant negative pressure gradient such that the difference between a clog state pressure transducer  1416  reading and a free flow state pressure transducer  1416  reading is amplified. Thus, a larger number of potential thromboembolic events are avoided, such as thrombus being release from the open distal end  1405  of the aspiration lumen  1404  of the aspiration catheter  1402 . The pressure variations on the pressure transducer  1416  tend to be significantly greater when using a peristaltic pump  1408  than when using a vacuum pump, or other vacuum source (e.g., evacuated syringe). One significant advantage is that the user can be made clearly aware when clot/thrombus is not being aspirated, and thus, when aspiration is free flow, causing loss of blood without removal of thrombus  1402 . It is much easier to be aware of the status at the open distal end  1405  of the aspiration catheter. Current vacuum pumps do not have a similar clear-cut manner of demonstrating active vs. resting states. The user is thus notified, and the pumps  1408 ,  1412  are stopped to minimize blood loss, and to allow repositioning onto thrombus. Peristaltic pumps  1408  also tend to be less noisy than vacuum pumps, and less likely to disturb communication of medial personnel during a procedure, or increase stress. 
     Stopping the peristaltic pump  1408  leaves at least one roller  1432  in a position compressing the compressible portion  1437  of the extension tube  1438 . Thus, an open/close valve or pinch valve, or stopcock, or other valve is not needed. The fact that the rotatable head  1430  is already moving means that roller  1432  moves to the occluding position rapidly, without a large inertial requirement, when the peristaltic pump  1408  is stopped. This can thus be faster than the activation of standard electrically-activated pinch valves, which are initially motionless and need to be placed into motion prior to pinching. The motor  1497  may comprise a stepper motor that is directed (e.g., by the controller  1484 ) such that the rotatable head directs one of the rollers  1432  to occlude the lumen  1444  of the extension tube  1438  at the compressible portion  1437 . In  FIG. 36 , the roller  1432   c  is in position (if the motor  1497  were stopped) to occlude the lumen  1444 . Thus, the peristaltic pump  1408  itself can inherently minimize the potential of distal embolization, as stoppage of pump immediately or almost immediately creates stasis. Alternatively, a non-stepper motor, such as a brushless DC motor, may be utilized along with an encoder (e.g., optical encoder), or another type of position sensor, in place of a stepper motor. Additionally, unmacerated clot can thus be stopped from entering the aspiration lumen  1404 . As discussed, in other embodiments, the rollers  1432  may be replaced by non-rotating bumps or protrusions, that slide over the compressible portion  1437  of the extension tube  1438 , instead of rolling over. In some embodiments, the bumps/protrusions and/or the external surface of the compressible portion  1437  may be coated with a silicone, hydrophilic, or other lubricious material to lower the friction. 
     The controller  1484  can be configured to control the operation of the pump  1412  to cause the pump  1412  to inject pressurized fluid in a pulsatile manner. The high pressure jet is applied in a pulsatile fashion to optimize the cutting ability of the jet on a piece of thrombus. For example, a portion of thrombus that is aspirated into the open distal end  1405  of the aspiration lumen  1404  of the aspiration catheter  1402  can be more readily severed by a pulsating jet, much in the manner that a reciprocating saw. The controller  1484  is configured to operate the pump  1412  to pressurize fluid through the injection lumen such that the one or more jets are pulsatile. The controller  1484  is also configured to operate the peristaltic pump  1408  to further aid that that pressurized fluid injected through the injection lumen causes the one or more jets to be pulsatile. For example, the controller  1484  may send a signal to cause a sinusoidal variation in the speed of the motor  1491 . The degree of pulsatility (pulse rate, peak pulse, pulse wave shape, rise time, on time, off time) can be tailored and controllably applied by the controller  1484  on the pump  1412  and/or the peristaltic pump  1408 . 
     The use of a peristaltic pump  1408  assures that the interior of the aspiration lumen  1404  and lumen  1444  of the extension tube  1438 , and its contents, are not contacted, thus further assuring maintenance of sterility. The use of a peristaltic pump  1408  also causes minimal or virtually no cavitation to blood being removed. If there were any cavitation during aspiration, proximal to the peristaltic pump  1408 , after the blood and aspirate passes through the rollers  1432 , the blood is exposed to atmospheric pressure, and the cavitation disappears. Thus, it is easier to judge the amount of blood that has been collected or is being collected into the canister  1458  for it is not obscured by bubbles or foam, such that an indicative volume of collected blood is clearly visible and reliable to measure. Additionally, it is easier to reuse the blood quickly, if, for example, it is to be reinjected into the subject. It is also safer and more reliable to infuse blood that does not have significant air bubbles. The use of a vacuum source such as a vacuum bottle or evacuated syringe can tend to create a larger amount of cavitation. Thus, the peristaltic pump  1408  can be used in order to provide an efficient procedure, and also to maximize the volume of blood that may be reinjected/reinfused. The tubing set  1464  separates the extension of the injection lumen  1410  from the aspiration lumen  1404  at the male luer  1410  of the connector  1424 , thus only the compressible portion  1437  of the extension tube  1438  need be compressed by the rollers  1432 . Other portions of the aspiration catheter  1402  are thus not compressed by the rollers  1432 , and therefore are not in danger of being crushed or otherwise damaged. The distal end  1483  of the aspiration catheter  1402  may in some embodiments resemble that of the catheter  516  of  FIG. 17 . The aspiration catheter  1402  may in some embodiments be replaced by the thrombectomy system  300  of  FIG. 34 , or the other embodiments of the thrombectomy catheter  306  described in U.S. Pat. No. 9,433,427, issued Sep. 6, 2016, and entitled “Systems and Methods for Management of Thrombosis,” which is hereby incorporated by reference in its entirety for all purposes. The use of the peristaltic pump  1408  has additional advantages in comparison to a vacuum pump. The peristaltic pump  1408  can be configured to be controlled by the controller  1484  such that it runs only when the pump  1412  is injecting. Thus, the noise is reduced in comparison to a system using a vacuum pump, as the vacuum pump is on (operating) the entire time. 
       FIG. 37  illustrates a subject  1500  in a hospital bed  1502  or table being injected with blood in three different modalities. During thrombectomy procedures, thrombus/clot is removed from the blood vessels of the subject  1500 . In some instances, the blood volume of the patient becomes abnormally low, and fluids or blood need to be reinjected into the patient. In a first modality, the peristaltic pump  1408  of the system  1400  of  FIG. 36  is shown. The aspiration catheter  1402  is inserted in the subject  1500  and the aspiration (thrombectomy) procedure is being performed. Instead of the canister  1458 , the extension tube  1438  at its distal end  1442  is connected to an intravascular (IV) line  1504  which is inserted into a vein of the subject  1500 . The blood is driven by the rollers  1432  of the peristaltic pump  1408  so that it passes through a blood filter  1506 , which removes any residual thrombus or particulate prior to the blood being infused into the veins of the subject. Heparin, or other additives may also be added to the blood as it is being injected into the subject  1500  at port  1481 , which communicates with the intravascular (IV) line  1504 . As the blood only flows through a single sterile composite conduit, an efficient, cleanly reinfusion method is provided. The blood may be purified, for example, to remove red blood cells or portions of red blood cells that have undergone hemolysis. One such reinfusion device is the Haemonetics Cell Saver® Elite+Autotransfusion System. It is believed that peristaltic pumps  1408  cause less damage to blood cells, and thus less cleaning may be needed, if any. Thus, a higher yield of blood after using the Cell Saver is possible because of the advantages of the peristaltic pump  1408 . Also, the blood can be easily transferred to the Cell Saver in a non-contact manner, directly from the extension tube  1438 , that is not possible in the transfer from a collection container used with a vacuum source. The blood may even be kept sterile upon being sent directly into the Cell Saver. In some embodiments, the extension tube  1438  may be significantly translucent, so that the thrombus can be assessed during aspiration. A video camera or magnifying element (low power microscope, etc.) may be focused on the extension tube  1438  to better identify the state of the thrombus being aspirated (quantity, amount of maceration). There can be an almost real-time feedback of the condition of the thrombus being removed from within the vasculature of the patient. 
     In a second modality, blood is collected in a prior procedure in the canister  1458  ( FIG. 36 ). The blood may then be filtered, or even spun in a centrifuge to obtain particular components. Heparin, or other additives may also be added to the blood. The blood is then placed in a blood bag  1508  (or blood bottle) and infused into the vein of the subject  1500  using a passive drip through an IV line  1510  (e.g., via gravity alone). In other cases, a pressurizable bag  1512  may be used around the blood bag  1508  to increase the compression on the blood bag  1508 , thus increasing the flow rate into the vein. In some cases, the blood may even by injected directly into the arterial system, for example, through an arterial line (a-line). The blood may additionally be purified as described above. 
     In a third modality, blood is collected in a prior procedure in the canister  1458  ( FIG. 36 ). The blood may then be filtered, or even spun in a centrifuge to obtain particular components. Heparin, or other additives may also be added to the blood. The blood is then placed into a blood bag  1514 , and pumped into a vein of the subject  1500  using an infusion pump  1516 . Insertion points  1518   a ,  1518   b ,  1518   c  are shown for the first, second, and third modalities, respectively. The blood may additionally be purified as described above. 
       FIG. 38  illustrates an alternative aspiration system  1400 ′ comprising an aspiration catheter  1402 ′ comprising an elongate shaft  1401 ′ including an aspiration lumen  1404 ′ having an open distal end  1405 ′ and a proximal end  1406 ′ configured to couple to the peristaltic pump  1408 . The peristaltic pump  1408  may be a roller pump having a base  1426 , a pressure shoe  1428  carried by the base  1426 , and a rotatable head  1430 , rotatably coupled to the base  1426 , and carrying two or more rollers  1432   a - d . The rollers  1432   a - d  are arrayed around a perimeter  1434  of the rotatable head  1430 . The rotatable head  1430  is configured to be rotatable in at least a first rotational direction  1436  with respect to a rotational axis  1499 . The rotatable head  1430  may be rotated by a motor  1497 , either directly, or with a gear train  1495 . The peristaltic pump  1408  may be battery powered, and the battery(ies) may be rechargeable by wired or wireless means. The peristaltic pump  1408  may alternatively, or additionally be powered by a power cord  1493  configured to connect to a power supply. An extension tube  1438  having a distal end  1440  and a proximal end  1442 , and having a lumen  1444  extending therethrough, is hydraulically coupled to the proximal end  1406 ′ of the aspiration lumen  1404 ′ via a connector  1424 ′. The extension tube  1438  may be supplied (e.g., sterile) with the aspiration catheter  1402 ′, or may be packaged and supplied separately. A Touhy-Borst seal  1446 ′ is coupleable and decouplable to the connector  1424 ′ (e.g., via luer connections  1750 ,  1752 ) and is configured to be loosened/opened to allow the insertion of a guidewire  1448  through the connector  1424 ′ and the aspiration lumen  1404 ′. The aspiration lumen  1404 ′ may thus be used to track the aspiration catheter  1402 ′ over the guidewire  1448  through a subject&#39;s vasculature. The Touhy-Borst  1446 ′ can be tightened to seal over the guidewire  1448 , to maintain hemostasis. Other types of seals may be incorporated in place of the Touhy Borst  1446 ′, including a spring-loaded, longitudinally compressible and acuatable seal. The distal end  1440  of the extension tube  1438  is slipped over a first barb fitting  1754  of a y-connector  1756 . A second extension tube  1760  has a distal end  1761  that is slipped over a second barb fitting  1758  of the y-connector  1756 . A third extension tube  1762  has a proximal end  1763  that is slipped over a third barb fitting  1764  of the y-connector  1756 . The second extension tube  1760  and third extension tube  1762  are configured to operate under negative pressure without collapsing, and may comprise standard suction tubing. A distal end  1765  of the third extension tube  1762  is coupled to a female luer  1452 ′ sideport of the connector  1424 ′, either permanently by molding, or an adhesive bond or weld, or by an attachable and detachable connection, such as a luer  1766 . The lengths of each of the second extension tube  1760  and third extension tube  1762  may be varied. In some embodiments, the third extension tube  1762  is relatively short, and the y-connector  1756  is configured to be located in a sterile area near the patient. In other embodiments, the third extension tube  1762  is configured to be relatively long, and the y-connector  1756  is configured to be located in a non-sterile area, away from the patient. The second extension tube  1760  is optional, as the third extension tube  1762  may have a much longer length and the pressure transducer  1416 /aspiration monitoring system  1414  may be attached directly to the y-connector  1756  at the location of the barb fitting  1758 . This connection may be direct, and so the barb fitting  1758  is also optional. With the longer third extension tube  1762 , the y-connector  1756  and the aspiration monitoring system  1414  can both be close to the pump  1412 , and can both reside in a non-sterile area. 
     In use, a compressible portion  1437  of the extension tube  1438  is placed within the pressure shoe  1428  of the peristaltic pump  1408  such that rotation of the rotatable head  1430  in the rotational direction  1436  causes fluid to be forced through the lumen  1444  of the extension tube  1438  from the distal end  1440  to the proximal end  1442 , via compression of the compressible portion  1437  by the rollers  1432 , one at a time. Optionally, an interface  1456  on the peristaltic pump  1408  is configured to allow a user to input information or commands to the peristaltic pump  1408  or other components of the system  1400 ′. Otherwise, hardware or firmware may be pre-programmed with specific run parameters (motor speed, rotation speed, etc.). In some embodiments, there are only two rollers  1432 . In other embodiments, there are three rollers  1432 . In still other embodiments, as shown, there are four rollers  1432 . As described, the rollers  1432  may be replaced by bumps or protrusions. The compressible portion  1437  may comprise silicone tubing, polyurethane tubing, polyvinyl chloride tubing, or other compressible tubing. The compressible section  1437  may be a relatively short section that is attachable to and detachable from the peripheral ends of the extension tube  1438 , or in other embodiments, may comprise the entirety of the extension tube  1438  between the distal end  1440  and the proximal end  1442 . The proximal end  1442  of the extension tube  1438  may be coupled to a hub  1457  of a canister  1458  having an interior  1460 , to allow fluid  1459  passing through the extension tube  1438  to pass into the interior  1460 . An additional hub  1462  in the canister  1458  may be left open (as shown) to allow the unfilled interior  1460  to match atmospheric pressure. Alternatively, the canister  1458  may be replaced by a bag, such as an empty infusion bag, configured for collecting aspirate therein. 
     The aspiration catheter  1402 ′ additionally has a high pressure injection lumen  1410 ′ for injecting saline from a fluid source  1479 , for example, via a high pressure pump  1412 . A tubing set  1464  may include a pump cartridge  1466  having a piston or bellows or other movable element that the pump  1412  may manipulate using an internal motor  1491 , thus pressurizing saline (or other fluid) from the fluid source  1479  with a significantly high pressure such that the saline is forced through the injection lumen  1410 ′ of the aspiration catheter  1402 ′. The tubing set  1464  includes proximal end  1468  having a spike  1489 , or other connecting element for hydraulically coupling the tubing set  1464  to the fluid source  1479 . The tubing set  1464  further has a distal end  1470  (which may include a male luer) which is configured to hydraulically couple to the injection lumen  1410 ′ via a female luer  1472 ′. In use, injected saline is forced through the injection lumen  1410 ′ by the pump  1412  and exits an orifice  1474 ′ at a distal end  1476 ′ of the injection lumen  1410 ′. The injection lumen  1410 ′ may extend within a separate tube  1478 ′ (injection tube) that is substantially entirely within the shaft  1401 ′. In some embodiments, the tube  1478 ′ is attached to the internal wall of the shaft  1401 ′ only at a distal end portion  1403 ′. Thus, the free-floating nature of the remainder of the tube  1478 ′ within the aspiration lumen  1404 ′ increases the flexibility and trackability of the shaft  1401 ′. The high pressure saline is forced through the injection tube  1478 ′ and out the orifice  1474 ′, causing a jet (similar to jet  1487  of  FIG. 36 ). The jet is aimed within the aspiration lumen  1404 ′, just proximal the open distal end  1405 ′ which may create a Venturi effect that forces blood or thrombus that is external and adjacent the open distal end  1405 ′ into the aspiration lumen  1404 ′. The combination of the operation of the peristaltic pump  1408  and the jet created by the high pressure saline cause the maceration of thrombus, and the movement/flow of material (saline/blood/macerated thrombus/small pieces of thrombus) through the aspiration lumen  1404 ′ from the open distal end  1405 ′ to the proximal end  1406 ′, through the female luer  1452 ′ of the connector  1424 ′, and through the lumen  1444  of the extension tube  1438  from its distal end  1440  to its proximal end  1442 , and finally into the interior  1460  of the canister  1458 . Thus, thrombus within a blood vessel of a subject may be macerated and removed by use of the system  1400 ′. Blood vessels may include peripheral blood vessels, coronary blood vessels, or blood vessels within the head or neck of the subject, including carotid arteries or cerebral arteries. 
     An aspiration monitoring system  1414  comprising a pressure transducer  1416  may be coupled, for example, proximal to the connector  1424 ′ and/or proximal to the proximal end  1406 ′ of the aspiration lumen  1404 ′ of the aspiration catheter  1402 ′, such that the pressure transducer  1416  is hydraulically coupled to the aspiration lumen  1404 ′. In the aspiration system  1400 ′ of  FIG. 38 , the aspiration monitoring system  1414  is spaced a distance from the y-connector  1756  by a relatively long second extension tube  1760  (or alternatively by a relatively long third extension tube  1762 , as in the aspiration system  2100  of  FIG. 74 ) such that the aspiration monitoring system  1414  resides in a non-sterile area. Thus, the aspiration monitoring system  1414  may be set up, prepped, calibrated, and operated by a technologist, sales representative, nurse, or other medical personnel that has not “scrubbed” and thus does not need to maintain sterility. For example, the aspiration monitoring system  1414  may be located near the pump  1412 , or on the same table as the pump  1412 . The aspiration monitoring system  1414  can include any of the features described in relation to the other aspiration monitoring systems  48 ,  62 ,  78 ,  900 ,  1216 ,  1270  disclosed herein. Signals from the pressure transducer  1416  are carried on an electric cable  1480  to an input  1482  of the pump  1412 . A controller  1484  within the pump  1412  is configured to control the operation of the pump  1412 , including motor  1491 , but the controller  1484  may also be configured to control the operation of the peristaltic pump  1408 , with via a cable  1486 , or wirelessly. The controller  1484  may comprise a microcontroller. The controller  1484  may alternatively be located within the peristaltic pump  1408 , or may be located at another location. Control using signals of measured pressure from the pressure transducer  1416  adds an additional safety element to the system  1400 ′. Additionally, a non-functional device (because of a leak, incomplete connection, incomplete priming, rupture, blockage) can be quickly identified. Unallowably high pressures can also be quickly identified, protecting the motor  1491  of the pump  1412  from burnout or overheating danger. The integrity of the tube  1478 ′ is also protected, e.g., avoiding unnaturally high pressures that could lead to burst. 
     The aspiration catheter  1402 ′ is similar to the aspiration catheter  1402  of  FIG. 36 , except that the female luer  1452 ′ is located distally on the connector  1424 ′ from the female luer  1472 ′. Thus, aspirated blood/thrombus/saline enters the female luer  1452 ′ without ever having to contact interior irregularities  1425 ′ (in geometry, shape) within the connector  1424 ′, that may otherwise cause flow resistance, or cause thrombus to catch (e.g., between the tube  1478 ′ and the interior of the connector  1424 ′. 
     A foot pedal  1451  has a base  1453  and a pedal  1455  that is coupled to the base  1453  and movable or activatable by application of the foot of a user. The pedal  1455  may be spring-loaded and depressible by application of a moment or a compressive force, or may instead comprise a membrane switch. The pedal  1455 , when activated, may in some embodiments toggle on and off, and in other embodiments may be activatable when a force, a pressure, or a moment is applied, and inactivated when the force, pressure, or moment is not applied. A first cable  1461  carries signals from the foot pedal  1451  to pump  1412  via a plug  1465  that is connected to an input jack  1467 . In some embodiments, activation of the pedal  1455  by the foot of a user starts the operation of the pump  1412  and starts the operation of the peristaltic pump  1408  at the same time, as a signal through the first cable  1461  is received by the controller  1484 , which commands the pump  1412  to start and, via the cable  1486 , commands the peristaltic pump  1408  to start. In some embodiments, activation of the pedal  1455  by the foot of a user starts the operation of the peristaltic pump  1408 , and then starts the operation of the pump  1412 , with a slight delay after the peristaltic pump  1408  is started. The delay is useful to assure that some aspiration, or a significant amount of aspiration, is being applied to the aspiration lumen  1404 ′ prior to the injection of pressurized fluid (e.g., saline) through the injection lumen  1410 ′. Thus, blood vessels or other vasculature in the vicinity of the open distal end  1405 ′ are spared any injection of fluid from a high pressure jet, as it is instead aspirated through the aspiration lumen  1404 ′, along with thrombus or blood. In some embodiments, the plug  1465  of the foot pedal  1451  may include a resistor  1759 , and the pump  1412  may include an identification circuit  1757  configured to read the resistance value of the resistor  1759 . For example, the resistor  1759  may complete a partial Wheatstone bridge carried on the identification circuit  1757 , such that the pump  1412  can recognize the foot pedal  1451 , and operate accordingly. Alternatively, the resistor  1759  may reside in the foot pedal  1451  itself, instead of the plug  1465 . The cable  1461  may provide the electrical connection to the resistor  1759  in that particular case. Alternatively, the resistor  1759  may be replaced by an RFID chip that is configured to be powered and read by the identification circuit  1757 . 
     In addition, in some embodiments, activation of the pedal  1455  by the foot of a user during the operation of the pump  1412  and the peristaltic pump  1408  stops the operation of the pump  1412  and the operation of the peristaltic pump  1408  at the same time. In other embodiments, a delay may be applied, for example, such that the pump  1412  is stopped, and then the peristaltic pump  1408  is stopped slightly afterwards. The length of the delays described may be between about 0.01 second and about 1.00 second, or between about 0.10 second and about 0.25 second. The operation (on/off) of the pump  1412  and/or peristaltic pump  1408  via the foot pedal  1451  allows hands-free activation, enabling a single user the manipulate the aspiration catheter  1402 ′ and guidewire  1448  with both hands. The location of the foot pedal  1451  can be tactilely found with the foot of the user, while the user maintains visual contact with the patient and/or any monitors, or even other medical personnel. Alternatively, a second cable  1463  carries signals from the foot pedal  1451  directly to the peristaltic pump  1408  via a plug  1469  that is connected to an input jack  1471 . Thus, the operation of the foot pedal  1451  may be configured to control the operation of the peristaltic pump  1408  in embodiments, for example, in which there is no cable  1486 . However, in the embodiment of  FIG. 38 , which includes the cable  1486 , the cable  1463  is not required. 
     In other embodiments, the foot pedal  1451  may be replaced by another type of switch, including, but not limited to a toggle on/off push button or hand switch, an audio-activated switch (voice activated, clap activated, click activated), an optical switch (beam/light sensor for hand or foot interruption), or any other kind of switch that can be activated by medical personnel. The switch may be remote (e.g., in a control room) or may be located near the procedural area. The switch may also be a sterile switch or sterilizable for location on a sterile area. 
     In some cases, the activation and deactivation (turning on and off) of the aspiration flow applied by the peristaltic pump  1408  on the aspiration lumen  1404 ′ may be done by leaving the peristaltic pump  1408  in a running condition, while the user opens and closes the stopcock  1454 . In some embodiments, the controller  1484  controls the initiation of both the peristaltic pump  1408  and the pump  1412  at substantially the same time. In some embodiments, the controller  1484  controls the initiation the peristaltic pump  1408  and, following a particular delay, the initiation of the pump  1412 . The delay may be within the ranges previously described. 
     The controller  1484  also monitors and controls several device safety functions, which include over pressure detection, air bubble detection, and vacuum or negative pressure charge. An additional pressure transducer  1415 ′ carried on the connector  1424 ′ monitors pressure (i.e. injection pressure), and senses the presence of air bubbles. Alternatively, or in conjunction, an optical device  1417 ′ may be used to sense air bubbles. In one contemplated embodiment, the pump pressure is proportional to the electric current needed by the pump  1412  to produce that particular pressure. Consequently, if the electric current required by pump  1412  exceeds a preset limit, the controller  1484  will disable the pump  1412  by cutting power to it. Air bubble detection may also be monitored by monitoring the electrical current required to drive the pump  1412  at any particular moment. In order for a pump  1412  to reach high fluid pressures, there should be little or no air (which is highly compressible) present in the pump  1412  or connecting system (including the aspiration lumen  1404 ′ of the aspiration catheter  1402 ′ and the tubing set  1464 ). The fluid volume is small enough that any air in the system will result in no pressure being generated at the pump head. A sufficient volume of liquid is needed proximally to flush any finite amount of air through. The controller  1484  monitors the pump  1412  current for any abrupt downward change that may indicate that air has entered the system. If the rate of drop is faster than a preset limit, the controller  1484  will disable the pump  1412  by cutting power to it until the problem is corrected. 
     In some embodiments, a fluid level sensor  1473  is carried on the side of the canister  1458  and is configured to sense when the canister  1458  has approached or reached its full level. The fluid level sensor  1473  is configured to output a signal through a cable  1475  that is attached to via an input  1477  (plug/jack) at the pump  4112 . The signal from the fluid level sensor  1473  may be received by the controller  1484  which can be configured to immediately stop the pump  1412  and, via cable  1486 , the peristaltic pump  1408  at the same time, or with a delay therebetween, as previously described. The fluid level sensor  1473  may comprise an optical sensor, and the canister  1458  may have a clear wall, to allow the optical sensor to measure the reflection variations when fluid is not adjacently present or when fluid is adjacently present. Alternatively, the fluid level sensor  1473  may comprise a piezoresistive pressure sensor that is within the volume  1460  of the canister  1458  at the desired height that represents a “full” canister  1458 . Other types of fluid sensors are also contemplated, including floats, strain gauges, laser sensors, ultrasonic sensors, or capacitive sensors. In each of these embodiments, a signal is sent wirelessly or through cable  1475  so that the peristaltic pump  1408  and/or pump  1412  may be shut down when a “full” level is reached. 
     In some embodiments, the peristaltic pump  1408  and the pump  1412  are combined into a single console. This allows for a smaller size that may be mounted on a standard IV pole.  FIG. 74  illustrates an aspiration system  2100  that has all the features of the aspiration system,  1400 ′ of  FIG. 38 , but the peristaltic pump features  2108  and the injection pump features  2112  are both included on a single console  2102 . The third extension tube  1762  is elongated and the aspiration monitoring system  1414  is directly coupled or couplable to the y-connector  1756 . The aspiration monitoring system  1414  may reside in a non-sterile area. Thus, the aspiration monitoring system  1414  may be set up, prepped, calibrated, and operated by a technologist, sales representative, nurse, or other medical personnel that has not “scrubbed” and thus does not need to maintain sterility. For example, the aspiration monitoring system  1414  may be located on the same table as the console  2102 . The cable  1486  of the system  1400 ′ of  FIG. 38  is not necessary, as similar connectivity is located inside the console  2100 . The cable  1463  of the system  1400 ′ of  FIG. 38  is also not necessary, as the cable  1461  is capable of transferring all of the signals to and from the foot pedal  1451 . The luer  1766  may be attachable and detachable, or in other embodiments may be permanently bonded to the female luer  1452 ′ of the connector  1424 ′. 
       FIG. 39  illustrates an alternative aspiration system  1400 ″ comprising the aspiration catheter  1402 ′ of  FIG. 38 . However, a centrifugal pump  1409  is substituted in place of the peristaltic pump  1408 . The proximal end  1442  of the extension tube  1438  coupled to an inlet  1413  which allows the aspirate to enter a chamber  1419 . An impeller  1421  is rotatably held within the chamber  1419  by a first bearing  1423  and a second bearing  1427 . A first seal  1429  and second seal  1431  allow the impeller  1421  to rotate (curved arrow) without the aspirate leaking. A motor  1433  is configured to rotate the impeller  1421 . The aspirate is forced out an outlet  1435  into an exit tube  1439  which is coupled to the hub  1457  of the canister  1458 . A user interface  1441  may be manipulated by a user to operate the centrifugal pump  1409 . In some embodiments, an Angiodynamics AngioVac centrifugal pump may be used as the centrifugal pump  1409 . 
     The aspiration catheters  1402 ,  1402 ′ of  FIGS. 36, 38, and 39  are illustrated as having pressurized fluid injection through injection lumens  1410 ,  1410 ′. However, other embodiments of the aspiration systems  1400 ,  1400 ′ in which the aspiration catheters  1402 ,  1402 ′ are replaced by a standard aspiration catheter, not having an injection lumen, such as the aspiration catheter  4  of  FIG. 1 . 
     As an alternative to collecting the aspirated material in a blood bag, blood bottle, or the canister  1458 , aspirated components (blood, thrombus, saline, slurry, etc.) can be placed into a reinfusion device, such as a Stryker ConstaVac (CBCII) Blood Conservation System, or a Haemonetics OrthoPAT Orthopedic Perioperative Autotransfusion System. The blood may be purified by the reinfusion device, for example, to remove red blood cells or portions of red blood cells that have undergone hemolysis. One such reinfusion device is the Haemonetics Cell Saver® Elite+Autotransfusion System. 
     In some embodiments, the blood may be cooled prior to being injected. In some embodiments, the blood may be heated prior to being injected. In some embodiments, other drugs may be added to the blood prior to it being inserted. In some cases, the blood may be diluted with saline, to decrease its viscosity, or decrease its hematocrit. This may allow for decrease hemolysis to occur. In some cases, blood collected in the canister  1458 , or blood coming from the extension tube  1438 , may even be used as donor blood, to infuse into a different patient. 
     In some embodiments, an additional or alternate sensor may be used to monitor flow conditions for the notification of the user, including, but not limited to: a Doppler sensor, an infrared sensor, or a laser flow detection device. In some embodiments, an externally-attached (non-contact) Doppler sensor may be employed. In some embodiments, an infrared sensor or a laser flow detection device may be employed around the extension tubing  1438 . The alternate sensor (e.g., flow sensor, etc.) may be located at a number of different locations along the aspiration path, including on or in the extension tube  1438 , distal to the impeller  1421  of the centrifugal pump  1409 , or on or in the exit tube  1439  proximal to the impeller  1421  of the centrifugal pump  1409 . Or in embodiments using a peristaltic pump  1408 , the alternate sensor may be located on or in the extension tube  1438 , distal or proximal to the rotatable head  1430  of the peristaltic pump  1408 . 
     An aspiration system  1600  utilizing an ultrasound sensor  1602  is shown in  FIGS. 40-42 . The aspiration system  1600  is similar to the aspiration system  1400 ′ of  FIG. 38 , with the addition of the ultrasound sensor  1602  and other related components. Alternative embodiments may utilize the teachings of other aspiration system embodiments disclosed herein. The ultrasound sensor may be configured for an analog output (e.g., with varying voltage output), for example, with a range of 0 Volts DC to 1 Volt DC, or 0 Volts DC to 5 Volts DC, or 0 Volts DC to 10 Volts DC. Turning to  FIG. 41 , the ultrasound sensor  1602  is inserted within a sideport  1606  of a y-connector  1604 . The y-connector  1604  has a distal connector  1608  attached to a proximal end  1603  of tubing  1610 . The tubing  1610  is slide over barbs  1605  which comprise the distal connector  1608 . A distal end  1607  of the tubing  1610  is coupled to the proximal end  1406 ′ of the aspiration lumen  1404 ′ of the aspiration catheter  1402 ′, via a connector  1609  and the aspiration monitoring system  1414 , attached to the female luer  1452 ′ of the connector  1424 ′. A proximal connector  1612  of the y-connector  1604  is connected to a friction fitting  1616  of an extension tube  1614 . The proximal connector  1612  also comprises barbs, The extension tube  1614  is connectable to the peristaltic pump  1608 , but may alternatively be coupled to the centrifugal pump  1409 , or one of the vacuum sources described herein. The ultrasound sensor  1602  is positioned so that its distal end  1618  is adjacent aspiration flow (straight arrow). A fitting  1620  at the proximal end of the ultrasound sensor  1602  is configured to secure the ultrasound sensor  1602  to the sideport  1606  in its desired position. This may be a friction fit, a screw attachment, a snap, and adhesive bond, a thermal bond, or other securement means. The output of the ultrasound sensor (e.g., voltage) is communicated through a cable  1622 . A strain relief  1601  coupled to the cable  1622  and the fitting  1620  serves to protect the first end  1611  of the cable  1622  from damage due to bending, tension, or compression. 
     In one embodiment, the ultrasound sensor  1602  has an analog channel that outputs a signal referenced to ground that varies between 0 to 5 Volts DC. For very small flow rates, the signal is often sinusoidal, but in the higher flow rates commonly occurring during the aspiration of clot/thrombus/blood the flow is substantial enough that it saturates the channel and appears as a variable digital pulse stream, roughly proportional to flow. The pulse frequency is relatively high on this channel. In other words, a pseudo-digital on/off occurs when flow rates exceed a particular value. This particular value may be adjusted by connecting appropriate electronics. Along with the pseudo-digital properties of the channel, a dedicated digital I/O pin is utilized that feeds a high-priority interrupt handler. This allows the counting of rising signal transitions in this pulse stream very efficiently over a fixed interval of time. The pulse count above/below one or more pre-determined thresholds is ultimately what determines whether the overall system is in a free-flow or clot removal state and to what degree. 
       FIG. 42  illustrates a console  1624  having an input jack  1626  into which a plug  1628  at the second end  1613  of the cable  1622  attaches. The console  1624  includes an internal measurement device  1630  which is configured to count the number of times N during a predetermined time period P that a signal being output by the ultrasound sensor  1602  surpasses a predetermined threshold amplitude A. The measurement device  1630  is further configured to determine whether the number of times N is (a) greater than (or greater than or equal to) or (b) less than (or less than or equal to) a predetermined value V. For example, in one embodiment, a predetermined time period P is entered into the measurement device  1630  (e.g., via a user interface  1632 ) as 0.33 seconds. An algorithm within the measurement device  1630  counts the number threshold crossings that are output by the ultrasound sensor  1602  during this predetermined time period P. The measurement device  1630  then applies a particular logic scheme. In some embodiments, this logic scheme may simply be “flow” or “no flow.” For example, if there are between 0 counts and 150 counts within the time period P, then a “no flow” condition is identified and if there are 151 or greater counts within the time period P, then a “flow” condition is identified. The measurement device  1630  may comprise a microprocessor. A communication device  1634  carried on the console  1624  may be controlled by the measurement device  1630 , or by a separate controller, to identify a first communication mode for the “no flow” condition and a second communication mode for the “flow” condition. In some embodiments, the first communication mode may comprise the non-existence of a signal (e.g., no light lit, no sound produced, no vibration or heat produced) from the communication device  1634 , and the second communication mode may comprise a light lit, or a message shown (e.g., the word “flow”), or an audio message played (a voice stating “aspiration occurring”), or an audio warning (e.g., “beep”), or a mechanical warning (e.g., vibration). The amplitude of the communication (e.g., dB of sound, intensity of light, etc.) may be increase by pressing increase button  1615  or decreased by pressing decrease button  1617 . The current level of the amplitude is displayed on display  1619 . The display may comprise a series of LEDs  1621  that are configured to be lit up such that a higher amplitude corresponds to a larger number of the LEDs being lit. 
     In other embodiments, the first communication mode and the second communication mode may each include some perceptible signal (audible, visual, tactile), each one different from the other. In other embodiments, a more complex logic scheme may be used. For example, for a predetermined time period P of 0.33 seconds, if there are between 0 counts and 150 counts within the time period P, then a “no flow” condition is identified; if there are between 151 and 225 counts within the time period P, then a “low flow” condition is identified; if there are between 226 and 350 counts within the time period P, then a “medium flow” condition is identified; and, if there are 351 counts or greater, then a “high flow” condition is identified. The “no flow” condition can correspond to a first communication mode, the “low flow” condition to a second communication mode, the “medium flow” condition to a third communication mode, and the “high flow” condition to a fourth communication mode. The first communication mode may be treated by the communication device  1634  remaining silent and/or non-visual/non-vibrational/non heating, etc. The second communication mode may be treated by the communication device beeping (via audio speaker) or flashing (via led or other light) at a frequency of 2 Hz. The third communication mode may be treated by the communication device beeping (via audio speaker) or flashing (via led or other light) at a frequency of 4 Hz. The fourth communication mode may be treated by the communication device beeping (via audio speaker) or flashing (via led or other light) at a frequency of 10 Hz. In another embodiment, the second communication mode may be treated by the communication device beeping (via audio speaker) or flashing (via led or other light) at a frequency of 0.5 Hz. The third communication mode may be treated by the communication device beeping (via audio speaker) or flashing (via led or other light) at a frequency of 1 Hz. The fourth communication mode may be treated by the communication device beeping (via audio speaker) or flashing (via led or other light) at a frequency of 2 Hz. Additionally, or alternatively, the intensity of the signal may increase from the second to the fourth communication modes. For example, by 10 dB from second to third and by 10 more dB from third to fourth. Or, by 5 dB, each time. 
     In an alternative embodiment, the ultrasound sensor  1602  may have an analog-to-digital module, and may output digital signals only, particular to 1 (flow at or above a particular threshold flow rate) or 0 (flow below a particular threshold flow rate). 
     The predetermined time period P, may be between about 0.01 seconds and about 1.00 seconds, or between about 0.10 seconds and about 0.50 seconds, or between about 0.20 seconds and about 0.40 seconds. The predetermined time period P may be adjustable by a user, for example, via the user interface  1632 . 
     In certain aspiration procedures, when thrombus is not being sufficiently aspirated but aspiration continues, an unacceptably large volume of blood may be aspirated from the patient. This may cause dehydration, decreased blood pressure, or even exsanguination of the patient, all potentially serious events which can risk the success of the procedure and endanger the patient. The ability to be aware at all times whether the blood is being aspirated at an unacceptable rate is an important factor for achieving a high degree of safety and efficiency. 
     Systems for catheter aspiration are disclosed herein which are configured to communicate flow status and/or flow rate information to a user as determined by weighing the fluid, blood, thrombus, or other materials being aspirated from the patient over a period of time. 
       FIG. 43  illustrates an aspiration system  200  comprising an aspiration catheter  202  comprising an elongate shaft  201  including an aspiration lumen  204  having an open distal end  205  and a proximal end  206  configured to couple to a peristaltic pump  208 . The peristaltic pump  208  may be a roller pump having a base  226 , a pressure shoe  228  carried by the base  226 , and a rotatable head  230 , rotatably coupled to the base  226 , and carrying two or more rollers  232   a - d . The rollers  232   a - d  are arrayed around a perimeter  234  of the rotatable head  230 . The rotatable head  230  is configured to be rotatable in at least a first rotational direction  236  (e.g., by a motor, directly, or with a gear train, as shown in  FIG. 36 ). The peristaltic pump  208  may be battery powered, and the battery(ies) may be rechargeable by wired or wireless means. The peristaltic pump  208  may alternatively, or additionally be powered by a power cord configured to connect to a power supply. An extension tube  238  having a distal end  240  and a proximal end  242 , and having a lumen  244  extending therethrough, is hydraulically coupled to the proximal end  206  of the aspiration lumen  204  of the aspiration catheter  202  via a connector  224 . The extension tube  238  may be supplied (e.g., sterile) with the aspiration catheter  202 , or may be packaged and supplied separately. A Touhy-Borst seal  246  carried on the connector  224  is configured to be loosened/opened to allow the insertion of a guidewire  248  through the connector  224  and the aspiration lumen  204 , which may be used to track the aspiration catheter  202  through a subject&#39;s vasculature. The Touhy-Borst  246  can be tightened to seal over the guidewire  248 , to maintain hemostasis. Other types of seals may be incorporated in place of the Touhy-Borst  246 , including a spring-loaded, longitudinally compressible and actuatable seal. The extension tube  238  includes a male luer  250  at its distal end  240 , for connecting to a female luer  252  of the connector  224 . Or, as shown, an aspiration monitoring system  214  may be attached therebetween. The male luer  250  may include a stopcock  254 , which is configured to be turned to select between an open position (shown) or a closed position. Alternatively, the extension tube  238  may be integral with the aspiration lumen  204 , or may be permanently attached to the connector  224 . In use, a compressible portion  237  of the extension tube  238  is placed within the pressure shoe  228  of the peristaltic pump  208  such that rotation of the rotatable head  230  (e.g., via input to an interface  256  by a user) in the rotational direction  236  causes fluid to be forced through the lumen  244  of the extension tube  238  from the distal end  240  to the proximal end  242 , via compression of the compressible portion  237  by the rollers  232 , one at a time. In some embodiments, there are only two rollers  232 . In other embodiments, there are three rollers  232 . In still other embodiments, as shown, there are four rollers  232 . As described, the rollers  232  may be replaced by bumps or protrusions. The compressible portion  237  may comprise silicone tubing, polyurethane tubing, polyvinyl chloride tubing, or other compressible tubing. The compressible portion  237  may be a relatively short section that is attachable to and detachable from the peripheral ends of the extension tube  238 , or in other embodiments, may comprise the entirety of the extension tube  238  between the distal end  240  and the proximal end  242 . The proximal end  242  of the extension tube  238  may be coupled to a hub  257  formed on a cap  213  of a canister  258 , the canister  258  having an interior  260 , to allow fluid  259  passing through the extension tube  238  to pass into the interior  260 . An additional hub  262  in the canister  258  may be provided, and can be left open (as shown) to allow the unfilled interior  260  to match atmospheric pressure. 
     In use, a distal section of the aspiration catheter  202  is inserted into the vasculature of a subject such that the open distal end  205  is adjacent or within a thrombus. Then, fluid, including thrombus, is aspirated into the aspiration lumen  204  by action of the peristaltic pump  208  and removed by use of the aspiration system  200 . Blood vessels treated may include peripheral blood vessels, pulmonary blood vessels, such as pulmonary arteries, coronary blood vessels, or blood vessels within the head or neck of the subject, including carotid arteries or cerebral arteries. 
     The aspiration system  200  further comprises an aspiration monitoring system  1800  which is configured to provide information to a user concerning the status of aspiration. The aspiration monitoring system  1800  functions by measuring the fluid  259  which has accumulated at the bottom of the interior  260  of the canister  258  at a plurality of points in time, thus estimating a (volumetric) flow rate of the fluid  259  issuing out the lumen  244  of the extension tube  238 . The aspiration monitoring system  1800  comprises a scale  1802  (or balance) having a base  1804 . A weighing platform  1806  is coupled to and movable with respect to the base  1804  (e.g., along a vertical axis V), such that the weight of the fluid  259  accumulated at the bottom of the canister  258  causes a signal  1808  indicative of the weight to be output. The scale may be configured to output a signal  1808  indicative of weight, or, in some embodiments, the particular elevation (above sea level) at which the scale  1802  resides may be input into the scale  1802  such that a value of mass can be output. A standard setting may assume that the procedure occurs at sea level, and may calculate mass accordingly. In some embodiments, the scale  1802  may even include an altimeter or other sensor to automatically determine elevation, such that mass can be output. Regardless, even when a weight is output, changes to the weight of the fluid  259  over time are proportional to changes to mass of the fluid  259  over time, at any particular elevation. Thus, the signal  1808  may be indicative of mass or indicative of weight, while remaining within the scope of allowing changes in the mass of the fluid  259  over time to be demonstrated. Thus, the system  200  can predict the loss of blood from the patient by its assessment of total cumulative weight/mass of blood captured in the canister  258 . Weight/mass of blood measured can be converted by the system  200  into volume of blood (ml) lost. 
     The signal  1808  is sent to a processor  1810 . See also,  FIG. 44 . The processor  1810 , which may comprise a microprocessor, includes a clock that allows the combination of time data with weight or mass values from the signal. In some embodiments, the scale  1802  may include a tare button or control, such that the tare weight of the canister  258  can be subtracted out from the amount being weighed by the scale  1802 . Thus, the scale  1802  is “zeroed” and only the weight or mass of the fluid  259  in the canister  258  is weighed at each time point. The sample rate at which values in the signal  1808  are obtained along with the time stamp may range between about 0.01 Hz and about 10 kHz, or between about 0.02 Hz and about 1 kHz, or between about 1 Hz and about 100 Hz. A processed signal  1812  is output to a graphic display  1814  for viewing by a user. In some embodiments, the graphic display  1814  may display an x-y graph  1816 , wherein the x-axis represents time and the y-axis represents weight or mass of the fluid  259  within the canister  258 . In other embodiments, the graphic display  1814  may display an x-y graph  1816 , wherein the x-axis represents time and the y-axis represents flow rate. The flow rate (FR) may be calculated from the formula: 
       FR=( W   c   −W   p )/( T   c   −T   p ), wherein 
     W c  is the current value for weight of the fluid  259   
     W p  is the previous value of weight of the fluid  259   
     T c  is the current time stamp value 
     T p  is the previous time stamp value 
     In other embodiments, the flow rate (FR) may be calculated from the formula: 
       FR=( W   c   −W   pn )/( T   c   −T   pn ), wherein 
     W c  is the current value for weight of the fluid  259   
     W pn  is the n th  prior value of weight of the fluid  259   
     T c  is the current time stamp value 
     T pn  is the n th  prior time stamp value 
     In other embodiments, the flow rate may be constructed as a moving average, such as a running average or rolling average. Several types of moving average may be used, including a simple moving average, a cumulative moving average, a weighted moving average, or an exponential moving average. 
     Instead of an x-y graph, a visual display comprising one or more LED lights may be used. For example, a higher flow rate may be indicated by a range of shades of green, while a lower flow rate may be indicated by a range of shades of red. Alternatively, the intensity of a light may be changed in response to changes in the flow rate, or changes in weight or mass. For example, the intensity of the light may be proportional to the measured/calculated flow rate. A loudspeaker may present the changes in weight/mass over time or changes in flow rate over time as a continuous or continual sound having a pitch that changes proportionally with changes in value. For example, a higher pitch with a larger flow rate. The sound intensity may alternatively be varied (higher flow rate=higher dB). 
     Changes in the flow rate can be indicative of a number of operation occurrences in the aspiration system  200 . For example, a flow rate that suddenly decreases a significant amount may be indicative of thrombus becoming clogged within the aspiration lumen  204  or the lumen  244  of the extension tube  238 . In some cases, a reduction in the flow rate of 90% or more may be indicative of clogging. When a clog occurs, the volume of fluid being aspirated and dispensed into the canister  258  can be severely limited. A loudspeaker  1818  is also configured to produce an audible alarm, when a threshold value of flow rate is crossed. A threshold flow rate may be input into a memory  1822  of the scale  1802  using a user interface  1820 . When the flow rate decreases to a value below the threshold flow rate, the loudspeaker  1818  is made to sound an alarm. In some embodiments, a controller  215  in the peristaltic pump  208  may be coupled to the processor  1810  (wired or wireless) and may be configured to activate the alarm of the loudspeaker  1818 . When the flow rate increases above the threshold flow rate, the loudspeaker  1818  may be deactivated such that the alarm is no longer sounded. Alternatively, the loudspeaker  1818  may be replaced by, or augmented with a visual alarm and/or a tactile alarm. The visual alarm may include one or more light, including one or more LEDs. The tactile alarm may include a vibration device, such as a piezoelectric, or a weight-offset rotational device. 
     Changes in the flow rate may also be indicative of other changes in status, such as a rupture in a wall of one of the tubular members or a disconnection of one of the connections. In one of these leak conditions, the flow rate may be significantly reduced, and thus identified by the flow rate changes measured by the aspiration monitoring system  1800 . The system  200  may be configured to activate the alarm (e.g., via the loudspeaker  1818 ) when a free flow of blood is detected. In other words, when the system is apparently aspirating only blood, and not aspirating thrombus. Thus, the measured flow rate crossing above a particular threshold stored in memory  1822  indicative of free flowing blood would cause the controller  215  to activate the alarm. 
     A secondary aspiration monitoring system  214  comprising a pressure transducer  216  may be coupled, for example, between the distal end  240  of the extension tube  238  and the connector  224  and/or proximal end  206  of the aspiration lumen  204  of the aspiration catheter  202 . Signals from the pressure transducer  216  may be carried wirelessly or by a cable (not shown) to the controller  215 . The controller  215  may comprise a microcontroller. The controller  215  may be located within the peristaltic pump  208 , or may alternatively be located at another component or location. Control using measured pressure adds an additional safety element to the system  200 . Additionally, a non-functional device (because of a leak, incomplete connection, incomplete priming, rupture, blockage) can be quickly identified. Unallowably high pressures or low pressures can also be quickly identified, protecting the motor of the peristaltic pump  208  from burnout or overheating danger. Data from the pressure transducer  216  and the scale  1802  can be used together to optimize or create a more correct signal indicative of aspiration flow, or indicative of the presence of clot/thrombus, or the presence of a clog, or the presence of a burst or disconnection in the fluid circuit. 
     A foot pedal  251  is illustrated having a base  253  and a pedal  255  that is coupled to the base  253  and movable or activatable by application of the foot of a user. The pedal  255  may be spring-loaded and depressible by application of a moment or a compressive force, or may instead comprise a membrane switch. The pedal  255 , when activated, may in some embodiments toggle on and off, and in other embodiments may be activatable when a force, a pressure, or a moment is applied, and inactivated when the force, pressure, or moment is not applied. A cable  263  carries signals from the foot pedal  251  to the peristaltic pump  208  via a plug  269  that is connected to an input jack  271 . The pedal  255  can be activated by the foot of a user to start or stop the operation of the peristaltic pump  208 . 
     In other embodiments, the foot pedal  251  may be replaced by another type of switch, including, but not limited to a toggle on/off push button or hand switch, an audio-activated switch (voice activated, clap activated, click activated), an optical switch (beam/light sensor for hand or foot interruption), or any other kind of switch that can be activated by medical personnel. The switch may be remote (e.g., in a control room) or may be located near the procedural area. The switch may also be a sterile switch or sterilizable for location on a sterile area. 
     In some cases, the activation and deactivation (turning on and off) of the aspiration flow applied by the peristaltic pump  208  on the aspiration lumen  204  may be done by leaving the peristaltic pump  208  in a running condition, while the user opens and closes the stopcock  254 . Alternatively, a pinch valve (not shown) coupled to the extension tube  238  may be used for opening and closing the lumen  244 , and thus starting and stopping aspiration. The pinch valve may be operated by a foot pedal (similar to the foot pedal  251 ), or may be operated by another control (e.g., on the interface  256  of the peristaltic pump  208 ). 
     After collecting the aspirated material in a blood bag, blood bottle, or the canister  258 , aspirated components (blood, thrombus, saline, slurry, etc.) can be placed into a reinfusion device, such as a Stryker ConstaVac (CBCII) Blood Conservation System, or a Haemonetics OrthoPAT Orthopedic Perioperative Autotransfusion System. 
     In some embodiments, the blood may be cooled prior to being injected. In some embodiments, the blood may be heated prior to being injected. In some embodiments, other drugs may be added to the blood prior to it being inserted. In some cases, the blood may be diluted with saline, to decrease its viscosity, or decrease its hematocrit. This may allow for decrease hemolysis to occur. In some cases, blood collected in the canister  258 , or blood coming from the extension tube  238 , may even be used as donor blood, to infuse into a different patient. 
     In some embodiments, an additional or alternate sensor may be used to monitor flow conditions for the notification of the user, including, but not limited to: a Doppler sensor, an infrared sensor, or a laser flow detection device. In some embodiments, an externally-attached (non-contact) Doppler sensor may be employed. In some embodiments, an infrared sensor or a laser flow detection device may be employed around the extension tubing  238 . The alternate sensor (e.g., flow sensor, etc.) may be located at a number of different locations along the aspiration path, including on or in the extension tube  238 , either proximal to or distal to the rotatable head  230  of the peristaltic pump  208 . 
       FIG. 45  illustrates a forced aspiration system  400  comprising an aspiration catheter  402  comprising an elongate shaft  401  including an aspiration lumen  404  having an open distal end  405  and a proximal end  406  configured to couple to a peristaltic pump  408 . The peristaltic pump  408  may be a roller pump having a base  426 , a pressure shoe  428  carried by the base  426 , and a rotatable head  430 , rotatably coupled to the base  426 , and carrying two or more rollers  432   a - d . The rollers  432   a - d  are arrayed around a perimeter  434  of the rotatable head  430 . The rotatable head  430  is configured to be rotatable in at least a first rotational direction  436  (e.g., by a motor, directly, or with a gear train, as shown in  FIG. 36 ). The peristaltic pump  408  may be battery powered, and the battery(ies) may be rechargeable by wired or wireless means. The peristaltic pump  408  may alternatively, or additionally be powered by a power cord configured to connect to a power supply. An extension tube  438  having a distal end  440  and a proximal end  442 , and having a lumen  444  extending therethrough, is hydraulically coupled to the proximal end  406  of the aspiration lumen  404  of the aspiration catheter  402  via a connector  424 . The extension tube  438  may be supplied (e.g., sterile) with the aspiration catheter  202 , or may be packaged and supplied separately. A Touhy-Borst seal  446  carried on the connector  424  is configured to be loosened/opened to allow the insertion of a guidewire  448  through the connector  424  and aspiration lumen  404 , which may be used to track the aspiration catheter  402  through a subject&#39;s vasculature. The Touhy-Borst  446  may be tightened to seal over the guidewire  448 , to maintain hemostasis. Other types of seals may be incorporated in place of the Touhy-Borst  246 , including a spring-loaded, longitudinally compressible and actuatable seal. The extension tube  438  includes a male luer  450  at its distal end  440 , for connecting to a female luer  452  of the connector  424 . Or, as shown, an aspiration monitoring system  414  may be attached therebetween. The male luer  450  may include a stopcock  454 , which is configured to be turned to select between an open position (shown) or a closed position. Alternatively, the extension tube  438  may be integral with the aspiration lumen  404 , or may be permanently attached to the connector  424 . In use, a compressible portion  437  of the extension tube  438  is placed within the pressure shoe  428  of the peristaltic pump  408  such that rotation of the rotatable head  430  (e.g., via input to an interface  456  by a user) in the rotational direction  436  causes fluid to be forced through the lumen  444  of the extension tube  438  from the distal end  440  to the proximal end  442 , via compression of the compressible portion  437  by the rollers  432 , one at a time. In some embodiments, there are only two rollers  432 . In other embodiments, there are three rollers  432 . In still other embodiments, as shown, there are four rollers  432 . As described, the rollers  432  may be replaced by bumps or protrusions. The compressible portion  437  may comprise silicone tubing, polyurethane tubing, polyvinyl chloride tubing, or other compressible tubing. The compressible portion  437  may be a relatively short section that is attachable to and detachable from the peripheral ends of the extension tube  438 , or in other embodiments, may comprise the entirety of the extension tube  438  between the distal end  440  and the proximal end  442 . The proximal end  442  of the extension tube  438  may be coupled to a hub  457  of a canister  458  having an interior  460 , to allow fluid  459  passing through the extension tube  438  to pass into the interior  460 . An additional hub  462  in the canister  458  may be left open (as shown) to allow the unfilled interior  460  to match atmospheric pressure. A filter  443  (optional) is placed in line between the extension tube  438  and canister  458  to catch thrombus that is aspirated from the patient. The filter  443  may have clear side walls so that the physician or other medical staff can visually assess the thrombus, such as the size of each piece, the number or pieces, the total amount of thrombus (e.g., volumetrically) or the condition of the thrombus or residual thrombus (organized/fibrous, or soft). The buildup of the thrombus within the filter  443 , or lack thereof, may be utilized as a cue for moving the open distal end  405  of the aspiration catheter  402  to a different location, or temporarily or permanently stopping the procedure, or even increasing or decreasing the speed of the pump(s). 
     The aspiration catheter  402  additionally has a high pressure injection lumen  410  for injecting saline from a fluid source  499 , for example, via a high pressure pump  412 . A tubing set  464  may include a pump cartridge  466  having a piston or bellows or other movable element that the pump  412  may manipulate using an internal motor (not shown), this applying a high pressure to saline from the fluid source  499  such that the saline is forced through the injection lumen  410  of the aspiration catheter  402 . The tubing set  464  includes proximal end  468  having a spike  497  or other element for hydraulically coupling it to the fluid source  499 . The tubing set  464  further has a distal end  470  (which may include a male luer) which is configured to hydraulically couple to the injection lumen  410  via a female luer  472 . Injected saline is forced through the injection lumen  410  by the pump  412  and exits an orifice  474  at a distal end  476  of the injection lumen  410 . The injection lumen  410  may be within a tube  478  that is substantially or entirely within the shaft  401 . In some embodiments, the tube  478  is attached to the internal wall of the shaft  401  only at a distal end portion  403 . Thus, the free-floating nature of the remainder of the tube  478  within the aspiration lumen  404  increases the flexibility and trackability of the shaft  401 . The high pressure saline is forced through the orifice  474 , causing a jet. The jet is aimed within the aspiration lumen  404 , just proximal the open distal end  405  which may create a Venturi effect that forces blood or thrombus external and adjacent the open distal end  405  into the aspiration lumen  404 . The combination of the operation of the peristaltic pump  408  and the jet caused by the high pressure saline cause the maceration of thrombus, and the movement/flow of material (saline/blood/macerated thrombus/small pieces of thrombus) through the aspiration lumen  404  from the open distal end  405  to the proximal end  406 , through the connector  424 , and through the lumen  444  of the extension tube  438  from its distal end  440  to its proximal end  442 , and finally into the interior  460  of the canister  458 . Thus, thrombus within a blood vessel of a subject may be macerated and removed by use of the system  400 . Blood vessels treated may include peripheral blood vessels, pulmonary blood vessels, such as pulmonary arteries, coronary blood vessels, or blood vessels within the head or neck of the subject, including carotid arteries or cerebral arteries. 
     The forced aspiration system  400  further comprises an aspiration monitoring system  1800  which is configured to provide information to a user concerning the status of aspiration. The aspiration monitoring system  1800  functions by measuring the fluid  459  which has accumulated at the bottom of the interior  460  of the canister  458  at a plurality of points in time, thus estimating a flow rate of the fluid  459  issuing out the lumen  444  of the extension tube  438 . The aspiration monitoring system  1800  comprises a scale  1802  (or balance) having a base  1804 . A weighing platform  1806  is coupled to and movable with respect to the base  1804  (e.g., along a vertical axis V), such that the weight of the fluid  459  accumulated at the bottom of the canister  458  causes a signal  1808  indicative of the weight to be output. The scale may be configured to output a signal  1808  indicative of weight, or, in some embodiments, the particular elevation (above sea level) at which the scale  1802  resides may be input into the scale  1802  such that a value of mass can be output. In some embodiment, the scale  1802  may even include an altimeter or other sensor to automatically determine elevation, such that mass can be output. Regardless, even when a weight is output, changes to the weight of the fluid  459  over time are proportional to changes to mass of the fluid  459  over time, at any particular elevation. Thus, the signal  1808  may be indicative of mass or indicative of weight, while remaining within the scope of allowing changes in the mass of the fluid  459  over time to be demonstrated. Thus, the system  400  can predict the loss of blood from the patient by its assessment of total cumulative weight/mass of blood captured in the canister  458 . Weight/mass of blood measured can be converted by the system  400  into volume of blood (ml) lost. 
     The signal  1808  is sent to a processor  1810 . See also,  FIG. 44 . The processor  1810 , which may comprise a microprocessor, includes a clock that allows the combination of time data with weight or mass values from the signal. In some embodiments, the scale  1802  may include a tare button or control, such that the tare weight of the canister  458  can be subtracted out from the amount being weighed by the scale  1802 . Thus, the scale  1802  is “zeroed” and only the weight or mass of the fluid  459  in the canister  458  is weighed at each time point. The sample rate at which values in the signal  1808  are obtained along with the time stamp may range between about 0.01 Hz and about 10 kHz, or between about 0.02 Hz and about 1 kHz, or between about 1 Hz and about 100 Hz. A processed signal  1812  is output to a graphic display  1814  for viewing by a user. In some embodiments, the graphic display  1814  may display an x-y graph  1816 , wherein the x-axis represents time and the y-axis represents weight or mass of the fluid  459  within the canister  458 . In other embodiments, the graphic display  1814  may display an x-y graph  1816 , wherein the x-axis represents time and the y-axis represents flow rate. The flow rate (FR) may be calculated from the formula: 
       FR=( W   c   −W   p )/( T   c   −T   p ), wherein 
     W c  is the current value for weight of the fluid  459   
     W p  is the previous value of weight of the fluid  459   
     T c  is the current time stamp value 
     T p  is the previous time stamp value 
     In other embodiments, the flow rate (FR) may be calculated from the formula: 
       FR=( W   c   −W   pn )/( T   c   −T   pn ), wherein 
     W c  is the current value for weight of the fluid  459   
     W pn  is the n th  prior value of weight of the fluid  459   
     T c  is the current time stamp value 
     T pn  is the n th  prior time stamp value 
     In other embodiments, the flow rate may be constructed as a moving average, such as a running average or rolling average. Several types of moving average may be used, including a simple moving average, a cumulative moving average, a weighted moving average, or an exponential moving average. 
     Instead of an x-y graph, a visual display comprising one or more LED lights may be used. For example, a higher flow rate may be indicated by a range of shades of green, while a lower flow rate may be indicated by a range of shades of red. Alternatively, the intensity of a light may be changed in response to changes in the flow rate or changes in weight or mass. For example, the intensity of the light may be proportional to the measured/calculated flow rate. A loudspeaker may present the changes in weight/mass over time or changes in flow rate over time as a continuous or continual sound having a pitch that changes proportionally with changes in value. For example, a higher pitch with a larger flow rate. The sound intensity may alternatively be varied (higher flow rate=higher dB). 
     Changes in the flow rate can be indicative of a number of operation occurrences in the forced aspiration system  400 . For example, a flow rate that suddenly decreases a significant amount may be indicative of thrombus becoming clogged within the aspiration lumen  404  or the lumen  444  of the extension tube  438 . In some cases, a reduction in the flow rate of 90% or more may be indicative of clogging. When a clog occurs, the volume of fluid being aspirated and dispensed into the canister  458  can be severely limited. A loudspeaker  1818  is also configured to produce an audible alarm, when a threshold value of flow rate is crossed. A threshold flow rate may be input into memory  1822  of the scale  1802  using a user interface  1820 . When the flow rate decreases to a value below the threshold flow rate, the loudspeaker  1818  is made to sound an alarm. In some embodiments, the controller  484  on the pump  412 , or a different controller in one of the other components may be coupled to the processor  1810  (wired or wireless) and may be configured to activate the alarm of the loudspeaker  1818 . When the flow rate increases above the threshold flow rate, the loudspeaker  1818  may be deactivated such that the alarm is no longer sounded. Alternatively, the loudspeaker  1818  may be replaced by, or augmented with a visual alarm and/or a tactile alarm. The visual alarm may include one or more light, including one or more LEDs. The tactile alarm may include a vibration device, such as a piezoelectric, or a weight-offset rotational device. 
     Changes in the flow rate may also be indicative of other changes in status, such as a rupture in a wall of one of the tubular members or a disconnection of one of the connections. In one of these leak conditions, the flow rate may be significantly reduced, and thus identified by the flow rate changes measured by the aspiration monitoring system  1800 . The system  400  may be configured to activate the alarm (e.g., via the loudspeaker  1818 ) when a free flow of blood is detected. In other words, when the system is apparently aspirating only blood, and not aspirating thrombus. Thus, the measured flow rate crossing above a particular threshold stored in memory  1822  indicative of free flowing blood would cause the controller  484  to activate the alarm. 
     A secondary aspiration monitoring system  414  comprising a pressure transducer  416  may be coupled, for example, between the distal end  440  of the extension tube  438  and the connector  424  and/or proximal end  406  of the aspiration lumen  404  of the aspiration catheter  402 . Signals from the pressure transducer  416  are carried on an electric cable  480  to an input  482  of the pump  412 . The controller  484  within the pump  412  is configured to control the operation of the pump  412 , but also may be configured to control the operation of the peristaltic pump  408 , with via a cable  486 , or wirelessly. The controller  484  may comprise a microcontroller. The controller  484  may alternatively be located within the peristaltic pump  408 , or may be located at another component or location. Control using measured pressure adds an additional safety element to the system  400 . Additionally, a non-functional device (because of a leak, incomplete connection, incomplete priming, rupture, blockage) can be quickly identified. Unallowably high pressures can also be quickly identified, protecting the motor of the pump  412  from burnout or overheating danger. The integrity of the tube  478  is also protected, e.g., avoiding unnaturally high pressures that could lead to a burst of the tube  478 . Data from the pressure transducer  416  and the scale  1802  can be used together to optimize or create a more correct signal indicative of aspiration flow, or indicative of the presence of clot/thrombus, or the presence of a clog, or the presence of a burst or disconnection in the fluid circuit. 
     The female luer  452  is located distally on the connector  424  from the female luer  472 . Thus, aspirated blood/thrombus/saline enters the female luer  452  without ever having to contact interior irregularities  425  (in geometry, shape) within the connector  424 , that may otherwise cause flow resistance, or cause thrombus to catch (e.g., between the tube  478  and the interior of the connector  424 . 
     A foot pedal  451  is illustrated having a base  453  and a pedal  455  that is coupled to the base  453  and movable or activatable by application of the foot of a user. The pedal  455  may be spring-loaded and depressible by application of a moment or a compressive force, or may instead comprise a membrane switch. The pedal  455 , when activated, may in some embodiments toggle on and off, and in other embodiments may be activatable when a force, a pressure, or a moment is applied, and inactivated when the force, pressure, or moment is not applied. A first cable  461  carries signals from the foot pedal  451  to the pump  412  via a plug  465  that is connected to an input jack  467 . A second cable  463  carries signals from the foot pedal  451  to the peristaltic pump  408  via a plug  469  that is connected to an input jack  471 . In some embodiments, activation of the pedal  455  by the foot of a user starts the operation of the pump  412  and starts the operation of the peristaltic pump  408  at the same time. In some embodiments, activation of the pedal  455  by the foot of a user starts the operation of the peristaltic pump  408 , and then starts the operation of the pump  412 , with a slight delay after the peristaltic pump  408  is started. The controller  484  is programmed or programmable to impart the delay, or the lack of delay. The delay is useful to assure that some aspiration, or a significant amount of aspiration, is being applied to the aspiration lumen  404  prior to the injection of pressurized fluid (e.g., saline) through the injection lumen  410 . All may be controlled by the controller  484  of the pump  412 , in response to a signal through the cable  463  from the foot pedal  451 . Thus, blood vessels or other vasculature in the vicinity of the open distal end  405  are spared any injection of fluid from a high pressure jet, as it is instead aspirated through the aspiration lumen  404 . 
     In addition, in some embodiments, activation of the pedal  455  by the foot of a user during the operation of the pump  412  and the peristaltic pump  408  stops the operation of the pump  412  and the operation of the peristaltic pump  408  at the same time. In other embodiments, a delay may be applied (e.g., by the controller  484 ), such that the pump  412  is stopped, and then the peristaltic pump  408  is stopped slightly afterwards. The length of the delays described may be between about 0.01 second and about 1.00 second, or between about 0.10 second and about 0.25 second. The operation (on/off) of the pump  412  and/or peristaltic pump  408  via the foot pedal  451  allows hands-free activation, enabling a single user the manipulate the aspiration catheter  402  and guidewire  448  with both hands. 
     In other embodiments, the foot pedal  451  may be replaced by another type of switch, including, but not limited to a toggle on/off push button or hand switch, an audio-activated switch (voice activated, clap activated, click activated), an optical switch (beam/light sensor for hand or foot interruption), or any other kind of switch that can be activated by medical personnel. The switch may be remote (e.g., in a control room) or may be located near the procedural area. The switch may also be a sterile switch or sterilizable for location on a sterile area. 
     In some cases, the activation and deactivation (turning on and off) of the aspiration flow applied by the peristaltic pump  408  on the aspiration lumen  404  may be done by leaving the peristaltic pump  408  in a running condition, while the user opens and closes the stopcock  454 . Alternatively, a pinch valve (not shown) coupled to the extension tube  438  may be used for opening and closing the lumen  444 , and thus starting and stopping aspiration. The pinch valve may be operated by a foot pedal (similar to the foot pedal  451 ), or may be operated by another control (e.g., on the interface  456  of the peristaltic pump  408  or even an interface on the pump  412 ). 
     The controller  484  also monitors and controls several device safety functions, which include over pressure detection, air bubble detection, and vacuum or negative pressure charge. An additional pressure transducer  415  monitors pressure (i.e. injection pressure), and senses the presence of air bubbles. Alternatively, or in conjunction, an optical device  417  may be used to sense air bubbles. In one contemplated embodiment, the pump pressure is proportional to the electric current needed to produce that pressure. Consequently, if the electric current required by pump  412  exceeds a preset limit, the controller  484  will disable the pump  412  by cutting power to it. Air bubble detection may also be monitored by monitoring the electrical current required to drive the pump  412  at any particular moment. In order for a pump  412  to reach high fluid pressures, there should be little or no air (which is highly compressible) present in the pump  412  or connecting system (including the aspiration lumen  404  of the aspiration catheter  402  and the tubing set  464 ). The fluid volume is small enough that any air in the system will result in no pressure being generated at the pump head. A sufficient volume of liquid is needed proximally to flush any finite amount of air through. The controller  484  monitors the pump  412  current for any abrupt downward change that may indicate that air has entered the system. If the rate of drop is faster than a preset limit, the controller  484  will disable the pump  412  by cutting power to it until the problem is corrected. 
     After collecting the aspirated material in a blood bag, blood bottle, or the canister  458 , aspirated components (blood, thrombus, saline, slurry, etc.) can be placed into a reinfusion device, such as a Stryker ConstaVac (CBCII) Blood Conservation System, or a Haemonetics OrthoPAT Orthopedic Perioperative Autotransfusion System. 
     In some embodiments, the blood may be cooled prior to being injected. In some embodiments, the blood may be heated prior to being injected. In some embodiments, other drugs may be added to the blood prior to it being inserted. In some cases, the blood may be diluted with saline, to decrease its viscosity, or decrease its hematocrit. This may allow for decrease hemolysis to occur. In some cases, blood collected in the canister  458 , or blood coming from the extension tube  438 , may even be used as donor blood, to infuse into a different patient. 
     In some embodiments, an additional or alternate sensor may be used to monitor flow conditions for the notification of the user, including, but not limited to: a Doppler sensor, an infrared sensor, or a laser flow detection device. In some embodiments, an externally-attached (non-contact) Doppler sensor may be employed. In some embodiments, an infrared sensor or a laser flow detection device may be employed around the extension tubing  438 . The alternate sensor (e.g., flow sensor, etc.) may be located at a number of different locations along the aspiration path, including on or in the extension tube  438 , either proximal to or distal to the rotatable head  430  of the peristaltic pump  408 . 
       FIG. 46  illustrates an alternative aspiration monitoring system  1900  that shares features with the aspiration monitoring system  1800  of  FIG. 44 , but is configured to weigh the fluid  259 ,  459  contained in the canister  258 ,  458  by suspending the canister  258 ,  458  from hooks  1902 ,  1904  that extend from a frame  1906  that is supported on the weighing platform  1806 . The frame  1906  comprises two vertical legs  1910 ,  1912  and a crossbar  1908  coupled to each of the vertical legs  1910 ,  1912 . The crossbar  1908  is configured to support the hooks  1902 ,  1904  and the canister  258 ,  458  (when hung). The canister  258 ,  458  may include hooks, indentations, or loops that are configured to engagingly interface with one or both of the hooks  1902 ,  1904 . 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments may be devised without departing from the basic scope thereof. Alternatively, instead of using the extension tube  238 ,  438  that is configured to be used with a peristaltic pump  208 ,  408 , an extension tube  238 ,  438  may comprise a luer connector (or other sealing connector) at its proximal end, and may be configured to attached to an evacuatable syringe (e.g., 20 ml or 30 ml). The syringe may be hung from the hooks  1902 ,  1904  (or the equivalent) and the weight of the syringe and extension tube  238 ,  438  may be tared from the scale  1802 . Thus, as the syringe fills, the increase of weight/mass of the aspirate collecting in the syringe is measured over time, in the same manner that the contents of the canister  258 ,  458  is weighed. The evacuatable syringe may even be replaced by a bell jar connected to a vacuum pump, again, with the bell jar and any connecting tubing tared from the measured weight/mass.  FIG. 47  illustrates an aspiration system  1928  similar to the aspiration system  200  of  FIG. 43 , except that the peristaltic pump  208  and canister  258  are replaced by a vacuum pump  1930  and a vacuum chamber  1934  or bell jar having a base  1936  and a lid  1938  sealably placed thereon. The vacuum pump  1930  may be operated by controls  1999  carried on its outer surface  1997 , or may be controllable (on/off) by the foot pedal  251 . A vacuum tubing  1932  connects the vacuum pump  1930  to an interior  1940  of the vacuum chamber  1934 . A control valve  1948  is adjustable for controlling the aperture between the vacuum tubing  1932  and the interior  1940  of the vacuum chamber  1934 . The interior  1940  communicates with the lumen  244  of the extension tube  238  via the proximal end  242 , which is coupled to a port  1942  of the vacuum chamber  1934 . An adjustable valve  1946  controls an aperture between the interior  1940  of the vacuum chamber  1934  and the lumen  244  of the extension tube  238 . The vacuum pump  1930  is supported separately on a table, cart, or other support. The weight of the vacuum tubing  1932  and extension tube  238  can be tared from the readout of the scale  1802 , so that only the weight of fluid/clot, etc. pulled into the interior  1940  of the vacuum chamber  1934  is measured over time. 
     Thrombosis (thrombus, clot) within vasculature, including blood vessels such as arteries or veins, is a significant risk factor that can be debilitating or even cause death. Aspiration systems including aspiration catheter include aspiration-only devices as well as forced aspiration devices, which are configured to inject pressurized fluid, such as heparinized saline, into the distal portion of an aspiration lumen, to create a larger aspiration pressure gradient, and thus more significant thrombus maceration and removal. Though many of these aspiration systems are used in peripheral or coronary arteries, thromboembolic stroke involving arteries of the neck and head is also of concern. Many of the arteries of the neck and head, including cerebral arteries, the basilar artery, and other communicating arteries in proximity, are located quite a distance from traditional insertion/puncture locations, such as the femoral artery or radial artery. The pathway to these arteries can also be quite tortuous, and the vessels are often of a small caliber, such that long, small diameter catheters with a great deal of flexibility at their distal ends are utilized. Many of these design criteria confound other physical requirements of an aspiration catheter, such as a large diameter aspiration lumen for increased aspiration flow, or the multiple lumens of a force aspiration catheter, which must now fit into a small overall catheter shaft diameter. 
     Clogging of aspiration catheters, for example by large pieces of thrombus, is a common concern for users. Techniques to avoid clogging/choking of material within the catheter often involve rapidly, aggressively advancing the aspiration catheter or gently plucking at edges of a thrombus to insure only small pieces or portions are introduced at a time, pieces which are small enough to not clog or occlude the aspiration lumen. When a device becomes clogged during use, the potential for inadvertent dislodgment of thrombus downstream increases; this is referred to as distal embolism. As aspiration procedures of this type are often used in highly technical emergent settings, early clog detection of the aspiration catheter for the user during aspiration can contribute to the success of the procedure and clinical outcome. Some sources have reported that up to 50% of aspiration catheters used get clogged during use. 
     The user may have difficulty determining whether there is a vacuum or a negative pressure gradient in the system or not. For example, the user may have difficulty determining whether the vacuum or negative pressure has been applied or not (e.g., the vacuum source or negative pressure supplying pump has been turned on or off). Additionally, the user may have difficulty determining whether there has been a loss of vacuum or negative pressure in the system, for example because of the syringe (or other vacuum source or negative pressure supplying pump) being full of fluid or because of a leak in the system. Blood is relatively opaque and can coat the wall of the syringe, thus making it difficult to determine when the syringe becomes full. This makes it difficult to determine whether sufficient vacuum or negative pressure is being applied to the aspiration catheter. The vacuum or negative pressure level may change to an unacceptable level even before the syringe becomes full. Extension tubing or other tubing may also cause a loss in vacuum or negative pressure gradient in the system. Certain tubing kinks may be difficult for a user to see or identify. It is also difficult to determine whether there is an air leak in the system, which can be another cause for a loss of vacuum or negative pressure even before the syringe becomes full of the aspirated fluid. 
       FIG. 48  illustrates an aspiration system  600  comprising an aspiration catheter  602  comprising an elongate shaft  601  including an aspiration lumen  604  having an open distal end  605  and a proximal end  606  configured to couple to a peristaltic pump  608 . The peristaltic pump  608  may be a roller pump having a base  626 , a pressure shoe  628  carried by the base  626 , and a rotatable head  630 , rotatably coupled to the base  626 , and carrying two or more rollers  632   a - d . The rollers  632   a - d  are arrayed around a perimeter  634  of the rotatable head  630 . The rotatable head  630  is configured to be rotatable in at least a first rotational direction  636  (e.g., by a motor, directly, or with a gear train, not shown). The peristaltic pump  608  may be battery powered, and the battery(ies) may be rechargeable by wired or wireless means. The peristaltic pump  608  may alternatively, or additionally be powered by a power cord (not shown) configured to connect to a power supply. An extension tube  638  having a distal end  640  and a proximal end  642 , and having a lumen  644  extending therethrough, is hydraulically coupled to the proximal end  606  of the aspiration lumen  604  via a connector  624 . A Touhy-Borst seal  646  allows the insertion of a guidewire  648  through the connector  624  and aspiration lumen  604 , as described herein, and the guidewire  648  may be used to track the aspiration catheter  602  through a subject&#39;s vasculature. The Touhy-Borst  646  may be tightened to seal over the guidewire  648 , to maintain hemostasis. The extension tube  638  may include a male luer  650  at its distal end  640 , for connecting to a female luer  652  of the connector  624 . The male luer  650  may include a stopcock  654 , which is configured to be turned between an open position (shown) or a closed position. Alternatively, the extension tube  638  may be integral with the aspiration lumen  604 , or may be permanently attached to the connector  624 . In use, a compressible portion  637  of the extension tube  638  is placed within the pressure shoe  628  of the peristaltic pump  608  such that rotation of the rotatable head  630  (e.g., via input to an interface  656  by a user) in the rotational direction  636  causes fluid to be forced through the lumen  644  of the extension tube  638  from the distal end  640  to the proximal end  642 , via compression of the compressible portion  637  by the rollers  632 , one at a time. In some embodiments, there are only two rollers  632 . In other embodiments, there are three rollers  632 . In still other embodiments, as shown, there are four rollers  632 . As described, the rollers  632  may be replaced by bumps or protrusions. The compressible portion  637  or any of the compressible portions described herein may comprise silicone tubing, polyurethane tubing, polyvinyl chloride tubing, thermoplastic elastomer (TPE), such as Bioprene®, a registered trademark of Watson-Marlow or Wilmington, Mass., USA, or other compressible tubing. The compressible section  637  may be a relatively short section that is attachable to and detachable from the peripheral ends of the extension tube  638 , or in other embodiments, may comprise the entirety of the extension tube  638  between the distal end  640  and the proximal end  642 . The proximal end  642  of the extension tube  638  may be coupled to a canister  658  having an interior  660 , to allow fluid  659  passing through the extension tube  638  to pass into the interior  660 . The proximal end  642  of the extension tube  638  is coupled to the canister  658  by a tubing clamp  657  which holds the extension tube  638  longitudinally without compromising the patency of the lumen  644 . To minimize fluid resistance at the proximal end  642  of the extension tube, besides an endhole  621 , there is also a plurality of sideholes  623 , similar to sump tubing. In other embodiments, the endhole  621  may be blocked off, with the outflow emanating only from the plurality of sideholes  623 . The sideholes  623  assure that the minimum area of flow resistance in the extension tube  638  is not at the proximal end  642 . The sideholes  623  help prevent against jetting into the canister  658 . Jetting of the blood would be a negative factor, adding shear stress to the blood, and causing hemolysis or platelet activation, and thus damaging or otherwise altering blood that might have been desired for reinfusion into the patient. An additional hub  662  in the canister  658  may be left open (as shown) to allow the unfilled interior  660  to match atmospheric pressure. 
     Because the aspiration catheter  602  is configured to be inserted into arteries that may feed to critical organs (heart, brain, etc.), strict control of flows through the catheter allow for a higher level of security. A recognition system is provided to assure that the aspiration catheter  602  is only used with the peristaltic pump  608  and the injection pump  612 , and not with alternative devices that do not have the same levels of control regarding aspiration and injection. An identification circuit  619  within the peristaltic pump  608  is coupled to the controller  684  (e.g., via cable  686 ) and also electrically connects to a first port  611  and a second port  613 . The extension tube  638  may be provided with a first tether  690  having a first identification module  607  configured to plug into or otherwise be secured in close proximity to the first port  611 . Additionally, or alternatively, the aspiration catheter  602  may be provided with a second tether  688  having a second identification module  609  configured to plug into or otherwise be secured in close proximity to the second port  613 . The controller  684  is configured to only allow the operation of the injection pump  612  and/or the peristaltic pump  608  to occur if one of both of the identification modules  607 ,  609  are identified by the identification circuit  619  as being correct components (e.g., correct models, correct sizes, correct clinical applications, etc.). Thus, the pumps  612 ,  608  are enabled or un-enabled by the controller  684 , depending upon the information provided by the identification modules  607 ,  609 . In some embodiments one or both of the identification modules  607 ,  609  make comprise an RFID (radiofrequency identification) chip, and the identification circuit  619  configured to power the RFID chips to receive and read data. In some embodiments, the identification circuit  619  may additionally be configured to write to the RFID chips. In other embodiments one or both of the identification modules  607 ,  609  make comprise a resistor, and the identification circuit  619  configured to read the resistance value of the resistor. For example, the resistor may complete a partial Wheatstone bridge carried on the identification circuit  619 . 
     The aspiration catheter  602  additionally has a high pressure injection lumen  610  for injecting saline from a fluid source  679 , for example, via a high pressure pump  612 . A tubing set  664  may include a pump cartridge  666  having a piston or bellows or other movable element that the pump  612  may manipulate using an internal motor  691 , thus pressurizing saline or other fluid from the fluid source  679  with a significantly high pressure such that the saline is forced through the injection lumen  610  of the aspiration catheter  602 . The tubing set  664  includes proximal end  668  having a spike  689  or other element for hydraulically coupling it to the fluid source  679 . The tubing set  1464  further has a distal end  670  (which may include a male luer) which is configured to hydraulically couple to the injection lumen  610  via a female luer  672 . Injected saline is forced through the injection lumen  610  by the pump  612  and exits an orifice  674  in a hollow end piece  675  coupled to a distal end  676  of an injection tube  678 , containing the injection lumen  610 . The tube  678  may be substantially or entirely within the shaft  601 . In some embodiments, the tube  678  is attached to the internal wall of the shaft  601  only at a distal end portion  603 . Thus, the free-floating nature of the remainder of the tube  678  within the aspiration lumen  604  increases the flexibility and trackability of the shaft  601 . The high pressure saline is forced through the orifice  674 , causing a jet, or one or more jets. The jet is aimed within the aspiration lumen  604 , just proximal the open distal end  605  which may create a Venturi effect that forces blood or thrombus that is external and adjacent the open distal end  605  into the aspiration lumen  640 . The combination of the operation of the peristaltic pump  608  and the jet created by the high pressure saline cause the maceration of thrombus, and the movement/flow of material (saline/blood/macerated thrombus/small pieces of thrombus) through the aspiration lumen  604  from the open distal end  605  to the proximal end  606 , through the connector  624 , and through the lumen  644  of the extension tube  638  from its distal end  640  to its proximal end  642 , and finally into the interior  660  of the canister  658 . Thus, thrombus within a blood vessel of a subject may be macerated and removed by use of the system  600 . Blood vessels may include peripheral blood vessels, coronary blood vessels, or blood vessels within the head or neck of the subject, including carotid arteries, cerebral arteries, and basilar and communicating arteries. An aspiration monitoring system  614  comprising a pressure transducer  616  may be coupled, for example, between the distal end  640  of the extension tube  638  and the connector  624  and/or proximal end  606  of the aspiration lumen  604  of the aspiration catheter  602 . The aspiration monitoring system  614  or any other described herein can include any of the features described in relation to aspiration monitoring systems described in U.S. Pat. App. Pub. No. 2017/0056032 to Look et al., filed Aug. 23, 2016 and published Mar. 2, 2017, which is hereby incorporated by reference in its entirety for all purposes. Signals from the pressure transducer  616  are carried on an electric cable  680  to an input  682  of the pump  612 . A controller  684  within the pump  612  is configured to control the operation of the pump  612 , including motor  691 , but the controller  684  may also be configured to control the operation of the peristaltic pump  608 , with via a cable  686 , or wirelessly. The controller  684  may comprise a microcontroller. The controller  684  may alternatively be located within the peristaltic pump  608 , or may be located at another location. Control using signals of measured pressure from the pressure transducer  616  adds an additional safety element to the system  600 . Additionally, a non-functional device (because of a leak, incomplete connection, incomplete priming, rupture, blockage) can be quickly identified. Unallowably high pressures can also be quickly identified, protecting the motor  691  of the pump  612  from burnout or overheating danger. The integrity of the tube  678  is also protected, e.g., avoiding unnaturally high pressures that could lead to burst. 
     The female luer  652  of the aspiration catheter  602  is located distally on the connector  624  from the female luer  672 . Thus, aspirated blood/thrombus/saline enters the female luer  652  without ever having to contact interior irregularities  625  (in geometry, shape) within the connector  624 , that may otherwise cause flow resistance, or cause thrombus to catch (e.g., between the tube  678  and the interior of the connector  624 . 
     A foot pedal  651  has a base  653  and a pedal  655  that is coupled to the base  653  and movable or activatable by application of the foot of a user. The pedal  655  may be spring-loaded and depressible by application of a moment or a compressive force, or may instead comprise a membrane switch. The pedal  655 , when activated, may in some embodiments toggle on and off, and in other embodiments may be activatable when a force, a pressure, or a moment is applied, and inactivated when the force, pressure, or moment is not applied. A first cable  661  carries signals from the foot pedal  651  to the pump  612  via a plug  665  that is connected to an input jack  667 . A second cable  663  carries signals from the foot pedal  651  to the peristaltic pump  608  via a plug  669  that is connected to an input jack  671 . In some embodiments, activation of the pedal  655  by the foot of a user starts the operation of the pump  612  and starts the operation of the peristaltic pump  608  at the same time. In some embodiments, activation of the pedal  655  by the foot of a user starts the operation of the peristaltic pump  608 , and then starts the operation of the pump  612 , with a slight delay after the peristaltic pump  608  is started. The delay is useful to assure that some aspiration, or a significant amount of aspiration, is being applied to the aspiration lumen  604  prior to the injection of pressurized fluid (e.g., saline) through the injection lumen  610 . Thus, blood vessels or other vasculature in the vicinity of the open distal end  605  are spared any injection of fluid from a high pressure jet, as it is instead aspirated through the aspiration lumen  604 . 
     In addition, in some embodiments, activation of the pedal  655  by the foot of a user during the operation of the pump  612  and the peristaltic pump  608  stops the operation of the pump  612  and the operation of the peristaltic pump  608  at the same time. In other embodiments, a delay may be applied, for example, such that the pump  612  is stopped, and then the peristaltic pump  608  is stopped slightly afterwards. The length of the delays described may be between about 0.01 second and about 1.00 second, or between about 0.10 second and about 0.25 second. The operation (on/off) of the pump  612  and/or peristaltic pump  608  via the foot pedal  651  allows hands-free activation, enabling a single user the manipulate the aspiration catheter  602  and guidewire  648  with both hands. The location of the foot pedal  651  can be tactily found with the foot of the user, while the user maintains visual contact with the patient, and/or any monitors, or even other medical personnel. 
     In other embodiments, the foot pedal  651  may be replaced by another type of switch, including, but not limited to a toggle on/off push button or hand switch, an audio-activated switch (voice activated, clap activated, click activated), an optical switch (beam/light sensor for hand or foot interruption), or any other kind of switch that can be activated by medical personnel. The switch may be remote (e.g., in a control room) or may be located near the procedural area. The switch may also be a sterile switch or sterilizable for location on a sterile area. 
     In some cases, the activation and deactivation (turning on and off) of the aspiration flow applied by the peristaltic pump  608  on the aspiration lumen  604  may be done by leaving the peristaltic pump  608  in a running condition, while the user opens and closes the stopcock  654 . In other embodiments, the stopcock may be replaced by a pinch valve (not shown) to open or compress the extension tubing  638 . The pinch valve may be operable by a foot switch or by a push button (on/off). 
     The controller  684  also monitors and controls several device safety functions, which include over pressure detection, air bubble detection, and vacuum or negative pressure charge. An additional pressure transducer  615  carried on the connector  624  monitors pressure (i.e. injection pressure), and senses the presence of air bubbles. Alternatively, or in conjunction, an optical device  617  may be used to sense air bubbles. In one contemplated embodiment, the pump pressure is proportional to the electric current needed by the pump  612  to produce that particular pressure. Consequently, if the electric current required by pump  612  exceeds a preset limit, the controller  684  will disable the pump  612  by cutting power to it. Air bubble detection may also be monitored by monitoring the electrical current required to drive the pump  612  at any particular moment. In order for a pump  612  to reach high fluid pressures, there should be little or no air (which is highly compressible) present in the pump  612  or connecting system (including the aspiration lumen  604  of the aspiration catheter  604  and the tubing set  664 ). The fluid volume is small enough that any air in the system will result in no pressure being generated at the pump head. A sufficient volume of liquid is needed proximally to flush any finite amount of air through. The controller  684  monitors the pump  612  current for any abrupt downward change that may indicate that air has entered the system. If the rate of drop is faster than a preset limit, the controller  684  will disable the pump  612  by cutting power to it until the problem is corrected. 
     The aspiration catheter  602  of  FIG. 48  is illustrated as having pressurized fluid injection through injection lumen  610 . However, other embodiments of the aspiration system  600  exist in which the aspiration catheter  602  is replaced by a standard aspiration catheter, not having an injection lumen. 
     As an alternative to collecting the aspirated material in a blood bag, blood bottle, or the canister  658 , aspirated components (blood, thrombus, saline, slurry, etc.) can be placed into a reinfusion device, such as a Stryker ConstaVac (CBCII) Blood Conservation System, or a Haemonetics OrthoPAT Orthopedic Perioperative Autotransfusion System. In some embodiments, the canister  658 , itself, may comprise the reinfusion device. Returning at least some of the aspirated blood to the patient via reinfusion helps to diminish what is one of the inherent drawbacks to aspiration, blood loss. 
     In some embodiments, the blood may be cooled prior to being injected. In some embodiments, the blood may be heated prior to being injected. In some embodiments, other drugs may be added to the blood prior to it being inserted. In some cases, the blood may be diluted with saline, to decrease its viscosity, or decrease its hematocrit. This may allow for decrease hemolysis to occur. In some cases, blood collected in the canister  658 , or blood coming from the extension tube  638 , may even be used as donor blood, to infuse into a different patient. 
     In some embodiments, an additional or alternate sensor may be used to monitor flow conditions for the notification of the user, including, but not limited to: a Doppler sensor, an infrared sensor, or a laser flow detection device. In some embodiments, an externally-attached (non-contact) Doppler sensor may be employed. In some embodiments, an infrared sensor or a laser flow detection device may be employed around the extension tubing  638 . The alternate sensor (e.g., flow sensor, etc.) may be located at a number of different locations along the aspiration path, including on or in the extension tube  638 , either proximal to or distal to the rotatable head  630  of the peristaltic pump  608 . 
       FIG. 49  illustrates an aspiration catheter  700  having an elongate shaft  702 , and with a radiopaque marker band  704  attached to the distal end  706  of the shaft  702 . The shaft  702  defines an aspiration lumen  708  having an open distal end  710 . An injection tube  712  having a distal end  714  is capped off with a microfabricated cap  716 . The microfabricated cap  716  has an inner cylindrical cavity  718  configured for placing over the distal end  714  of the injection tube  712 . An outer cylindrical surface  720  at the distal end  714  of the injection tube  712  is sealingly coupled to the microfabricated cap  716  at the inner cylindrical cavity  718 , so that the injection lumen  722  of the injection tube  712  is closed and sealed at the distal end  714  to resist a high pressure. The outer cylindrical surface  720  may be bonded to the microfabricated cap  716  at the inner cylindrical cavity  718  by at least one of an adhesive, an epoxy, a weld (e.g., ultrasonic weld, or other fusing of materials), or a solvent. Alternatively, a circumferential seal (thin elastomeric ring) may be interposed between the outer cylindrical surface  720  and the microfabricated cap  716  at the inner cylindrical cavity  718  to create a seal, and a friction fit. The microfabricated cap  716  may comprise a number of different materials, including polymers or metals. The microfabricated cap  716  may be constructed by a number of different processes, including: micromachining, micro injection molding, three-dimensional printing, photolithography, shadow masking, etching, or microforming. These processes include additive processes and subtractive processes. An orifice  730  is formed in a wall  732  of the injection tube  712  and has a similar function to the orifice  674  of  FIG. 48 . High pressure fluid is forced out of the orifice  730  and into the aspiration lumen  708  (arrow) because the distal end  714  of the injection tube  712  is sealed. 
     An outer surface  724  of the injection tube  712  is bonded to an inner surface  726  of the aspiration lumen  708  with an adhesive  728  (or epoxy, or other joining means). The injection tube  712  is bonded at a particular rotational orientation with respect to the aspiration lumen  708  such that the orifice  730  is oriented toward an opposing surface  734  in the aspiration lumen  708 . An unbonded section  736  extends a significant portion of the length of the aspiration catheter  700  in the proximal direction, thus allowing for enhanced flexibility and trackability. The center of the orifice  730  may be located a distance d 2  from the proximal end of the microfabricated cap  716 , such as between about 0.05 mm and about 10.00 mm so that a jet emanating from the orifice  730  clears the microfabricated cap  716 . The center of the orifice  730  is located a distance d 1  from the open distal end  710  of the aspiration lumen  708  such that the distal end of the microfabricated cap  716  does not extend from the aspiration lumen  708 . However, in some embodiments, the microfabricated cap may be configured to extend from the aspiration lumen  708 , as long it does not have any sharp leading features. 
       FIG. 50  illustrates an aspiration catheter  740  having an elongate shaft  742 , and with a radiopaque marker band  744  attached to the distal end  746  of the shaft  742 . The shaft  742  defines an aspiration lumen  748  having an open distal end  750 . An injection tube  752  having a distal end  754  is capped off with a microfabricated cap  756 . The microfabricated cap  756  has an inner cylindrical cavity  758  configured for placing over the distal end  754  of the injection tube  752 . An outer cylindrical surface  760  at the distal end  754  of the injection tube  752  is sealingly coupled to the microfabricated cap  756  at the inner cylindrical cavity  758 , so that the injection lumen  762  of the injection tube  752  is closed and sealed at the distal end  754  to resist a high pressure. A reinforcement ring  795  is fit into the injection lumen  762  of the injection tube  752  at the distal end  754  to reinforce the distal end  754  and allow for higher strength seal. The reinforcement ring  795  may also be configured to allow a friction fit seal. The reinforcement ring may comprise a high strength metallic material such as stainless steel, or a rigid polymer. The outer cylindrical surface  760  may be bonded and/or sealed to the microfabricated cap  756  at the inner cylindrical cavity  758  by any of the methods or materials described in relation to the aspiration catheter  700  of  FIG. 49 . The microfabricated cap  756  may comprise any of the materials and be formed by any of the processes described in relation to the microfabricated cap  716  in  FIG. 49 . An orifice  770  is formed in a wall  772  of the injection tube  752  and has a similar function to the orifice  674  of  FIG. 48 . High pressure fluid is forced out of the orifice  770  and into the aspiration lumen  748  because the distal end  754  of the injection tube  752  is sealed. 
     An outer surface  764  of the injection tube  752  is bonded to an inner surface  766  of the aspiration lumen  748  with an adhesive  768  (or epoxy, or other joining means). The injection tube  752  is bonded at a particular rotational orientation with respect to the aspiration lumen  748  such that the orifice  770  is oriented toward an opposing surface  774  in the aspiration lumen  748 . The adhesive  768  bond extends a significant portion of the length of the aspiration catheter  740  in the proximal direction. 
       FIG. 51  illustrates an aspiration catheter  701  having an elongate shaft  703 , and with a radiopaque marker band  705  attached to the distal end  707  of the shaft  703 . The shaft  703  defines an aspiration lumen  709  having an open distal end  711 . An injection tube  713  having a distal end  715  is capped off with a microfabricated cap  717 . The distal end  715  is necked down from the rest of the injection tube  713  by a heating and/or tensile stretching process to create a smaller outer diameter of the distal end  715 . The microfabricated cap  717  has an inner cylindrical cavity  719  configured for placing over the reduced diameter distal end  715  of the injection tube  713 . An outer cylindrical surface  721  at the distal end  715  of the injection tube  713  is sealingly coupled to the microfabricated cap  717  at the inner cylindrical cavity  719 , so that the injection lumen  723  of the injection tube  713  is closed and sealed at the distal end  715  to resist a high pressure. The smaller diameter of the distal end  715  and the inner cylindrical cavity  719 , allow for a relatively higher strength bond, because of the thereby increased hoop strength of the distal end  715 . The outer cylindrical surface  721  may be bonded and/or sealed to the microfabricated cap  717  at the inner cylindrical cavity  719  by any of the methods or materials described in relation to the aspiration catheter  700  of  FIG. 49 . The microfabricated cap  717  may comprise any of the materials and be formed by any of the processes described in relation to the microfabricated cap  716  in  FIG. 49 . An orifice  731  is formed in a wall  733  of the injection tube  713  and has a similar function to the orifice  674  of  FIG. 48 . High pressure fluid is forced out of the orifice  731  and into the aspiration lumen  709  because the distal end  715  of the injection tube  713  is sealed. 
     An outer surface  725  of the injection tube  713  is not bonded to an inner surface  727  of the aspiration lumen  709 . Instead, the microfabricated cap  717  is bonded to the inner surface  727  with an adhesive  729  (or epoxy, or other joining means). An unbonded section  737  of the injection tube  713  extends a significant portion of the length of the aspiration catheter  701  in the proximal direction, thus allowing for enhanced flexibility and trackability. The microfabricated cap  717  is bonded such that the injection tube  713  is held at a particular rotational orientation with respect to the aspiration lumen  709  such that the orifice  731  is oriented toward an opposing surface  735  in the aspiration lumen  709 . 
       FIG. 52  illustrates an aspiration catheter  741  having an elongate shaft  743 , and with a radiopaque marker band  745  attached to the distal end  747  of the shaft  743 . The shaft  743  defines an aspiration lumen  749  having an open distal end  751 . An injection tube  753  having a distal end  755  is capped off with a microfabricated cap  757 . The microfabricated cap  757  has an inner cylindrical cavity  759  which includes a proximal portion  799  configured for placing over the distal end  755  of the injection tube  753 . An outer cylindrical surface  761  at the distal end  755  of the injection tube  753  is sealingly coupled to the microfabricated cap  757  at the inner proximal portion  799  of the cylindrical cavity  759 , so that the injection lumen  763  of the injection tube  753  is sealed to resist a high pressure. The outer cylindrical surface  761  may be bonded and/or sealed to the microfabricated cap  757  at the proximal portion  799  of the inner cylindrical cavity  759  by any of the methods or materials described in relation to the aspiration catheter  700  of  FIG. 49 . The microfabricated cap  757  may comprise any of the materials and be formed by any of the processes described in relation to the microfabricated cap  716  in  FIG. 49 . An orifice  771  is an exit of a distal portion  797  of the inner cylindrical cavity  759  that communicates with the proximal portion  799 . The inner cylindrical cavity  759  in  FIG. 52  has a curved shape, but may alternatively form an L-shape, or make take a 45° angle with respect to the longitudinal axis of the aspiration catheter  741 . The angle may vary between 45° and 135°. The orifice  771  is formed in a wall  773  of the microfabricated cap  757  and has a similar function to the orifice  674  in  FIG. 48 . High pressure fluid is forced through the inner cylindrical cavity  759 , out of the orifice  771 , and into the aspiration lumen  749  because the distal end  755  of the injection tube  753  is sealed. 
     An outer surface  765  of the injection tube  753  is bonded to an inner surface  767  of the aspiration lumen  708  with an adhesive  769  (or epoxy, or other joining means). The injection tube  753  is bonded at a particular rotational orientation with respect to the aspiration lumen  749  such that the orifice  771  is oriented toward an opposing surface  775  in the aspiration lumen  749 . An unbonded section  777  extends a significant portion of the length of the aspiration catheter  741  in the proximal direction, thus allowing for enhanced flexibility and trackability. One of more of the individual features of the aspiration catheters  700 ,  740 ,  701 ,  741  of  FIGS. 49-52  may be rearranged to create other new embodiments. The individual features each allow the production of a small diameter aspiration catheter capable of tracking into distal vasculature, such as the vasculature of the head and neck, and also provide for aspiration including high pressure forced injection. 
       FIGS. 53-56  illustrate an insertable injection tube  920 , and a method for using it in a patient. The patient is not shown, for simplicity, and the devices are shown in a straight configuration, but in use, it is common for the devices to be tracked through tortuosities of a patient&#39;s vasculature. In  FIG. 53 , a microcatheter  924  is configured for tracking into the neurovasculature of a patient, including the Circle of Willis and the cerebral arteries. The microcatheter  924  may be incorporated as a component of an aspiration system  922  ( FIGS. 54-56 ), or may be a standard microcatheter purchased separately by a user. The microcatheter  924  comprises a shaft  926  having a proximal end  928  and a distal end  930 , with a lumen  932  extending through the shaft  926 . A luer hub  934  (e.g., female luer connector) is sealingly attached to the proximal end  928  of the shaft  926 . The microcatheter  924  may have a distal radiopaque marker (not shown), which is allied in a similar manner to the radiopaque marker bands  704 ,  744 ,  705 ,  745  in the aspiration catheters  700 ,  740 ,  701 ,  741  of  FIGS. 49-52 . A connector  936  includes a male luer  938  for connecting to the luer hub  934 , and can include a valve  940 , which may comprise a Touhy-Borst or the equivalent. The sideport  942  of the connector  936  may include a female luer for connecting to the male luer  650  of the extension tube  638  of the system  600  described in detail in relation to  FIG. 48 . In  FIG. 53  a user tracks the microcatheter  924  over a guidewire  944  into the blood vessels that are the region of interest. In some cases, the region of interest may be one of the cerebral arteries or other arteries in the vicinity, where a thrombus  946  ( FIG. 54 ) is causing a thromboembolic stroke in the patient. 
     In  FIG. 54 , the user removes the guidewire  944  and inserts the insertable injection tube  920  through the Touhy-Borst  940  and into the connector  936  and the lumen  932  of the microcatheter  924 . The insertable injection tube  920  may include a microfabricated cap  948 , as described in any of the embodiments of  FIGS. 49-52 , or may comprise an alternative configuration. However, the insertable injection tube  920  at the minimum comprises a high strength hollow tube  952  which may comprise stainless steel, nickel-titanium alloy, polyimide, or other high strength materials having sufficient column strength to be inserted through the lumen  932  of the microcatheter  924 . The microfabricated cap  924  includes an orifice  950  configured to provide a jet of pressurized fluid, similar to the orifice  771  of the microfabricated cap  757  in  FIG. 52 . In  FIG. 55 , the user advances the insertable injection tube  920  further through the lumen  932  of the microcatheter  924 , toward the distal end  930 . A stop  954  is bonded to the outside of the high strength hollow tube  952  and has a front face  956  configured to butt up against a proximal face  958  of the connector  936  when the center of the orifice  950  is located at the preferred distance (e.g., d 1 , as in  FIG. 49 ) from the distal end of the microcatheter  924 . The insertable injection tube  920  may be provided with different models, each having a different length between the front face  956  and the center of the orifice  950 , and each configured to be used with a particular length of microcatheter  924 , or a particular model of microcatheter  924 , or a particular microcatheter  924  model/connector  936  model combination. In some embodiments, the connector  936  may be a component of the insertable injection tube  920 , and instead of the Touhy-Borst  940 , may instead be permanently sealed and coupled to the high strength hollow tube  952  at a proximal region. Thus, the coupling of the male luer  938  to the luer hub  934  provides the longitudinal stop that controls the d 1  distance. 
     It may not always be possible to track an aspiration catheter  602  having high pressure injection forced aspiration capabilities ( FIG. 48 ) into the neurovasculature, because of the smaller diameters and tortuosities of the vessels. Thus, the insertable injection tube  920  allows a microcatheter  924  to be converted into a forced aspiration catheter. Thus, forced aspiration can occur in very distal locations, and locations that are distal to significant tortuosity, where normally microcatheters are the preferred access means. The small diameter insertable injection tube  920  is capable of being inserted through the lumen  932  of a microcatheter  924  after the microcatheter  924  is inserted into the region of interest. In alternative procedures and alternative embodiments of a system, a microcatheter  924  being inserted over a guidewire  944  may be replaced by a flow-directed catheter having a lumen configured for placement of the insertable injection tube  920  being inserted to the region of interest without a guidewire. 
       FIG. 57  illustrates a particular distal configuration of a distal end  913  of the insertable injection tube  920 . This configuration allows the microfabricated cap  948  and orifice  950  to be controllably and repeatably inserted through the lumen  932  of the microcatheter  924  such that the orifice is automatically oriented and the one or more jets emanating from the orifice  950  (or one or more orifices  950 ) are directed against an opposite wall  929  in the lumen  932  of the microcatheter  924 . The microfabricated cap  948  has a distal taper  960 , that may comprise a fillet or a bevel, or other type of lead-in shape. The purpose of the distal taper  960  is to facilitate the insertion into the connector  936 , the luer hub  934 , or the lumen  932  ( FIG. 54 ), and to ease the advancement of the microfabricated cap  948  through the lumen  932 , especially when the shaft  926  is in a tortuous condition. A spline loop  962  is coupled to the microfabricated cap  948  and may be formed from a wire, such as stainless steel or cobalt-chromium-nickel-molybdenum, or may comprise a superelastic material, such as a nickel-titanium alloy. The spline loop  962  is configured to have a diameter that is slightly less than, equal to, or slightly greater than the diameter of the lumen  932  of the microcatheter  924 . Turning to  FIG. 58 , a first end  921  of the spline loop  962  is bonded into a circumferential groove  923  in the microfabricated cap  948 . There is a gap  925  between the first end  921  and a second end  927  of the spline loop  962 , which allows space for the two ends  921 ,  927  to approach each other, and thus the diameter of the spline loop  962  to be forced smaller, for example, by stress placed on the spline loop  962  from the wall around the lumen  932  of the microcatheter  924 . Because the rotational orientation between the spline loop  962  and the microfabricated cap  948  are fixed in relation to each other (by the bonding of the first end  921  into the groove  923 ), the orifice  950  remains oriented toward an opposite wall  929  in the lumen  932 . The spline loop  962  is located at a different longitudinal position on the microfabricated cap  948  than the orifice  950 , and thus, the spline loop  962  does not block or deflect the jet emanating from the orifice  950 . In this embodiment, the spline loop  962  is slightly distal to the orifice  950 , though in other embodiments, it may instead be located proximally. In other alternative embodiments, the spline loop  962  (or any analogous structure) may actually be used to at least somewhat deflect the jet emanating from the orifice  950 , with the purpose of changing the shape or direction of the jet, for instance, deflecting it at least partially in a proximal longitudinal direction. In these alternative embodiments, therefore, it may actually be desired to have the spline loop  962  located at substantially the same longitudinal location as the orifice  950 . 
       FIG. 59 , the spline loop  962  is replaced by a spline ring  933 , which is attached to the high strength hollow tube  952  instead of to the microfabricated cap  948 . The spline ring  933  is formed from a flat wire (stainless steel or nickel-titanium alloy, or other) or from a stiff polymeric strip (polyimide or other stiff polymer), and has a shape somewhat like the number “6,” extending between a first end  935  and a second end  937 . A first loop portion  939  is configured to extend around the high strength hollow tube  952  for bonding thereon, and a second loop portion  941  serves the same purpose as the spline loop  962  of  FIGS. 57-58 , to guide the microfabricated cap  948  and to rotationally orient the orifice  950  within the lumen  932 . Other spline shapes may alternatively be used which also serve to maintain the microfabricated cap  948  against the wall on one side of the lumen  932 , and/or serve to resist rotation between the shaft  926  of the microcatheter  924  and either the high strength hollow tube  952  or the microfabricated tip  948  (whichever of the two includes the orifice  950 ). The spline loop  962  or the spline ring  933  may each be made from a radiopaque material, or may include a radiopaque material as a base, or plating or coating. Thus, during a procedure, it will be easier to visualize on x-ray or fluoroscopy the movement of the orifice  950  down the lumen  932  of the microcatheter  924 . The microfabricated cap  948  may also or may alternatively comprise a radiopaque material or radiopaque coating or plating. The insertable injection tube  920  in the embodiments presented, is configured to be removable from the lumen  932  of the microcatheter  924 , so that the microcatheter  924  may be subsequently used for one of its other functions (delivering embolic coils or embolic materials, drugs, replacing the guidewire  944  or even aspirating through the empty lumen  932 ). In alternative embodiments, the orifice  950  of the microfabricated cap  948  may be used to inject drugs or other materials into the vasculature, for example, by stopping or avoiding any vacuum or negative pressure placed on the proximal end of the lumen  932 . 
       FIGS. 60-63  illustrate a method for treating a patient using the aspiration system  600  of  FIG. 48 , using aspiration catheter  602 , or any of the alternative aspiration catheters  700 ,  740 ,  701 ,  741 . Alternatively, the method may be accomplished using the aspiration system  922 , or using the insertable injection tube  920  with a standard single lumen catheter, such as a microcatheter  924 , a guiding catheter, or a guide sheath (long sheath). In all of these systems, the pump  612  and the peristaltic pump  608  as described in  FIG. 48  can be utilized. In  FIG. 60 , an aspiration catheter  602  has been tracked into a blood vessel  943  (e.g., using a guidewire  648 ) and is advanced so that the open distal end  605  is adjacent the proximal end  945  of a thrombus  947 . In some cases, aspiration utilizing the high pressure injection from the pump  612  through the tubing set  664  combined with distal-to-proximal flow impulse imparted on the extension tube  638  by the peristaltic pump  608  are not enough to cause the thrombus  947  to be sufficiently aspirated into the open distal end  605  and into the aspiration lumen  604  so that it may be macerated and aspirated. At times, the cause for this is that a space  949  distal to the thrombus  947  acts as a relative vacuum and pulls on the thrombus with a force (e.g., distally, away from the aspiration catheter  602 ), thus making it difficult to aspirate the thrombus. Though the blood vessel  943  is shown in a relatively normal state, at time the blood vessel may have become collapsed because of lack of blood pressure from occlusion by the thrombus  947 . Other times, some of the thrombus  947  may have significantly solid or semi-solid portions that impede the ability to flow from a distal to proximal direction. 
     A user has encountered this condition while attempting to aspirate through operation of the pump  612  and peristaltic pump  608 , and the aspiration catheter  602  is inserted and advanced into the blood vessel  943  as shown in  FIG. 60 . The user then may use a technique with the aspiration system  600  to alleviate the substantially no flow condition. In  FIG. 61 , the user advances the aspiration catheter  602  so that the open distal end  605  of the aspiration lumen  604  is distal to the thrombus  947 . The advancement of the open distal end  605  of the aspiration catheter  602  through or past the thrombus  947  may be done without using a guidewire  648 , but in certain instances, the guidewire  648  will need to be used to cannulate and pass through or past the thrombus  947  and then to track the aspiration catheter  602 . 
     In  FIG. 62 , the user operates the pump  612  to inject fluid, while the peristaltic pump  608  is not being operated. Thus, pressurized fluid (e.g., heparinized saline, or saline mixed with a thrombolytic drug) is injected through the injection lumen  610  of the tube  678 , through the orifice  674 , into the aspiration lumen  604 , and then out the open distal end  605  (arrows) and into the space  949  in the blood vessel  943 . This occurs because there is no aspiration through the aspiration lumen  604 , and the stopped peristaltic pump  608  acts as a closed valve, with one of the rollers  632  compressing the compressible portion  637  of the extension tube  638 . The injection of the fluid increases the fluid volume of the space  949 , and by doing so, is able to also increase its internal pressure, thus neutralizing the prior relative vacuum effect caused by the space  949 . There is now flowable material in the space  949 , such that aspiration using the peristaltic pump  608  with the pump  612  can allow maceration and aspiration of the thrombus  947  to begin (by now turning on the peristaltic pump  608 ). The aspiration catheter  602  can also be retracted as shown in  FIG. 63 , to better contact the thrombus  947  and to increase the percentage of thrombus  947  being aspirated. This can be continued until all or at least a clinically significant portion of the thrombus  947  is aspirated. 
     Returning to  FIG. 62 , in certain cases, such as thromboembolic stroke, the downstream tissue may not be receiving sufficient flow because of the occlusion caused by the thrombus  947 . The user may run the fluid from the fluid source  679  through a cooling system, such as a heat exchanger or thermoelectric cooler  951  ( FIG. 48 ) through which the tubing set  664  may run, and by which the fluid may be cooled. Additionally, an extracorporeal circuit  953  ( FIG. 62 ) may be attached to the tubing set  664 , so that blood removed from the patient (e.g., via a femoral artery, femoral vein, or jugular vein sheath  955 ) is added to the fluid from the fluid source  679 , so that there is some oxygenated blood being injected into the space  949 , some which may potentially feed downstream tissue with oxygen or nutrients. The cooled fluid (saline, blood, or saline plus blood) can additionally reduce the metabolic demands of the downstream tissue by actively cooling it. The inventors have demonstrated that using a pump  612  that utilizes a removable cartridge having a piston, hemolysis can be maintained at an acceptably low value during this sort of injection and mixing of blood with the injected saline, from a mixture that includes about 10% blood, to a mixture that includes about 80% blood. 
       FIGS. 64-65  illustrate a method for treating a patient using the aspiration system  600  of  FIG. 48 , but incorporating an aspiration catheter  957  having a translatable injection tube  959 . The aspiration catheter  957  has an elongate shaft  963  having an aspiration lumen  965  with a proximal end  971  and an open distal end  961 . The translatable injection tube  959  has an injection lumen  973  having a proximal end  975  and a distal end  977 . The distal end  977  is coupled to a microfabricated cap  979  having an orifice  981 , such that pressurized fluid injected through the injection lumen  973  exits from the orifice  981 , as in the orifice  771  in  FIG. 52 . At a high enough injection pressure, the fluid may emanate from the orifice  981  in a jet. Alternatively, the distal end  977  of the injection lumen  973  may be plugged or capped, and there may be an orifice formed in the wall of the injection tube  959 , as in  FIGS. 49-51 . The pump  612  and the peristaltic pump  608  as described in  FIG. 48  can be utilized. In  FIG. 64 , the aspiration catheter  957  has been tracked into a blood vessel  943  (e.g., using a guidewire  648 ) and is advanced so that the open distal end  961  is adjacent the proximal end  945  of a thrombus  947 . A proximal female luer connector  983  is coupled to the injection lumen,  973 , and configured to couple to the male luer/distal end  670  of the tubing set  664 . A filter  985  may be interposed between the female luer connector  983  and the male luer  670 , to filter out particulate ( FIG. 65 ). 
     The filter has a proximal female luer  987  and a distal male luer  989 . The filter  985  may be used with any of the embodiments described herein, in which fluid may be injected (intentionally or not) into the bloodstream of a patient. 
     As described, in some cases, aspiration utilizing the high pressure injection from the pump  612  through the tubing set  664  combined with distal-to-proximal flow impulse imparted on the extension tube  638  by the peristaltic pump  608  are not enough to cause the thrombus  947  to be sufficiently aspirated into the open distal end  961  and into the aspiration lumen  965  so that it may be macerated and aspirated. A stiff tube  991  is bonded coaxially over the injection tube  959  at a proximal length, or the injection tube  959 , itself, may be made stiff proximally. The stiff tube  991  and/or the female luer connector  983  and/or the attached filter  985  can be gripped by the user, such that the user is able to advance the stiff tube  991  and the injection tube  959 , in turn, distally, such that the microfabricated cap  979  and the orifice  981  are translated distally, through the thrombus  947  and into the space  949  distal to the thrombus  947 . In some cases, being translated distally into a distal portion of the thrombus  947  may be sufficient. A dynamic seal  993  (o-ring, quad ring, etc.) can be sealed over the stiff tube  991  at all longitudinal positions of the stiff tube  991 . Once the orifice  981  is located within the space  949 , the pump  612  is operated without the operation of the peristaltic pump  608  (or with a significantly low setting of the peristaltic pump), such that fluid is injected through the injection lumen  973  and out the orifice  981 , into the space  949 . 
     The injection of the fluid increases the fluid volume of the space  949 , and by doing so, is able to also increase its pressure, thus neutralizing the prior relative vacuum effect from the space  949 . There is now flowable material within the space  949  such that aspiration using the peristaltic pump  608  with the pump  612  can allow maceration and aspiration of the thrombus  947  to begin (by now turning on the peristaltic pump  608 ). The shaft  963  of the catheter  957  can also be advanced and retracted during aspiration, to increase the percentage of thrombus  947  being aspirated. In addition, the injection tube  959  can be advanced or retracted, in relation to the catheter. The orifice  981  may be adjusted to an appropriate position inside the aspiration lumen  965 , or even slightly outside the aspiration lumen  965 . This can be continued until all or at least a clinically significant portion of the thrombus  947  is aspirated. As described, in relation to certain ischemic conditions caused by the thrombus  947 , including stroke, the user may run the fluid from the fluid source  679  through a cooling system, such as a heat exchanger or thermoelectric cooler  951  ( FIG. 48 ) through which the tubing set  664  may run, and by which the fluid may be cooled. Additionally, an extracorporeal circuit  953  (as in  FIG. 62 ) may be attached to the tubing set  664 , so that blood removed from the patient (e.g., via a femoral artery, femoral vein, or jugular vein sheath  955 ) is added to the fluid form the fluid source  679 , so that there is some oxygenated blood being injected into the space  949 , some which may potentially feed downstream tissue. The cooled fluid (saline, blood, or saline plus blood) can additionally reduce the metabolic demands of the downstream tissue. 
       FIGS. 66-69  illustrate a method for treating a patient using the aspiration system  600  of  FIG. 48 , but incorporating an aspiration catheter  967  having a translatable injection tube  969 . The aspiration catheter  967  has an elongate shaft  995  having an aspiration lumen  997  with a proximal end  999  and an open distal end  2066 . The translatable injection tube  969  has an injection lumen  2068  having a proximal end  2070  and a distal end  974 . The distal end  974  has a distal orifice  2072 , such that pressurized fluid injected through the injection lumen  2068  exits from the orifice  2072 , as in  FIG. 69 . At a high enough injection pressure, the fluid may emanate in a jet. The pump  612  and the peristaltic pump  608  as described in  FIG. 48  can be utilized. Turning to  FIG. 68  and  FIG. 70 , an occluder  976  comprising an elongate shaft  978 , and a handle  980  at its proximal end  984 , has an elastomeric occlusion element  982  coupled to its distal end  986  by a connection member  988 . The occlusion element  982  may comprise a circular ring or a spheroid or ovoid, and be formed of any elastomeric material, such as silicone, or thermoplastic elastomers. The occlusion element  982  has a diameter that is slightly larger than the diameter of the injection lumen  2068 , and is configured to significantly occlude flow distally to its particular longitudinal position within the injection lumen  2068 . The position shown in  FIG. 70  shows the occlusion element  982  occluding the injection lumen  2068  at a longitudinal position that is distal to a side orifice  990  in the wall  992  in the injection tube  969 . Thus, when the occluder  976  is in the position shown in  FIGS. 68 and 70 , the orifice  2072  is blocked by the occlusion element  982 , and pressurized fluid flows through the side orifice  990  (curved arrow,  FIG. 70 ). The connection member  988  may comprise a radiopaque material. A radiopaque marker  994  attached to the injection tube  969  may be viewed on x-ray or fluoroscopy along with the radiopaque connection member  988  to assess the particular relative longitudinal position of the occlusion element  982  with respect to the side orifice  990 . If desired, the radiopaque marker  994  may be located just proximal to the side orifice  990 , though it is shown just distal to the side orifice  990  in  FIG. 70 . If the occlusion element  982  is retracted as shown in  FIG. 71 , and the occluder  976  removed, as shown in  FIG. 69 , injection of fluid through the injection lumen  2068  may exit the orifice  2072 . The size of the side orifice  990  may be made small enough such that, when the occluder  976  is removed, most of the fluid injected exits the orifice  2072 , due to the fact that there is more resistance through the side orifice  990  than through the orifice  2072 . Thus, with the injection tube  969  in a particular longitudinal position in relation the shaft  995 , either injection through the orifice  2072  and into the space  949 , or injection through the side orifice  990  and into the aspiration lumen  997  of the aspiration catheter  967  may be selected, using the occluder  976 . 
       FIG. 72  illustrates an additional or alternative embodiment and step, that may be used in conjunction with the systems and steps of  FIGS. 66-69 . A blocking member  996  includes an elongate shaft  998 , which may be a larger diameter proximally and a smaller diameter distally. The blocking member  996  also includes a spiral blocking element (or feature)  899  at its distal end and a handle  897  at its proximal end. The blocking member  996  may be constructed of any of the or may include embodiments or features described in relation to blocking members described in the co-owned PCT Pub. No. PCT/US2018/029196 to Incuvate, LLC, filed Apr. 24, 2018 and published Nov. 1, 2018 as WO 2018/200566 A1, which is hereby incorporated by reference in its entirety for all purposes. The blocking element  899  is configured to be placed down the injection lumen  2068  and delivered out of the orifice  2072  and into the space  949 , as shown in  FIG. 72 , to catch potential distal emboli, and protect downstream tissue (brain tissue, heart tissue, etc.). In some embodiments, the blocking element  899  may be attached to the distal end of the occluder  976 , so that they are combined into a single component. Thus, the occluding described in relation to  FIGS. 68-71  may occur along with the distal protection/blocking described in relation to  FIG. 72 . 
     An alternative mode of using the aspiration system  1400 ′ of  FIG. 38  is shown in  FIG. 73 . The controller  1484  is programmed or programmable to command the peristaltic pump  1408  to operate bidirectionally, such that the rotatable head  1430  rotates in a back-and-forth manner, as shown in double-ended, curved arrow  1701 . The back-and-forth rotation can create a “regurgitate” mode for thrombus that has been pulled into the aspiration lumen  1404 ′ of the aspiration catheter  1402 ′. The controller  1484  may also be configured to shut down the pump  1412  while the peristaltic pump  1408  is in the “regurgitate” mode. The automatic cycling, by continual reversal of the motor, for example, allows the thrombus to be further macerated by the repetitive pulling and pushing cycles. The controller  1484  can be configured to perform a certain number of cycles and then to switch back to the aspiration direction (first rotational direction  1436  of  FIG. 38 ) to fully remove the thrombus. 
     Using  FIG. 36  as an example, but applying the description globally, in any of the embodiments described utilizing the peristaltic pump  1408 , an alternative operation mode is possible, wherein the peristaltic pump  1408  may be run backwards (opposite of the first rotational direction  1436 ), so that it is causing at least some of the fluid within the extension tubing lumen  1444  and/or the aspiration lumen  1404  of the aspiration catheter  1402  to be injected out of the open distal end  1405  of the aspiration lumen  1404 . For example, if the aspiration catheter  1402  is removed from the patient, material (thrombus, emboli, other clogged material) may be emptied out the open distal end  1405 , prior to reusing the aspiration catheter  1402 . In another use, with the aspiration catheter  1402  inside the vasculature, the proximal end  1442  of the extension tube  1438  may be placed into a container filled with contrast media or a lytic drug, or other drug, the peristaltic pump  1408  may then be run backwards to inject the contrast media, or drug into the vasculature of the patient. Thus, an additional injection site or the detaching of a luer connection is not required. 
     In another alternative operation mode, the peristaltic pump  1408  is stopped, or caused to be stopped by the controller  1484 , and a lytic drug is used as the fluid source  1479 . The pump  1412  is then used for pulsing lytic into the patient&#39;s vasculature (e.g., at or near a thrombus) through the open distal end  1405  of the aspiration lumen  1404 , via the high pressure injection lumen  1410  of the tube  1478 . By shutting off the peristaltic pump  1408 , the injection through the injection lumen  1410  (and out the orifice  1474 ) allows the lytic drug to be sent out the open distal end  1405 , into the vasculature of the patient. 
     Any of the aspiration systems  1400 ,  1400 ′,  1400 ″,  400 ,  600 ,  2100  utilizing the peristaltic pump  1408 ,  408 ,  608 ,  2102 / 2108  or the centrifugal pump  1409  together with an aspiration catheter  1402 ,  1402 ′,  402 ,  602  having both an aspiration lumen and an injection lumen can alternatively also be used with an aspiration catheter  202  having an aspiration lumen  204  and no injection lumen, or with an aspiration catheter  1402 ,  1402 ′,  402 ,  602  without injecting through the injection lumen. The peristaltic pump  1408 ,  408 ,  608 ,  2102 / 2108  or the centrifugal pump  1409  alone can be used for the aspiration of thrombus. 
     Using any of the aspiration systems described herein, a distal blood pressure may be measured in a diseased coronary artery, peripheral artery, or other artery by the open distal end of the aspiration lumen  1404  of the aspiration catheter  1402 , with the pumps  1408 ,  1412  turned off or uncoupled, in order to determine a value for Fractional Flow Reserve (FFR), as disclosed in U.S. Pat. No. 6,565,514, Method and System for Determining Physiological Variables, to Svanerudh et al., which is incorporated herein by reference in its entirety for all purposes. The pressure sensor  1416  may be used to measure the pressure in the aspiration lumen  1404 . For example, in a first step, the user assures that the pump  1412  is not actively pumping saline through the injection lumen  1410  and assures that the peristaltic pump  1408  is not actively aspirating through the aspiration lumen  1404 . In a second step, the user places the open distal end  1405  of the aspiration lumen  1404  distal to an atherosclerotic lesion, stenosis, or partial blockage of interest in an artery, or a partial blockage or stenosis caused significantly by thrombus, or by a combination of atherosclerosis and thrombus. The user then in a third step measures a pressure at the open distal end  1405  of the aspiration lumen  1404  using the aspiration monitoring system  1414  while also measuring a pressure proximal to the lesion, for example, with a pressure transducer coupled to a guiding catheter. In a fourth step, the user obtains or calculates the Fractional Flow Reserve (FFR), to help determine the significance of the stenosis of partial blockage. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments may be devised without departing from the basic scope thereof. 
     The ranges disclosed herein also encompass any and all overlap, sub-ranges, and combinations thereof. Language such as “up to,” “at least,” “greater than,” “less than,” “between,” and the like includes the number recited. Numbers preceded by a term such as “approximately”, “about”, and “substantially” as used herein include the recited numbers (e.g., about 10%=10%), and also represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of the stated amount.