Patent Publication Number: US-2020281610-A1

Title: Aspiration monitoring system and method

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/245,124, filed Aug. 23, 2016, which claims the benefit of priority to U.S. Provisional Application No. 62/211,637, filed on Aug. 28, 2015, U.S. Provisional Application No. 62/213,385, filed on Sep. 2, 2015, U.S. Provisional Application No. 62/239,795, filed on Oct. 9, 2015, U.S. Provisional Application No. 62/239,953, filed on Oct. 11, 2015, and U.S. Provisional Application No. 62/318,388, filed on Apr. 5, 2016, 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, or lumen of the body, such as a blood vessel. 
     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 (i.e. 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, a system for real time monitoring of catheter aspiration includes a pressure 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 vacuum source, 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 continuous signal which is proportional to measured fluid pressure. 
     In another embodiment, a system for real time monitoring of catheter aspiration includes a pressure sensor configured for placement in fluid communication with an aspiration lumen of a catheter, the aspiration lumen configured to couple to a vacuum source, a measurement device coupled to the pressure sensor and configured for measuring variations in fluid pressure, and a communication device coupled to the measurement device and configured to generate a continuous signal which varies proportionally as a result of variation in fluid pressure. 
    
    
     
       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 vacuum. 
         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 a syringe with a rotatable element according to an embodiment of the present disclosure. 
         FIG. 37  is a perspective view of an aspiration system utilizing one modification of the syringe of  FIG. 36  according to an embodiment of the present disclosure. 
         FIG. 38  is a side view of aspiration system utilizing another modification of the syringe of  FIG. 36  according to an embodiment of the present disclosure. 
         FIG. 39  is a plan view of an aspiration system according to another 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. 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 in the system or not. For example, the user may have difficulty determining whether the vacuum 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 is being applied to the aspiration catheter. The vacuum 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 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 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 vacuum 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 vacuum pressure 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 proper vacuum 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. 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 vacuum 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 vacuum. 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 vacuum may only exist from the proximal end of the aspiration lumen and distally up to the point of the thrombus. Thus, an insufficient vacuum may exist 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 vacuum 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 (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 amount of vacuum 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). 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 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 in the system of not. For example, whether the vacuum 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 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 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 vacuum) and a tubing kink proximal to the vacuum sensor  50  may be identified (for example, by a loss or degradation of vacuum). 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 vacuum). In some cases, a user may even forget to open the valve  8  to begin suction, 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 vacuum status. 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 over time for the condition of  FIG. 4A . The curve  98  represents vacuum 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  increases the vacuum up (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 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 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 the vacuum, 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 vacuum, 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 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 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 pressure is a negative pressure, 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 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. 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) measured by the sensor  50 . For example, as the amount of vacuum increases, an audible sound may increase in sound intensity or in sound pressure level (dB) proportionally. Or, as the amount of vacuum increases, the pitch (frequency) of an audible sound may made to rise, and as the amount of vacuum 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 vacuum 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 being applied at a pressure drop  808 , and a maintenance of vacuum  810   a  with a decrease in vacuum  812  and an increase in vacuum  814 . A removal of vacuum  816  is shown at the end of the pressure curve  802 . In some cases, the decrease in vacuum  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  812  is shown as temporary, as a subsequent maintenance of vacuum  810   b  is illustrated. The increase in vacuum  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 applied in the pressure curve  802  varies, in some embodiments, it may only be desirable to show to a user only whether the vacuum 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, thus giving the user an “on/off” awareness of the vacuum being applied. 
       FIG. 7  illustrates a graph  820  of time (x-axis) and multiple variables (y-axis). A pressure curve  822  shows a vacuum being applied at a pressure drop  828 , and a maintenance of vacuum  830   a  with a decrease in vacuum  832  and an increase in vacuum  834 . A removal of vacuum  836  is shown at the end of the pressure curve  822 . In some cases, the decrease in vacuum  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  832  is shown as temporary, as a subsequent maintenance of vacuum  830   b  is illustrated. The increase in vacuum  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 (or pressure 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 being applied, thus becoming louder as the vacuum is increased. 
       FIG. 8  illustrates a graph  840  of time (x-axis) and multiple variables (y-axis). 
     A pressure curve  842  shows a vacuum being applied at a pressure drop  848 , and a maintenance of vacuum  850   a  with a decrease in vacuum  852  and an increase in vacuum  854 . A removal of vacuum  856  is shown at the end of the pressure curve  842 . In some cases, the decrease in vacuum  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  852  is shown as temporary, as a subsequent maintenance of vacuum  850   b  is illustrated. The increase in vacuum  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 (or pressure 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 ×|(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 (l/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 being applied. In this embodiment, the pitch of the sound becomes “higher” when vacuum is increased (fluid pressure decreases), and “lower” when the vacuum is decreased. Alternatively, the opposite may instead by chosen, wherein the pitch of the sound becomes lower when vacuum is increased. 
       FIG. 9  illustrates a graph  860  of time (x-axis) and multiple variables (y-axis). A pressure curve  862  shows a vacuum being applied at a pressure drop  868 , and a maintenance of vacuum  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) 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) 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 is increased, and a decreased number of LEDs being lit when the level of vacuum 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 /ΔP )
         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 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 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 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 greater (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 lower (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 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 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 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 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 of the vacuum 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 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), 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 (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. Other contemplated embodiments of an assisted aspiration system  510  which may be utilized are disclosed in U.S. Patent Application No. 2010/0094201 to Mallaby (“Mallaby”) published Apr. 15, 2010, which is incorporated herein by reference in its entirety for all purposes. Other contemplated aspiration catheters are disclosed in U.S. Patent Application No. 2008/0255596 to Jenson et al. (“Jenson”) published Oct. 16, 2008, which is incorporated herein by reference in its entirety for all purposes. 
       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 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 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 suction function. 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 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 . 
       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 a syringe  10 ″ having a barrel  20 ″ that is configured to rotate as the plunger  86 ″ of the syringe  10 ″ is drawn from the barrel  20 ″. In some embodiments, the barrel  20 ″ and the corresponding plunger  86 ″ may include cooperating rotation elements that cause the barrel  20 ″ to rotate as the plunger  86 ″ is moved axially along (i.e., forced into or withdrawn from) a receptacle  24 ″ of the barrel  20 ″. 
     In one specific embodiment, an interior surface  23 ″ of the barrel  20 ″ carries one or more threads  27 ″ (two threads  27 ″ are shown in the illustrated embodiment). The threads  27 ″ are elongate, curved elements that may be at least partially helically oriented and configured to engage or to be engaged by cooperating features of the plunger  86 ″ and to cause rotational movement of barrel  20 ″ relative to the plunger  86 ″. In one particular embodiment, the threads  27 ″ protrude from the interior surface  23 ″ into the receptacle  24 ″ (e.g., as male threads). In another particular embodiment, the threads  27 ″ extend into the interior surface  23 ″ into the receptacle  24 ″ (e.g., as female threads). 
     An embodiment of the plunger  86 ″ that corresponds to the barrel  20 ″ may include an engagement feature  87 ″, such as the depicted notch, that receives and cooperates with a corresponding thread  27 ″, for example a male thread. In some embodiments, the engagement feature  87 ″ may be a protrusion which engages and cooperates with a corresponding thread  27 ″, for example a female thread. In a more specific embodiment, each engagement feature  87 ″ is formed in an alignment element  88 ″ of the plunger  86 ″. Even more specifically, each engagement feature  87 ″ may be formed in an edge  89 ″ of alignment the alignment element  88 ″ (illustrated as an alignment disk) of the plunger  86 ″. As shown, the alignment element  88 ″ may be located at a proximal end of the plunger  86 ″ (e.g., the end that will be located closest to an individual operating a syringe that includes the barrel  20 ″ and the plunger  86 ″). Edge  89 ″ of the alignment element  88 ″ may abut the interior surface  23 ″ of the barrel  20 ″ to align the plunger  86 ″ with the receptacle  24 ″ of the barrel  20 ″ as the plunger  86 ″ is forced through the receptacle  24 ″, along the length of the barrel  20 ″. As the plunger  86 ″ is inserted into the receptacle  24 ″ of the barrel  20 ″ and is driven axially along the length of the barrel  20 ″, each engagement element  87 ″ continues to engage its corresponding thread  27 ″. Due to the helical orientation of threads  27 ″, non-rotational movement of the plunger  86 ″ along the length of the barrel  20 ″ causes the barrel  20 ″ to rotate relative to the plunger  86 ″ as the plunger  86 ″ is forced through (i.e., into or out of) the receptacle  24 ″. In the depicted embodiment, movement of the plunger  86 ″ out of the receptacle  24 ″ (i.e., proximally, toward an individual using a syringe including the barrel  20 ″ and the plunger  86 ″) is effected as members  82 ″ and  84 ″ of handle  80 ″ are forced together. Members  82 ″ and  84 ″ of the handle  80 ″ may be rotationally joined to each other at a hinge joint  70 ″. In one embodiment, the barrel  20 ″ is rotationally and sealably held within a stationary cylindrical housing  40 ″ which is secured to member  82 ″ of the handle  80 ″. The barrel  20 ″ may be locked axially within the cylindrical housing  40 ″ by a snap fit, or other locking means. In another embodiment, the barrel  20 ″ is permanently and sealingly bonded within the cylindrical housing  40 ″ such that the barrel  20 ″ and the cylindrical housing  40 ″ are configured to rotate in unison. In this particular embodiment, the cylindrical housing is rotatably held by the member  82 ″ of the handle  80 ″. 
     Embodiments of syringes with rotatable elements and barrels  20 ″ that rotate relative to their plungers  86 ″ may be used in a variety of procedures, including, but not limited to, processes in which material (e.g., biological samples, samples from the body of a subject, aspiration of blood or thrombus/clot, etc.) is removed and/or obtained. 
     In a biopsy embodiment, a biopsy needle may be rigidly secured to the barrel  20 ″, for example at coupling element  28 ″. The coupling element  28 ″ may comprises a standard luer connector, such as a male luer lock connector. Movement of the plunger  86 ″ along the length of the barrel  20 ″ may cause the barrel  20 ″ and the attached biopsy needle to rotate about axes extending along their lengths, enabling use of the biopsy needle in a coring and aspiration technique to manually obtain a sample. A hand held syringe incorporating teachings of the present disclosure may be advanced and operated manually, even with a single hand, which may free the operator&#39;s other hand for a variety of purposes, including, without limitation, stabilization of a patient, control of an imaging device, such as an ultrasound apparatus, or the like. 
     In embodiments wherein a catheter is rigidly coupled to a barrel  20 ″(e.g., at the coupling element  28 ″) that rotates as its corresponding plunger  86 ″ is driven along its length, actuation of the plunger  86 ″ may rotate the catheter about an axis extending along its length, which may be useful in breaking up or dislodging obstructions, macerating and/or removing blood clots or thrombi, or in mixing fluids prior to or during their aspiration. 
       FIG. 37  illustrates an aspiration system  2 ″ utilizing an embodiment of the syringe  10 ″ which includes a first one-way valve  71 ″ between the aspiration catheter  73 ″ and the barrel  20 ″, which allows flow (for example of thrombus or blood) from the aspiration lumen  81 ″ of the aspiration catheter  73 ″ into the interior of the barrel  20 ″, in the direction of arrow B, but does not allow flow in the opposite direction. The flow may travel, for example, into the interior of the barrel  20 ″ during aspiration (e.g., when the members  82 ″ and  84 ″ are squeezed together). A vacuum source  77 ″ may be used to collect aspirated material (thrombus, blood, etc.) via an extension tube  75 ″.  FIG. 38  illustrates a system  3 ″ including a second one-way valve  79 ″ within the plunger  86 ″ which allows flow from the interior of the barrel  20 ″ to the vacuum source  77 ″, in the direction of arrow C, but does not allow flow in the opposite direction. The flow may travel, for example, towards the vacuum source  77 ″ when the members  82 ″ and  84 ″ are released. Both the first one-way valve  71 ″ and the second one-way valve  79 ″ may be incorporated together in either the system  2 ″ of  FIG. 37  or the system  3 ″ of  FIG. 38 . A pressure transducer  12  may be used as part of any of the aspiration monitoring systems described herein to determine the status of the aspiration utilizing the system  2 ″ or the system  3 ″. In system  2 ″ of  FIG. 37 , the pressure transducer  12  is located within the interior of the barrel  20 ″, while in system  3 ″ of  FIG. 38 , the pressure transducer  12  is located in-line between the aspiration catheter  73 ″ and the coupling element  28 ″. In some embodiments, the pressure transducer  12  may be a separate component that is attached at one end to the aspiration catheter  73 ″ and at the other end to the coupling element  28 ″. For example, the pressure transducer  12  may be supplied separately, and may be configured for the user to couple to the aspiration catheter  73 ″ and the coupling element  28 ″ in order to perform a procedure. In some embodiments, the pressure transducer  12  may be supplied as part of the coupling element  28 ″, and be configured to be attached to the aspiration catheter  73 ″. In some embodiments, the pressure transducer  12  may be supplied as part of the aspiration catheter  73 ″ and be configured to be attached to the coupling element  28 ″. Feedback from the pressure transducer  12  via the aspiration monitoring system may alert the user when to squeeze the members  82 ″ and  84 ″, or when to release the members  82 ″ and  84 ″, or when to replace the vacuum source  77 ″. For example, the aspiration monitoring system may be configured to alert the user when the vacuum has decreased below a threshold, and may send a message to the user, such as, “squeeze handle.” Additionally, the aspiration monitoring system may be configured to alert the user when a no-flow condition is identified, indicating possible clogging, and may send a message to the user such as “release handle” or “replace syringe.” 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2014/0200483 to Fojtik, published Jul. 17, 2014, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Fojtik, U.S. Patent Application No. 2014/0200483, while remaining within the scope of the present disclosure. 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2004/0116873 to Fojtik, published Jun. 17, 2004, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Fojtik, U.S. Patent Application No. 2004/0116873, while remaining within the scope of the present disclosure. 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2012/0022404 to Fojtik, published Jan. 26, 2012, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Fojtik, U.S. Patent Application No. 2012/0022404, while remaining within the scope of the present disclosure. 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2014/0142594 to Fojtik, published May 22, 2014, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Fojtik, U.S. Patent Application No. 2014/0142594, while remaining within the scope of the present disclosure. 
     Any of the embodiments described herein may be used conjunction with any model of the Aspire Aspiration Platform syringe (Control Medical Technology, LLC, Park City, Utah, USA), having either a rotating barrel or a non-rotating barrel. 
     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, a manually-actuated syringe configured to aspirate liquid, the syringe including one or more actuation elements which control the amount of vacuum applied to the interior of the syringe and a connector configured for fluid connection, and a monitoring device including a housing having a first port adapted for detachable connection to the connector of the syringe and a second port adapted for detachable connection with the catheter, a pressure sensor in fluid communication with an interior of the housing, a measurement device coupled to the pressure sensor and configured for measuring one or more deviations in fluid pressure, and a communication device coupled to the measurement device and configured to generate a signal related to a deviation in fluid pressure measured by the measurement device. 
     In another 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, a manually-actuated syringe configured to aspirate liquid, the syringe including one or more actuation elements which control the amount of vacuum applied to the interior of the syringe and a connector configured for fluid connection, and a monitoring device including a pressure sensor in fluid communication with an interior of the syringe, a measurement device coupled to the pressure sensor and configured for measuring one or more deviations in fluid pressure, and a communication device coupled to the measurement device and configured to generate a signal related to a deviation in fluid pressure measured by the measurement device. 
     An aspiration system  1400  is illustrated in  FIG. 39  and comprises an aspiration catheter  1402  that is configured to be deliverable over a guidewire  28 . The aspiration catheter  1402  includes a high pressure fluid injection lumen  1404  and an aspiration lumen  1406 . The aspiration lumen  1406  extends from the proximal end  1412  of the aspiration catheter to a distal end and is configured to also serve as a guidewire lumen. A first y-connector  1410  is coupled to the proximal end  1412  of the aspiration catheter  1402  and communicates with for the high pressure fluid injection lumen  1404  and the aspiration lumen  1406 . The high pressure fluid injection lumen  1404  may be configured in a similar manner to the high pressure fluid injection lumen  536  of the embodiment of  FIG. 17 , the injection lumen  1225  of the embodiment of  FIG. 18  or the injection lumen  1257  of  FIG. 21 . A sideport  1420  of the first y-connector  1410  is in fluid communication with the high pressure injection lumen  1404  and a proximal port  1422  is in fluid communication with the aspiration lumen  1406 . The first y-connector  1410  may be permanently attached to the proximal end  1412  of the aspiration catheter  1402 , or may be connectable to the proximal end  1412 , for example, by luer connections. A tubing set  1414  having a cassette  1416  with a piston  1418  is configured to be coupled to the sideport  1420  of the first y-connector  1410 , and is also configured to be coupled to and used with the pump  1254  of  FIG. 24 , or other equivalent pumps. The proximal port  1422  of the first y-connector  1410  is configured to be coupled to a distal port  1424  of a second y-connector  1426 . The proximal port  1422  of the first y-connector  1410  and the distal port  1424  of the second y-connector  1426  may be luer connectors, but alternatively, they may be permanently connected. Alternatively, the first y-connector  1410  and the second y-connector  1426  may be integrally formed, for example by injection molding or casting. The second y-connector  1426  includes a sideport  1428  and a hemostasis valve  1430  (Touhy-Borst, spring-loaded seal, etc.). The hemostasis valve  1430  is configured for sealing over the guidewire  28  and may be adjustable or actuatable in order to more easily move advance and retract the guidewire  28 , distally and proximally. The sideport  1428  is configured to couple to a pressure sensor  1432  having a cable  1434  for carrying one or more signals. The pressure sensor  1432  is configured to interface with the console  1276  of  FIG. 22  or other equivalent consoles. A vacuum source  1436  may be coupled to the sideport  1428 /pressure sensor  1432  as described herein. In this particular embodiment, the vacuum source  1436  is syringe. A valve  1438  is placed in between the vacuum source  1436  and the pressure sensor  1432 , in fluid communication with each, and allows the user to open or close the connection between the vacuum source  1436  and the pressure sensor  1432 . 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2007/0073233 to Thor et al. (“Thor”) published Mar. 29, 2007, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Thor, while remaining within the scope of the present disclosure. 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2001/0051811 to Bonnette et al. (“Bonnette”) published Dec. 13, 2001, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Bonnette, while remaining within the scope of the present disclosure. 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2014/0155931 to Bose et al. (“Bose”) published Jun. 5, 2014, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Bose, while remaining within the scope of the present disclosure. 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2010/0204672 to Lockhart et al. (“Lockhart”) published Aug. 12, 2010, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Lockhart, while remaining within the scope of the present disclosure. 
     Any of the embodiments described herein may include some or all features of any of the embodiments described in U.S. Patent Application No. 2007/0225739 to Pintor et al. (“Pintor”) published Sep. 27, 2007, which is incorporated herein by reference in its entirety for all purposes; in addition, any of the features described herein may be incorporated into any of the embodiments described in Pintor, while remaining within the scope of the present disclosure. 
     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.