Patent Publication Number: US-11040140-B2

Title: Deep vein thrombosis therapeutic methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 13/340,120, filed Dec. 29, 2011, which claims priority to and the benefit of U.S. Provisional Patent Application No. 61/429,058, filed Dec. 31, 2010, which are incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     This invention relates to monitoring functional parameters of a vessel when an interventional therapy is administered. 
     BACKGROUND 
     Deep vein thrombosis (DVT) is a medical condition that results from the formation of a blood clot, or thrombus, within a vein. Thrombi often develop in the calves, legs, or other lower abdomen, but may occur in other vessels. The clot is typically formed from a pooling of blood within the vein due to abnormally long periods of rest, e.g. when an individual is bed ridden following surgery or suffering a debilitating illness. Thrombi are likely to form at the location of a stenosis, an unnatural narrowing of an artery. Other causes of thrombosis include genetic deficiencies, autoimmune disorders, and endothelial cell injury. 
     The thrombus may partially or completely block blood flow. In some circumstances, the thrombus may break off and travel through the blood stream causing serious health issues. For example, when a thrombus of the lower extremities breaks off, the thrombus may travel through the lungs and cause a pulmonary embolism. A pulmonary embolism is a blockage of the blood supply to the lungs that causes severe hypoxia and cardiac failure. It frequently results in death. 
     Thrombolysis, also known as thrombolytic therapy, is a procedure that disrupts and eliminates blood clots (such as those causing DVT) within the vasculature. Currently, there are several different thrombolytic treatment procedures. For example, thrombolysis may involve the delivery of pharmaceutical drugs designed to dissolve clots within the bloodstream. The drugs can be intravenously injected or can be delivered directly to the blood clot using a catheter. Other modes of treatment include using interventional catheters with ablative, cutting, or ultrasonic elements that mechanically break-up the blood clot within the vasculature. 
     Removal of blockages using a catheter (drug delivery or interventional) is a complicated procedure that requires complete dissolution of the blockage to restore blood flow/pressure and reduce re-clotting. Some techniques use angiography to monitor the blockage removal; however, angiogram images alone do not provide enough information to determine whether dissolution is complete. 
     SUMMARY 
     Methods of the invention provide for more complete dissolution of thrombi within a vessel than possible using angiography and other external imaging modalities. Aspects of the inventions are accomplished by using a sensing device with one or more functional measurement sensors before, during, and/or after the thrombolytic therapy. In preferred embodiments, the sensing device is a sensing guidewire. By measuring functional parameters (such as pressure and flow) with a sensing guidewire, one is able to continually monitor the thrombolytic procedure because the interventional catheter for removing the thrombi can be driven over the sensing guidewire. In certain embodiments, the sensing device may also include an imaging element. 
     Methods of the invention may be used to assess and monitor treatment of any stenosis or thrombosis, and are particularly well-suited to assess thrombolysis of clots associated deep vein thrombosis. Because functional flow measurements may be obtained prior to initiation, during, and after thrombolytic treatment, sensing devices of the invention may be used to assess the extent of the blockage, monitor progress of the clot dissolution throughout the procedure, and evaluate the success of the deep vein thrombosis treatment. Specifically, sensing devices, in accordance with the invention, may be used to determine when blood flow and pressure has been re-established, determine the extent to which flow and pressure has been established, guide a clinician to determine if more therapy is needed, determine when therapy is complete, and assess the health of the vessel after treatment. 
     Sensing devices for use in methods of the invention may include a guidewire, catheter, or other intraluminal device with one or more data collectors for obtaining functional measurements. Typically, the data collector for obtaining functional data is a pressure sensor, flow sensor, or combination thereof. Preferably, the intraluminal device is a guidewire with both a pressure sensor and a flow sensor on a distal portion of the device. Pressure sensors are able to obtain pressure measurements and flow sensors are able to obtain velocity measurements within a blood vessel. The ability to measure and compare both the pressure and flow significantly improves the diagnostic accuracy of ischemic testing. 
     Functional measurements obtained from the data collectors can include, for example, determinations of pressure and/or flow in the vicinity of a clot. In certain embodiments, functional measurements are obtained proximal and distal to a clot, which can then be compared to discern the extent of the blockage and the success of the treatment. Other suitable functional measurements can involve manipulations of the pressure and/or flow data to arrive at other functional parameters, including without limitation, fractional flow reserve (FFR), instantaneous wave-free ratio (iFR), and coronary flow reserve (CFR). 
     Methods of the invention may be used to monitor any thrombolytic treatment used to break-up or dissolve blood clots within the vasculature of a patient. The thrombolytic treatment may be non-invasive or invasive. Non-invasive thrombolytic treatment may involve injecting clot-dissolving medications into one&#39;s bloodstream. Invasive thrombolytic treatment commonly includes introducing an interventional catheter into the vasculature and mechanically/chemically dissolving the blood clot. Several different types of interventional catheters may be used for thrombolytic treatment, including morcellating catheters, ablative catheters, drug delivery catheters, and ultrasonic catheters. In certain aspects, clot-dissolving medicines are used in combination with any of the above-described interventional catheters to perform thrombolysis. 
     In addition, methods of the invention may be used to assess and treat clotting associated with multiple sclerosis (MS), pulmonary embolisms, clots associated with ischemic stroke, and clots associated with dialysis bypass grafts. In one series of embodiments, the invention consists of methods and devices for identifying patients whose MS, or MS symptoms, are likely exacerbated if not caused, at least in part, by blockages of one or more of the patient&#39;s internal jugular veins (UV) or azygous veins (AZV). In preferred embodiments of the diagnostic methods, the stenoses in the patient&#39;s affected veins are identified. In other embodiments of the present diagnostic methods, the nature of such lesions and whether there is a significant disruption of blood pressure or flow, or both, is ascertained. 
     The invention will be described hereafter in detail with particular reference to the drawings. Throughout this description, like elements, in whatever embodiment described, refer to common elements wherever referred to and referenced by the same reference number. The characteristics, attributes, functions, interrelations ascribed to a particular element in one location apply to that element when referred to by the same reference number in another location unless specifically stated otherwise. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         FIG. 1  is a flow chart of a method for treating an occluded vessel according to certain embodiments. 
         FIG. 2  is a flow chart of another method for treating an occluded vessel according to certain embodiments. 
         FIG. 3  is a flow chart of an embodiment of the diagnostic method of the present invention. 
         FIG. 4  is a flow chart of another embodiment of the diagnostic method of the present invention. 
         FIG. 5  is a flow chart of another embodiment of the diagnostic method of the present invention. 
         FIG. 6  is a flow chart of another embodiment of the diagnostic method of the present invention. 
         FIG. 7  is a schematic view of an embodiment of the diagnostic device of the present invention. 
         FIG. 8  is a flow chart of an embodiment of the therapeutic method of the present invention. 
         FIG. 9  is a flow chart of an alternate embodiment of the therapeutic method of the present invention. 
         FIG. 10  is a flow chart of an embodiment of the therapy delivered as the therapeutic method of the present invention. 
         FIG. 11  is a side cross-sectional schematic view of a device of a therapy that could be applied as the therapy of the any of the therapeutic methods of the present invention. 
         FIG. 12  is a side cross-sectional schematic view of a device of a therapy that could be applied as the therapy of the any of the therapeutic methods of the present invention. 
         FIG. 13  is an end schematic view of the device of  FIG. 12 . 
         FIG. 14  is a side cross-sectional schematic view of a device of a therapy that could be applied as the therapy of the any of the therapeutic methods of the present invention. 
         FIG. 15  is a side cross-sectional schematic view of an alternate embodiment of the device of  FIG. 14 . 
         FIG. 16  is a side cross-sectional schematic view of a device of a therapy that could be applied as the therapy of the any of the therapeutic methods of the present invention. 
         FIG. 17  is a schematic view of an embodiment of the therapeutic device of the present invention. 
         FIG. 18  is a flow chart of another embodiment of the therapeutic method of the present invention. 
         FIG. 19  is a flow chart of another embodiment of the therapeutic method of the present invention. 
         FIG. 20  is a flow chart of another embodiment of the therapeutic method of the present invention. 
         FIG. 21  is a flow chart of another embodiment of the therapeutic method of the present invention. 
         FIG. 22  is a flow chart of another embodiment of the therapeutic method of the present invention. 
         FIGS. 23 and 24  illustrate a sensing device suitable for use in methods of the invention. 
         FIGS. 25 and 26  illustrate a sensor housing of the sensing device of  FIGS. 23 and 24 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention provides methods for assessing a thrombolytic procedure through the use of functional or physiological parameters. Methods of the invention involve introducing a sensing device into a vessel having a thrombus (and/or stenosis) and using the sensing device to evaluate the thrombus before, during, or after thrombolytic treatment. In some embodiments, the sensing device is used throughout the thrombolytic procedure. Methods of the invention are well suited to monitor the success of deep vein thrombosis treatment, but may also be used to assess thrombolysis of other thrombotic conditions, including multiple sclerosis and stroke ischemia. 
     Any functional or physiological measurement is useful for practicing the invention. Exemplary physiological parameters include blood pressure or flow (velocity) inside the vasculature within the vicinity of the thrombosis. Pressure, flow, or both are measured at various stages of the thrombolytic procedure near the thrombosis. The pressure and flow measurements may be compared to a reference baseline. The reference baseline may be measurements associated with a normal, healthy population or a reference baseline specific to the individual subject to therapy (e.g., measured pressure/flow levels of the patient prior to the thrombosis). According to methods of the invention, a clinician may use those functional measurements to assess whether the thrombus has dissolved/removed to an extent that normal or acceptable blood flow and pressure has been established. 
     In certain aspects of the invention, these initial functional measurements may be further processed to determine other clinically relevant measurements, such as Fractional Flow reserve measurements, Coronary Flow reserve measurements, instantaneous wave-free ratio (iFR), combined P-V curves. 
     Coronary flow reserve is defined as the ratio of maximal coronary flow with hyperemia to normal flow. Coronary flow reserve is based on the principle that blood velocity is proportional to volume flow if the lumen area remains constant. Coronary flow reserve signifies the ability of the myocardium to increase blood flow in response to maximal exercise. A ratio at or above 2 is considered normal. Coronary flow reserve measures the velocity of the flow. The fractional flow reserve is defined as the ratio of maximal blood flow achievable in a thrombotic artery relative to the maximal flow in the same vessel if it were normal. Fractional flow reserve measure pressure differences across a portion of a vessel to determine whether a level of constriction or thrombosis of the vessel will impede oxygen delivery to the heart muscle. In order to obtain FFR, a level of pressure distal to a portion of a vessel under examination can be compared to a level of pressure proximal to a portion of a vessel under examination. When used in methods of the invention, changes in coronary flow reserve or fractional flow reserve within a vessel during thrombolytic procedure are indicative that the clot is being dissolved. The procedure may continue until ideal coronary or fractional flow reserve measurements are obtained, thereby indicating the success of the procedure. 
     P-V loops provide a framework for understanding cardiac mechanics. Such loops can be generated by real time measurement of pressure and volume within the left ventricle. Several physiologically relevant hemodynamic parameters such as stroke volume, cardiac output, ejection fraction, myocardial contractility, etc. can be determined from these loops. To generate a P-V loop for the left ventricle, the LV pressure is plotted against LV volume at multiple time points during a single cardiac cycle. The presence of a thrombus can alter the curve/shape of P-V loop from a normal P-V loop. 
     The instantaneous wave-free ratio (iFR) is a vasodilator-free pressure-only measure of the hemodynamic severity of a stenosis or thrombosis comparable to fractional flow reserve (FFR) in diagnostic categorization. 
     The pressure and velocity measurements, particularly regarding the pressure drop-velocity relationship such as Fractional Flow reserve (FFR), Coronary flow reserve (CFR), iFR, and combined P-V curves, can be used to reveal information about the thrombosis and the thrombolytic proceedure. For example, in use, a functional flow device may be advanced to a location relatively distal to a thrombus. The pressure and/or flow velocity may then be measured for a first time. Then, the device may be advanced to a location relatively proximal to the thrombosis and the pressure and/or flow is measured for a second time. The pressure and flow relationships at these two time points are then compared to assess the current state of the thrombolytic procedure and provide improved guidance for the need to continue with or stop the procedure. The ability to take the pressure and flow measurements at the same location and same time with a combined pressure/flow guidewire, improves the accuracy of these pressure-velocity loops and therefore improves the accuracy of the diagnostic information. 
     Coronary flow reserve, Fractional flow reserve, iFR, and P-V loops may require measurements taken at different locations in the artery. In order to provide measurements for these parameters, systems and methods of the invention may assess pressure and flow at a first location of the data collector against a second location of the data collector within the vasculature. For example, a first location that is distal to a segment of a vessel under examination and a second location that is proximal to that segment of a vessel. 
     In order to obtain the physiological data described above, methods of the invention may involve the use of a functional measurement or sensing device. The functional measurement device may be equipped with a pressure sensor, a flow sensor, or any combination thereof. Exemplary functional measurement devices suitable for use in practicing the invention include FloWire Doppler Guidewire and the ComboWire XT Guidewire by Volcano Corporation. 
     Preferably, the sensing device is a guidewire, although the sensing device may also be a catheter. Sensing guidewires are particularly advantageous because they may remain in the vasculature during the thrombolytic procedure while an interventional catheter is driven (ridden) over the sensing guidewire. In this manner, functional flow measurements may be obtained at the same time the thrombolytic catheter is mechanically (ablation, morcellation, or ultrasonic) and/or chemically (with clot dissolving substances) breaking up the blockage. 
     Guidewires are described in more detail in reference to  FIGS. 23-26 . In particular embodiments, a pressure sensor can be mounted on the distal portion of a guidewire. In certain embodiments, the pressure sensor is positioned distal to a compressible and bendable coil segment of the guidewire. This allows the pressure sensor to move along with the along coil segment as bended and away from the longitudinal axis. The pressure sensor can be formed of a crystal semiconductor material having a recess therein and forming a diaphragm bordered by a rim. A reinforcing member is bonded to the crystal and reinforces the rim of the crystal and has a cavity therein underlying the diaphragm and exposed to the diaphragm. A resistor having opposite ends is carried by the crystal and has a portion thereof overlying a portion of the diaphragm. Electrical conductor wires can be connected to opposite ends of the resistor and extend within the flexible elongate member to the proximal portion of the flexible elongate member. Additional details of suitable pressure sensors that may be used with devices of the invention are described in U.S. Pat. No. 6,106,476. U.S. Pat. No. 6,106,476 also describes suitable methods for mounting the pressure sensor  104  within a sensor housing. 
     A flow sensor can be used to measure blood flow velocity within the vessel, which can be used to assess coronary flow reserve (CFR). The flow sensor can be, for example, an ultrasound transducer, a Doppler flow sensor or any other suitable flow sensor, disposed at or in close proximity to the distal tip of the guidewire. The ultrasound transducer may be any suitable transducer, and may be mounted in the distal end using any conventional method, including the manner described in U.S. Pat. Nos. 5,125,137, 6,551,250 and 5,873,835. 
     A pressure sensor allows one to obtain pressure measurements within a body lumen. A particular benefit of pressure sensors is that pressure sensors allow one to measure of FFR in vessel. FFR is a comparison of the pressure within a vessel at positions prior to the stenosis and after the stenosis. The level of FFR determines the significance of the stenosis, which allows physicians to more accurately identify clinically relevant stenosis. For example, an FFR measurement above 0.80 indicates normal coronary blood flow and a non-significant occlusion. Another benefit is that a physician can measure the pressure before and after an intraluminal intervention procedure to determine the impact of the procedure. 
     The acquisition of functional measurements typically involves the insertion of a pressure, flow, or combination guidewire into a blood vessel and measuring pressure and/or flow inside the vessel with the device. In practice, measuring pressure and/or flow inside the vessel may also involve injecting a local anesthetic into the skin to numb the area of the patient prior to surgery. A puncture is then made with a needle in either the femoral artery of the groin or the radial artery in the wrist before the provided guidewire is inserted into the arterial puncture. Once positioned, the guidewire may then be used to measure pressure and/or flow in the vessel. 
       FIG. 1  provides a flow chart for assessing and treating a thrombus, such as a blood clot located in the deep veins, according to one embodiment. As shown in  FIG. 1 , the first step includes identifying venous outflow obstruction site(s)  310 . Typically, venous obstruction sites, which are the locations of the thrombus and/or stenosis, are identified using an external imaging modality, such as angiogram, fluoroscopy, ultrasound, etc., although internal imaging modalities, such as IVUS or OCT, can also be used. Next in step  310 , a sensing device is inserted into the identified obstruction site in order to obtain functional data regarding the severity of the obstruction due to the thrombus or stenosis. Based on the functional data, the thrombolytic procedure may be performed (as indicated in step  330 ). The functional data may provide guidance as to whether the thrombolytic procedure required to treat the thrombus should be invasive or non-invasive. For example, if the functional data indicates that the thrombus is only partially blocking the vessel, then non-invasive therapy with anticoagulants may be indicated. However, if the functional data indicates that the thrombus is a total occlusion, then thrombolysis with an interventional catheter may be indicated. 
       FIG. 2  provides a flow chart for assessing and treating a thrombus, such as a blood clot located in the deep veins, according to another embodiment. This embodiment includes steps  310 ,  320 , and  330  of  FIG. 1 , but also involves monitoring functional data during the thrombolytic therapy. As indicated in  FIG. 2 , after commencement of interventional therapy (step  330 ), the method further provides for assessing one or more functional measurements during commencement of the therapy (as in step  340 ). When the sensing device is a guidewire, the sensing device can obtain the functional measurements without having to remove the interventional catheter because the interventional catheter can be ridden over the sensing guidewire. In addition, when the thrombolysis procedure is non-invasive, the sensing device, whether guidewire or catheter) can remain in the vessel during administration of the thrombolysis medicine. In both cases, the sensing device can obtain functional measurements while the interventional therapy is commencing. In further embodiments, the sensing device can be used to obtain functional measurements between bouts of interventional therapy. Based on the assessment step  340 , methods of the invention provide for stopping interventional therapy if the functional measurements indicate that the pressure, flow, and related parameters (e.g. FFR or CFR) are normal or acceptable (as in step  350 ). Alternatively, methods of the invention provide for continuing interventional therapy if the functional measurements indicate that the pressure, flow and related parameters are not normal or acceptable (as in step  350 ). In such case, the method repeats steps  330  and  340  until the functional measurements indicate that thrombolytic therapy should stop (as in step  350 ). 
     The following describes variations of the framework method for assessing stenosis and/or thrombosis of a vessel outlined in  FIG. 1 . The variations include specific diagnostic and treatment applications, such as specific ways for identifying the venous outflow obstruction sites and specific types of interventional therapy. While subsequent flow charts state diagnosis and treatment of stenosis, it is understood that the diagnostic and treatment methods described herein are applicable to any obstructions, including thrombus and thrombus caused by stenosis. The interventional therapy for thrombolysis may also be used for angioplasty procedures, as invasive thrombolysis is often the same procedure angioplasty. 
       FIGS. 3-6  depict variations of diagnosing steps (i.e. identifying step  310  and assessing step  320  of  FIGS. 1 and 2 ) the thrombus or stenosis prior to interventional therapy (step  330  of  FIGS. 1 and 2 ). 
     In a diagnostic method  26  shown in  FIG. 3 , the diagnostic method begins at step  36  where venous outflow obstruction sites are identified. A preferred method of identifying these obstruction sites is by sequentially accessing the vasculature by selective venography at each of these sites to confirm or exclude a significant stenosis or flow disruption. For deep vein thrombosis, the lower vasculature will be examined, such as the inferior vena cava and femoral veins. For multiple sclerosis assessment, the superior vena cava and common jugular veins should ideally be assessed first. Venography, which is also called phlebography, involves taking an x-ray of the veins, a venogram, after a special dye is injected via a catheter into the vein of interest. Typically, the dye is injected constantly via a catheter. As a result, a venography is an invasive procedure. Although venography has been a preferred method for selecting sites having significant stenosis or flow disruption, ultrasonography, including duplex ultrasonography, could also be used in the alternative or in addition to identify obstructed outflow sites. Ultrasonography incorporates two elements: 
     1) Grayscale Ultrasound (e.g., from an IVUS imaging system  2 ) is used to visualize the structure or architecture of the vein to identify stenoses (cross-sectional narrowing of the vein); 
     2) Color-Doppler ultrasound imaging (e.g., from Volcano Corporation) is then used to visualize the flow or movement of a blood within the vein; and typically presents both displays on the same screen (“duplex”) to facilitate interpretation. 
     Where ultrasonography is used, a stenosis having cross-sectional narrowing greater than about 70% is considered worthy of treatment as are blood flow velocities greater than 250 cm/sec (which also indicate a region of narrowing or resistance produced by a major stenosis). Ultrasonography can also be enhanced by tissue characterization such as the virtual histology characterization described above, for example, as part of the s5i™ Imaging System with VH capability sold by Volcano Corporation of San Diego, Calif. 
     Besides venography and ultrasonography, transcutaneous echography applied to an accessible section of the targeted veins could also be used to identify venous outflow obstruction sites and to confirm or exclude a significant stenosis or flow disruption at those sites. Further, in an embodiment of the invention, radionuclides that bind to proteins specific to fibrin, such as radionuclides bound to insulin-like growth factor (IGF) binding proteins (IGFBPs) are applied intravenously, preferably near where an obstruction is believed to be located, or orally. Then, external detectors such as gamma cameras capture and form images from the detected radiation emitted by the radionuclides that are bound to the proteins of the fibrin. This allows the areas of venous outflow obstruction caused by the buildup of thrombus to be located and to confirm or exclude a significant stenosis or flow disruption at the site. These last two methods have the desirable characteristic of being non-invasive. 
     In a modification of the invention above where something is bound to proteins specific to fibrin, plasmin, other plasmids or any like substance that dissolves fibrin is bound to the same IGFBP that contains the radionuclide or to an entirely different IGFBP and then delivered to the site of the fibrin as described above. The plasmin, plasmid or other substance that dissolves fibrin in whatever form may be self-activated (i.e., it is active upon delivery) or may be activated by the exposure to either a specific light frequency or by ultrasound at a specific frequency or any like energy source delivered either intravascularly or noninvasively. Where these substances are active by a specific light frequency or by ultrasound at a specific frequency, the light or ultrasound or both may be delivered via the distal optics or transducer, respectively. 
     Once the venous outflow obstruction sites have been identified by whatever method, the method passes to step  38 . In step  38 , the nature of the stenotic lesion or thrombosis is assessed. This assessment is preferably accomplished by applying an imaging system such as an IVUS or OCT system or a system having both IVUS and OCT or applying both IVUS and OCT imaging to suspected areas of narrowing or flow disruption to identify intraluminal abnormalities including webs, flaps, inverted or incompetent valves and membranes as well as stenoses caused by plaque or the buildup of fibrin or thrombus. Here, a significant stenosis or thrombosis, of whatever kind, is defined as luminal reduction greater than 50% of the normal venous diameter near the stenosis or thrombosis as obtained during step  36  or a significant flow disruption associated with an intraluminal abnormality noted during the IVUS or OCT imaging of this step  38 . An exemplary IVUS system is outlined in  FIG. 7 . 
     Both IVUS and OCT will provide vessel information whereby vessel circumference measurements can be made. This will allow the physician to check the lumen narrowing to determine whether such narrowing is significant as defined above (i.e., cross-sectional narrowing greater than about 70% or blood flow velocities greater than 250 cm/sec). In a preferred embodiment of the invention, software is provided on the imaging system  2  to correlate these measurements. Once IVUS or OCT or both IVUS and OCT has been used to assess the nature of the stenotic lesion, the method passes to step  40 . 
     In step  40 , the pressure, flow, or related parameters are determined. The functional data is preferably determined using a pressure wire, flow wire or any other sensing device if the suspected significant venous thrombosis, stenosis, or other intraluminal abnormality is confirmed by any of the methods of step  38 . Examples of pressure wires are the PrimeWire PRESTIGE™ guide wire, PrimeWire® guide wire and the ComboWire® XT guide wire all made and sold by Volcano Corporation of San Diego, Calif. 
     A pressure gradient larger than 1-2 mm Hg may indicate the presence of a significant thrombosis. Information on the pressure gradient is preferably but not required to be communicated to the healthcare provider via an IVUS console shown in  FIG. 7 . The communication in this step  40  may take the form of a message displayed on an IVUS console  4 , the modifying of an image of a vascular structure displayed on the console  4  such as by appending a text or color indicator that the patient&#39;s physiology at that location on the vessel is such that the patient&#39;s pressure gradient exceeds the targeted amount, the communication of the parameter values themselves separately or by any other means well within the skill of one skilled in the art to communicate such values. 
     In the diagnostic method  26  described above, the listed steps  36 - 40  were performed in the order given. However, it is within the scope of the invention for steps  38  and  40  to be reversed. In this embodiment of the invention shown in  FIG. 4 , the diagnostic method  26  has the form of the steps above performed in the following sequential order: 
     Step  36 : Identify venous outflow obstruction sites; 
     Step  40 : Determine pressure gradient across the stenosis or thrombosis; and 
     Step  38 : Assess the nature of the stenotic lesion or thrombosis. 
     Further, in another embodiment of the diagnostic method  26 , the method shown in  FIG. 3  could be simplified so that either step  38  or step  40  is done without doing the other so that the method takes the following forms, shown in  FIGS. 5 and 6 , respectively, of the steps above performed in the following sequential order: 
     Step  36 : Indentify venous outflow obstruction sites; and 
     Step  38 : Assess the nature of the stenotic lesion or thrombosis, and, 
     Step  36 : Indentify venous outflow obstruction sites; and 
     Step  40 : Determine pressure gradient across the stenosis or thrombosis. 
     As mentioned above, the diagnostic method  26  in all forms assesses has a form of deep vein thrombosis, that are likely amenable to treatment by thrombolytic therapy in the patient&#39;s vein and, as a result, has diagnostic value as a diagnostic tool. This diagnostic value occurs in all the embodiments of the diagnostic method  26  described above. 
     The diagnostic method  26  is typically run as software on a computing device  8  and thus the combination of the computing device  8  and the diagnostic methods  26 , as described above, becomes the diagnostic device  28 .  FIG. 7  shows an embodiment of the diagnostic device  28  where the steps  36 - 38  are performed on the computing device  8 . Although the diagnostic device  28  is preferably operated on a computing device  8 , the diagnostic device  28  may also be operated separately on any system having sufficient computing capability to perform the steps of the diagnostic method  26  and be operatively connected to the console  4 , computing device  8 , characterization application  12  or database  10  or any combination of these. In addition, the diagnostic device  28  may also be an application specific device or hardwired specifically to perform the functions described herein. 
     The diagnostic device  28 , in preferred embodiments, acts according to algorithms described above in connection with the diagnostic method  26 . The diagnostic device  28  may be implemented on or may be an adjunct to an imaging system  2 . The imaging system  2  may take the form of an intravascular ultrasound (IVUS) imaging system  2  as described above including a console  4 , IVUS catheter  6 , a computing device  8  comprising a database  10  and a characterization application  12  electrically connected to the database  10  and typically run on the computing device  8 . Alternately or in addition, the imaging system  2  may take the form of an optical coherence tomography (OCT) system that also includes a console  4 , OCT catheter  6 , a computing device  8  comprising a database  10  and a characterization application  12  electrically connected to the database  10  and typically run on the computing device  8 . 
     Although IVUS and OCT systems singly or in combination have been described as the imaging system  2 , any imaging system that obtains images of the patient&#39;s vascular may be used. Such alternate imaging systems  2  will also typically include a console  4 , a catheter  6  appropriate for that imaging system  2 , a computing device  8  comprising a database  10  and a characterization application  12  electrically connected to the database  10  and typically run on the computing device  8 . Regardless of the imaging system  2 , the diagnostic device  28  is adapted to communicate, that is both receive and transmit data and information, with the console  4  or the computing device  8 . 
     Where it has been determined that a patient has a form of deep vein thrombisis that is likely amenable to thrombolytic treatment directed to the thombosis in the patient&#39;s vein, it is also desirable to have a tool that, under the physician&#39;s control, directs a desired therapy to the stenosis. The therapeutic method  30  and its corresponding therapeutic device  32 , as described hereafter, is such a tool. 
     In one embodiment of the therapeutic method  30  shown in  FIG. 8 , the diagnostic method  26  is included as a diagnostic precursor to applying a desired therapy. So, the therapeutic method  30  in a preferred embodiment includes a diagnostic method  26  that operates as described above in all the variants of diagnostic method  26 . In another embodiment of the therapeutic method  30  shown in  FIG. 9 , the therapeutic method  30  does not include a diagnostic method  26  but includes only the delivery of a therapy  42  as will be described hereafter. 
     In the embodiment of the therapeutic method  30  of  FIG. 8  including a diagnostic method  26 , after the diagnostic steps have been accomplished and it has been determined that a patient&#39;s physiology has a stenosis or thrombus, the program passes to step  42 . In step  42 , a desired therapy is applied to treat the thrombus or stenotic lesion. The therapy applied is preferably one that, as a result of the application of the therapy, produces a reduction of the stenosis or dissolution of the blood clot such that the residual stenosis or thrombus no longer is flow limiting or that a pressure gradient exceeding 1-2 mm Hg is no longer observed or both. 
     In one embodiment of the therapeutic method  30 , the therapy in step  42  is invasive thrombolytic therapy, such as therapy with an interventional catheter. Interventional catheters may be used to mechanically cut (e.g., morcellate) the thrombus or stenosis, ablate the thrombus or stenosis, or dissolve the thrombus or stenosis with ultrasonic energy. 
       FIG. 10  shows a flow chart of the steps involved in the therapeutic method  30  to accomplish such an invasive thrombolysis procedure. The goal of the thrombolysis procedure will be to restore the venous outflow structure to where it is no longer flow limiting, flow disruption is resolved and pressure gradient is minimal. 
     In  FIG. 10 , the thrombolytic therapy is begun at step  44  where the appropriate thrombolytic balloon to be used is determined based on measurements previously made such as during a venogram. It is preferable but not required for the balloon to be a non-compliant balloon that will have a nominal inflated diameter of at least 80% of the normal proximal non-clotted or non-stenosed vein. The benefit of using a non-compliant balloon here is to obtain high pressure to increase the opportunity for compression of the obstruction. 
     The balloon is preferably a one piece balloon. Such a balloon may, but is not required to be, coated with or exuding a drug such as tissue plasminogen activator, urokinase, streptokinase, collagenace, hepranoids and any other fibrinolytic or direct anti-thrombin drug or drugs or antigens or both that may promote more rapid healing of a vessel. 
     Further, as mentioned above, the balloon may be a cutting or scoring balloon. A cutting balloon is one that has small blades that are activated (moved outward) by actuation of the balloon. The cutting blades score the fibrin of a lesion, particularly thrombus that is attached to and incorporated into the vein wall, thereby creating space that allows the rest of the fibrin to be compressed into a larger opening by the opening of the balloon. When the appropriate balloon to be used to remove the blockage has been determined, by whatever means, the program then passes to step  46 . The scoring balloon is one that scores the thrombus and any plaque circumferentially to dilate the obstructed vessel. Suitable scoring balloons include, for example, the AngioSculpt Scoring Balloon Catheter made and sold by AngioScore Inc. of Fremont, Calif. 
     At step  46 , the patient is loaded with intravenous weight based load of heparin (50-100 U/kg) to confirm an Activated Clotting Time (ACT) of at least 250 as is well understood in the art. After loading the patient with heparin to confirm ACT, the program then passes to step  48 . 
     In step  48 , the balloon is placed at the stenosis and inflated as is well understood in the art. After confirmation of the ACT, an exchange length 0.035″ exchange length glide wire is advanced into the proximal vein of interest (before the obstruction) and the non-compliant balloon is placed across the blockage. The balloon is slowly inflated, for example, with one atmosphere per 30 seconds until reaching nominal pressure (e.g., 8-12 atmospheres) to open the stenosis. The dilated balloon is left in place for a clinically significant time as is well understood in the art. After the balloon has been left in place for a clinically significant time, the method then passes to step  50 . 
     In step  50 , the balloon is deflated and withdrawn. The balloon is preferably deflated at a moderate rate (e.g., one atmosphere per 15 seconds) and then withdrawn from the patient&#39;s vascular by techniques well understood in the art. 
       FIG. 11  shows a device of another therapy that could be applied as the therapy in step  42 . In this embodiment of the therapeutic method  30 , an occlusive balloon is shown generally labeled  46 . The balloon catheter  52  has a catheter body  54  with a distal end  56 , an ultimate distal end  58 , a proximal end  60 , a central lumen  62 , a balloon  64  and a balloon lumen  66 . The balloon  64  is located a small distance from the ultimate distal end  58  and the central lumen  62  extends from the proximal end of the balloon catheter  52  to the ultimate distal end  58 . 
     The balloon catheter  52  also has an imaging transducer  14  located at the distal end  56  of the balloon catheter  52 . The imaging transducer  14  is preferably an IVUS or OCT imaging transducer that is part of an imaging system  2  such as has been described above that allows the user to identify intravascular stenoses or thrombi. The imaging system  2  may also include so-called virtual histology (VH) technology to help the physician recognize and identify the morphology of tissue, particularly plaque associated with a lesion, in vivo (i.e., the location and composition of plaque in the patient&#39;s body). 
     The following systems for detecting and characterizing plaque and thrombi using IVUS with VH are disclosed in U.S. Pat. No. 6,200,268 entitled “VASCULAR PLAQUE CHARACTERIZATION” issued Mar. 13, 2001 with D. Geoffrey Vince, Barry D. Kuban and Anuja Nair as inventors, U.S. Pat. No. 6,381,350 entitled “INTRAVASCULAR ULTRASONIC ANALYSIS USING ACTIVE CONTOUR METHOD AND SYSTEM” issued Apr. 30, 2002 with Jon D. Klingensmith, D. Geoffrey Vince and Raj Shekhar as inventors, U.S. Pat. No. 7,074,188 entitled “SYSTEM AND METHOD OF CHARACTERIZING VASCULAR TISSUE” issued Jul. 11, 2006 with Anuja Nair, D. Geoffrey Vince, Jon D. Klingensmith and Barry D. Kuban as inventors, U.S. Pat. No. 7,175,597 entitled “NON-INVASIVE TISSUE CHARACTERIZATION SYSTEM AND METHOD” issued Feb. 13, 2007 with D. Geoffrey Vince, Anuja Nair and Jon D. Klingensmith as inventors, U.S. Pat. No. 7,215,802 entitled “SYSTEM AND METHOD FOR VASCULAR BORDER DETECTION” issued May 8, 2007 with Jon D. Klingensmith, Anuja Nair, Barry D. Kuban and D. Geoffrey Vince as inventors, U.S. Pat. No. 7,359,554 entitled “SYSTEM AND METHOD FOR IDENTIFYING A VASCULAR BORDER” issued Apr. 15, 2008 with Jon D. Klingensmith, D. Geoffrey Vince, Anuja Nair and Barry D. Kuban as inventors and U.S. Pat. No. 7,463,759 entitled “SYSTEM AND METHOD FOR VASCULAR BORDER DETECTION” issued Dec. 9, 2008 with Jon D. Klingensmith, Anuja Nair, Barry D. Kuban and D. Geoffrey Vince, as inventors, the teachings of which are hereby incorporated by reference herein in their entirety. 
     In one embodiment of the present invention, a characterization application of the IVUS system is adapted to receive and store venous characterization data (e.g., tissue type, etc.) that is subsequently utilized to classify the tissue type of a patient. For example, after a venous vessel has been interrogated (e.g., IVUS data has been collected), a histology correlation is prepared. In other words, the venous vessel is dissected or cross-sectioned for histology. In one embodiment of the present invention, the cross-section is marked, for example with one or more sutures, so that the histology can be correlated to a portion of the IVUS image based on the marker(s). The cross-section is then prepared with a fixing and staining process that is well known in the art. The staining process allows a trained clinician to identify a tissue type(s), or a chemical(s) found within (e.g., a chemical corresponding to a particular tissue type, etc.). It should be appreciated that the particular method used to identify or characterize the cross-sectional venous vessel is not a limitation of the present invention. Thus, all identification/characterization methods generally known to those skilled in the art are within the spirit and scope of the present invention. 
     The identified tissue type or characterization (i.e., characterization data) is then provided to the characterization application for storage and access in future procedures. Accordingly, in some instances the characterization data is stored in a venous tissue characteristic database. It should be appreciated that the data may input to the characterization application and/or database using any suitable input device(s) generally known to those skilled in the art. It should further be appreciated that the term tissue type or characterization, as these terms are used herein, include, but are not limited to, fibrous tissues, fibro-lipidic tissues, calcified necrotic tissues, calcific tissues, collagen compositions, cholesterol, thrombus, compositional structures (e.g., the lumen, the vessel wall, the medial-adventitial boundary, etc.) and all other identifiable characteristics generally known to those skilled in the art. 
     One method of populating the venous tissue characteristic database begins with collecting IVUS data (i.e., RF backscatter data) from a portion of a venous vessel. This data is then used to create an IVUS image at step. The interrogated portion of the venous vessel is cross-sectioned and a tissue type (or a characterization thereof) is identified. This information (i.e., characterization data) is then transmitted to a computing device (or the equivalent thereof). An image of the cross-sectioned vascular object is created and at least one region of interest is identified (e.g., by an operator). This image is then morphed, if needed, to substantially match it to the initially obtained IVUS image. This may include identifying at least one landmark and applying at least one algorithm (e.g., a morphometric algorithm, a thin plate spline deformation technique, etc.). The region(s) of interest is mapped to the IVUS image and associated IVUS data is identified. Spectral analysis is then performed on the associated IVUS data, and at least one parameter is identified. The at least one parameter and the characterization data are then stored in the database. In one embodiment of the present invention, the at least one parameter is stored such that it is linked to the characterization data. It should be appreciated that the order in which these steps are presented is not intended to limit the present invention. Thus, for example, creating an IVUS image after the vascular object is cross-sectioned is within the spirit and scope of the present invention. 
     The above-described process is repeated for each tissue component desired to be identified and repeated for each component as many times as desired in order to obtain a more accurate range of signal properties. With the database populated, a tissue type or characteristic can be automatically and accurately identified if the acquired parameters substantially match parameters stored in the database. With the venous tissue characteristic database populated, the characterization application of the IVUS system can then be utilized to receive IVUS data, determine parameters related thereto, and use the venous tissue characteristic parameters stored in the database (i.e., histology data) to identify tissue type(s) or characterization(s) thereof. 
     The central lumen  62  of the balloon catheter  52  is attached to a source of suction (not shown) at the proximal end  60  of the balloon catheter  52  by means well understood in the art. The distal end  56  of the balloon catheter  52  is advanced in the patient&#39;s vein of interest past the lesion but where the balloon  64  is downstream of the obstruction. The balloon  64  is inflated so that it occludes blood flow in the vein. In this configuration, the ultimate distal end  58  is located near the lesion. The suction is activates so that suction is applied at the ultimate distal end  58 . Because the ultimate distal end  58  is located in close proximity of the lesion, thrombus will be subject to the suction force and sucked into the balloon catheter to travel through the central lumen  62  to be removed through the proximal end  60 . 
     Another embodiment of a device of another therapy that could be applied as the therapy in step  42  is shown in  FIGS. 12 and 13 . In this embodiment, a cutting catheter  68  is shown. The cutting catheter  68  has a catheter body  70  with a distal end  72 , a proximal end  74 , a central lumen  76  through which a guide wire (preferably the sensing guidewire as discussed above) may be passed and an outer surface  78 . The cutting catheter  68  includes, but is not limited to, the types disclosed in U.S. Pat. No. 5,421,338 entitled “Acoustic Imaging Catheter and the Like” issued to Robert J. Crowley, Mark A. Hamm and Charles D. Lennox on Jun. 6, 1995; U.S. Pat. No. 6,283,921 entitled “Ultrasonic Visualization and Catheters Therefor” issued to Elvin Leonard Nix, Amit Kumar Som, Martin Terry Rothman and Andrew Robert Pacey on Sep. 4, 2001; U.S. Pat. No. 5,800,450 entitled “Neovascularization Catheter” issued to Banning Gray Lary and Herbert R. Radisch, Jr. on Sep. 1, 1998; U.S. Pat. Nos. 5,507,761 and 5,512,044 both entitled “Embolic Cutting Catheter” issued to Edward Y. Duer on Apr. 16, 1996 and Apr. 30, 1996, respectively; U.S. Pat. No. 5,925,055 entitled “Multimodal Rotary Abrasion and Acoustic Ablation Catheter” issued to Sorin Adrian and Paul Walinsky on Jul. 20, 1999; U.S. Pat. No. 4,917,085 entitled “Drive Cutting Catheter Having a New and Improved Motor” issued to Kevin W. Smith on Apr. 17, 1990 and US Published Patent Application No. 2006111704 entitled “Devices, Systems, and Methods for Energy Assisted Arterio-venous Fistula Creation” filed by Rodney Brenneman, Dean A. Schaefer and J. Christopher Flaherty on Nov. 16, 2005, the teachings of which are incorporated herein in their entirety by reference. 
     The cutting catheter  68  preferably has an imaging transducer  14  as part of an imaging system  2  located at its distal end  72 . Further, the cutting catheter  68  includes cutting blades  80  located on its outer surface  78  near the distal end  72 . The cutting blades  80  are preferably anywhere from about 0.5-2 mm in depth and from about 5-20 mm in length although other lengths can be used depending on the vessel that the cutting catheter  68  will be used in. The cutting blades  80  can be spaced radially around the outer surface  78  for cutting or scoring circumferentially or can be spaced on one side of the catheter  68  for selective cutting or scoring. When the catheter  68  is pulled back during an imaging procedure, the cutting blades  80  contact and score thrombus and other substance that is attached to and incorporated into the vein wall. In certain embodiments, after some of the thrombus is removed, the rest of the thrombus and/or atheroma material can be compressed into a larger opening by the opening of the balloon. 
     Yet another embodiment of a device of another therapy that could be applied as the therapy in step  42  is shown in  FIG. 14 . In this embodiment, an ablation catheter  82  is shown. Such ablation catheter  82  delivers ablation energy through laser, so-called Radio Frequency Ablation or “RFA”, both ablative and thermal, cryoablation, ultrasound, microwave or other energy sources. Examples of such ablation catheters  80  include, but are not limited to, those disclosed in U.S. Pat. No. 6,245,066 entitled “Ablation Catheter” issued to John Mark Morgan and Andrew David Cunningham on Jun. 12, 2001; U.S. Pat. No. 5,267,954 entitled “Ultra-sound catheter for removing obstructions from tubular anatomical structures such as blood vessels” issued to Henry Nita on Dec. 7, 1993; U.S. Pat. No. 6,325,797 entitled “Ablation Catheter and Method for Isolating a Pulmonary Vein” issued to Mark T. Stewart, William J. Flickinger, David E. Franscischelli, Rahul Mehra and Xiaoyi Min on Dec. 4, 2001; U.S. Pat. No. 6,203,537 entitled “Laser-driven Acoustic Ablation Catheter” issued to Sorin Adrian on Mar. 20, 2001; U.S. Pat. No. 5,427,118 entitled “Ultrasonic Guidewire” issued to John H. Wang, Henry Nita, Timothy C. Mills, and Douglas H. Gesswin on Jun. 27, 1995; U.S. Pat. No. 6,701,176 entitled “Magnetic-resonance-guided imaging, electrophysiology, and ablation” issued to Henry R. Halperin, Ronald D. Berger, Ergin Atalar, Elliot R. McVeigh, Albert Lardo, Hugh Calkins and Joao Lima on Mar. 2, 2004; U.S. Pat. No. 6,231,518 entitled “Intrapericardial electrophysiological procedures” issued to James R. Grabek, Carl M. Beaurline, Cecil C. Schmidt, Lawrence A. Lundeen and Patricia J. Rieger on May 15, 2001; U.S. Pat. No. 6,949,094 entitled “Miniature Refrigeration System for Cryothermal Ablation Catheter” issued to Ran Yaron on Sep. 27, 2005; U.S. Pat. No. 6,592,612 entitled “Method and apparatus for providing heat exchange within a catheter body” issued to Wilfred Samson, Hoa Nguyen, Mike Lee, Brady Esch, Eric Olsen and Jeff Valko on Jul. 15, 2003; U.S. Pat. No. 7,291,146 entitled “Selectable Eccentric Remodeling and/or Ablation of Atherosclerotic Material” issued to Tom A. Steinke, Corbett W. Stone, Stephen O. Ross, Brian S. Kelleher, Raphael M. Michel and Donald H. Koenig on Nov. 6, 2007; U.S. Pat. No. 7,742,795 entitled “Tuned RF energy for Selective Treatment of Atheroma and Other Target Tissues and/or Structures” issued to Corbett W. Stone, Michael F. Hoey, Tom A. Steinke, Raphael M. Michel and Arthur G. Blanck on Jun. 22, 2010; US Published Patent Application Nos. 2003092995 entitled “System and method of positioning implantable medical devices” filed by David L. Thompson on Feb. 28, 2002; 2006184048 entitled “Tissue Visualization and Manipulation System” filed by Vahid Saadat on Oct. 25, 2005; 2010256616 entitled “Recanalizing Occluded Vessels Using Radiofrequency Energy” filed by Osamu Katoh and Wayne Ogata on Apr. 2, 2010, 2008262489 entitled “Thrombus Removal” and filed by Tom A. Steinke on Apr. 23, 2008; 2008125772 entitled “Tuned RF Energy and Electrical Tissue Characterization for Selective Treatment of Target Tissues” filed by Corbett W. Stone, Michael F. Hoey, Tom A. Steinke, Raphael M. Michel, Arthur G. Blanck, Marlene Kay Truesdale and Bret Herscher on Oct. 18, 2007 and 2010125268 entitled “Selective Accumulation of Energy With or Without Knowledge of Tissue Topography” filed by Rolfe Tyson Gustus, Linas Kunstmanas and Arthur G. Blanck on Nov. 12, 2009 and WIPO Published Patent Application No. WO03073950 entitled “Optical Fibre Catheter for Thermal Ablation” filed by Andrea Venturelli on Jan. 27, 2003, the teachings of which are incorporated by reference herein in their entirety. Further examples of RF ablation systems include, but are not limited to ablative systems such as that sold by Halt Medical Inc. of Livermore, Calif. that use the heat energy of radio frequency waves to ablate tissue, those sold by Covidien plc through its Valleylab brand in Boulder, Colo. and the VNUS® RF (radiofrequency) Ablation system sold by AngioDynamics of Latham, N.Y. 
     The ablation catheter  82  has a catheter body  84  with a distal end  86 , a proximal end  88 , a central lumen  90  through which a guide wire (such as sensing guidewire discussed above) may be passed, an outer surface  92  and ablation system  94 . The ablation catheter  82  preferably has, but is not required to have, an imaging transducer  14  as part of an imaging system  2  located at its distal end  86 . As the ablation catheter  82  is advanced to the site of the occlusion, the imaging system  2 , if present, helps the physician to locate the occlusion. Once the ablation catheter  82  is located at the lesion, the ablation therapy is applied by the ablation system  94  to ablate the occlusion. The imaging system  2  may be particularly useful in helping the physician apply the ablation therapy and assess the extent of such ablation. 
     In an alternate embodiment of the device of  FIG. 14  shown in  FIG. 15 , the imaging system  2  is an OCT system and ablation system  94  is combined with the distal optics  22  of the imaging system  2 . In a variant of this embodiment, the ablation provided by the ablation system  94  is laser ablation that is supplied to the ablation system  94  from the same light source  20  used by the OCT system to produce the OCT images, typically through optical fibers  24  connecting the light source  20  to the distal optics  22 . Although the light source  20  used to produce the OCT images would typically be located remotely from the distal optics  22  supplied light via the optical fibers  24 , it is within the scope of the present invention in all embodiments for the light source  20  to be located in close proximity to the distal optics  22 . In a variant of this, this same light source  20  provides not only the light needed to produce the OCT images but also the laser light used by the ablation system  94  to do the ablation. 
     Yet another embodiment of a device of another therapy that could be applied as the therapy in step  42  is shown in  FIG. 16 . In this embodiment, a therapeutic agent deliver catheter  96  is shown. Such therapeutic agent deliver catheter  96  delivers a therapeutic agent to the lesion to dissolve fibrin or thrombus present at or causing the lesion or otherwise treat the lesion. Examples of such therapeutic agent delivery catheters  92  include, but are not limited to, those disclosed in U.S. Pat. No. 5,135,516 entitled “Lubricious Antithrombogenic Catheters, Guidewires and Coatings” issued to Ronald Sahatjian and Kurt Amplatz on Aug. 4, 1992; U.S. Pat. No. 6,535,764 entitled “Gastric treatment and diagnosis device and method” issued to Mir A. Imran, Olivier K. Colliou, Ted W. Layman, Deepak R. Gandhi and Sharon L. Lake on Mar. 18, 2003; U.S. Pat. No. 5,336,178 entitled “Intravascular Catheter with Infusion Array” issued to Aaron V. Kaplan, James R. Kermode and Enrique J. Klein on Aug. 9, 1994; U.S. Pat. No. 7,063,679 entitled “Intra-aortic Renal Delivery Catheter” issued to Mark Maguire and Richard Geoffrion on Jun. 20, 2006; U.S. Pat. No. 7,292,885 entitled “Mechanical Apparatus and Method for Dilating and Delivering a Therapeutic Agent to a site of Treatment” issued to Neal Scott and Jerome Segal on Nov. 6, 2007; U.S. Pat. No. 6,179,809 entitled “Drug Delivery Catheter with Tip Alignment” issued to Alexander Khairkhahan, Michael J. Horzewski, Stuart D. Harman, Richard L. Mueller and Douglas R. Murphy-Chutorian on Jan. 30, 2001; U.S. Pat. No. 5,419,777 entitled “Catheter for Injecting a Fluid or Medicine” issued to Berthold Hofling on May 30, 1995; U.S. Pat. No. 6,733,474 entitled “Catheter for Tissue dilatation and drug Delivery” issued to Richard S. Kusleika on May 11, 2004; and 2010168714 entitled “Therapeutic Agent Delivery System” filed by Jessica L. Burke, Grant T. Hoffman and Drew P. Lyons, Ellettsville, Ind. 1US) on Feb. 3, 2010; 2010125238 entitled “Iontophoretic Therapeutic Agent Delivery System” filed by Whye-Kei Lye and Kareen Looi on Nov. 7, 2009; 2003032936 entitled “Side-exit Catheter and Method for its Use” filed by Robert J. Lederman on Aug. 10, 2001, the teachings of which are incorporated by reference herein in their entirety. Examples of therapeutic agents that may be delivered to the lesion include, but are not limited to tissue plasminogen activator, urokinase, streptokinase, collagenace, hepranoids and any other fibrinolytic or direct anti-thrombin drug. 
     The therapeutic agent deliver catheter  96  has a catheter body  98  with a distal end  100 , a proximal end  102 , a central lumen  104  through which a guide wire (such as sensing guidewire discussed above) may be passed, an outer surface  106 , a balloon  108  and a balloon lumen  110 . The therapeutic agent deliver catheter  96  preferably has, but is not required to have, an imaging transducer  14  as part of an imaging system  2  located at its distal end  100 . The balloon  108  is inflated and deflated via the balloon lumen  110  as is well understood in the art. The balloon  108  delivers the therapeutic agent. The therapeutic agent may coat the balloon  108  so that as the balloon is inflated, the therapeutic agent is brought into contact with a lesion so that the therapeutic agent may be applied to the lesion. Alternately, the balloon  108  may be porous or have slits or other fenestrations to allow therapeutic agent present within the balloon to pass through the pores, slits or other fenestrations to come into contact with the tissue at or near a stenosis. As the therapeutic agent deliver catheter  96  is advanced to the site of the lesion, the imaging system  2 , if present, helps the physician to locate the lesion. Once the therapeutic agent deliver catheter  96  is located at the lesion, the therapeutic agent to is applied to the lesion as described above. The imaging system  2  may be particularly useful in helping the physician apply the therapeutic agent and assess the extent of such therapy. 
     The therapeutic method  30  is also typically run as software on a computing device  8  and thus the combination of the computing device  8  and the therapeutic methods  24 , as described above, becomes the therapeutic device  32  ( FIG. 17 ). Although the therapeutic device  32  is preferably operated on a computing device  8 , the therapeutic device  32  may also be operated separately on any system having sufficient computing capability to perform the steps of the therapeutic method  30 , and diagnostic method  26  if present, and be operatively to the console  4 , computing device  8 , characterization application  12  or database  10  or any combination of these. In addition, the therapeutic device  32  may also be an application specific device or hardwired specifically to perform the functions described herein. 
     The therapeutic device  32 , in preferred embodiments, acts according to algorithms described above in connection with the therapeutic method  30 . The therapeutic device  32  may be implemented on or may be an adjunct to an imaging system  2 . The imaging system  2  may take the form of an intravascular ultrasound (IVUS) imaging system  2  as described above including a console  4 , IVUS catheter  6 , a computing device  8  comprising a database  10  and a characterization application  12  electrically connected to the database  10  and typically run on the computing device  8 . Alternately or in addition, the imaging system  2  may take the form of an optical coherence tomography (OCT) system that also includes a console  4 , OCT catheter  6 , a computing device  8  comprising a database  10  and a characterization application  12  electrically connected to the database  10  and typically run on the computing device  8 . 
     In several embodiments of the invention described herein, the therapy delivery device  26  such as the balloon catheter  52 , cutting catheter  68 , ablation catheter  82  and therapeutic agent deliver catheter  96  included an imaging transducer  14  as part of an imaging system  2  that allowed the therapy delivery device to be located with respect to the lesion so that the therapy could be most effectively applied. In any of the therapy delivery systems described herein, it is preferable but not required but not required to add an imaging transducer  14  as part of an imaging system  2 , typically near the distal end of such therapy delivery devices, to also allow the therapy delivery device to be located with respect to the lesion so that the therapy can be most effectively applied. 
     In any of the embodiments for administering a therapy described above, it may also be useful to apply embolic protection to prevent pieces of fibrin, thrombus or other tissue dislodged by the application of therapy in step  42  from moving downstream with the blood flow. This will remove unwanted material will move with the blood downstream into the patient&#39;s heart and ultimately into the patient&#39;s lungs where such material may cause an embolism. Consequently, the use of embolic protection such as the SpiderFX® Embolic Protection Device made and sold by ev3, Inc. of Plymouth, Minn. and the FilterWire EZTM Embolic Protection System for SVG&#39;s made and sold by Boston Scientific, Inc. of Natick, Mass. may help prevent the occurrence of such embolisms. The therapeutic method  30  in another embodiment shown in  FIG. 18  includes a step  114  so that the program passes from step  42  to step  114 . In step  114 , intraluminal abnormalities are assessed to see if the therapy of step  42  worked. The intraluminal abnormalities may be assessed (as in step  42 ) using the sensing guidewire, or by introducing an imaging catheter into vessel being treated. 
       FIG. 19  illustrates using a sensing guidewire to assess the pressure gradient across the stenosis or thrombosis after the therapy of step  42  has been applied Consequently, after step  42  has been completed, the method passes to step  116 . At step  116 , the pressure gradient across the stenosis is assessed as described in step  38  to determine, post-therapy, whether adequate blood flow is now present as a result of the therapy of step  42 . In addition to assessing pressure gradient and as discussed, other functional measurements can also be assessed such as flow, CFR, and FFR in order to determine whether adequate blood flow has been re-established. A sensing guidewire advantageous allows one to determine whether flow and pressure has been restored to normal or acceptable levels without the need to introduce a separate diagnostic catheter. In addition, the therapeutic catheter can remain in the vessel during assessment, and can apply further treatment if data collected from the sensing guidewire indicates further treatment is necessary. 
     Further, it may be desirable to assess the nature of the treated vessel post-therapy. Post-therapy may be any time after intervention has concluded, and can be immediately after intervention, days, weeks, or months after intervention. Consequently, in another embodiment of the therapeutic methods  24 , as shown in  FIG. 20 , this assessment of the nature of the treatment site post-therapy is preferably accomplished as step  118  by using the sensing guidewire to measure functional parameters or by applying IVUS or OCT or both IVUS and OCT to the area of the applied therapy in step  42 . When using functional measurements to assess the vessel post-therapy, the functional measurements can be compared to a normal or baseline reference to determine whether flow or pressure is presenting at healthy or acceptable levels. In addition, IVUS and OCT can be used to assess the diameter of the vessel after intervention. As discussed above, a significant occlusion (i.e. stenosis, thrombosis, or both) is defined as luminal reduction greater than 50% of normal venous diameter as obtained during step  36  or a significant flow disruption associated with an intraluminal abnormality noted during the IVUS or OCT imaging at step  38 . Consequently, a successful therapy occurs when the stenosis now has a luminal reduction less than 50% of normal venous diameter as obtained during step  36  with no significant flow disruption. 
     Although embodiments of the therapeutic method  30  have been described above in connection with a step  42  with may optionally include either step  116  or  118 , an alternate therapeutic method  30  may also include both step  116  and  118  performed in any order. 
     In addition, if the therapy of step  42  was not sufficient to provide the desired blood flow or the desired reduction of the stenosis, in an additional embodiment of the therapeutic method  30 , additional therapy of any of the types described above may be applied as shown in  FIG. 21 . In certain embodiments, the desired reduction of the stenosis is such that the residual stenosis is less than 75% of the normal proximal diameter of the stenotic vein or that a pressure gradient exceeding 1 mm Hg is no longer observed. In this embodiment of the therapeutic method  30 , additional therapy will be performed if these therapy goals are not observed. Consequently, in this embodiment of the therapeutic method  30 , if the therapy goals are not met, the program passes from step  42  to step  120  where step  120  is the application of an additional therapy. The therapy of step  120  may be either the reapplication of the same therapy that was applied in step  42  or the application of an entirely new therapy of the types described above. In this embodiment of the therapeutic method  30 , steps  114 ,  116  may also be applied as described in connection with step  42  or applied singly or in combination to step  120 . 
     Further, as shown in  FIG. 22 , after either step  42  or step  120 , additional therapy may also be performed at step  122  on all affected veins using the same techniques described above in step  42  if there are additional affected veins with significant occlusions due to stenosis, thrombosis or both. Further, additional therapies or the reapplication of any of the therapies listed above in connection with steps  42  and  120  may be applied to these additional affected veins. 
     The present invention has been described in connection with many different diagnostic and therapeutic methods and devices. The present invention also anticipates that more than one diagnostic method and device may be applied or combined into a single method or device. Likewise, the present invention also anticipates that more than one therapeutic method and device may be applied or combined into a single method or device. Further, various permutations and combinations of diagnostic and therapeutic devices may be combined together, each acting according to the descriptions above, into a single method or single device. 
     As discussed above, methods of the invention for assessing functional flow measurements during an interventional procedure, such as thrombolysis, preferably involve use of a sensing guidewire. Referring now to  FIG. 23 ,  FIG. 23  provides a schematic illustration of a sensing guidewire being used during a procedure to assess occlusion (stenosis ro thrombosis) in a patient  622 . The patient  622  is shown lying on a bed  623  in a surgical lab. The guide wire  621  is used with apparatus  624  which consists of a cable  626  which connects the guide wire  621  to an interface box  627  as shown or directly to a connected to an instrument such as a computing device (e.g. a laptop, desktop, or tablet computer) or a physiology monitor. Interface box  627  is connected by another cable  628  to a control console  629  which has incorporated as a part thereof a video screen  631  on which a waveform  632  displaying functional measurements may be provided. For example, the ECG measurements may appear as traces  632 ,  633  and  634 . 
     The guide wire  621  is shown more in detail in  FIG. 24  and as shown therein, the guide wire  621  can be constructed utilizing the various constructions as shown in U.S. Pat. Nos. 5,125,137; 5,163,445; 5,174,295; 5,178,159; 5,226,421; and 5,240,437. As disclosed therein, such a guide wire consists of a flexible elongate element  641  having a proximal and distal extremities  642  and  643  and which can be formed of a suitable material such as stainless steel having an outside diameter for example of 0.035″, 0.018″, 0.014″ or less and having a suitable wall thickness as for example, 0.001″ to 0.002″ and conventionally called a “hypotube” having a length of 150-170 centimeters. Where a smaller guide wire is desired, the hypotube  641  can have an exterior diameter of 0.014″ or less. Typically such a guide wire includes a core wire (not shown) of the type disclosed in the above identified patents which extends from the proximal extremity to the distal extremity of the flexible elongate element  641  to provide the desired torsional properties for guide wires (See U.S. Pat. No. 5,163,445, col. 18:40-51) to facilitate steering of the guide wire  621  in the vessel. 
     A coil spring  646  is provided and is formed of a suitable material such as stainless steel. It has an outside diameter of 0.018″ and is formed from a wire having a diameter of 0.003″. The spring  646  is provided with a proximal extremity  47  which is threaded onto the distal extremity  43  of the flexible elongate member  641 . The distal extremity  648  of the coil spring  646  is threaded onto the proximal extremity  649  of an intermediate or transition housing  651  such as disclosed in U.S. Pat. No. 5,174,295, formed of a suitable material such as stainless steel having an outside diameter of 0.018″ and having a suitable wall thickness as for example, 0.001″ to 0.002″. The housing includes one or more sensors, such as pressure sensor or flow sensor (See  FIGS. 25-26 ). 
     A torquer  666  of the type described in U.S. Pat. No. 5,178,159 is mounted on the proximal extremity  642  of the flexible elongate member  641  for causing a rotation of a guide wire  621  when used in connection with catheterization procedures in a manner well known to those skilled in the art. 
     The proximal extremity  642  is also provided with a plurality of conducting sleeves (not shown) of the type disclosed in U.S. Pat. No. 5,178,159. In the present invention, one or more additional sleeves can be provided to make connection to the conductors hereinafter described. The proximal extremity  642  of the flexible elongate member is removably disposed within a housing  668  of the type described in U.S. Pat. Nos. 5,178,159, 5,348,481 and 5,358,409 that makes electrical contact with the sleeves on the proximal extremity  642  while permitting rotation of the sleeves and the flexible elongate member  641 . The housing  668  carries female receptacles (not shown) which receive the sleeves and which are connected to a cable  671  connected to a connector  672 . The connector  672  is connected to another mating connector  673  carried by the cable  626  and connected into the interface box  627 . 
     In addition,  FIGS. 25 and 26  show a sensor tip  400  of a guidewire  621  that may be suitable to use with methods of the invention. The combination sensor tip  400  includes a pressure sensor  404  within sensor housing  403 , flow sensor  501  (which is an ultrasound transducer) and optionally includes a radiopaque tip coil  405  distal to proximal coil  406 .  FIG. 26  gives a cross-sectional view through combination sensor tip  400 , showing ultrasound transducer  501  disposed therein. The ultrasound transducer  501  may be any suitable transducer, and may be mounted in the distal end using any conventional method, including the manner described in U.S. Pat. No. 5,125,137, which is fully incorporated herein by reference. Conductors (not shown) may be secured to the front and rear sides of the ultrasound transducer  501 , and the conductors may extend interiorly to the proximal extremity of a guide wire. The pressure sensor  404  may be of the type described in U.S. Pat. No. 6,106,476, which is fully incorporated herein by reference. For example, the pressure sensor  404  may be comprised of a crystal semiconductor material having a recess therein and forming a diaphragm bordered by a rim. A reinforcing member may be bonded to the crystal to reinforce the rim of the crystal, and may have a cavity therein underlying the diaphragm and exposed to the diaphragm. A resistor having opposite ends may be carried by the crystal and may have a portion thereof overlying a portion of the diaphragm. Leads may be connected to opposite ends of the resistor and extend proximally within the guide wire. 
     Additional details of suitable pressure sensors that may be used as the pressure sensor  404  are described in U.S. Pat. No. 6,106,476. U.S. Pat. No. 6,106,476 also describes suitable methods for mounting the pressure sensor  404  within the combination sensor tip  400 . In one embodiment, the pressure sensor  404  is oriented in a cantilevered position within a sensor housing  403 . For example, the sensor housing  403  preferably includes a lumen surrounded by housing walls. When in a cantilevered position, the pressure sensor  404  projects into the lumen of the sensor housing  403  without contacting the walls of the sensor housing  403 . 
     In  FIG. 26 , ultrasound transducer  501  is illustrated as disposed near distal end  202 . One advantage of the sensor housing  403  is that because the sensor housing  403  encloses both the ultrasound transducer  501  and the pressure sensor  404 , the need for two separate housings, i.e., one for an ultrasound transducer and one for a pressure sensor, is eliminated. Accordingly, the use of a common sensor housing  403  for the ultrasound transducer  501  and the pressure sensor  404  makes the combination sensor tip  400  easier to manufacture than current designs. In certain embodiments, the distance between the pressure sensor  404  and the flow sensor  501  is 0.5 mm, 1.0 mm, 1.5 mm, or 2.0 mm. The placement of both the ultrasound transducer  501  and the pressure sensor  404  near the distal end of the combination sensor tip  400  increases overall flexibility in a guide wire that incorporates the combination sensor tip  400 . For example, a prior art guide wire that includes separate sensors, with the pressure sensor being located substantially proximal from the ultrasound transducer, has a longer relatively rigid area that must be devoted to the pressure and flow sensors, i.e., the distance from the ultrasound transducer to the pressure sensor. The guidewire  621 , in contrast, substantially reduces or entirely eliminates the distance between the ultrasound transducer and the pressure sensor, thereby allowing for increased flexibility across this length. 
     It should be noted that in an alternative embodiment of the combination sensor tip  400  (not shown) both the ultrasound transducer  501  and the pressure sensor  404  may be offset from the distal end of the combination sensor tip  400 , such as, e.g., 1.5 cm to 3.0 cm from the distal end, but still located in close proximity to each other relative to prior art designs. Thus, the aforementioned advantages over the prior art design are still achieved. 
     In an alternative embodiment, the pressure sensor housing includes a tubular member having an opening on the outer wall in communication with the lumen and a tip. The tip is constructed of a solder ball. Alternatively a weld, braze, epoxy or adhesive can be used. The lumen of the housing is counter-bored so that the lumen has a smaller inner diameter at the proximal end of the tubular member. For example, the housing may be constructed in the counter-bore fashion with a 0.010″ inner diameter at the proximal end and a 0.012″ inner diameter at the distal end, with the pressure transducer coaxially housed in the lumen. In addition, a flow sensor may be placed in the sensor tip instead of the weld, braze, epoxy or adhesive to provide a combo sensor tip. The advantage of the counter bore is that the housing is easier to make. The transducer is simply slid into place in the lumen and bonded (adhesive or epoxy) where the sides meet the proximal 0.010″ inner diameter  314 . The distal 0.012″ inner diameter allows enough room for the pressure sensitive section of the transducer to be free from any contact with the housing. Because of the counter-bored lumen, there is no ledge that has to be made on the outer wall of the lumen, rather the pressure transducer communicates with the outside via an opening in the outer wall of lumen. Constructions suitable for use with a guidewire of the invention are discussed in U.S. Pub. 2013/0030303 to Ahmed, the contents of which are incorporated by reference. 
     A radiopaque tip coil  405  may be provided at the proximal end of the combination sensor tip  400 . The radiopaque tip coil  405  is coupled to a proximal coil  406 , and the proximal coil  406  may be coupled to the elongate tubular member. Another improvement of the present invention over current designs that use separate pressure sensor and ultrasound transducer housings is that the present invention provides a smoother transition from the elongate tubular member to the combination sensor tip  400 , i.e., the connection between the radiopaque tip coil  405 , the proximal coil  406 , and the rest of the guide wire is optimized relative to current designs. Specifically, the transition is smoother and more flexible because of the absence of the housing between the radiopaque tip coil  405  and the proximal coil  406 . Current designs generally have a tip coil attached to a pressure sensor housing, which in turn is connected to a proximal coil. The present invention eliminates or greatly reduces the separation between the tip coil and the proximal coil that is required in current devices. Suitable coils for use with the present invention are described in U.S. Pat. No. 6,106,476. 
     In a preferred embodiment, methods of the invention employ a Doppler guidewire wire sold under the name FLOWIRE by Volcano Corporation, the pressure guidewire sold under the name PRIMEWIRE PRESTIGE by Volcano Corporation, or both. Suitable guidewires are also discussed in U.S. Pat. Nos. 5,125,137, 5,163,445, 5,174,295, 5,178,159, 5,226,421, 5,240,437 and 6,106,476. 
     In certain embodiments, the sensing device, such as sensing guidewire  621 , includes an imaging element. Preferably, the imaging element is an ultrasound transducer, although any other imaging elements can be used. Imaging guidewires are described in, for example, U.S. Pat. No. 7,060,033. 
     The present invention has been described in connection with certain embodiments, combinations, configurations and relative dimensions. It is to be understood, however, that the description given herein has been given for the purpose of explaining and illustrating the invention and are not intended to limit the scope of the invention. In addition, it is clear than an almost infinite number of minor variations to the form and function of the disclosed invention could be made and also still be within the scope of the invention. Consequently, it is not intended that the invention be limited to the specific embodiments and variants of the invention disclosed. It is to be further understood that changes and modifications to the descriptions given herein will occur to those skilled in the art. Therefore, the scope of the invention should be limited only by the scope of the claims. 
     References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes.