Patent Publication Number: US-2004059244-A1

Title: Thermography catheters allowing for rapid exchange and methods of use

Description:
[0001] This is a continuation of U.S. application Ser. No. 10/253,391, filed Sep. 23, 2002, which is incorporated herein by reference in its entirety. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates to intravascular thermography devices useful for detection and treatment of vulnerable plaques, and in particular thermography catheters that allow for rapid removal and replacement by an interventional therapeutic catheter. The presence of inflammatory cells within vulnerable plaque and thus the vulnerable plaque itself can, according to the present invention, be identified by detecting heat associated with the metabolic activity of these inflammatory cells.  
       BACKGROUND  
       [0003] Cardiovascular disease is one of the leading causes of death worldwide. In the United States each year approximately 1.5 million patients experience a myocardial infarction from atherosclerotic coronary disease. Atherosclerosis is a common form of arteriosclerosis in which deposits of yellowish plaques or atheromas are formed within the intima and inner media of large and medium-sized arteries. These atheromas usually contain cholesterol, lipoid material, and lipophages. The pathological sequence of events leading to acute myocardial infarction includes plaque rupture with exposure of the subintimal surface of the plaque to coronary blood flow. As a result, activation of platelets and the coagulation pathway occurs as the contents of the atherosclerotic plaque interact with circulating blood components. Platelet activation also releases numerous chemical mediators, including thromboxane A2, a vasoconstrictive substance that often leads to localized vasospasm that further impedes coronary artery blood flow. The net result of these events is thrombus formation causing interruption of coronary blood flow to myocardial tissues, causing myocardial necrosis.  
       [0004] According to recent studies, plaque rupture may trigger 60 to 70 percent of fatal myocardial infarction. Plaque erosion or ulceration is the trigger in approximately 25 to 30 percent of fatal infarctions. Unfortunately, vulnerable plaques are often undetectable using conventional techniques such as angiography. The majority of vulnerable plaques that lead to infarction occur in coronary arteries that appeared normal or only mildly stenotic on angiogram performed prior to infarction. Studies on the composition of vulnerable plaque suggest that the presence of inflammatory cells, such as leukocytes and macrophages, is the most powerful predictor of ulceration and/or imminent plaque rupture. For example, in plaque erosion, the endothelium beneath the thrombus is replaced by or interspersed with inflammatory cells.  
       [0005] If vulnerable plaques can be identified, systemic or localized treatments may be performed to prevent development of acute coronary syndromes. These treatments include inserting a catheter into the coronary artery to remove or remodel the plaque using atherectomy or balloon angioplasty. Localized or light activated drug, or localized thermal, cryogenic, ultrasound or radiation therapy may be delivered to combat inflammation. At the present time, when more than one interventional device, such as a thermography catheter, an angioplasty catheter, a stent deployment catheter, and an atherectomy catheter, are used during a procedure, exchange of one catheter for another occurs frequently and becomes problematic. The process of introducing the second catheter may require the use of an “exchange length” navigating wire that can be as long as 300 centimeters in length. The wire can be quite awkward to use, requiring two individuals to assure that the wire does not engage in erratic movements or exit the sterile area of the operation. In addition, manipulating a standard length guidewire (175-190 cm) also can require two operators when the thru-lumen of the catheter extends its entire length (140-150 cm), as for an over-the-wire catheter. Operating such a wire may also increase the procedural time because the operators need to coordinate their manipulation of the catheter and wire to prevent accidental movement of a device that is intended to remain stationary during this exchange.  
       [0006] Devices and methods are therefore needed to provide accurate detection, treatment, and/or removal of vulnerable plaque in blood vessels, especially in the coronary arteries, and to allow for rapid removal and replacement of working or therapeutic devices by a single operator.  
       SUMMARY OF THE INVENTION  
       [0007] The present invention provides intravascular thermography devices useful for detection and treatment of vulnerable plaques. The presence of inflammatory cells within vulnerable plaque and thus the vulnerable plaque itself can, according to the present invention, be identified by detecting heat associated with the metabolic activity of these inflammatory cells. Specifically, activated inflammatory cells have a heat signature that is slightly above that of connective tissue cells. Accordingly, one can determine whether a specific plaque is vulnerable to rupture and/or ulceration by measuring the temperature of the arterial wall in the region of the plaque. Thermography catheters that are capable of thermally mapping blood vessels to identify thermal hot spots are described in Campbell et al., U.S. Pat. No. 6,245,026, Brown, U.S. Pat. No. 5,871,449, Cassells et al., U.S. Pat. No. 5,935,075, and Campbell, U.S. Pat. No. 5,924,997, each of which are incorporated herein by reference.  
       [0008] The devices of the present invention, however, do not require usage of the conventional “exchange length” guidewire, thereby allowing rapid exchange (by a single operator) with other interventional devices, such as an angioplasty catheter, stent deployment catheter, or an atherectomy catheter. In certain embodiments, the device includes an elongate catheter having a proximal end, a distal end, a distal guidewire port in the distal end of the catheter, a proximal guidewire port at a location closer to the distal end of the catheter than the proximal end, and a lumen shaped to slideably receive a guidewire. The guidewire lumen extends between the proximal guidewire port and the distal guidewire port.  
       [0009] An expansion frame is attached to the catheter at a location distal to the proximal guidewire port. The expansion frame is contained in a contracted or low profile condition that facilitates movement through tortuous vessels so that its can be positioned within a region of interest in a coronary artery. The frame is thereafter expanded, and may achieve contact with the endoluminal surface of the vessel in certain embodiments. The expansion frame carries at least one temperature sensor, e.g., a thermocouple or a thermistor. Each temperature sensor carried by the expansion frame is connected to wires extending to the proximal end of the thermography device so that temperature readings may be recorded after deployment of the expansion frame. In certain embodiments, the expansion frame consists of a plurality of flexible struts that, when deployed, bow radially outward. The frame may include three struts, four struts, five struts, six struts, or any other suitable number of struts. In other embodiments, each strut carries a temperature sensor.  
       [0010] A capture sheath is slideably disposed around the expansion frame and contains the expansion frame in its low-profile condition. The capture sheath is operated from the proximal end of the catheter to slide either proximally or distally and thereby release the expansion frame. The capture sheath has a slotted aperture in its distal region. The slot aligns with the proximal guidewire port of the catheter and allows passage of the guidewire from the guidewire lumen of the catheter to the outside surface of the capture sheath. The slot, typically longitudinally elongated, allows the capture sheath to slide relative the inner catheter and still accommodate passage of the guidewire.  
       [0011] A registry mechanism is provided to maintain circumferential alignment between the proximal guidewire port of the catheter and the slot in the distal region of the capture sheath. The registry mechanism in certain embodiments consists of the complimentary fit between the catheter and the capture sheath where the catheter and the capture sheath have an oval or elliptical cross-section. In other embodiments, the registry mechanism comprises a complimentary fit between a longitudinal rib on the outer surface of the catheter and a longitudinal groove on the inner surface of the capture sheath.  
       [0012] Where the expansion frame comprises a plurality of struts, the struts may be formed of a self-expanding material, in certain cases a shape memory alloy or a shape memory polymer. In other embodiments, the material will be superelastic, e.g., nitinol. Shape memory alloys are desirable because of their ability to be processed and “shape set” into a desired final configuration, then manipulated into a low profile configuration that may be more easily navigated through a torturous location in the body, such as a coronary artery. This shape setting is typically achieved by heating the shape memory alloys above a certain temperature known as the “transition temperature,” which causes any deformation introduced below the transition temperature to be reversed.  
       [0013] Additionally, the use of stress-induced martensite alloys decreases the temperature sensitivity of the devices, making them easier to navigate and deploy. The use of these alloys are discussed in detail in Krumme, U.S. Pat. No. 4,485,816, and Jervis, U.S. Pat. Nos. 4,665,906 and 6,306,141, each of which are incorporated herein by reference.  
       [0014] Shape memory polymers can be shape set in seconds at around 70° C., and can withstand deformations of several hundred percent. For example, oligo(e-caprolactone) dimethacrylate incorporates a crystallizable transitioning segment that determines both temporary and permanent shape of the polymer. By manipulating the quantity of co-monomer, n-butyl acrylate, in the polymer, the cross-link density can be adjusted, thereby allowing one to vary mechanical strength and transition temperature over a side area, depending on the needs of a particular device. Homo-polymers of both monomers are known to be biocompatible. In addition, binary alloys such as tantalum-tungsten and tantalum-niobium have been used in the manufacture of medical devices such as stents and other supportive structures as a means of enhancing their radiopacity. This enhanced radiopacity allows for better visual tracking, and increases the accuracy of device placement when used in conjunction with fluoroscopy and quantitative coronary angiography. The use of binary alloys is discussed in detail in Pacetti et al., WO02/05863, which is incorporated herein by reference.  
       [0015] The thermography device of the present invention may also be equipped with capabilities for flushing blood from an annulus between the catheter and the capture sheath. For example, where flushing is to occur down the central lumen of the catheter, the guidewire lumen of the catheter may extend and communicate with the proximal end of the catheter. In this case, the lumen terminates proximally in a flushing port, typically having a luer adaptor to receive flushing solution. The proximal port typically includes a valve to prevent blood loss when flushing is not performed, for example, a one-way valve, a pressure-activated valve, or a luer-activated valve. Flushing ports in a distal region of the catheter allow fluid to pass into the annulus between the catheter and the capture sheath and a seal will prevent the fluid from flowing proximally within the annulus. On the other hand, where flushing is to occur down the annulus between the catheter and the capture sheath, the annulus will extend and communicate with the proximal end of the catheter. Ports and valves, as noted above, are provided to inject flushing solution into the annulus.  
       [0016] In use, the interventional cardiologist introduces a first guidewire (such as an 0.035″ guidewire for guiding catheter introduction) into a peripheral artery and advances the first guidewire and guiding catheter to the aortic arch. The first guidewire is pulled back, allowing the guiding catheter to position in the coronary ostium. The first guidewire is removed. A second guidewire (such as a 0.014″ coronary guidewire) is then advanced to a position across a region of interest within a target vessel. Typically the devices are introduced into a femoral artery, brachial artery, axillary artery, or a subclavian artery. The region of interest is generally within a coronary artery having a vulnerable plaque, generally the left anterior descending coronary artery, the left circumflex coronary artery, the right coronary artery, the left obtuse marginal artery, the left diagonal arteries, and the posterior descending artery. The region of interest may alternatively be within an artery of the head and neck, i.e., an artery that supplies blood to the head, including the common carotid artery, the internal carotid artery, the middle cerebral artery, the anterior cerebral artery, the posterior cerebral artery, the vertebral artery, and the basilar artery.  
       [0017] A guiding catheter is advanced over the first guidewire and positioned to facilitate entry into the artery of interest, e.g., into the coronary ostium where a coronary artery is to be studied. After removal of the first guidewire, the proximal end of the second guidewire is inserted into the distal guidewire port of the catheter and is advanced through the guidewire lumen, through the proximal guidewire port, and through the slot in the distal region of the capture sheath. The capture sheath covers the expansion frame. The catheter and capture sheath are then advanced as an assembly along the guidewire until the expansion frame is located within the region of interest. The capture sheath is slid proximally or distally to release the expansion frame. Alternatively, the capture sheath could be held in place, and the catheter advanced out of the capture sheath to release the expansion frame. The expansion frame and the temperature sensors expand, and preferably contact the endoluminal surface of the vessel. The temperature sensors then measure the temperature of the endoluminal surface of the vessel. This temperature reading is then compared with temperature readings taken at different locations along the endoluminal surface, and/or a temperature reading of blood within the vessel. An elevated temperature reading at the region of interest will indicate a likelihood of having vulnerable plaques.  
       [0018] After thermography, the capture sheath is slid into a position covering the expansion frame, thereby regaining a low-profile configuration. The catheter and the capture sheath are then withdrawn over the guidewire and removed from the patient. It will be understood that the thermography catheter can be exchanged for an interventional procedural catheter with minimal guidewire length extending from the patient. This fact is due to the ability of the catheter to track over the guidewire for only a relatively short distance at the distal end of the catheter. The proximal guidewire port is located closer to the distal end of the catheter than the proximal end, and will typically be located 10 centimeter or more from the distal end of the catheter, 15 centimeters or more from the distal end of the catheter, 20 centimeters or more from the distal end of the catheter, 25 centimeters or more from the distal end of the catheter, 30 centimeters or more from the distal end of the catheter, but in any case the proximal guidewire port will be closer to the distal end of the catheter than the proximal end of the catheter.  
       [0019] It is typically desirable to have the proximal guidewire port located at a position where the guidewire will emerge from both the catheter and the capture sheath but remain within the guiding catheter so that the guidewire is not exposed to the vascular endothelium in order to prevent injury to the vessel wall. It may also be desirable to have the proximal guidewire port located at a position within the guiding catheter that is relatively straight, i.e., it is desirable to avoid having the proximal guidewire port located at a position within the highly curved region of the curved region of “the guiding catheter shape,” and it may even be desirable to avoid having the proximal guidewire port located within the guiding catheter in the moderately curved aortic arch. Where the proximal guidewire port is located at a position within the guiding catheter in a highly curved anatomy, it may be difficult for the catheter to track smoothly over the guidewire.  
       [0020] After the thermography catheter is removed, the cardiologist can insert over the guidewire an angioplasty catheter, a stent placement catheter, an atherectomy catheter, or catheters for localized thermal, cryogenic, radiation, or ultrasonic therapy to stabilize or remove vulnerable plaques. After treatment of the vulnerable plaques, the interventional therapeutic catheter is removed.  
       [0021] In another embodiment, the thermography catheter includes an inner assembly that nests within an outer assembly. The inner assembly comprises an elongate member that is a mandrel or a tubular mandrel. An expansion frame is coupled to the distal end of the elongate member. The expansion frame will carry at least one temperature sensor and typically a plurality of temperature sensors, for example, three temperature sensors, four temperature sensors, five temperature sensors, six temperature sensors, or any other suitable number of temperature sensors. The expansion frame operates to expand from a low-profile contracted condition suitable for navigating tortuous vessels, to an expanded condition that preferably achieves contact with the endoluminal surface at the region of interest. The inner assembly further includes a first tubular member bonded adjacent the distal end of the elongate member, the first tubular member adapted to receive and slide over a guidewire.  
       [0022] The outer assembly comprises an elongate tubular member having a proximal end, a distal end, and a lumen therebetween. A second tubular member is bonded adjacent the distal end of the elongate tubular member. A capture sheath is coupled to the distal end of the elongate tubular member and extends distally thereof. The thermography catheter is assembled by sliding the inner assembly within the outer assembly so that the expansion frame is covered by the capture sheath, the elongate member of the inner assembly fits within the elongate tubular member, and the first tubular member of the inner assembly fits within the second tubular member of the outer assembly. In certain embodiments, the expansion frame is carried at the distal end of the elongate member of the inner assembly. In other embodiments, the expansion frame is bonded to a third tubular member that is coupled in turn to the distal end of the elongate member of the inner assembly. As with the thermography catheter of other embodiments described above, here the expansion frame may be formed of a plurality of flexible struts that bow radially outward, and the struts may be a shape-memory alloy or polymer, or a superelastic material, e.g., nitinol.  
       [0023] The lumen of the elongate tubular member of the outer assembly may communicate with a flushing port at a proximal end of the thermography catheter. In this case, the lumen is adapted to receive a solution for flushing blood from the annulus between the capture sheath and the expansion frame, the annulus between the first tubular member of the inner assembly and the second tubular member of the outer assembly, and the annulus between the elongate tubular member of the outer assembly and the elongate member of the inner assembly. In certain cases, the elongate member of the inner assembly is a tubular mandrel or tubular member. In this case, the lumen of the tubular member of the inner assembly may communicate with a flushing port at the proximal end and one or more ports at the distal end of the thermography catheter. This lumen receives fluid for flushing blood from the annulus between the first tubular member of the inner assembly and the second tubular member of the outer assembly, the annulus between the capture sheath and the expansion frame, and the annulus between the elongate tubular member of the outer assembly and the elongate member of the inner assembly. Where flushing capabilities are present, the flushing port at the proximal end of the thermography catheter includes a valve to prevent blood loss when flushing is not performed, and to prevent bleed-back proximally into the catheter and annulus, which might inhibit smooth movement of sliding components. The valve can be any of a one-way valve, a pressure-activated valve, and a luer-activated valve.  
       [0024] The flushing port at the proximal end of the thermography catheter may include, in addition to the aforementioned valve, a fluid chamber having a dynamic seal that permits relative axial movement between the two assemblies without loss of fluid. In certain cases the slider moves proximal to withdraw the capture sheath to release the expansion frame. In other cases, the injection tube slides forward to advance the expansion frame beyond the capture sheath. The fluid chamber is defined by a support tube that contains the point of fluid entry (i.e., the valve), a tubular slider that is bonded to a proximal region of the outer assembly, and a dynamic seal between the support tube and the tubular slider. In this arrangement, the lumen of the elongate tubular member of the outer assembly communicates with the fluid chamber and allows sliding of the outer assembly relative to the inner assembly without loss of fluid. When the lumen of the tubular member of the inner assembly is used for flushing, the tubular member advantageously includes an annular seal to provide fluid resistance, and preferably to prevent fluid from escaping proximally through the lumen of the elongate tubular member of the outer assembly.  
       [0025] Each temperature sensor includes wires extending to the proximal end of a catheter to record temperature readings at the region of interest. In certain embodiments, the temperature sensor wires extend proximally within the lumen of the tubular member of the inner assembly. In other embodiments, the temperature sensor wires extend proximally within the elongate tubular member of the outer assembly.  
       [0026] The elongate tubular member of the outer assembly may be formed of hypo tube. It may be desirable to construct the thermography catheter so that the distal end of the catheter is more flexible than the proximal end of the catheter. Moreover, a gradual transition between these two sections is desired to avoid kinking and to maximize advancing capabilities. This can be accomplished by creating a flexible transition region on the distal section of the elongate member of the inner or outer assembly, e.g., a spiral cut hypo tube, a laser-welded spring, a tapered mandrel bonded to the distal end of a tubular elongate member of the inner or outer assembly, or a tapered mandrel where the mandrel is the elongate member of the inner assembly.  
       [0027] The methods of use of this thermography catheter will be understood to be similar to the methods described above. A guidewire is positioned across a region of interest within a target vessel. The proximal end of the guidewire is inserted into the first tubular member of the inner assembly. The catheter is advanced along the guidewire until the temperature sensors are located within the region of interest. The capture sheath is slid proximally or distally to release the temperature sensors. The temperature sensors are operated to measure the temperature of an endoluminal surface of the vessel.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0028]FIG. 1A depicts a thermography catheter according to the present invention having a slotted capture sheath slid proximally to release a strutted temperature sensor assembly.  
     [0029] 
     [0030]FIG. 1B depicts the thermography catheter of FIG. 1A with the capture sheath disposed about the strutted temperature sensor assembly.  
     [0031]FIG. 2A depicts a guidewire and guiding catheter disposed within a region of interest within a blood vessel.  
     [0032]FIG. 2B depicts a thermography catheter according to the present invention advanced over the guidewire and disposed within the region of interest.  
     [0033]FIG. 2C depicts the thermography catheter of FIG. 2B measuring temperature of a plaque after release of the expansion frame.  
     [0034]FIG. 2D depicts the removal of the thermography catheter from the region of interest after collapse of the expansion frame by the capture sheath.  
     [0035]FIG. 2E depicts angioplasty at the region of interest after exchange of an angioplasty catheter for the thermography catheter.  
     [0036]FIG. 2F depicts stent deployment at the region of interest after exchange of a stent-placement catheter for the thermography catheter.  
     [0037]FIG. 2G depicts the removal of the guidewire after removal of the stent-placement catheter.  
     [0038]FIG. 2H depicts the stent at the region of interest after removal of the guiding catheter.  
     [0039]FIG. 3A depicts a thermography catheter having a slotted capture sheath, and wherein the catheter and the capture sheath have an oval cross-section that provides a complimentary fit between the catheter and the capture sheath.  
     [0040]FIG. 3B depicts a cross-sectional view of the thermography catheter of FIG. 3A taken through section line B-B.  
     [0041]FIG. 3C depicts the catheter of FIG. 3A having a circular guidewire lumen.  
     [0042]FIG. 3D depicts a cross-sectional view of the thermography catheter of FIG. 3C taken through section line D-D.  
     [0043]FIG. 3E depicts the catheter of FIG. 3A having a circular outer diameter and circular guidewire lumen.  
     [0044]FIG. 3F depicts a cross-sectional view of the thermography catheter of FIG. 3E taken through section line F-F.  
     [0045]FIG. 3G depicts a catheter and capture sheath having a square-geometry complementary fit.  
     [0046]FIG. 3H depicts a catheter and capture sheath having a triangular-geometry complementary fit.  
     [0047]FIG. 4A depicts a cross-sectional view of the thermography catheter and capture sheath, wherein the catheter includes a longitudinal rib and the capture sheath includes a longitudinal groove.  
     [0048]FIG. 4B depicts a cross-sectional view of the thermography catheter and capture sheath, wherein the catheter includes a longitudinal rib and the capture sheath includes a longitudinal groove.  
     [0049]FIG. 4C depicts a cross-sectional view of the thermography catheter and capture sheath, wherein the catheter includes a pair of longitudinal ribs and the capture sheath includes a pair of longitudinal grooves.  
     [0050]FIG. 4D depicts a cross-sectional view of the thermography catheter and capture sheath, wherein the catheter includes a pair of longitudinal ribs and the capture sheath includes a pair of longitudinal grooves.  
     [0051]FIG. 5A depicts an inner assembly of a thermography catheter.  
     [0052]FIG. 5B depicts an outer assembly of a thermography catheter.  
     [0053]FIG. 5C depicts the inner assembly of a thermography catheter nested within the outer assembly.  
     [0054]FIG. 6 depicts the proximal end of the outer assembly with luer adaptor and a dynamic seal for flushing.  
     [0055]FIG. 6A depicts a longitudinal cross-section of the proximal end of the outer assembly of FIG. 6 taken through section line A-A.  
     [0056]FIG. 7A depicts a cross-sectional view through the elongate tubular member of the outer assembly and the mandrel of the inner assembly showing temperature sensor wires disposed alongside the mandrel and within the elongate tubular member.  
     [0057]FIG. 7B depicts cross-sectional view through the elongate tubular member of the outer assembly and the tubular mandrel of the inner assembly showing temperature sensor wires carried within the tubular mandrel.  
     [0058]FIG. 7C depicts cross-sectional view through the elongate tubular member of the outer assembly and the tubular mandrel of the inner assembly showing temperature sensor wires alongside the tubular mandrel and within the elongate tubular member.  
     [0059]FIG. 7D depicts cross-sectional view through the elongate tubular member of the outer assembly and the tubular mandrel of the inner assembly showing temperature sensor wires carried within the tubular mandrel.  
     [0060]FIG. 8A depicts a region of a thermography catheter having a tubular mandrel for flushing and a toroidal seal to prevent escape of fluid proximally.  
     [0061]FIG. 8B depicts a region of a thermography catheter having a matched diameter between the inner assembly and the outer assembly to prevent escape of fluid proximally. 
    
    
     DETAILED DESCRIPTION  
     [0062] In a first embodiment, a thermography catheter is provided as shown in FIG. 1A. Catheter  10  carries expansion frame  11  at the distal end of catheter  10 . Expansion frame  11  comprises of a plurality of struts that bow radially outward when released. Each strut carries temperature sensor  13  at a position on the strut, preferably at the point of maximum expansion. Catheter  10  includes orifice  12  that allows passage of guidewire  20  from the lumen of catheter  10  to a position outside the lumen of catheter  10 . Orifice  12  will generally be located closer to the distal end of catheter  10  than the proximal end of the catheter, and will generally be 10 centimeters or more proximal the distal end of catheter  10 , and more preferably 20 centimeters or more proximal the distal end of catheter  10 . Capture sheath  30  is slideably disposed about catheter  10 . Capture sheath  30  includes slotted aperture  33  to allow passage of guidewire  20  to an area outside of capture sheath  30 . It is desirable to maintain alignment between orifice  12  and slotted aperture  33  in order to maintain a clear passage for guidewire  20 .  
     [0063] When capture sheath  30  slides distally, it compresses and covers expansion frame  11  to provide a low-profile configuration for passage through tortuous vessels. Slotted aperture  33  allows for sliding of capture sheath  30  proximally (to release expansion frame  11 ) and distally (to compress expansion frame  11 ), and at all times maintains a clear passage for guidewire  20 . By using such an assembly that tracks over guidewire  20  for only a distal portion of the catheter, the thermography catheter can be exchanged for an interventional therapeutic catheter with only a minimal length guidewire outside of the patient&#39;s body, and the exchange can be performed by a single operator.  
     [0064] Although the present thermography catheter may initially find use in coronary vessels, it can be used in any vessels where thermographic measurements are desired. Vessel  100  having vulnerable plaque  99  is depicted in FIG. 2A. Coronary guidewire  20  is first introduced through a peripheral artery, such as the femoral artery, the subclavian artery, the brachial artery, or a carotid artery, and advanced to the region of interest and beyond vulnerable plaque  99 . The thermography catheter is advanced over guidewire  20  to the region of interest as shown in FIG. 2B. Guidewire  20  passes through distal guidewire port  15  of catheter  10  and exits catheter  10  proximally through orifice  12 . Guidewire  20  passes through slotted aperture  33  of capture sheath  30 , but preferably is maintained within guiding catheter  40 . Expansion frame  11  is positioned adjacent vulnerable plaque  99 . Capture sheath  30  is then withdrawn proximally to release expansion frame  11  as shown in FIG. 2C.  
     [0065] Thermographic measurements are taken from the endoluminal surface of plaque  99 . Expansion frame  11  is then collapsed by distally advancing capture sheath  30 . Thermography catheter  10  and capture sheath  30  are then removed from the region of interest as shown in FIG. 2D. Following removal of the thermography catheter from the proximal end of guidewire  20 , an interventional therapeutic procedure can be performed as shown in FIGS. 2E and 2F. Angioplasty catheter  50  is advanced over guidewire  20  as shown in FIG. 2E. After balloon  51  is aligned adjacent plaque  99 , angioplasty is performed to compress plaque  99 . Alternatively, stent-placement catheter  60  can be advanced over guidewire  20  as shown in FIG. 2F. Stent  61  is deployed to compress plaque  99  after the stent is properly positioned within the region of the vulnerable plaque. In certain embodiments, the stent will incorporate a drug for treating the vulnerable plaque. Stent-placement catheter  60  is then removed, and guidewire  20  is then withdrawn as shown in FIG. 2G. Guiding catheter  40  is then removed, leaving stent  61  as shown in FIG. 2H. Other alternative treatments of vulnerable plaque may include delivering localized or light-activated drugs, or localized thermal, cryogenic, ultrasonic, or radiation therapy to combat inflammation.  
     [0066] In certain embodiments it is desirable to maintain circumferential alignment between slotted aperture  33  and orifice  12  in order to maintain a clear passage for guidewire  20 . To this end, catheter  10  and capture sheath  30  may be constructed with an oval or an elliptical cross-section as shown in FIG. 3A. FIG. 3B shows a cross-sectional view of the assembly of FIG. 3A taken through section line B-B. When catheter  10  is nested within sheath  30 , the complementary geometry provides a registry mechanism to maintain circumferential alignment between orifice  12  and slotted aperture  33  of capture sheath  30 . Guidewire lumen  15  may have an elliptical geometry as shown in FIG. 3A or circular geometry as shown in FIG. 3C. FIG. 3D shows a cross-sectional view of the assembly of FIG. 3C taken through section line D-D. In other embodiments, the outer diameter of the capture sheath is circular while an elliptical registry mechanism is present, as shown in FIG. 3E, and in cross-section  3 F.  
     [0067] Alternative mechanisms for circumferential registry are depicted in FIGS. 3G and 3H, and in FIGS. 4A, 4B,  4 C, and  4 D. In FIG. 3G a registry mechanism based on square geometry is used. In FIG. 3H a registry mechanism based on triangular geometry is used. In FIG. 4A, catheter  10  includes longitudinal rib  19  shaped to fit within groove  39  formed within the inner surface of capture sheath  30 . The outer diameter of capture sheath  30  maintains a smooth cylindrical geometry. In FIG. 4B, catheter  10  includes longitudinal rib  19  shaped to fit within groove  39 . Here, both the inner diameter and outer diameter of sheath  30  are formed with groove  39 . In FIG. 4C, a pair of longitudinal ribs  19  in catheter  10  and longitudinal grooves  39  in sheath  30  are placed approximately 180° apart. In FIG. 4D, a pair of longitudinal ribs  19  in catheter  10  and longitudinal grooves  39  in sheath  30  are placed adjacent to each other.  
     [0068] In another embodiment, a thermography catheter having an inner assembly that fits within an outer assembly is shown in FIGS. 5A, 5B, and  5 C. The inner assembly comprises elongate member  70 , e.g., a mandrel, as shown in FIG. 5A. A first tubular member  71  is bonded adjacent the distal end of mandrel  70 . Tubular member  71  includes a lumen adapted to slideably receive a guidewire. Expansion frame  11 , having at least one temperature sensor and being operable between a contracted condition and an expanded condition, is bonded to a distal end of catheter  10 . Second tubular member  72  is disposed about the distal end of catheter  10 , but terminates proximal expansion frame  11 .  
     [0069] The outer assembly comprises elongate tubular member  80  having a lumen that extends from the proximal end to the distal end of tubular member  80  as shown in FIG. 5B. Second tubular member  81  is bonded adjacent the distal end of tubular member  80 . Capture sheath  30  is bonded distally to transition tubing  82 . Tubular member  81  is shaped to receive tubular member  71  of the inner assembly.  
     [0070] The thermography catheter is assembled by nesting the inner assembly within the outer assembly as shown in FIG. 5C. Mandrel  70  is slideably received within tubular member  80  while tubular member  71  is slideably received within tubular member  81 . A guidewire is slideably received through the distal end of expansion frame  11  and passes proximally through the lumen of tubular member  71  and tubular member  81 . It will be understood that the configuration described above ensures that a clear passage will be maintained at all times for the guidewire to emerge proximally from the guidewire lumen of the inner assembly and the capture sheath. Stated differently, the assembly shown in FIG. 5C will resist rotation of the inner assembly relative to the outer assembly and thereby prevent obstruction of the guidewire passageway.  
     [0071] The methods of use of this thermography catheter will be understood to be similar to the methods described above in FIGS. 2A to  2 H. A guidewire is positioned across a region of interest within a target vessel. The proximal end of the guidewire is inserted into tubular member  71  of the inner assembly. The catheter is advanced along the guidewire until the temperature sensors are located within the region of interest. Capture sheath  30  is slid proximally to release the temperature sensors and expansion frame. The temperature sensors are operated to measure the temperature of the endoluminal surface of the vessel at the site of vulnerable plaque  99 . The thermography catheter is removed after closing the expansion frame with the capture sheath. Interventional therapeutic catheters as discussed above are then exchanged for the thermography catheter and advanced over the guidewire to treat vulnerable plaque  99 .  
     [0072] In certain cases it will be desirable to flush blood from the annulus between tubular member  80  and mandrel  70 , the annulus between tubular member  71  of the inner assembly and tubular member  81  of the outer assembly, and the annulus between capture sheath  30  and expansion frame  11 . Flushing can be used to avoid penetration of blood between sliding members of the inner and outer assemblies. Penetration of blood is undesirable because blood may clot between the sliding members of the inner and outer assemblies. Even in the absence of clotting, blood will inhibit proper movement due to the higher viscosity of blood.  
     [0073] In order to perform flushing the lumen of tubular member  80  of the outer assembly communicates with a flushing port at the proximal end of the thermography catheter as shown in FIGS. 6 and 6A. Tubular member  80  of the outer assembly is bonded proximally to slider body  90 , and terminates proximally at flushing port  88 . Port  88  communicates with chamber  98  and receives fluid, such as saline, lactated Ringers, or water, for flushing. Chamber  98  is defined by slider body  90  and communicates proximally with injection tube  91 . Slider body  90  includes radial hole  96  for a knob. Dynamic seal  92 , e.g., an  0 -ring, is disposed between slider body  90  and injection tube  91  to enable relative longitudinal movement without loss of fluid. Slider cap  95  is a further component of the assembly for the dynamic seal. The proximal end of injection tube  91  is bonded to coupling  94 , which is connected to luer  93 , which provides for input of fluid. A one-way valve, a pressure activated valve, or a luer-activated valve may be included to prevent blood escape when flushing is not needed.  
     [0074] In this manner, fluid injected through luer  93  will pass through coupling  94 , injection tube  91 , and fill chamber  98 . Fluid will then pass distally to port  88  and through the lumen of tubular member  80 , thereby flushing the annuli between sliding components of the inner and outer assemblies. In cases where a tubular mandrel is used for flushing (e.g., FIGS. 7C and 7D), it may be desirable to dimension tubular member  71  and tubular member  81  (see FIG. 5C) so that a somewhat narrow annulus exists between these members when they are slideably assembled. Having a narrow annulus between these members will serve to maximize flushing distally to the annulus between the expansion frame and capture sheath, and minimize escape of saline proximally through the annulus between tubular members  71  and  81 .  
     [0075] Various possibilities for the placement of temperature sensor wires and flushing lumens are shown in FIGS. 7A, 7B,  7 C, and  7 D, each of which is a cross-sectional view of FIG. 5C taken through section line  7 - 7 . Temperature sensor wires  77  are attached distally to temperature sensors  13  (see FIG. 1A) and extend proximally beyond the useable length or working section of the thermography catheter and into a monitor that measures and records temperature readings taken from vulnerable plaque. As shown in FIG. 7A, annulus  66  between tubular member  80  of the outer assembly and mandrel  70  of the inner assembly may be used both for flushing and to carry temperature sensor wires  77 . In the arrangement shown in FIG. 7B, mandrel  70  comprises a tubular structure. Tubular mandrel  70  carries temperature sensor wires  77  while annulus  66  provides flushing capabilities. In FIG. 7C, tubular mandrel  70  is equipped with flushing ports  68  near the distal end of mandrel  70 . The lumen of mandrel  70  provides flushing capabilities while temperature sensor wires  77  are carried in the annulus between tubular member  80  and mandrel  70 . Finally, FIG. 7D shows an arrangement wherein both temperature sensor wires  77  and flushing capabilities are provided through lumen  67  of mandrel  70 .  
     [0076] Where flushing capabilities are provided through a tubular mandrel as shown in FIGS. 7C and 7D, it may be necessary to prevent escape of fluid proximally as shown in FIGS. 8A and 8B. Fluid for flushing travels distally through tubular mandrel  70  and flows through ports  68  into the annulus between tubular member  80  and mandrel  70 . Toroidal seal  55  may be bonded to the inner surface of tubular member  80  to block proximal fluid flow. Alternatively, toroidal seal  55  may be bonded to the outer surface of mandrel  70  to block proximal fluid flow. In another alternative, tubular member  80  has a tapered inner lumen that fits tightly to mandrel  70 , creating a very small annulus. In this manner, mandrel  70  remains slideable within tubular member  80 , but fluid flow proximally through the annulus is prevented.  
     [0077] A lubricious coating may be provided on certain components to improve sliding of components. Teflon, parylene, or other materials may be used as the lubricious material. Mandrel  70  (FIG. 5A), tubular member  80  (FIG. 5B), and injection tube  91  (FIG. 6A) are among the components that will benefit from lubricious coating.  
     [0078] The working length of the thermography catheter will generally be between 50 and 200 centimeters, preferably approximately between 75 and 150 centimeters. The outer diameter of the thermography catheter shaft will generally be between 1 French and 8 French, preferably approximately between 1.5 French and 4 French. The diameter of the expansion frame when expanded will generally be between 1 and 10 mm, preferably approximately 2 and 5 mm for coronary artery applications. The foregoing ranges are set forth solely for the purpose of illustrating typical device dimensions. The actual dimensions of a device constructed according to the principles of the present invention may obviously vary outside of the listed ranges without departing from those basic principles.  
     [0079] Although the foregoing invention has, for the purposes of clarity and understanding, been described in some detail by way of illustration and example, it will be obvious that certain changes and modifications may be practiced that will still fall within the scope of the appended claims. For example, the devices and features depicted in any figure or embodiment can be used in any of the other depicted embodiments.