Patent Publication Number: US-2003233052-A1

Title: Catheter with thermal sensor for detection of vulnerable plaque

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates generally to intravascular catheters. More particularly, the present invention relates to intravascular catheters adapted to make measurements within the body of a patient.  
       BACKGROUND OF THE INVENTION  
       [0002] Therapy modalities for heart disease have traditionally focused on treating blood vessels which have become occluded (blocked) or stenotic (narrowed) by calcified plaque deposits. Blood vessels that have become occluded or stenotic in this manner may interrupt the flow of blood that supplies oxygen to the heart muscle. Occluded or stenotic blood vessels may be treated with a number of medical procedures including angioplasty and atherectomy. Angioplasty techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA) are relatively noninvasive methods of treating restrictions in blood vessels. In these procedures, a balloon catheter is advanced over a guidewire until the balloon is positioned proximate a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. During an atherectomy procedure, the stenotic lesion is mechanically cut or abraded away from the blood vessel wall using an atherectomy catheter.  
       [0003] Calcified plaque deposits typically comprise hard materials. Plaque may also comprise soft materials or combinations of soft and hard materials. Soft plaque typically comprises deposits of cholesterol and other fats which build up within the blood vessels as a patient ages. The build up of plaque in the blood vessels is sometimes referred to as atherosclerosis, or hardening of the arteries.  
       [0004] Atherosclerosis often begins as a small injury to an artery wall. This injury triggers a cyclic cascade of injury and response, inflammation, and healing, which may ultimately lead to the narrowing of the artery. As the atherosclerotic plaque worsens, inflammatory cells, especially macrophages, collect at the site to isolate the debris of the damaged tissue. The result is a core of lipid, macrophages or foam cells and nectrotic tissue, covered by a fibrous cap of scar tissue. If the fibrous cap becomes weakened or is subjected to excessive stress, it may rupture, exposing the thrombogenic contents of the core to the blood stream. If the resulting blood clot is severe enough, it may occlude the artery. If this obstruction persists in a coronary artery, a myocardial infarction may result.  
       [0005] Plaque deposits with a risk of rupturing are sometimes referred to as vulnerable plaque. Vulnerable plaque typically comprises a core of soft materials covered with a fibrous cap. Many vulnerable plaque deposits do not limit the flow of blood through the blood vessels. It has recently been appreciated that vulnerable plaques that do not limit flow may be particularly dangerous because they produce no warning symptoms, but can rupture suddenly causing heart attack and death. This may occur, for example, when the vulnerable plaque ruptures, forming a blood clot inside the blood vessel lumen and causing a blockage.  
       [0006] Recently, the pivotal role of inflammation in the progression of athersclerosis has been recognized. A systemic increase in temperature is often associated with infection (e.g., a fever). Likewise, a local infection or localized damage to tissue may result in a localized increase in temperature. An increase in temperature is thought to be caused by the response of the immune system to infection, known as inflammation. It has been observed that the inflamed necrotic core of a vulnerable plaque maintains itself at a temperature that may be one or more degrees Celsius higher than that of the surrounding tissue. For example, an inflamed plaque in a human heart, where the normal temperature is about 37° C. may be at a temperature as high as 40° C.  
       SUMMARY OF THE INVENTION  
       [0007] The present invention is directed to methods and devices for the detection of vulnerable plaque within an artery. A device in accordance with one embodiment of the present invention includes an elongate shaft having a distal end and a proximal end. A detector assembly is fixed to the elongate shaft proximate the distal end thereof.  
       [0008] In one method in accordance with the present invention, a catheter including a detector assembly disposed within a balloon is provided. The catheter is advanced through the vasculature of a patient until a distal end of the catheter is proximate a target region of a vessel. The balloon of the catheter is then inflated, for example, with a gas. When the balloon is inflated, blood within the vessel is displaced. The detector assembly detects infrared radiation from the body of the patient. In a preferred method, the infrared radiation is absorbed by the detector assembly and converted to an electrical signal. The electrical signal is transmitted to an external display and/or recording device. In an additional method in accordance with the present invention, a bolometer is placed proximate a target tissue.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009] Other objects of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the Figures thereof and wherein:  
     [0010]FIG. 1 is a perspective view of a distal portion of a catheter in accordance with an exemplary embodiment of the present invention;  
     [0011]FIG. 2 is a perspective view of a guidewire in accordance with an exemplary embodiment of the present invention FIG.  
     [0012]FIG. 3 is a perspective view of a device in accordance with an exemplary embodiment of the present invention;  
     [0013]FIG. 4 is a perspective view of a distal portion of a catheter in accordance with an exemplary embodiment of the present invention;  
     [0014]FIG. 5 is a perspective view of a distal portion of a catheter in accordance with an exemplary embodiment of the present invention;  
     [0015]FIG. 6 is a perspective view of a distal portion of a catheter in accordance with an exemplary embodiment of the present invention;  
     [0016]FIG. 7 is a cross sectional view of a detector assembly in accordance with an exemplary embodiment of the present invention; and  
     [0017]FIG. 8 is a diagrammatic representation of a device in accordance with an exemplary embodiment of the present invention;  
     [0018]FIG. 9 is a partial cross sectional view of a therapeutic catheter in accordance with an additional embodiment of the present invention;  
     [0019]FIG. 10 is an additional partial cross sectional view of the therapeutic catheter of FIG. 9; and  
     [0020]FIG. 11 is a partial cross-sectional view of a therapeutic catheter in accordance with an additional embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0021] The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. In some cases, the drawings may be highly diagrammatic in nature. Examples of constructions, materials, dimensions, and manufacturing processes are provided for various elements. Those skilled in the art will recognize that many of the examples provided have suitable alternatives which may be utilized.  
     [0022]FIG. 1 is a perspective view of a distal portion  102  of a catheter  100  in accordance with the present invention. Catheter  100  includes an elongate shaft  104  having a distal end  106  and a proximal end  108  (not shown). In the embodiment of FIG. 1, catheter  100  includes a distal guidewire port  172  disposed proximate distal end  106  of elongate shaft  104 . Elongate shaft  104  includes a plurality of walls defining a guidewire lumen  170  that is in fluid communication with distal guidewire port  172  and a proximal guidewire port  174  (not shown). A guidewire  176  is partially disposed within guidewire lumen  170 . It is to be appreciated that catheter  100  may comprise various general types of catheters. Examples of catheter types include over-the-wire catheters and single operator exchange (SOE) catheters.  
     [0023] A balloon  178  is disposed about elongate shaft  104  proximate distal end  106  thereof. Elongate shaft  104  also includes a plurality of walls defining an inflation lumen  122 . Elongate shaft  104  also defines an inflation orifice  120  that is in fluid communication with inflation lumen  122  and balloon  178 . A fluid source  124  (not shown) may be coupled to catheter  100  proximate proximal end  108 . Balloon  178  may be inflated by urging fluid from fluid source  124  into balloon  178  via inflation lumen  122  and inflation orifice  120 . For the purposes of this disclosure, the term fluid may refer to a liquid and/or a gas. In a preferred method associated with catheter  100  of FIG. 1, balloon  178  is inflated with a gas or liquid that is substantially transparent to infrared energy.  
     [0024] Catheter  100  of FIG. 1 is a type of catheter that may be generally referred to as a balloon catheter. It is to be appreciated that catheter  100  may comprise various general types of catheters. Examples of catheter types include percutaneous myocardial revascularization (PMR) catheters, atherectomy catheters, and stent delivery catheters.  
     [0025] Those of skill in the art will appreciate that elongate shaft  104  may comprise various materials without deviating from the spirit and scope of the present invention. Elongate shaft  104  may also be comprised of a single material, or a combination of materials. For example, elongate shaft  104  may include an inner tube. In a presently preferred embodiment, the inner tube is comprised of PTFE (polytetrafluoroethylene). PTFE is a preferred material because it creates a smooth, low-friction surface for the passage of other devices through the elongate shaft  104 . Elongate shaft  104  may also include a support member, wound or braided around the inner tube. In a presently preferred embodiment, the support member is comprised of a plurality of filaments. The filaments may be stainless steel wire. Those with skill in the art will appreciate that other embodiments of a support member are possible without deviating from the spirit and scope of the present invention. For example, a support member may comprise a woven polymer fabric. By way of a second example, a support member may comprise polymer fibers wound in a braided pattern.  
     [0026] In a presently preferred embodiment, elongate shaft  104  comprises polyether block amide (PEBA). Polyether block amide is commercially available from Atochem Polymers of Birdsboro, Pa. under the trade name PEBAX. Also in a presently preferred embodiment, elongate shaft  104  is fabricated using an extrusion process. In this process, molten PEBA may be extruded onto the combined layers of an inner tube and a support member. When this process is utilized, the extruded material fills any interstitial spaces in the support member.  
     [0027] It is to be understood that other manufacturing processes can be used without departing from the spirit and scope of the present invention. Elongate shaft may also comprise other materials without departing from the spirit of scope of this invention. Examples of materials that may be suitable in some applications include: polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane, and polytetrafluoroethylene (PTFE).  
     [0028] Catheter  100  also includes a detector assembly  126 . In the embodiment of FIG. 1, detector assembly  126  is fixed to an outer surface  128  of elongate shaft  104 . Also in the embodiment of FIG. 1, detector assembly  126  is disposed within a cavity  130  of balloon  178 . A conductor  132  is coupled to detector assembly  126 . Conductor  132  may include a plurality of signal paths. In the embodiment of FIG. 1, conductor  132  is partially disposed within inflation lumen  122  of elongate shaft  104 .  
     [0029] In a preferred embodiment, detector assembly  126  comprises a plurality of infrared radiation sensors each having a low thermal mass. In a particularly preferred embodiment, detector assembly  126  comprises a microbolometer array fabricated utilizing micro electro mechanical machining (MEMS) fabrication processes (e.g., photolithographic processes). Also in a preferred embodiment, detector assembly  126  produces an electrical signal that is indicative of the infrared energy that impinges upon detector assembly  126 . Several detector assemblies  126  may be disposed about elongate shaft  104 . The output from each assembly can be separately monitored to determine the angular location of the plaque on the vessel wall. Alternately, a single detector assembly  126  could be used while shaft  104  is rotated in the vessel. Then the output of detector assembly  126  can be correlated with the angular position of detector assembly  126  to determine the angle location of the plaque on the vessel wall. These latter two options can also be utilized for the detector assemblies described below with respect to the alternate embodiments of the invention.  
     [0030] In a method in accordance with the present invention, distal end  106  of catheter  100  is advanced through the vasculature of a patient until distal portion  102  of catheter  100  is proximate a target region of a vessel. Balloon  178  is then inflated, for example, with a gas. When balloon  178  is inflated, it displaces blood within the vessel. Detector assembly  126  detects infrared radiation from the body of the patient. In a preferred method, detector assembly  126  is utilized to produce an electrical signal that is indicative of the infrared energy that impinges upon detector assembly  126 . The electrical signal is transmitted to an external display and/or recording device via conductor  132 .  
     [0031]FIG. 2 is a perspective view of a guidewire  276  in accordance with the present invention. Guidewire  276  includes an elongate shaft  204 . A coil  234  is fixed to elongate shaft  204  proximate a distal end  106  thereof. A detector assembly  226  overlays an outer surface  228  of elongate shaft  204 . A conductor  232  is coupled to detector assembly  226 . Conductor  232  may include multiple signal conducting paths.  
     [0032] In the embodiment of FIG. 2, a sheath  236  is disposed about detector assembly  226 , a portion of elongate shaft  204 , and a portion of conductor  232 . In a preferred embodiment, sheath  236  comprises shrink tubing. In a particularly preferred embodiment, sheath  236  comprises polytetrafluoroethylene (PTFE) shrink tubing. PTFE shrink tubing which may be suitable in some applications is commercially available Zeus Industries of Orangeburg, S.C. and Raychem Corporation of Menlo Park, Calif. Embodiments of guidewire  276  have been envisioned which do not include sheath  236 .  
     [0033]FIG. 3 is a perspective view of device  340  in accordance with the present invention. Device  340  includes an elongate shaft  304  defining a guidewire lumen  370 . A guidewire  376  is disposed within guidewire lumen  370 . A detector assembly  326  is fixed to an outer surface  328  of elongate shaft  304 . A conductor  332  is coupled to detector assembly  326 . Conductor  332  may include multiple signal conducting paths.  
     [0034]FIG. 4 is a perspective view of a distal portion  402  of a catheter  400  in accordance with the present invention. Catheter  400  includes an elongate shaft  404  having a distal end  406  and a proximal end (not shown). In the embodiment of FIG. 4, catheter  400  includes a distal guidewire port  472  disposed proximate distal end  406  of elongate shaft  404 . Elongate shaft  404  includes a plurality of walls defining a guidewire lumen  470  that is in fluid communication with distal guidewire port  472  and a proximal guidewire port  474  (not shown).  
     [0035] Elongate shaft  404  also includes a plurality of walls defining an inflation lumen  422  in fluid communication with a balloon  478  that is disposed about elongate shaft  404 . A fluid source  424  (not shown) may be coupled to catheter  400  proximate proximal end  408 . Balloon  478  may be inflated by urging fluid from fluid source  424  into balloon  478  via inflation lumen  422 . Catheter  400  also includes a detector assembly  426 . In the embodiment of FIG. 4, detector assembly  426  is fixed to an outer surface  428  of balloon  478 . A conductor  432  is coupled to detector assembly  426 . Conductor  432  may include a plurality of signal paths.  
     [0036] In a method in accordance with the present invention, distal end  406  of catheter  400  is advanced through the vasculature of a patient until distal portion  402  of catheter  400  is proximate a target region of a vessel. Balloon  478  is then inflated, for example, with a gas. When balloon  478  is inflated, blood within the vessel is displaced and detector assembly  426  is placed in intimate contact with a portion of the vessel wall. Detector assembly  426  detects infrared radiation from the body of the patient. In a preferred method, detector assembly  426  produces an electrical signal that is indicative of the infrared energy that impinges upon detector assembly  426 . The electrical signal is transmitted to an external display and/or recording device via conductor  432 .  
     [0037]FIG. 5 is a perspective view of a distal portion  502  of an additional embodiment of a catheter  500  in accordance with the present invention. Catheter  500  includes an elongate shaft  504  having a distal end  506  and a proximal end (not shown). In the embodiment of FIG. 5, catheter  500  includes a distal guidewire port  572  disposed proximate distal end  506  of elongate shaft  504 . Elongate shaft  504  includes a plurality of walls defining a guidewire lumen  570  that is in fluid communication with distal guidewire port  572  and a proximal guidewire port  574  (not shown).  
     [0038] A balloon  578  is disposed about elongate shaft  504 . Elongate shaft  504  also includes a plurality of walls defining an inflation lumen  522  in fluid communication with balloon  578 . A fluid source  524  (not shown) may be coupled to catheter  500  proximate proximal end  508 . Balloon  578  may be inflated by urging fluid from fluid source  524  into balloon  578  via inflation lumen  522 .  
     [0039] Catheter  500  also includes a detector assembly  526 . In the embodiment of FIG. 5, detector assembly  526  overlays an outer surface  528  of elongate shaft  504 . A conductor  532  is coupled to detector assembly  526 . Conductor  532  may include a plurality of signal paths.  
     [0040]FIG. 6 is a perspective view of a distal portion  602  of an additional embodiment of a catheter  600  in accordance with the present invention. Catheter  600  includes an elongate shaft  604  having a distal end  606  and a proximal end (not shown). A first balloon  678  is disposed about elongate shaft  604  proximate distal end  606  thereof. A second balloon  679  is disposed about elongate shaft  604  proximally of first balloon  678 .  
     [0041] Elongate shaft  604  includes a plurality of walls defining an inflation lumen  622  in fluid communication with first balloon  678  second balloon  679 . A fluid source  624  (not shown) may be coupled to catheter  600  proximate proximal end  608 . First balloon  678  and second balloon  679  may be inflated by urging fluid from fluid source  624  into balloon  678  via inflation lumen  622 . Embodiments of catheter  600  have been envisioned in which elongate shaft includes a first inflation lumen and a second inflation lumen. In this envisioned embodiment, first balloon  678  and second balloon  679  may be selectively inflated.  
     [0042] Catheter  600  also includes a detector assembly  626 . In the embodiment of FIG. 6, detector assembly  626  is disposed between first balloon  678  and second balloon  679 . A conductor  632  is coupled to detector assembly  626 . Conductor  632  may include a plurality of signal paths.  
     [0043]FIG. 7 is a cross sectional view of a detector assembly  726  in accordance with the present invention. Detector assembly  726  includes substrate  742  and a cover  744  that define a sensor array chamber  746 . In a preferred embodiment, cover  744  is sealingly fixed to substrate  742  by a bond  748 . Also in a preferred embodiment, sensor array chamber  746  is substantially filled with a gas having a low thermal conductivity. In a particularly preferred embodiment, sensor array chamber  746  contains a vacuum.  
     [0044] A plurality of pixels  751  are disposed on a top surface of substrate  742  of detector assembly  726  to obtain a thermal image of a strip of plaque and nearby vessel wall. In the embodiment of FIG. 7, each pixel comprises a sensing element  752  and a cavity  750  defined by substrate  742 . In FIG. 7 it may be appreciated that each sensing element  752  is disposed above a cavity  750 . In a preferred embodiment, each sensing element  752  comprises a thin film resistor. In the embodiment of FIG. 7, each sensing element  752  is supported by a beam  754 . Disposing each sensing element  752  above a cavity  750  preferably thermally isolates the sensing elements  752  from the substrate  742 .  
     [0045]FIG. 8 is a diagrammatic representation of a device  840  in accordance with the present invention. Device  840  includes an elongate shaft  804  and a detector assembly  826  fixed to an outer surface  828  of elongate shaft  804 . Detector assembly  826  comprises a plurality of pixels  825  disposed on a substrate  827 . Each pixel  825  comprises a sensing element  85  coupled to a switching device  856 . In the embodiment of FIG. 8, each switching device  856  comprises a diode  858  and each sensing element  852  comprises a resistor  853 . In a preferred embodiment each sensing element comprises a thin film resistor. Embodiments of detector assembly  826  are possible in which each switching device  856  comprises other elements, for example, transistors.  
     [0046] A first common conductor  868  is coupled to the switching devices  856  of a first group  870  of pixels  825 . In the embodiment of FIG. 8, the pixels  825  of first group  870  form a first row  872 . First common conductor  868  is also coupled to a group address circuit  874 . Group address circuit  874  may be utilized to selectively activate the switching devices  856  of the pixels  825  of first group  870 . A second common conductor  876  is also coupled to group address circuit  874 .  
     [0047] Second common conductor  876  is coupled to the switching devices  856  of a second group  878  of pixels  825 . Group address circuit  874  may selectively activate the switching devices  856  of pixels  825  of second group  878 , for example by applying a voltage to second common conductor  876 . In the embodiment of FIG. 8, the pixels  825  of second group  878  form a second row  880 . Detector assembly  826  of FIG. 8 also includes a third row  882  and an Nth row  884 , each row comprising a plurality of pixels  825  to obtain a thermal image of a strip of plaque and nearby vessel wall. It is to be appreciated that detector assembly  826  may comprise any number of pixels  825 , and that these pixels may be arranged in any number of groups without deviating from the spirit and scope of the present invention.  
     [0048] In the embodiment of FIG. 8, a first interrogation conductor  886  is coupled to the first pixel  825  in each group. First interrogation conductor  886  is coupled to a sensor interrogation circuit  888 . Sensor interrogation circuit  888  may be utilized to interrogate a sensing device  852  of a pixel  825 . For example, group address circuit  874  may selectively activate the switching devices  856  of pixels  825  of first group  870 , and sensor interrogation circuit  888  may selectively couple the sensing device  852  of a pixel {1,1}  890  to a readout conductor  892 . Readout conductor  892  is preferably coupled to a measurement instrument that is adapted to assess the current state of a sensing device  852 . In FIG. 8 it may be appreciated that a bus  894  is coupled to sensor interrogation circuit  888  and group address circuit  874 . Bus  894  may include any number of conductors. These conductors may be used, for example, to communicate command signals between group address circuit  874  and a measurement instrument.  
     [0049]FIG. 9 is a partial cross sectional view of a therapeutic catheter  803  in accordance with an additional embodiment of the present invention. Once a plaque deposit is located, therapeutic catheter  803  may be used, for example, to inject lipid/plaque stabilizing drugs into the plaque deposit. Therapeutic catheter  803  comprises an outer shaft  805  and a laterally flexible portion  807  that is fixed to a distal end of outer shaft  805 . In the embodiment of FIG. 9, laterally flexible portion  807  comprises a bellows  837 .  
     [0050] Therapeutic catheter  803  includes a catheter lumen  833  defined by outer shaft  805  and bellows  837 . In FIG. 9, an inner shaft  835  is shown slidingly disposed in catheter lumen  833 . In the embodiment of FIG. 9, inner shaft  835  forms a point  843  proximate the distal end thereof. Inner shaft  835  defines an injection port  845  proximate point  843  and an injection lumen  847  in fluid communication with injection port  845 . In a preferred embodiment, injection port  845  may be fluidly coupled to a fluid source via injection lumen  847 . Fluid from the fluid source may be injected into a plaque deposit by piercing the outer portion of the deposit with point  843  so that injection port  845  is disposed within a core of the plaque deposit. Fluid from the fluid source may then be urged through injection lumen  847  and injection port  845 . The fluid injected into the plaque deposit may preferably include lipid/plaque stabilizing drugs.  
     [0051] In FIG. 9, it may be appreciated that bellows  837  comprises a wall  849  forming a plurality of corrugations  853 . In the embodiment of FIG. 9, a plurality of hoops  857  are fixed to bellows  837 . A pull wire  859  is shown in FIG. 9 extending through hoops  857  and an aperture  855  defined by outer shaft  805 . A distal end of pull wire  859  is fixed to laterally flexible portion  807  of therapeutic catheter  803  distally of hoops  857 . A proximal portion of pull wire  859  preferably extends proximally beyond a proximal end of outer shaft  805 . Pull wire  859  may preferably be used to change the shape of laterally flexible portion  807  of therapeutic catheter  803 . In a preferred embodiment, laterally flexible portion  807  of therapeutic catheter  803  may have a generally straight shape as shown in FIG. 9, and may selectively have a generally curved shape.  
     [0052]FIG. 10 is an additional partial cross sectional view of therapeutic catheter  803  of FIG. 9. In FIG. 10 therapeutic catheter  803  is shown disposed within a blood vessel  883 . In the embodiment of FIG. 10, laterally flexible portion  807  of therapeutic catheter  803  has been urged into a generally curved shape having radius of curvature  863 .  
     [0053] Inner shaft  835  is slidingly disposed within catheter lumen  833  and inner shaft  835  may be advanced distally so that point  843  is disposed distally of the distal end of laterally flexible portion  807 . With laterally flexible portion  807  of therapeutic catheter  803  having a generally curved shape, point  843  may be directed toward a plaque deposit  865 . In the embodiment of FIG. 10, point  843  of inner shaft  835  has pierced a wall of plaque deposit  865  and injection port  845  is disposed within a core  867  of plaque deposit  865 . In a preferred embodiment, injection port  845  is fluidly coupled to a fluid source via an injection lumen  847 . Fluid from the fluid source may be injected into the core  867  of plaque deposit  865  by urging the fluid through injection lumen  847  and injection port  845 . The fluid injected into the plaque deposit preferably includes lipid/plaque stabilizing drugs.  
     [0054]FIG. 11 is a partial cross sectional view of a therapeutic catheter  903  in accordance with an additional embodiment of the present invention. Therapeutic catheter  903  comprises an outer shaft  905  and a laterally flexible portion  907  that is fixed to a distal end of outer shaft  905 . In the embodiment of FIG. 11, laterally flexible portion  907  comprises a coil  973  having a plurality of turns  975 . In a preferred embodiment, adjacent turns  975  are disposed in close proximity to one another. In a particularly preferred embodiment, adjacent turns  975  contact each other across substantially their entire length. In this particularly preferred embodiment, coil  973  has a high level of longitudinal pushability and a high level of lateral flexibility.  
     [0055] Therapeutic catheter  903  includes a catheter lumen  933  defined by outer shaft  905  and coil  973 . In FIG. 11, an inner shaft  935  is shown slidingly disposed within catheter lumen  933 . In the embodiment of FIG. 11, inner shaft  935  forms a point  943  proximate the distal end thereof. Inner shaft  935  defines an injection port  945 , proximate point  943  and an injection lumen  947  in fluid communication with injection port  945 . In a preferred embodiment, injection port  945  may be fluidly coupled to a fluid source via injection lumen  947 . Fluid from the fluid source may be injected into a plaque deposit by piercing a wall of the deposit with point  943  so that injection port  945  is disposed within a core of the plaque deposit. Fluid from the fluid source may then be urged through injection lumen  947  and injection port  945 . The fluid injected into the plaque deposit may preferably include lipid/plaque stabilizing drugs.  
     [0056] In FIG. 11, it may be appreciated that therapeutic catheter  903  includes a pull wire  959  that extends through an aperture  955  defined by outer shaft  905 . A distal end of pull wire  959  is fixed to coil  973  of therapeutic catheter  903  proximate a distal end thereof. A proximal portion of pull wire  959  preferably extends proximally beyond a proximal end of outer shaft  905 . Pull wire  959  may preferably be used to change the shape of coil  973  of therapeutic catheter  903 . In a preferred embodiment, coil  973  of therapeutic catheter  903  may assume a generally straight shape and may also selectively assume a generally curved shape. In the embodiment of FIG. 11, therapeutic catheter  903  is shown having a generally curved shape with a radius of curvature  963 .  
     [0057] Inner shaft  935  is slidingly disposed within a catheter lumen  933 . In FIG. 11 it may be appreciated that catheter lumen  933  includes a shaft lumen  977  defined by outer shaft  905  and a coil lumen  979  defined by coil  973 . Inner shaft  935  may be advanced distally so that point  943  is disposed distally of the distal end of coil  973 . Point  943  of inner shaft  935  may be directed toward a plaque deposit  965 , for example, by urging coil  973  into a generally curved shape. Coil  973  may be urged into a generally curved shape, for example, by applying a pulling force to the proximal portion of pull wire  959 .  
     [0058] Having thus described the preferred embodiments of the present invention, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached. Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the invention.