Abstract:
A system for locating inflamed plaque in a vessel is provided herein. The system includes a receiver, a positioner and a sensor. The receiver receives information about a vessel wall of the vessel. The positioner is used to position the receiver in the vessel to receive information from the vessel wall. The sensor is connected to the receiver. In use, the positioner selectively moves the receiver in the vessel to collect information about the vessel wall. The information is then transferred to the sensor to determine the temperature at the vessel wall. Temperatures at various locations can be taken, with elevated temperatures being indicative of inflamed plaque.

Description:
[0001]    This application is a continuation-in part of applicants&#39; copending application Ser. No. 08/774,022, filed on Dec. 27, 1996, entitled “Device and Method for Locating Inflamed Plaque In An Artery”, the contents of which are incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention pertains generally to medical devices and methods for evaluating and/or locating plaque in a vessel. The present invention is particularly useful for evaluating and/or locating inflamed or unstable plaque in a vessel.  
         BACKGROUND  
         [0003]    Plaque can develop in different locations in a patient&#39;s cardiovascular system. The plaque can vary in size and shape. For example, the plaque can be quite extensive and occlude a substantial length of the vessel. Alternately, the plaque can be quite short and small.  
           [0004]    Further, the condition of the plaque can vary. For example, the plaque can be inflamed and unstable, or the plaque can be quite stable. It is important to recognize that, inflamed and unstable plaque is subject to rupture, erosion or ulceration which can cause the patient to experience a myocardial infarction.  
           [0005]    Presently, a number of procedures are available for locating plaque in a vessel. One commonly performed procedure is angiography, which involves taking x-ray pictures of vessels after injecting a radiopaque substance into the vessels. While this procedure is quite effective for locating large plaque in vessels, this procedure is unable to evaluate whether the plaque is inflamed and unstable. Therefore, there is a need of a device and procedure for precisely and accurately locating the position of unstable, inflamed plaque.  
           [0006]    In light of the above, it is an object of the present invention to provide a device and method for locating unstable, inflamed plaque in a vessel. Another object of the present invention is to provide a system for determining the size of the unstable, inflamed plaque in the vessel. Another object of the present invention is to provide a device and method for locating inflamed plaque which is relatively easy and inexpensive to manufacture and relatively easy to operate.  
         SUMMARY  
         [0007]    The present invention is directed to a device and method which satisfies the objectives for locating inflamed plaque on the wall of a vessel of a patient. A device having features of the present invention, includes at least one receiver for receiving information about the patient, a sensor for determining the presence of inflamed plaque based upon the information received from the receiver, and a positioner for selectively positioning each of the receivers in the vessel.  
           [0008]    Importantly, unstable and inflamed plaque can cause the temperature of the vessel wall to elevate up to two and a half degrees Centigrade or Celsius proximate the inflamed plaque. With the present invention, each receiver is inserted into the vessel to receive information from the vessel wall. The information is subsequently transferred to the sensor. The sensor determines temperature at each receiver based upon the information received from each receiver. Therefore, the present invention is able to locate inflamed plaque by monitoring the vessel wall for elevated temperatures.  
           [0009]    Typically, each receiver includes a single carrier for transferring the information to the sensor. As provided herein, each carrier can be an optical fiber and each receiver can be an aperture formed on the optical fiber which contacts the vessel wall. Preferably, a plurality of receivers are positioned circumferentially around the positioner to decrease the chance of the receivers missing small inflamed plaque.  
           [0010]    Optimally, the device includes a radiopaque marker which is positioned proximate each receiver so that the location of the receiver in the vessel can be determined with a fluoroscope.  
           [0011]    The sensor can include a monitor, a comparator and an indicator. The monitor displays and/or records temperature at each receiver as the receivers are moved through the vessel. The comparator determines whether a temperature difference exists between each receiver and/or whether a temperature change occurs at each receiver. The indicator indicates when the temperature difference or the temperature change exceeds a predetermined value. Because inflamed plaque can cause the temperature of the vessel wall to elevate up to two and a half degrees Centigrade or Celsius, the predetermined value is typically between 0.5-2.5 degrees Centigrade or Celsius. When the predetermined value is exceeded, the inflamed plaque is located.  
           [0012]    The positioner can be an expander which is moveable between a first configuration and a second configuration. Typically, the first configuration is dimensioned for insertion of the receivers into the vessel and the second configuration is dimensioned for positioning the receivers proximate to the vessel wall. An inflatable balloon makes an excellent expander. Additionally, the expander can be used to simultaneously dilate the vessel.  
           [0013]    Alternately, for example, the positioner can be a flexible guidewire having a movable section which is adapted to be maneuvered in the vessel. In this embodiment, the receivers are attached to the movable section and the movable section is maneuvered to position the receivers near the vessel wall in the vessel.  
           [0014]    The receiver can be implemented in a number of alternate ways. For example, in one embodiment, each receiver could receive infrared radiation from the vessel wall. Alternately, the receiver could include a luminescent material which is positioned near the vessel wall. In this embodiment, the sensor utilizes the change in emissions from the luminescent material to determine temperature. Still alternately, the receiver can utilize ultrasound wave to determine a temperature profile in the vessel.  
           [0015]    The invention is also a method for locating inflamed plaque in a vessel of a patient. The method comprises the steps of providing a receiver, positioning the receiver in the vessel of the patient, and determining the existence of inflamed plaque from the information received form the receiver.  
           [0016]    It is important to recognize that a device, in accordance with the present invention can accurately locate inflamed plaque by locating elevated temperatures of the vessel wall. Thus, the inflamed plaque may be treated prior to the life threatening rupture or ulceration. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0018]    [0018]FIG. 1 is a perspective view of a device having features of the present invention;  
         [0019]    [0019]FIG. 2 is a perspective view of a second embodiment of a device having features of the present invention;  
         [0020]    [0020]FIG. 3 is a side cut-away view taken on line,  3 - 3  and positioned in a vessel;  
         [0021]    [0021]FIG. 4A is a side cut-away view taken on line  4 - 4  of FIG. 1 with a positioner in a first configuration;  
         [0022]    [0022]FIG. 4B is a cut-away view taken of line  4 - 4  of FIG. 1 with the positioner in a second configuration;  
         [0023]    [0023]FIG. 5A is a side cut-away view of a third embodiment of a device having features of the present invention with a positioner in a first configuration;  
         [0024]    [0024]FIG. 5B is a side cut-away view of the embodiment of FIG. 5A with the positioner in a second confirmation;  
         [0025]    [0025]FIG. 6A is a side cut-away view of another embodiment of a device having features of the present invention positioned in a portion of an vessel;  
         [0026]    [0026]FIGS. 6B is an enlarged view of a portion of the device of FIG. 6A;  
         [0027]    [0027]FIG. 7A is a perspective view, in a partial cut-away, of another embodiment of the present invention;  
         [0028]    [0028]FIG. 7B is an enlarged cut-away view taken of line  7 B- 7 B in FIG. 7A;  
         [0029]    [0029]FIG. 8A is a perspective view of another embodiment of the present invention;  
         [0030]    [0030]FIG. 8B is an enlarged illustration of another embodiment of the present invention;  
         [0031]    [0031]FIG. 8C is an enlarged illustration of yet another embodiment of the present invention; and  
         [0032]    [0032]FIG. 9 illustrates a side cut-away view of a balloon catheter positioned in a vessel. 
     
    
     DESCRIPTION  
       [0033]    The present invention is a device  10  and method which are particularly suited for locating unstable, inflamed plaque  12  on a vessel wall  14  of a vessel 16 . In the embodiment illustrated in FIG. 1, the device  10  includes at least one receiver  18 , at least one carrier  20 , a sensor  22 , a catheter  24 , and a positioner  26 . The temperature of the inflamed plaque  12  is elevated approximately 0.5 to 2.5 degrees Centigrade or Celsius. The present device  10  locates the unstable, inflamed plaque  12  by measuring the temperature of the vessel wall  14  as the device is moved through vessel  16  and locating areas of elevated temperature.  
         [0034]    In the embodiment illustrated in the FIGS.  1 - 5 , each receiver  18  receives information, i.e. infrared radiation, from the vessel wall  14  and each receiver  18  is an aperture proximate a carrier distal end  28  of each carrier  20  which exposes the carrier  20  to the vessel wall  14 . Alternately for this embodiment, for example, each receiver  18  can be a projection (not shown) which extends between the vessel wall  14  and the carrier  20 .  
         [0035]    As illustrated in FIG. 1, the device  10  can include a plurality of spaced apart receivers  18  positioned circumferentially around the positioner  26  so that the temperature can be monitored around the circumference of the vessel wall  14 . For this embodiment, the sensitivity of the device  10  increases as the number of receivers  18  increases, because small inflamed plaque  12  is less likely to pass between the receivers  18 . In the embodiments shown in the FIGS.  1 - 4 , the device includes four, circumferentially, spaced apart receivers  18 . Importantly, the positioning of the receivers  18  on the positioner  26  can vary. For example, as shown in FIGS. 5A and 5B the device  10  can also include a plurality of receivers  18  spaced apart axially along the positioner  26  for additional sensitivity. Also, the receivers  18  can be staggered along the positioner  26 .  
         [0036]    In the embodiment illustrated in FIGS.  1 - 4 , each receivers  18  is located above the surface of the positioner  26 . Alternately, for example, each receiver  18  may be located on, within or beneath the surface of the positioner  26 .  
         [0037]    The carrier  20  transfers the information from each receiver  18  to the sensor  22 . In the embodiments shown in the FIGS.  1 - 5 , each receiver  18  includes a separate carrier  20  for transferring infrared radiation to the sensor  22 . As provided herein each carrier  20  can be an optical fiber having an aperture at the carrier distal end  28  which forms each receiver  18 . As shown in phantom in FIG. 1, a carrier proximal end  30  of each carrier  20  is attached to the sensor  20 . For this embodiment, any optical fiber which transmits infrared radiation should make a suitable carrier  20 .  
         [0038]    The carrier  20  can be secured to the catheter  24  and positioner  26  in a number of alternate ways. For example, in the embodiment shown in FIGS. 1, 3,  4 A and  4 B, the carriers  20  are positioned and secured to an outer surface  32  of the catheter  20  and the positioner  26 . Alternately, in the embodiment shown in FIG. 2, the carrier  18  can extend through apertures in the positioner  26 . In yet another embodiment shown in FIGS. 5A and 5B, the carrier  20  can extend through a first lumen  32  of the catheter  24  and through the positioner  26 .  
         [0039]    Preferably, the device  10  includes a marker  36  positioned proximate each receiver  18  so that the location of each receiver  18  can be determined. For example, each marker  36  can be a radiopaque material, such as silver which is deposited on each carrier  20  proximate each receiver  18 . In this version, the position of the radiopaque marker  36  is visible with x-rays and a fluoroscope.  
         [0040]    The sensor  22  receives the information from each receiver  18  through each carrier  20  and determines temperature at each receiver  18  based upon the information received or determines if a change of temperature occurs at each receiver  18 . Preferably, the sensor  22  receives information from a plurality of receivers  18  and determines the temperature or a temperature difference at each receiver  18 . For the embodiment illustrated in FIG. 1, the sensor  22  may be any suitable infrared radiation sensor. For example, a sensor  22  made with a suitable pyroelectrical material can be utilized. As is well known to those skilled in the art, pyroelectric material generates an electric charge that is related to the amount of temperature change in the pyroelectric material.  
         [0041]    The sensor  22  can include a monitor  40 , a comparator  42  and an indicator  44 . The monitor  40  displays and/or records the temperature at each receiver  18  for review as the device  10  is moved in the vessel  16 . The comparator  42  compares the temperature between the receivers  18  to determine whether a temperature difference exists between the receivers  18 . Further, the comparator  42  also compares the temperature at each receiver  18  to determine whether a temperature change occurs at each receiver  18  as the device  10  is moved in the vessel.  
         [0042]    The indicator  44  is connected to the comparator  42  and notifies the user of the device  10 , i.e., a surgeon, when the temperature difference between each receiver  18  or the temperature change exceeds a predetermined value. For example, if the temperature difference or the temperature change is above the predetermined value, e.g., approximately 0.5-2.5 degrees Centigrade or Celsius, the indicator  44  will notify the user. The indicator  44  can be implemented in a number of alternate ways, such as, an audio signal, i.e., a bell, or a visual signal, i.e., a digital readout.  
         [0043]    The catheter  24  can be used to position the positioner  26  and the receivers  18  in the proper location in the vessel  16 . Typically, the catheter  24  is cylindrical or elongated shaped and has a catheter distal end  46  which is inserted into the vessel  16  and a catheter proximal end (not shown) which is outside the vessel  16  for manipulating the catheter  24  in the vessel  16 . Preferably, the catheter  24  is formed from a flexible and somewhat stiff material such as PET to facilitate movement through the vessel  10 .  
         [0044]    The design of the catheter  24  varies according to the design of the expander  26 . For example, the catheter  24  can include the first lumen  34  (as discussed previously) and a second lumen  50 . Referring to FIG. 3, the first lumen  34  can carry a guidewire  52  for guiding the catheter  24  in the vessel  16  or as shown in FIGS. 5A and 5B can retain the carriers  20 . As discussed below, the second lumen  50  can facilitate movement of the positioner  26  between a first configuration  54  (shown in FIG. 4A) and a second configuration  56  (as shown in FIG. 4B).  
         [0045]    The positioner  26  positions the receivers  18  proximate the vessel wall  14 . Further, some of the positioners  26  provided herein can also be used to dilate the vessel  16 . In the embodiments illustrated in FIGS.  1 - 5 , the positioner  26  is an expander which moves between the first configuration  54  for insertion into the vessel  16  and the second configuration  56 . As shown in FIGS.  1 - 4 , the positioner  26  can be an inflatable balloon attached proximate to the catheter distal end  28 . Referring now to FIG. 3, fluid (not shown) may pass from a pressurized fluid source (not shown) through the second lumen  50  and a balloon aperture  58  in the second lumen  50  to selectively inflate the expander  26 . Inflation of this nature may be appreciated by comparison of FIG. 4A, where the balloon is shown in the first configuration  54 , and FIG. 4B, where the balloon is shown substantially in the second configuration  56 . For the purposes of the present invention, numerous devices, e.g., pumps or syringes may be adapted to function as a source of fluid pressure.  
         [0046]    It may be seen in FIG. 3, that when the positioner  26  moves towards its second configuration  56 , each receiver  18  contacts the vessel wall  14 . It may be appreciated that the positioner  26  may be expanded more or less than the expansion shown in FIG. 3.  
         [0047]    Alternate embodiments of the positioner  26  are also possible. For example, as shown in FIGS. 5A and 5B, the positioner  26  can be a cylindrical sleeve that is attached to the catheter distal end  46 . The cylindrical sleeve is preferably formed from a wire mesh and has a sleeve distal end  60  and a sleeve proximal end  62 . The sleeve proximal end  62  is attached to the catheter distal end  46 . A grommet  64  is attached to the sleeve distal end  60 . An actuator wire  66  can pass through the second lumen  50  and connect to the grommet  64 .  
         [0048]    In this embodiment, the guidewire  52  extends through a positioning guidewire lumen in the actuator wire  66 . The actuator wire  66  is movable within the second lumen  50  to cause the grommet  64  to move translationally. Translational movement of the grommet  64  moves the sleeve distal end  60  translationally towards, or translationally away from, the catheter distal end  46 . Movement of this type may be visualized by comparison of FIG. 5A and FIG. 5B. In particular, it may be seen in FIG. 5A that cylindrical sleeve has a shorter overall length and increased overall width over the cylindrical sleeve illustrated in FIG. 5B. In this fashion, the actuator wire  66  may be manipulated to selectively expand the cylindrical sleeve.  
         [0049]    The device  10  can also include at least one flow passageway  70  which allows for the flow of fluids, e.g., blood past the expander  26  when the expander  26  is proximate the second configuration  56 . Referring to FIG. 3, the flow passageway  70  can include a first port  72  and a second port  74  which are in fluid communication with the first lumen  34  and the vessel  16  on each side of the expander  26 .  
         [0050]    Alternately, in the embodiment shown in FIGS. 5A and 5B, a series of apertures (not shown) can be formed in the grommet  64  which allows for the passage of fluid, e.g., blood past the expander  26 . In yet another embodiment, the expander  26  can be ribbed (not shown) or include grooves (not shown) which form the flow passageway  70  and allow for the flow of blood past the expander  26 .  
         [0051]    Preferably, the device also includes a heat source  26  which can be connected to the carriers  20  for heating the inflamed plaque  12 . In certain situations, it is desirable to treat inflamed plaque  12  with heat. Therefore, the present invention allows the inflamed plaque  12  to be treated almost immediately. The amount of heat which can be applied to the plaque  12  can vary. It is anticipated that a heat source  26  which supplies sufficient heat through the carriers  20  to heat the vessel wall  14  to about 40-45 degrees centigrade is desirable.  
         [0052]    Additionally, referring to FIG. 2, the positioner  26  can also include one or more fluid passageways  78  having opening  80  for delivering fluid medications to the inflamed plaque  12 . This allows positioner  26 , for example to immediately apply medications to the inflamed plaque  12  which can seal the inflamed plaque  12 , thereby inhibiting erosion or rupture. An inflatable balloon having delivery conduits is disclosed in U.S. Pat. No. 5,336,178, Kaplan et al. which is incorporated herein by reference.  
         [0053]    Further, it is anticipated that the positioner  26 , in some instances, can be expanded to preform angioplasty or deliver a supporting stent (not shown) if necessary.  
         [0054]    In an alternate embodiment illustrated in FIGS.  6 A- 6 B, the positioner  26  can be a positioning guidewire  82 . In this embodiment, one or more receivers  18  can be attached directly to the positioning guidewire  82 . More specifically, the receivers  18  are secured on a movable section  84  near a distal end  86  of the positioning guidewire  82 . The movable section  84  can be maneuvered so that the receivers  18  contact the vessel wall  14 . FIG. 6A illustrates the positioning guidewire  82  operationally positioned within the vessel  16  of a patient  88 . In this embodiment, a guiding catheter  90  is used to extend through the patient  88  into the vessel  16 . In the embodiment illustrated, the movable section  84  is a bend in the positioning guidewire  82 . The movable section  84  is maneuvered through the guiding catheter  90  into the vessel  16 . Subsequently, a proximal end  92  of the positioning guidewire  82  is maneuvered and/or torqued until the movable section  84  is near or in contact with the vessel wall  14 . In this position, the receivers  18  can detect the temperature at the vessel wall  14 . Subsequently, the information can be transferred from the receivers  18  to the sensor  22 .  
         [0055]    [0055]FIG. 6B illustrates an enlarged view of the movable section  84 . In this embodiment, a pair of receivers  18  are secured to the movable section  84  while a carrier  20  transfers the information from the receivers  18  to the sensor  22 . Similar to the embodiments described above, each carrier  20  can be an optical fiber having an aperture which forms the receiver  18 . The carrier  20  can transfer infrared radiation to the sensor  22 . The carrier  22  illustrated in FIG. 6B extends through a center of the positioning guidewire  82 . Alternatively, the carrier  22  can run along an outer surface of the positioning guidewire  82  and be attached with an epoxy or shrink wrap (not shown). Further, any number of receivers  18  can be attached to the positioning guidewire  82 .  
         [0056]    In yet an alternate embodiment illustrated in FIGS.  7 A- 7 B, the device  10  includes the positioner  26 , i.e. an inflatable balloon and a catheter  24  having a first lumen  34  and a second lumen  50 . In this embodiment, the receiver  18  includes a coating  94  which coats the positioner  26  and an optical fiber  96  positioned in the first lumen  34 . The coating  94  preferably includes a luminescent material such as magnesium germanate or magnesium flourogermanate activated with tetravalent manganese. A more detailed description of the luminescent material can be found in U.S. Pat. No. 4,652,143, the contents of which are incorporated herein by reference. The coating  94  can be positioned around a portion or the entire circumference of the balloon. The coating  94  is subsequently positioned near or in contact with the vessel wall  14 . In this embodiment, light can be emitted from the optical fiber  96  positioned within the coating  94 . The vessel wall  14  excites the luminescent material in the coating  94  and causes the luminescent material to emit radiation with characteristics that are proportional to the temperature of vessel wall  14 . Subsequently, the optical fiber  96  receives the information from the luminescent material and transfers the information to the sensor  22 . From this information, the sensor  22  is able to determine the presence of inflamed plaque  12 . Alternately, for example, separate optical fibers (not shown) can be used to illuminate and receive information in this embodiment.  
         [0057]    In still another embodiment illustrated in FIGS.  8 A- 8 C, the device utilizes sound waves to locate the inflamed plaque. More specifically, the device  10  utilizes ultrasound to plot or make thermal measurements of the vessel wall  14 . In particular, the speed of sound is modified by the temperature of the medium through which the sound waves are directed. Thus, the sound waves can be used to determine a temperature profile for the vessel  16  and/or locate areas with higher temperatures. With this information, the inflamed plaque  12  can be located along the vessel  16 .  
         [0058]    In this embodiment, the device  10  includes the positioner  26  and one or more receivers  18 . The positioner  26  is a shaft which carries the receivers  18 . In the embodiment illustrated in FIGS.  8 A- 8 C, each receiver  18  is a transducer which produces sound waves from a voltage signal. Subsequently, the sound waves are received by the transducer to produce an electrical signal. Subsequently, the electrical signal is transferred to the sensor  22  to establish a temperature profile for the vessel  16 . A suitable transducer is made of crystal such as P 2 T (lead zirconate-tifanate). Alternately, for example, separate transducers could be used for producing and receiving the sound waves.  
         [0059]    Three versions of this sound wave embodiment are illustrated in FIGS.  8 A- 8 C. More specifically, in FIG. 8A, the device  10  includes a plurality of spaced apart receivers  18  which are positioned near a distal end  98  of the positioner  26 . Alternately, the embodiment in FIG. 8B, the device  10  includes a single receiver  18  which is rotated by a receiver motor  100  which is coupled to the receiver  18  with a drive shaft  102 . In the alternate embodiment illustrated in FIG. 8C, the device  10  includes a single receiver  18 . However, in this embodiment, a mirror  104  is rotated by a mirror motor  106  which is coupled to the mirror  104  with a mirror drive shaft  106 . This allows for the collecting of information around the circumference of the vessel  16 . Those skilled in the art will recognize alternate designs for the device  10  which utilizes ultrasound to located inflamed plaque  12 . A more complete discussion of ultrasound is provided in the book entitled,  Intravascular Ultrasound,  R. Erbel, JR T C Roelandt, J Ge, G Gorge, eds. Martin Dunitz, London 1998, the contents of which are incorporated herein by reference.  
         [0060]    Importantly, the device  10  is able to evaluate whether plaque is inflamed and unstable. The inflamed and unstable plaque  12  is subject to rupture and/or ulceration which can cause the patient to experience a myocardial infarction. FIG. 9 illustrates a balloon catheter  108  positioned in a vessel  16  adjacent to inflamed plaque  12 . In this embodiment, after the inflamed plaque  12  is located by device  10  (not shown in FIG. 9), the balloon catheter  108  is used to treat the inflamed plaque  12 . Thus, the balloon catheter  108  is used to treat the inflamed plaque  12  after it is located with the device  10 . During treatment, the balloon catheter  108  dilates the vessel and induces injury and/or ruptures the inflamed plaque  12 . This treatment can prevent subsequent rupture of the inflamed plaque  12 .  
       Operation  
       [0061]    The operation of one embodiment of the present invention, is best appreciated with reference to FIGS. 1 and 3, and begins with insertion of the guidewire  52  into the vessel  16 . Next, the device  10  is inserted into the vessel  16  over the guidewire  52 , with the positioner  26  in substantially its first configuration  54 . The advancement of the device  10  will continue until the positioner  26  is at the position where testing of the vessel  16  is to begin.  
         [0062]    Next, the positioner  26  is moved from its first configuration  54  toward its second configuration  56 . If the positioner  26  is a balloon, fluid is supplied under pressure through the second lumen  50  to inflate the balloon. The expansion of the positioner  26  functions to move the receivers  18  to contact the vessel wall  14 .  
         [0063]    Once the receivers  18  are against or near the vessel wall  14 , the plurality of receivers  18  begin receiving information from the vessel wall  14 . The information is transmitted through the carriers  20  to the sensor  22 . The sensor  22  receives the information and determines the temperature at each receiver  18 . The monitor  40  displays and/or records the temperature at each receiver  18 . The comparator  42  compares the temperature at the receivers  18  to determine if a temperature difference exists between the receivers  18 . If the temperature difference exceeds the predetermined value, the indicator  44  notifies the user of the device  10  and the inflamed plaque  12  is located.  
         [0064]    Next, the positioner  26  is returned to its first configuration  54  for movement to a different site and then returned to proximate its second configuration  56 , with the receivers  18  proximate the vessel wall  14 . Alternately, depending upon the design of the positioner  26 , the positioner  26  may be moved in the vessel  16  with the receivers  18  proximate the vessel wall  14 .  
         [0065]    As the receivers  18  are moved in the vessel  16 , the sensor  22  continues to determine the temperature at each receiver  18  and the comparator  42  continues to determine whether a temperature difference exists between the receivers  18 . Further, during this time, the comparator  42  compares the temperatures to determine if a temperature change occurs at any of the receivers  18 . Again, if the temperature difference or the temperature change exceeds the predetermined value, the indicator  44  notifies the user of the device  10 .  
         [0066]    It is important to recognize that the positioner  26  can be moved between its first and second configurations  54 ,  56  as necessary to facilitate movement of the device  10  through the vessel  16  and to keep the receivers  18  proximate the vessel wall  14 .  
         [0067]    It is also important to recognize that the size of the inflamed plaque  12  can also be determined from the temperatures as the device  10  is moved through the vessel  16 .  
         [0068]    Further, it is anticipated that the present device  10  can be used in conjunction with existing procedures such as angiography to precisely locate inflamed plaque  12 .  
         [0069]    While the particular device  10  as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention. Therefore, no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.