Abstract:
A medical apparatus is disclosed for determining the degree of restenosis of a stent comprising a stent, an energy transmitter, an energy receiver, and a processor to compare the transmitted energy and the received energy.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]    This application is a continuation-in-part of co-pending patent application U.S. Ser. No. 10/208,288, filed on Jul. 30, 2002, which in turn is a continuation of co-pending patent application U.S. Ser. No. 10/131,361 filed on Apr. 240, 2002, which in turn is a continuation of co-pending patent applications U.S. Ser. No. 09/918,078 and 09/918,076, both filed on Jul. 30, 2001, which in turn were continuations of patent application U.S. Ser. No. 08/850,250 filed on May 7, 2001, which issued as U.S. Pat. No. 6,488,704 on Dec. 3, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates, in one embodiment, to methods for the detection of stenosis and restenosis, and more particularly to a stent adapted to detect restenosis.  
         BACKGROUND OF THE INVENTION  
         [0003]    Medical stents are commonly used to treat blocked or obstructed lumens, such as blood vessels. Such an obstruction is often referred to as stenosis. Stents find uses in a number of medical fields, including cardiovascular, gastroenterology, urology, and the like.  
           [0004]    One serious deficiency of stent technology is the reocclusion of the lumen by restenosis. After a stent has been inserted, there is a tendency for smooth muscle cells and/or plaque to proliferate on the surface of the stent, thus causing a blockage of the lumen.  
           [0005]    Current treatments for restenosis generally involve invasive procedures wherein plaque buildup is physically removed. An alternative procedure involves the complete replacement of the blocked stent with a replacement stent.  
           [0006]    U.S. Pat. No. 6,015,387 to Schwartz et al. describes and claims a stent adapted to measure blood flow. “The device includes a piezoelectric crystal for generating an ultrasonic wave that is directed toward the blood vessel. The same or a second piezoelectric crystal is employed to detect the reflected vibrational wave from the blood vessel and produce an RF signal that is indicative of blood flow within the blood vessel.” The patent also teaches that the stent “can also provide a therapeutic function by applying heat or vibration to the blood to inhibit restenosis. In one embodiment, a feed-back control loop regulates the therapeutic functions based on measurements of blood flow.” Thus, this patent teaches one method for indirectly measuring restenosis, but fails to teach or suggest a method for the direct measurement of plaque accumulation. The contents of U.S. Pat. No. 6,015,387 are hereby incorporated by reference.  
           [0007]    U.S. Pat. No. 6,170,488 to Spillman et al. discloses a method for detecting the status of an implanted medical device based on acoustic harmonics. “For example, the presence of harmonics in a stent  32  may increase or decrease as a function of the degree of restenosis which occurs within the stent. Thus, by monitoring the presence of harmonics over the course of periodic testing (e.g., trending), it is possible to track the build-up of restenosis.” Thus, this patent teaches one method for indirectly measuring plaque accumulation, but fails to teach or suggest a method for the direct measurement of restenosis. Additionally, a significant amount of restenosis must occur before the acoustic harmonics of the stent are significantly altered. Frequently exposing the stent to vibration energy also causes damage to the stent and the surrounding issues. The contents of U.S. Pat. No. 6,170,488 are hereby incorporated by reference.  
           [0008]    U.S. Pat. No. 6,200,307 to Kasinkas et al. teaches a method for the treatment of in-stent restenosis. The specification teaches “. . . method of treating in-stent restenosis by applying radiation to the smooth muscle cells which have grown within or around a stent implant in a manner that does not substantially damage the surrounding lumen wall or the stent itself, while resulting in a reduction of smooth muscle cell mass.” The radiation is introduced into a stent by way of a flexible catheter. Thus, this patent teaches one method for removing plaque accumulation, but fails to teach or suggest a means for detecting the degree of plaque accumulation. The prior art also fails to teach or suggest the use of a stent that removes restenosis without the aid of an external device. The contents of U.S. Pat. No. 6,200,307 are hereby incorporated by reference.  
           [0009]    U.S. Pat. No. 6,488,704 to Connelly teaches et al. describes a stent adapted to function as a flow cytometer. The implantable stent contains “ . . . several optical emitters located on the inner surface of the tube, and several optical photodetectors located on the inner surface of the tube.” As labeled particles pass through the stent, the optical emitters and photodetectors are capable of detecting the labeled cells. Thus, this patent teaches one method for detecting particles flowing through a stent. The contents of U.S. Pat. No. 6,488,704 are hereby incorporated by reference.  
           [0010]    U.S. Pat. Nos. 6,491,666 and 6,656,162 to Santini et al each disclose and claim a medical stent adapted to release molecules in response to a signal from a microchip which is attached to the surface of the stent. The integration of microchip devices into stents is described in this patent. In one embodiment, the molecules that are released by the stent are anti-restenosis drugs. The contents of U.S. Pat. Nos. 6,491,666 and 6,656,162 are hereby incorporated by reference.  
           [0011]    It is an object of this invention to provide at least one of the following: a stent capable of directly detecting the presence of plaque within the stent, a stent capable of removing plaque within the stent, and a process for the direct detection of plaque within a stent.  
         SUMMARY OF THE INVENTION  
         [0012]    In accordance with the present invention, there is provided an apparatus and method for the detection of in-stent restenosis by comparison of the intensity of a transmitted wave and a received wave. When a fluid is flowing through an unblocked stent, a baseline measurement is made. As the stent accumulates plaque, the intensity of the received wave slowly decreases relative to the intensity of the transmitted wave. This decrease can be optionally coupled to a therapeutic treatment to inhibit the restenosis.  
           [0013]    The technique described above is advantageous because it more simple than the prior art stents. The use of low intensity electromagnetic waves does not cause damage to the stent or the surrounding issue. Thus, the technique can be used frequently or even continuously to monitor the degree of restenosis. Additionally, the invention allows the monitoring of restenosis without using invasive techniques. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The invention will be described by reference to the following drawings, in which like numerals refer to like elements, and in which:  
         [0015]    [0015]FIG. 1A is a cut away view of an apparatus that uses one embodiment of the instant invention;  
         [0016]    [0016]FIG. 1B is an end view of a stent;  
         [0017]    [0017]FIG. 1C is an end view of a stent suffering from restenosis;  
         [0018]    [0018]FIG. 2 is a cross sectional view of one embodiment of the invention;  
         [0019]    [0019]FIG. 3 is a cross sectional view of one embodiment of the invention showing the transmission of parallel energy in one direction;  
         [0020]    [0020]FIG. 4 is an end view of a stent similar to that shown in FIG. 3;  
         [0021]    [0021]FIG. 5 is a cross sectional view of one embodiment of the invention showing the transmission of energy through plaque;  
         [0022]    [0022]FIG. 6 is an end view of a stent similar to that shown in FIG. 5;  
         [0023]    [0023]FIG. 7 is a cross sectional view of one embodiment of the invention showing the transmission of parallel energy in multiple directions;  
         [0024]    [0024]FIG. 8 is an end view of a stent similar to that shown in FIG. 7;  
         [0025]    [0025]FIG. 9 is a cross sectional view of one embodiment of the invention showing the transmission of non-parallel energy;  
         [0026]    [0026]FIG. 10 is an end view of a stent similar to that shown in FIG. 9;  
         [0027]    [0027]FIG. 11 is an end view of a stent similar showing communication with a remote unit;  
         [0028]    [0028]FIG. 12 is a flow diagram illustrating one process of the invention; and  
         [0029]    [0029]FIG. 13 is a flow diagram illustrating another process of the invention. 
     
    
       [0030]    The present invention will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiment described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.  
       DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    In describing the present invention, a variety of terms are used in the description.  
         [0032]    The term “stent” refers to a cylinder or scaffold made of metal or polymers that may be permanently implanted into a blood vessel following angioplasty procedure. Reference may be had to U.S. Pat. No. 6,190,393, the ensure disclosure of which is hereby incorporated by reference. The term stent also refers to such a cylinder or scaffold used in lumens other than blood vessels.  
         [0033]    The term “stenosis” refers to the constriction or narrowing of a passage, duct, stricture, or lumen, such as a blood vessel. “Restenosis” refers to the reoccurrence of stenosis in a lumen (or implanted medical device).  
         [0034]    The term “baseline value” refers to the measurement taken at specified period in time, which is later to be used as a reference point for comparison to a second measurement. Baseline measurements are typically taken when the stent is in pristine condition. The baseline measurement allows the user to correct for energy reading variations due to the fluids that may fill the stent. A certain amount of deviation from the baseline reading is acceptable, as this may account for the inhomogeneity of many fluids.  
         [0035]    [0035]FIG. 1A is a cut away view of an apparatus that utilizes one embodiment of the instant invention. In the embodiment depicted in FIG. 1A, apparatus  10  comprises stent  14  is disposed within lumen  12 . In one embodiment, a fluid flows through lumen  12  in the direction of arrow  11 . In one embodiment, stent  14  is substantially flexible. In another embodiment, stent  14  is substantially inflexible.  
         [0036]    [0036]FIG. 1B is a cross sectional view of stent  14 . In the embodiment depicted in FIG. 1B, stent  14  comprises a cavity  20 , an outer wall  16 , and an inner wall  18 . In the embodiment depicted in FIG. 1C, stent  14  suffers from the buildup of plaque  22 . This restenosis causes the obstruction of cavity  20 . In one embodiment, inner wall  18  is optional. When the stent is implanted within a living organism, it is preferable that the tissue-contacting surfaces be biocompatible. In the embodiment depicted in FIG. 1B, outer wall  16  and inner wall  18  are biocompatible. In one embodiment, the wall is comprised of one or more of the biocompatible materials disclosed in U.S. Pat. No. 6,124,523, the contents of which are hereby incorporated by reference. In another embodiment, the wall is comprised of polytetrafluoroethylene. In additional embodiments, other fluorinated plastics are used.  
         [0037]    [0037]FIG. 2 is a cross sectional view of another embodiment of the invention. In the embodiment depicted in FIG. 2, stent  25  comprises cavity  20 , outer wall  28 , inner wall  30 , and middle layer  26 . Disposed within middle layer  26  are elements  24   a  to  24   e  and  32   a  to  32   e . In one embodiment, elements  24   a  to  24   e  function as transmitters of electromagnetic energy while elements  32   a  to  32   e  function as receivers of electromagnetic energy. In another embodiment, elements  24   a  to  24   e  and  32   a  to  32   e  function as both transmitters and receivers of electromagnetic energy. In one embodiment, the transmitters  24  and receivers  32  are comprised of one or more of the transmitters and receivers disclosed in U.S. Pat. No. 6,488,704. In another embodiment, transmitters  24  and receivers  32  are comprised of VCSEL (vertical cavity surface emitting lasers). Reference may had, for example, or U.S. Pat. No. 6,686,216 (“Electro-optical transceiver system with controlled lateral leakage and method of making it”). In one embodiment of the invention, elements  24   a  to  24   e  function as transmitters of vibrational energy. In another embodiment, both vibrational and electromagnetic energy is generated. In another embodiment, an energy wave is generated using a piezoelectric crystal. In this embodiment, the energy wave is a vibrational energy wave. In yet another embodiment, element  24   a  emits a first type of energy while element  24   b  emits a second type of energy. By way of illustration, and not limitation, element  24   a  may emit light of a given wavelength, while element  24   b  emits light of a second wavelength. Alternatively or additionally, one such transmitting element may emit electromagnetic energy, while a second element emits vibrational energy. In one embodiment, the transmitting elements are activated simultaneously. In another embodiment, the elements are activated sequentially.  
         [0038]    Receivers  32  may be comprised of a variety of materials. In one embodiment, the receiver element is a traditional antenna that is commonly utilized by one skilled in the art. In one embodiment, the receiver is a coil or circuit imposed on or within walls  26 ,  28 , and/or  30 . Reference may be had to U.S. Pat. Nos. 5,737,699 and 5,627,552 (“Antenna structure for use in a timepiece”), U.S. Pat. No. 5,495,260 (“Printed circuit dipole antenna”), U.S. Pat. No. 5,206,657 (“Printed Circuit Radio Frequency Antenna”), U.S. Pat. No. 6,650,301 (“Electrically conductive patterns, antennas, and methods of manufacture”), U.S. Pat. No. 5,535,304 (“Optical transceiver unit”), U.S. Pat. No. 4,549,314 (“Optical communication apparatus”), and the like. In another embodiment, the receiving elements are those described in U.S. Pat. No. 5,602,647 (“Apparatus and method for optically measuring concentrations of components”). The content of each of these patents is hereby incorporated by reference.  
         [0039]    In the embodiment shown in FIG. 2, only ten such elements are shown. The embodiment has been illustrated as such only to simplify the illustration and prevent overcrowding of the drawing. As would be apparent to one skilled in the art, any number of transmitting and receiving elements may be used. In one embodiment, there is at least 1 such element per square centimeter surface area of inner wall  30 . In another embodiment, there is at least 1 such element per square millimeter surface area. It is advantageous to place enough transmitting and receiving elements within stent  38  to ensure that any restenosis that begins to occur is detected. In one embodiment, inner wall  30  further comprises a filtering element that is adapted to selectively filter the wavelength of the energy transmitted from elements  24  and  32 . By wall of illustration, and not limitation, transmitting element  24  may emit energy of wavelengths 400 nm to 750 nm and inner wall  30  may act as a filter such that only wavelengths of between 600 and 700 nm are allowed into cavity  20 .  
         [0040]    [0040]FIG. 3 is a cross sectional view of one embodiment of the invention wherein stent  34  comprises elements  24   a  to  24   e  which transmit electromagnetic energy  36  to receiving elements  32   a  to  32   e . Stent  34  further comprises cavity  20 , outer wall  28 , inner wall  30  and middle layer  26 . In the embodiment depicted in FIG. 3, the electromagnetic wave  36  is comprised of substantially parallel waves. In one embodiment, polarized light is used. In another embodiment, laser light is used. As is apparent from FIG. 3, the transmitting and receiving elements are aligned such that they are opposite to each other. Thus, in the embodiment depicted, transmitting element  24   a  will transmit energy  36  to receiving element  32   a . The effect of the energy transmitted from transmitting element  24   a  will have a minimal impact on receiving elements  32   b  to  32   e . In one embodiment, transmitting elements  24   a  to  24   e  are activated simultaneously. In another embodiment, transmitting elements  24   a  to  24   e  are activated sequentially. In yet another embodiment, transmitting elements  24   a  to  24   e  are activated sequentially in groups. For example, transmitting elements  24   a  and  24   e  transmit an energy wave, and afterwards, elements  24   b  and  24   d  transmit an energy wave.  
         [0041]    In one embodiment of the invention, a baseline measurement is taken when cavity  20  is in its pristine state. When cavity  20  is filled with particles (not shown), these particles will absorb and/or scatter the energy  36  as energy  36  interacts with the particles. As such, the energy received by receiving element  32  will be less than the energy transmitted by transmitting element  24 . When the environment within cavity  20  is relatively constant, a baseline measurement can be taken and the amount of energy that is successfully received by receiving element  32  can be recorded. As would be appreciated by those skilled in the art, the environment of a dynamic lumen undergoes minor changes. By way of illustration, and not limitation, as blood flows through a stent, the exact composition of the blood may not be precisely constant. As such, the amount of energy received by receiving element  32  may not be constant. Nevertheless, a sampling of data points over a period of time allows one to obtain a baseline measurement, as well as obtain a range of typical deviations from the baseline. Such deviations may be caused by the change in blood flow due to the beating of the heart, localized concentrations of red blood cells or other particles, and the like.  
         [0042]    [0042]FIG. 4 depicts an end view of another embodiment similar to that depicted in FIG. 3. In the embodiment depicted, stent  38  comprises an inner wall  30 , an outer wall  28 , and a middle layer  26 . Disposed within middle layer  26  are transmitting elements, such as  24   a  and receiving elements, such as  32   a . In the embodiment shown in FIG. 4, transmitting element  24   a  transmits energy  36  which is sensed by receiving element  32   a.    
         [0043]    [0043]FIG. 5 is a cross section view of stent  34  depicting the restenosis of the stent. In the embodiment depicted, stent  34  comprises cavity  20 , inner wall  30 , outer wall  28 , middle layer  26 . Disposed within middle layer  26  are transmitting elements  24   a  to  24   e  and receiving elements  32   a  to  32   e . As depicted in FIG. 5, stent  34  further comprises plaque  22  and  23 . It is clear from the figure that the energy  36  that is transmitted from transmitting element  24   a  to receiving element  32   a  is not obstructed by plaque  22 . As such, the intensity of energy  36  detected at  32   a  is equal to the intensity of the energy transmitted from  24   a , minus the energy lost to the environment in cavity  20  (for example, scattering of energy due to the presence of blood in the cavity  20 ). The energy received by  32   a  is then compared to the baseline measurements taken when stent  38  was in pristine condition. In the embodiment depicted in FIG. 5, the energy received by  32   a  would be within the acceptable deviation limits as compared to the baseline measurements. In comparison, it is clear that the energy received by receiving element  32   b  is outside of the deviations expected, relative to the previously measured baseline. This is due to the additional scattering due to plaque  22 . Similarly, element  32   b  would receive somewhat less energy, as compared to the baseline, due to the thin layer of plaque. The plaque need not be present at the receiving elements. For example, plaque  23  diminishes the energy received at receiving element  32   d , even though it is at least partially covering transmitting element  24   d.    
         [0044]    [0044]FIG. 6. depicts an end view of an embodiment similar to that shown in FIG. 5. Stent  38  comprises an inner wall  30 , an outer wall  28 , a middle layer  26 , and plaque  22 . Disposed within middle layer  26  are transmitting elements, such as  24   a  and receiving elements, such as  32   a . In the embodiment shown in FIG. 6, transmitting element  24   a  transmits energy  36  which is sensed by receiving element  32   a . It is clear from FIG. 6 that the energy received by receiving element  32   a  is less than the baseline due to the presence of plaque  22 . Similarly, the energy received by receiving element  32   b  is less than the baseline, due to the thin layer of plaque  22 . By contrast, the energy received at receiving element  32   c  would be within the typical deviation of the baseline value, as there is no significant scattering or absorbance of the energy due to a foreign body.  
         [0045]    [0045]FIG. 7 is a cross sectional view of another embodiment of the invention which is similar that depicted in FIG. 3. In this embodiment, elements  24   a  to  24   e  and elements  32   a  to  32   e  function both as transmitting and receiving elements. Thus energy  36  may be transmitted in two directions.  
         [0046]    [0046]FIG. 8 is an end view of an embodiment similar to that depicted in FIG. 7. Elements  24   a  and  32   a  function as both transmitters and receivers of electromagnetic energy. In the embodiment depicted, the energy used comprises substantially parallel waves of energy. In another embodiment, the waves are non-parallel.  
         [0047]    [0047]FIG. 9 is a cross sectional view of another embodiment of the invention which employs non-parallel waves of energy. In the embodiment depicted in FIG. 9, elements  24   a  to  24   e  and  32   a  to  32   e  are adapted to both transmit and receive energy. As shown in FIG. 9 element  24   b  broadcasts a wave of non-parallel wave energy, which is detected by receiving elements  32   a  to  32   e . As would be apparent to one skilled in the art, the energy at receiving element  32   b  is most intense, but a certain portion of the energy is detected at the other receiving elements. In one embodiment, a portion of the energy is reflected off of the surface of the elements  32 , and redirected back to elements  24 . In one embodiment, none of the energy is redirected. In another embodiment, between 0.01% and 10% of the light is redirected. In another embodiment, between 10% and 50% of the light is redirected. In yet another embodiment, between 50% and 90% of the light is redirected. In the embodiment depicted, element  24   b  is functioning as a transmitter, while elements  24   a ,  24   c  to  24   e , and  32   a  to  32   e  are all in “receive mode.” At another point in time, element  32   d , for example, may be in “transmit mode” and the other elements in “receive mode.” In a similar manner, the elements can be sequentially activated and a map of the inner surface of stent  34  may be constructed. By conducting such measurements when the stent is in pristine condition, a baseline measurement may be obtained.  
         [0048]    [0048]FIG. 10 is an end view of an embodiment of the device similar to that depicted in FIG. 9. Stent  38  comprises an inner wall  30 , an outer wall  28 , and a middle layer  26 . Disposed within middle layer  26  are transmitting elements, such as  24   a  and receiving elements, such as  32   a . In the embodiment shown in FIG. 10, transmitting element  24   a  transmits non-parallel energy  36  which is sensed most strongly by receiving element  32   a , but is also sensed by the other receiving elements. A portion of the energy  36  is reflected off of inner wall  30  and detected by other elements. It is clear from the previous discussions that any obstructions, such as plaque depositions during restenosis, would be detected when a comparison is made to the baseline energy values.  
         [0049]    [0049]FIG. 11 is an end view of yet another embodiment of the invention, wherein power source  40  is shown. In the embodiment depicted, stent  38  comprises an inner wall  30 , an outer wall  28 , and a middle layer  26 . Disposed within middle layer  26  are transmitting elements, such as  24   a  and receiving elements, such as  32   a . In the embodiment shown in FIG. 11, transmitting element  24   a  transmits energy  36  which is sensed by receiving element  32   a . In one embodiment, power source  40  is a convention power supply. Power source  40  provides a source of electrical power to elements  24  and  32 . Thus, by way of illustration, one may use a lithium-iodine battery, and/or a battery that is chemically equivalent thereto. The battery used may, for example, have an anode of lithium or carbon and a cathode of iodine, carbon, or of silver vanadium oxide, and the like. By way of further illustration, one may use one or more of the batteries disclosed in U.S. Pat. No. 5,658,688, “Lithium-silver oxide battery and lithium-mercuric oxide battery,” U.S. Pat. No. 4,117,212, “Lithium-iodine battery,” and the like. In FIG. 11, power source  40  is disposed within middle layer  26 . It is clear to those skilled in the art that the power source may be disposed elsewhere without deviating from the teaching of this invention.  
         [0050]    [0050]FIG. 11. depicts an embodiment wherein remote unit  44  communicates with antenna  42 . Antenna  42  is adapted to both transmit and receive signals from remote unit  44 . In the embodiment shown, antenna  42  is disposed within middle layer  26 . In another embodiment, the antenna is disposed in outer wall  28 . In one embodiment, stent  38  comprises a microprocessor  43  that is operatively connected to transmitting element  24 , receiving element  32 , power source  40 , and antenna  42 . In one embodiment, the remote unit  44  is a data acquisition unit. In another embodiment, the remote unit  44  is a control unit. In yet another embodiment, the remote unit  44  is both a data acquisition unit and a control unit. For example, one may use the telemetry system disclosed in U.S. Pat. No. 5,843,139, “Remotely operable stent.” By way of further illustration, one may use the remote system disclosed in U.S. Pat. No. 5,843,139 and the like. Acoustic energy may also be employed. See, for example, U.S. Pat. No. 6,170,488, “Acoustic-based remotely interrogated diagnostic implant device and system.” 
         [0051]    [0051]FIG. 12 is a flowchart that illustrates one process of the invention. In steps  46  to  54 , a baseline measurement is obtained. In step  46 , the stent is exposed to the conditions of operation. By way of illustration, if the stent is to be disposed in a blood vessel, then blood is allowed to flow through the stent. In step  48 , a wave is transmitted across the lumen of the stent. The intensity of the wave is recorded in the microprocessor of the stent. In step  50 , the energy wave is received. Step  52  then compares the intensity of the wave received in step  50  to the intensity of the wave transmitted in step  48 . In step  54 , this comparison value (i.e. the baseline value) is recorded in the stent&#39;s microchip. Alternatively or additionally, the recorded value may be transmitted to a remote unit (see, for example, FIG. 11). In one embodiment, several baseline values are recorded, and an acceptable “baseline range” is obtained.  
         [0052]    In steps  56  to  66  illustrated in FIG. 12, the stent performs a diagnostic procedure to detect any possible restenosis that may have occurred since the baseline measurement was recorded. In step  56 , the stent is allowed to operate normally for a period of time. In step  58 , a wave is transmitted across the lumen of the stent. The intensity of the wave is recorded in the microprocessor of the stent. In step  60 , the energy wave is received. Step  62  then compares the intensity of the wave received in step  60  to the intensity of the wave transmitted in step  58 . Step  64  compares the value obtained from step  62  to the baseline (or baseline range). Step  66 , which is optional, is a step the stent performs depending on the value obtained in step  64 .  
         [0053]    [0053]FIG. 13 is a flow chart that depicts step  64  in more detail. In step  68 , the value obtained from step  64  is compared to the baseline obtained in step  54 . If the value is within an acceptable range, then path  78  will be followed. In one embodiment, step  70  is executed, wherein no action is taken. In another embodiment, step  72  is followed, wherein the value obtained in step  64  is transmitted to a remote unit. If the value obtained in step  64  is outside of an acceptable range, then path  80  is followed. In one embodiment, not shown, no action is taken. In another embodiment, step  74  is taken, wherein the value obtained in step  64  is transmitted to a remote unit (step  74 ). In another embodiment, a therapeutic response is triggered (step  76 ). In yet another embodiment, both step  74  and  76  are executed.  
         [0054]    A number of therapeutic responses may be triggered. In one embodiment, an anticoagulant is released to counteract restenosis. In another embodiment, a therapeutic agent is released. In another embodiment, the therapeutic agent released acts to counteract restenosis. Reference may be had, for example, to U.S. Pat. Nos. 5,865,814; 6,613,084; 6,613,082; 6,656,162; 6,589,546; 6,545,097; 6,491,666; 6,379,382; 6,344,028; 5,865,814 and the like. The content of each of these patents is hereby incorporated by reference. As would be apparent to one skilled in the art, the release of the agent may be triggered remotely by remote unit  44 , and need not necessarily be coupled to the value obtained in step  64 .  
         [0055]    In another embodiment, the therapeutic response comprises a release of energy of sufficient intensity to counteract restenosis. Reference may be had to U.S. Pat. Nos. 6,709,693; 6,200,307; 5,964,751 and the like. The content of each of these patents is hereby incorporated by reference.  
         [0056]    The telemetry means taught above may also be used to reprogram microprocessor  43  in vivo. Thus, it is possible to trigger the remote activation of steps  46  to  54  without removing the stent from the body. Additionally or alternative, a range of acceptable deviation values may be remotely programmed or reprogrammed via remote unit  44 .  
         [0057]    As would be apparent to one skilled in the art, a variety of forms of energy may be used with the instant invention. In one embodiment, vibrational energy is used. In another embodiment, acoustic energy is used. In one embodiment, a piezoelectric crystal is used to generate the acoustic energy. In another embodiment electromagnetic radiation is used. In one embodiment, the electromagnetic energy used is vacuum UV radiation. In another embodiment, the energy used is near UV energy. In another embodiment the energy used is visible light. In another embodiment the energy used is infrared radiation. In yet another embodiment, the energy used is radio frequency energy. In one embodiment, the energy used has a wavelength between about 400 nm and about 750 nm. In another embodiment, the energy used has a wavelength between about 600 nm and about 700 nm. In another embodiment, the wavelength of the energy is between about 1 nm and about 400 nm. In another embodiment, the wavelength of energy used is between about 750 nm and about 3 μm. In yet another embodiment, the wavelength of energy used is between about 3 μm and 30 μm. In yet still another embodiment, the wavelength of energy used is between 30 μm and 1 mm. In another embodiment, the wavelength of energy used is between about 1 m and about 10 5  m, and preferably between 1 m and 10 3  m. In yet another embodiment, the wavelength of energy used is between 10 −3  m and 1 m.  
         [0058]    Numerous methods for the manufacturing and implantation of stents and modified stents are well known to those skilled in the art. Reference may be had to U.S. Pat. Nos. 6,527,919; 6,190,393; 6,124,523; 6,096,175 and the like.  
         [0059]    It is, therefore, apparent that there has been provided, in accordance with the present invention, a method and apparatus for the detection of restenosis within a stent. While this invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.