Abstract:
A blood flow sensing system is disclosed, including a sensor coupled to an antenna, such that the sensor measures a flow of blood within a blood vessel when stimulated with a short range radio frequency energy field detectable by the antenna. Such a system additionally can include a transmitter and receiver unit (i.e., a transmitter/receiver), which can transmit the short range radio frequency energy field to the antenna of the sensor. The transmitter and receiver unit can also receive data transmitted from the sensor via the antenna. Such a system additionally includes a stent integrated with sensor, wherein the stent comprises a small diameter cylinder that props open a blood vessel and wherein the stent is moveable into the blood vessel to form a rigid support for holding the blood vessel open in order to measure the flow of blood within the blood vessel.

Description:
TECHNICAL FIELD  
       [0001]     Embodiments are generally related to flow sensing devices and techniques. Embodiments are also related to stents, such as, for example, arterial stents utilized in medical procedures. Embodiments are also related to surface wave sensor devices and systems, including interdigital sensors.  
       BACKGROUND OF THE INVENTION  
       [0002]     Cardiac output or blood flow is one of the key indicators of the performance of the heart. Blood flow can be defined as volume of blood or fluid flow per time interval. Fluid or fluid velocity is generally a function of flow area at the measurement site. Use of blood flow measurements allows discrimination between physiologic rhythms, such as sinus tachycardia, which is caused by exercise or an emotional response, and other pathologic rhythms, such as ventricular tachycardia or ventricular fibrillation.  
         [0003]     Cardiac arrhythmia is defined as a variation of the rhythm of the heart from normal. The cardiac heartbeat normally is initiated at the S-A node by a spontaneous depolarization of cells located there during diastole. Disorders of impulse generation include premature contractions originating in abnormal or ectopic foci in the atria or ventricles, paroxysmal supraventricular tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia and ventricular fibrillation. Ventricular arrhythmia can occur during cardiac surgery or result from myocardial infarction. Ventricular tachycardia presents a particularly serious problem because the patient, if left untreated, may progress into ventricular fibrillation.  
         [0004]     Blood flow measurements allow discrimination between normal and pathologic rhythms by providing a correlation between the electrical activity of the heart and the mechanical pumping performance or fluid flow activity of the heart. During sinus tachycardia, an increase in heart rate will usually be accompanied by an increase in cardiac output or blood flow. During ventricular tachycardia or ventricular fibrillation, heart rate increase will be accompanied by a decrease in, or perhaps a complete absence of, cardiac output or blood flow. A number of important cardiac and clinical devices may be improved by a more accurate measure of cardiac output. The ability to measure blood flow can be applied to the following four areas: (1) automatic implantable defibrillators, (2) rate adaptive pacemakers, (3) cardiac output diagnostic instruments and (4) peripheral blood flow instruments.  
         [0005]     Conventional methods of measuring blood flow have included blood thermal dilution, vascular flow monitoring, and injectionless thermal cardiac output. Such procedures are typically extremely invasive or can be unreliable. The ability to measure and detect blood flow is thus of key importance to maintaining proper health, before, during and following surgical procedures such as angioplasty.  
         [0006]     Medical stents are used within the body to restore or maintain the patency of a body lumen. Blood vessels, for example, can become obstructed due to plaque or tumors that restrict the passage of blood. A stent typically has a tubular structure defining an inner channel that accommodates flow within the body lumen. A stent can be configured in the form of a small, expandable wire mesh tube. The outer walls of the stent engage the inner walls of the body lumen. Positioning of a stent within an affected area can help prevent further occlusion of the body lumen and permit continued flow.  
         [0007]     A stent typically is deployed by percutaneous insertion of a catheter or guide wire that carries the stent. The stent ordinarily has an expandable structure. Upon delivery to the desired site, the stent can be expanded with a balloon mounted on the catheter. Alternatively, the stent may have a biased or elastic structure that is held within a sheath or other restraint in a compressed state. The stent expands voluntarily when the restraint is removed. In either case, the walls of the stent expand to engage the inner wall of the body lumen, and generally fix the stent in a desired position.  
         [0008]     Stents can be utilized in a procedure known as “stenting,” which is a non-surgical treatment utilized is association with balloon angioplasty to treat coronary artery disease. Immediately following angioplasty, which can result in the widening of a coronary artery, the stent can be inserted into the blood vessel. The stent assists in holding open the newly treated artery, thereby alleviating the risk of the artery re-closing over time.  
         [0009]     An example of a stent is disclosed in non-limiting U.S. Pat. No. 6,709,440, “Stent and Catheter Assembly and Method for Treating Bifurcations,” which issued to Callol et al on Mar. 23, 2004, and which is incorporated herein by reference. Another example of a stent is disclosed in non-limiting U.S. Pat. No. 6,699,280, “Multi-Section Stent,” which issued to Camrud et al on Mar. 2, 2004, and which is incorporated herein by reference. A further example of a stent is disclosed in non-limiting U.S. Pat. No. 6,695,877, “Bifurcated Stent,” which issued to Brucker et al on Feb. 24, 2004, and which is incorporated herein by reference.  
         [0010]     Surface wave sensors can be utilized in a number of sensing applications. Examples of surface wave sensors include devices such as acoustic wave sensors, which can be utilized to detect the presence of substances, such as chemicals. An acoustic wave (e.g., SAW/SH-SAW/Love/SH-APM) device acting as a sensor can provide a highly sensitive detection mechanism due to the high sensitivity to surface loading and the low noise, which results from their intrinsic high Q factor.  
         [0011]     Surface acoustic wave devices are typically fabricated using photolithographic techniques with comb-like interdigital transducers placed on a piezoelectric material. Surface acoustic wave devices may have either a delay line or a resonator configuration. The change of the acoustic property due to the flow can be interpreted as a delay time shift for the delay line surface acoustic wave device or a frequency shift for the resonator (SH-SAW/SAW) acoustic wave device.  
         [0012]     Acoustic wave sensing devices often rely on the use of piezoelectric crystal resonator components, such as the type adapted for use with electronic oscillators. In a typical flow sensing application, the heat convection can change the substrate temperature, while changing the SAW device resonant frequency. With negative temperature coefficient materials such as LiNbO 3 , the oscillator frequency is expected to increase with increased liquid flow rate. The principle of sensing is similar to classical anemometers.  
         [0013]     Flow rate is an important parameter for many applications. The monitoring of liquid (e.g., blood, saline, etc.) flow rate within and/or external to a living body (e.g., human, animal, etc) can provide important information for medical research and clinical diagnosis. Such measurements can provide researchers with insights into, for example, the physiology and functioning of the heart and other human organs, thereby leading to advances in medical, nutrition and related biological arts. Blood/liquid flow rate measurements can also provide useful information regarding the safety and efficacy of pharmaceuticals and the toxicity of chemicals.  
         [0014]     It is believed that the use of passive, wireless acoustic wave devices for blood flow rate monitoring can provide for great advances in physiological, pharmaceutical and medical applications to name a few. Surface acoustic wave sensors have the potential to provide flow sensor systems with higher sensitivity and wider dynamic ranges than the solid state flow sensor devices currently available. To date such devices have not been incorporated successfully into medical applications, particularly those involving the use of stents.  
       BRIEF SUMMARY OF THE INVENTION  
       [0015]     The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.  
         [0016]     It is, therefore, one aspect of the present invention to provide for improved blood flow sensor devices and sensing techniques.  
         [0017]     It is another aspect of the present invention to provide for an improved surface wave flow sensor device that can be adapted for use in blood flow sensing applications.  
         [0018]     It is yet a further aspect of the present invention to provide for an interdigital surface wave device, such as, for example, surface acoustic wave (SAW) resonator or surface acoustic wave (SAW) delay line sensing devices, which can be adapted for use in blood flow sensing applications.  
         [0019]     It is a further aspect of the present invention to provide for a wireless blood flow sensor, which can be integrated with a stent used in medical procedures, for blood flow sensing activities thereof.  
         [0020]     It is an additional aspect of the present invention to provide for a blood flow sensor that also measures temperature and pressure utilizing interdigital (IDT) temperature and pressure sensor elements integrated with the blood flow sensor.  
         [0021]     The aforementioned aspects of the invention and other objectives and advantages can now be achieved as described herein A blood flow sensing system is thus disclosed, which can include a sensor coupled to an antenna, such that the sensor measures a flow of blood within a blood vessel when stimulated with a short range radio frequency energy field detectable by the antenna. Such a system additionally can include a transmitter and receiver unit (i.e., a transmitter/receiver), which can transmit the short range radio frequency energy field to the antenna of the sensor.  
         [0022]     The transmitter and receiver unit can also receive data transmitted from the sensor via the antenna. Such a system additionally includes a stent integrated with sensor, wherein the stent comprises a small diameter cylinder that props open a blood vessel and wherein the stent is moveable into the blood vessel to form a rigid support for holding the blood vessel open in order to measure the flow of blood within the blood vessel. The stent can also be configured to include a wire mesh that supports the functionality of the antenna. The sensor itself measures heat transfer to blood within the blood vessel. The sensor can be configured, however, to incorporate pressure and temperature sensing elements. Such pressure and temperature sensing elements may be interdigital transducer components.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.  
         [0024]      FIG. 1  illustrates a perspective view of an interdigital surface wave device, which can be adapted for use with one embodiment of the present invention;  
         [0025]      FIG. 2  illustrates a cross-sectional view along line A-A of the interdigital surface wave device depicted in  FIG. 1 , which can be adapted for use with one embodiment of the present invention;  
         [0026]      FIG. 3  illustrates a perspective view of an interdigital surface wave device, which can be adapted for use with one embodiment of the present invention;  
         [0027]      FIG. 4  illustrates a cross-sectional view along line A-A of the interdigital surface wave device depicted in  FIG. 3 , which can be adapted for use with one embodiment of the present invention;  
         [0028]      FIG. 5  illustrates a block diagram of a wireless surface acoustic wave flow sensor system, which can be implemented in accordance with another embodiment of the present invention;  
         [0029]      FIG. 6  illustrates a block diagram of an in-vivo acoustic wave flow sensor system, which can be implemented in accordance with another embodiment of the present invention;  
         [0030]      FIG. 7  illustrates a block diagram of an in-vivo acoustic wave flow sensor system, which can be implemented in accordance with an alternative embodiment of the present invention;  
         [0031]      FIG. 8  illustrates a block diagram of a wireless surface acoustic wave flow sensor system without a heater, which can be implemented in accordance with an alternative embodiment of the present invention;  
         [0032]      FIG. 9  illustrates a block diagram of a cylindrical shape wireless surface acoustic wave flow sensor system, which can be implemented in accordance with an alternative embodiment of the present invention; and  
         [0033]      FIG. 10  illustrates a perspective view of a wireless blood flow sensor system, comprising a sensor integrated with a stent for measuring blood flow, in accordance with an embodiment of the present invention;  
         [0034]      FIG. 11  illustrates a perspective view of a wireless blood flow sensor system, comprising one or more sensors integrated with a stent for measuring blood flow, in accordance with an alternative embodiment of the present invention;  
         [0035]      FIG. 12  illustrates a perspective view of a wireless blood flow sensor system, comprising one or more sensors measuring blood flow, in accordance with an alternative embodiment of the present invention;  
         [0036]      FIG. 13  illustrates a perspective view of a wireless blood flow sensor system, comprising an upstream sensor and a downstream sensor integrated with a stent for measuring blood flow, in accordance with an alternative embodiment of the present invention; and  
         [0037]      FIG. 14  illustrates a perspective view of an in-line sensor connected to a stent, in accordance with an alternative embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]     The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment of the present invention and are not intended to limit the scope of the invention.  
         [0039]      FIG. 1  illustrates a perspective view of an interdigital surface wave device  100 , which can be implemented in accordance with one embodiment of the present invention. Surface wave device  100  can be adapted for use in blood flow sensing activities, as described in further detail herein. Surface wave device  100  can be configured to generally include an interdigital transducer  106  formed on a piezoelectric substrate  104 . The surface wave device  100  can be implemented in the context of a sensor chip. Interdigital transducer  106  can be configured in the form of an electrode.  
         [0040]      FIG. 2  illustrates a cross-sectional view along line A-A of the interdigital surface wave device  100  depicted in  FIG. 1 , in accordance with one embodiment of the present invention. Piezoelectric substrate  104  can be formed from a variety of substrate materials, such as, for example, quartz, lithium niobate (LiNbO 3 ), lithium tantalite (LiTaO 3 ), Li 2 B 4 O 7 , GaPO 4 , langasite (La 3 Ga 5 SiO 14 ), ZnO, and/or epitaxially grown nitrides such as Al, Ga or Zn, to name a few. Interdigital transducer  106  can be formed from materials, which are generally divided into three groups. First, interdigital transducer  106  can be formed from a metal group material (e.g., Al, Pt, Au, Rh, Ir, Cu, Ti, W, Cr, or Ni). Second, interdigital transducer  106  can be formed from alloys such as NiCr or CuAl. Third, interdigital transducer  106  can be formed from metal-nonmetal compounds (e.g., ceramic electrodes based on TiN, CoSi 2 , or WC). Depending on the biocompatibility of the substrate and interdigital transducer materials, a thin layer of biocompatible coating  102  may be used to cover the interdigital transducer and the substrate.  
         [0041]      FIG. 3  illustrates a perspective view of an interdigital surface wave device  300 , which can be implemented in accordance with an alternative embodiment of the present invention. The configuration depicted in  FIGS. 3-4  is similar to that illustrated in  FIGS. 1-2 , with the addition of an antenna  308 , which is connected to and disposed above a wireless excitation component  310  (i.e., shown in  FIG. 4 ). Surface wave device  300  generally includes an interdigital transducer  306  formed on a piezoelectric substrate  304 . Surface wave device  300  can therefore function as an interdigital surface wave device, and one, in particular, which utilizing surface-skimming bulk wave techniques. Interdigital transducer  306  can be configured in the form of an electrode. A biocompatible coating  302  can be selected such that there will be no adverse effect to a living body (e.g., human, animal). Various selective coatings can be utilized to implement coating  302 .  
         [0042]     A change in acoustic properties can be detected and utilized to identify or detect the substance or species absorbed and/or adsorbed by the interdigital transducer  306 . Thus, interdigital transducer  306  can be excited via wireless means to implement a surface acoustical model. Thus, antenna  308  and wireless excitation component  310  can be utilized to excite one or more frequency modes associated with the flow of a fluid such as blood for fluid flow analysis thereof.  
         [0043]      FIG. 4  illustrates a cross-sectional view along line A-A of the interdigital surface wave device  300  depicted in  FIG. 3 , in accordance with one embodiment of the present invention. Thus, antenna  308  is shown in  FIG. 4  disposed above coating  302  and connected to wireless excitation component  310 , which can be formed within an area of coating  302 . Similar to the configuration of  FIG. 2 , Piezoelectric substrate  304  can be formed from a variety of substrate materials, such as, for example, quartz, lithium niobate (LiNbO 3 ), lithium tantalite (LiTaO 3 ), Li 2 B 4 O 7 , GaPO 4 , langasite (La 3 Ga 5 SiO 14 ), ZnO, and/or epitaxially grown nitrides such as Al, Ga or Zn, to name a few.  
         [0044]     Interdigital transducer  306  can be formed from materials, which are generally divided into three groups. First, interdigital transducer  106  can be formed from a metal group material (e.g., Al, Pt, Au, Rh, Ir, Cu, Ti, W, Cr, or Ni). Second, interdigital transducer  106  can be formed from alloys such as NiCr or CuAl. Third, interdigital transducer  306  can be formed from metal-nonmetal compounds (e.g., ceramic electrodes based on TiN, CoSi 2 , or WC).  
         [0045]      FIG. 5  illustrates a block diagram depicted a perspective view of a wireless SAW flow sensor system  500 , which can be implemented in accordance with a preferred embodiment of the present invention. System  500  includes a compartment or structure  504  in which a self-heating heater  506  and an upstream SAWu sensor device  516  can be located. Structure  504  additionally can include a down stream SAWd sensor device  514 . Sensor devices  516  and  514  can be implemented as interdigital transducers similar to those depicted in  FIGS. 1-4 .  
         [0046]     Arrows  502  and  504  respectively indicate blood (or other fluid, such as saline) flow in and blood out from compartment or structure  504 . An antenna  508  can be integrated with and/or connected to up stream SAWu sensor device  516 . System  500  can be, for example, located external to a living body or located within a living body (e.g., within a blood vessel). System  500  can be, for example, implemented within the context of a saline drip device for delivering saline to a living body. Similarly, a second antenna  512  can be integrated with and/or connected to SAWd down stream sensor device  514 . Additionally, a third antenna  510  can be integrated with and/or connected to self-heating heater  506 . Note that self-heating heater  506  can be powered by converting RF power to heat.  
         [0047]     The self-heating heater  506  can absorbs energy from RF power and convert it to heat. This self-heating portion can be formed from acoustically “lossy” materials, or acoustical absorber, in which the dissipation of acoustic energy in such material causes heating of the substrate. For a given thermal conductivity and effective thermal mass of the substrate, the quiescent surface temperature can eventually achieve steady state. Self-heating heater  506  can also be configured from a resistor-heater type material.  
         [0048]      FIG. 6  illustrates a block diagram of an in-vivo acoustic wave flow sensor system  600 , which can be implemented in accordance with a preferred embodiment of the present invention. System  600  generally includes an acoustic wave flow sensor device  608 , which can be implemented in a configuration similar to that of sensor system  500  depicted in  FIG. 5 . For example, acoustic wave flow sensor device  608  can be equipped with one or more digital transducers, such as those depicted in  FIG. 5 .  
         [0049]     Device  608  can be configured to include an acoustic coating such as that depicted in  FIG. 1 . Acoustic wave flow sensor device  608  can be coupled to and/or integrated with an antenna  603 . Antenna  603  can receive and/or transmit data to and from a transmitter/receiver  604 . In general, the antenna  603  can be connected to device  608 , such that antenna  605  receives one or more signals, which can excite an acoustic device thereof to produce a frequency output associated with the flow of blood for analysis thereof.  
         [0050]     Note that acoustic wave flow sensor device  608  can be associated with a microprocessor (i.e., not shown in  FIG. 6 ), which can process and control data for controlling one or more sensing functions of acoustic wave flow sensor device  608 . An example of a microprocessor that can be adapted for use with the embodiments disclosed herein include a central processing unit (CPU) or other similar device, such as those found in personal computers, personal digital assistant (PDA) and other electronic devices. Such a microprocessor can control logical operations associated with, for example, acoustic wave flow sensor device  608 . Such a microprocessor can be integrated with acoustic wave flow sensor device  608  or located separately from device  608 , while still controlling and processing data associated with sensing functions thereof, depending upon design considerations.  
         [0051]     Acoustic wave flow sensor device  608  and antenna  603  together can form a passive, wireless, in vivo acoustic wave flow sensor device  601 , which can be implanted within a human being. Wireless interrogation, as represented by arrow  606  can provide the power and data collection necessary for the proper functioning of device  601 . Device  601  can be implemented via a variety of surface acoustic wave technologies, such as Rayleigh waves, shear horizontal waves, love waves, and so forth.  
         [0052]      FIG. 7  illustrates a block diagram of an in-vivo acoustic wave flow sensor system  700 , which can be implemented in accordance with an alternative embodiment of the present invention. Note that in  FIGS. 6 and 7 , identical parts or elements are generally indicated by identical reference numerals. System  700  is therefore similar to system  600  depicted in  FIG. 6 , but includes some slight modifications. For example, a sensor device  702  is utilized in place of device  520 . Sensor device  702  incorporates device  100  depicted in  FIG. 1 . Thus, sensor device  702  and transmitter/receiver  602  together form a sensing device  701 , which can be utilized to monitor liquid flow rate, such as, for example, that of human blood flowing within a human body.  
         [0053]     Note that as utilized herein the terms “transmitter/receiver” and “transmitter and receiver unit” can be utilized interchangeably and can also refer to an integrated unit that comprises both a transmitter and receiver, or to separate transmitters and receivers, which may be located remotely from one another. Additionally, the terms “transmitter unit” and “transmitter” can be utilized interchangeably to refer the same device. The terms “receiver unit” and “receiver” can also be utilized interchangeably to refer to the same device. The transmitter and/or receiver can thus transmit short range radio frequency energy field(s) to one or more antennae associated with said sensor, such that the transmitter and the receiver can receive data transmitted from the sensor via one or more antennae.  
         [0054]      FIG. 8  illustrates a block diagram of a wireless surface acoustic wave flow sensor system  800 , which can be implemented without a heater, in accordance with an alternative embodiment of the present invention. System  800  generally includes a compartment or structure  806  in which an upstream SAWu sensor device  812  (i.e., a sensor) can be located. Structure  806  additionally can include a down stream SAWd sensor device  814  (i.e., as sensor). Note that the term “sensor device” and “sensor” as utilized herein can be utilized interchangeably to refer to the same feature. Sensor devices  812  and  814  can be implemented, for example, as interdigital transducers similar to those depicted in  FIGS. 1-4 . Structure  806  can be implemented as or integrated with a stent.  
         [0055]     Arrows  808  and  810  respectively indicate fluid or blood flow in out of compartment or structure  806 . An antenna  802  can be integrated with and/or connected to up stream SAWu sensor device  812 . Similarly, a second antenna  814  can be integrated with and/or connected to SAWd down stream sensor device  814 . Note that the antennas such as antenna  802  and the other antennas discussed herein can be utilized for a variety of purposes. For example, one antenna can be utilized to receive excitation signals, while the other antenna can be utilized to transmit results.  
         [0056]      FIG. 9  illustrates a block diagram of a cylindrical shape wireless surface acoustic wave flow sensor system  900 , which can be implemented in accordance with an alternative embodiment of the present invention. System  900  includes a cylindrical-shaped compartment or structure  906  in which a self-heating heater  918  and an upstream SAWu sensor device  912  can be located. Structure  906  additionally can include a down stream SAWd sensor device  914 . Sensor devices  912  and  914  can be, for example, implemented as interdigital transducers similar to those depicted in  FIGS. 1-4 .  
         [0057]     The SAWu sensor device  912 , heater  918  and SAWd sensor device  914  can be located on the inside wall of structure  906  with respective connections at the ends thereof. In the configuration of system  900 , 350 degrees of the inside circumference can be utilized for the heater resistor or heater  918 , which leaves sufficient space for configuring all connects at the edges of structure  906 . Structure  906  can comprise, for example, a stent used in medical procedures. System  900  can be implemented in the context of a stent. Heater  918  can, for example, be integrated into the walls of the stent (e.g., structure  906 ) to permit a small amount of heating of blood flowing through structure  906  (i.e., a stent). The blood can be heated by heater  918  a few degrees above ambient.  
         [0058]     In terms of coating selection, biocompatibility involves the acceptance of an artificial implant by the surrounding tissue and by the body as a whole. Biocompatible materials do not irritate the surrounding structures, do not provoke an abnormal inflammatory response, do not incite allergic reactions, and do not cause cancer.  
         [0059]      FIG. 10  illustrates a perspective view of a wireless blood flow sensor system  1000 , comprising a sensor  1004  integrated with a stent  1002  for measuring blood flow, in accordance with one embodiment of the present invention. Stent  1002  comprises a cylindrical-shaped structure that includes a continuous cylindrical shaped wall (or walls)  1006 . Sensor  1004  can be integrated into walls  1006  of stent  1002 . Arrows  1008  and  1010  respectively represent the flow of blood through stent  1002  when stent  1002  is located within a blood vessel.  
         [0060]     Stent  1002  further includes a cylindrically shaped internal gap  1012  through which blood flows through stent  1002 , as indicated by arrows  1008  and  1010 . Sensor  1004  can comprise, for example, a device that includes one or more antennas and a sensor component or sensor device such as an interdigital transducer. Sensor  1004  is generally analogous to, for example, upstream SAWu sensor device  812  or downstream SAWu sensor device  814  depicted in  FIG. 8 .  
         [0061]     As indicated in  FIG. 10  by a dashed circle  1009 , which represents an enhanced view of sensor  1002 , an antenna  1007 , such as, for example, antenna  802  and/or antenna  804  depicted in  FIG. 8 , can be integrated with or connected to sensor  1004 . Additionally, system  1000  can include a transmitter/receiver  1020  which is connected to an antenna  1022 . Antenna  1007  of sensor  1004  can receive and/or transmit data to and from transmitter/receiver  1020 .  
         [0062]     In general, antenna  1007  of sensor  1004  is analogous to antenna  506  of  FIG. 5 , antenna  603  of  FIGS. 6-7  and/or antennas  802  and  804  of  FIG. 8 . Antenna  1022  of transmitter/receiver  1020  (i.e., a transmitter and receiver unit) can transmit one or more signals to sensor  1004 , which can excite sensor  1004  to produce a frequency output associated with the flow of blood through stent  1002  for analysis thereof. Note that in  FIGS. 10-13 , similar or identical parts, components or elements are generally indicated by identical reference numerals. Thus,  FIGS. 11-13  represent variations to the embodiment of system  1000  disclosed in  FIG. 10 .  
         [0063]      FIG. 11  illustrates a perspective view of a wireless blood flow sensor system  1100 , comprising one or more sensors  1004  and  1005  integrated with stent  1002  for measuring blood flow, in accordance with an alternative embodiment of the present invention. System  1100  of  FIG. 11  is thus similar to system  1000  of  FIG. 10 , with the exception that a plurality of sensors  1004  and  1005  can be integrated into the walls  1006  of stent  1002 . Note that sensor  1004  and  1005  can be implemented as identical sensors, which are structurally identical to one another. Thus, sensor  1005  can include an antenna similar to that of  1007  depicted in  FIG. 10 .  
         [0064]      FIG. 12  illustrates a perspective view of a wireless blood flow sensor system  1200 , comprising one or more sensors  1004  and  1005  for measuring blood flow, in accordance with an alternative embodiment of the present invention. System  1200  of  FIG. 12  is thus similar to system  1100  of  FIG. 11  and system  1000  of  FIG. 10 , but differs in the addition of a wire mesh  1014  integrated with stent  1002 . The stent wire mesh can not only structurally support stent  1002 , but may support the functions of antennas such as,  1007  of sensor  1004  and antennas associated with sensor  1005 . Additionally, wire mesh  1014  can support the function of the antenna  1022  of the transmitter/receiver  1020  depicted in  FIG. 10 .  
         [0065]      FIG. 13  illustrates a perspective view of a wireless blood flow sensor system  1300 , comprising an upstream sensor  1004  and a downstream sensor  1016  integrated with a stent  1002  for measuring blood flow, in accordance with an alternative embodiment of the present invention. Upstream sensor  1004  can be implemented as a sensor device, such as, for example, upstream SAWu sensor device  812  depicted in  FIG. 8 . Downstream sensor  1016  can be implemented as a sensor device, such as, for example, downstream sensor  814  depicted in  FIG. 8 . Dashed circle  1017  indicates that upstream sensor  1016  is structurally similar to that of downstream sensor  1004  in that upstream sensor  1016  includes an antenna  1018  similar to that of antenna  1007 . Antennas  1007  and  1018  can be implemented similar to that of antenna  308  depicted in  FIG. 3 .  
         [0066]     Additionally sensors  1007  and  1016  can function similar to that of surface wave device  309  of  FIG. 3 , such that each antenna  1007  and  1018  is connected to and disposed above a wireless excitation component similar to that of wireless excitation component  310  depicted in  FIG. 4 . Sensors  1006  and  1016  can be configured to include an interdigital transducer (e.g., interdigital transducer  306  of  FIGS. 3-4 ) formed on a piezoelectric substrate  304 . Surface wave device  300  can therefore function as an interdigital surface wave device, and one, in particular, which utilizing surface-skimming bulk wave techniques. Interdigital transducer  306  can be configured in the form of an electrode. A biocompatible coating  302  can be selected such that there will be no adverse effect to the human body. Various selective coatings can be utilized to implement coating  302 .  
         [0067]      FIG. 14  illustrates a perspective view of an in-line sensor  1402  connected to a stent  1404 , in accordance with an alternative embodiment of the present invention. Sensor  1402  can function not only as a flow sensor, such as flow sensor  1004 , but also as a temperature and/or pressure sensor. Thus, sensor  1402  can be located in series or “in-line” with stent  1404 , and can be, for example approximately half the length of stent  1404 . The length of sensor  1402  is indicated by L 1 , while the length of stent  1404  is indicated by L 2  such that L 1 =½ L 2 . Sensor  1402  includes a cylindrical gap  1404  through which blood and/or fluid can flow, as indicated by arrows  1408  and  1410 .  
         [0068]     Sensor  1402  is generally connected to stent  1404  at interface  1406 . The connection between sensor  1402  and stent  1404  can be implemented, for example, via an interlocking mechanism. Sensor  1402  butts up against stent  1404  such that sensor  1402  and stent  1404  have the same inner diameter and outer diameter dimensions. Sensor  1402  can be configured to include one or more microstructure temperature sensing elements formed on a substrate within a hermetically sealed area thereof. Sensor  1402  can be equipped with an antenna similar to that, for example, of antennas  1007  and/or  1018  in order to communicate with transmitter/receiver  1420 . Thus, in addition to providing blood flow data, sensor  1402  can also provide pressure and/or temperature data.  
         [0069]     The microstructure temperature-sensing elements of sensor  1402  can be implemented, for example, as SAW (surface acoustic wave) temperature-sensing elements. Sensor  1402  can be, for example, a cylindrically shaped Interdigital Transducer (IDT). Additionally, one or more microstructure pressure-sensing elements can be implemented on or above a sensor diaphragm (not shown in  FIG. 14 ) on a substrate from which sensor  1402  is formed.  
         [0070]     The embodiments and examples set forth herein are presented to best explain the present invention and its practical application and to thereby enable those skilled in the art to make and utilize the invention. Those skilled in the art, however, will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. Other variations and modifications of the present invention will be apparent to those of skill in the art, and it is the intent of the appended claims that such variations and modifications be covered.  
         [0071]     The description as set forth is not intended to be exhaustive or to limit the scope of the invention. Many modifications and variations are possible in light of the above teaching without departing from the scope of the following claims. It is contemplated that the use of the present invention can involve components having different characteristics. It is intended that the scope of the present invention be defined by the claims appended hereto, giving full cognizance to equivalents in all respects.