Abstract:
A miniature light device delivers high energy modular photonic energy to an internal tissue region for diagnostic and/or therapeutic purposes. The miniature light device is a light source that can be placed at or near a distal end of an interventional device, providing localized application of energy in an efficient and cost effective manner.

Description:
CROSS-REFERENCE TO RELATED 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 08/922,263, filed Sep. 2, 1997, which claims the benefit of U.S. Provisional Patent Application No. 60/033,335, filed Nov. 21, 1996. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to light sources and, more particularly, to miniature light sources for placement inside a body for tissue characterization and treatment. 
       BACKGROUND 
       [0003]    Physicians have used light for performing diagnosis and therapy of tissue by delivering light to the tissue. Medical applications that use light include, for example, photoactivation of drugs, monitoring of blood glucose levels, tissue spectroscopy, illumination of internal tissue, and tissue ablation. Light system designers have come up with a variety of methods to deliver light to a tissue region of interest. Medium powered light emitting diode arrays placed on catheters and probes are available for activating photoactive drugs such as HPD (Photofrin) and SNeT 2  (Tin Etlopurpurin Dichloride) to perform photodynamic therapy (PDT). Most of the light system that generate high energy light are external light sources that use optical fibers to deliver the light to a variety of anatomical locations inside the body. Other ways to deliver energy to an internal tissue region include direct heating via conduction loss through a catheter or balloon electrodes, radioactive seeding passed through needles or catheters, inserting cryogenically cooled catheter tips, and using various light diffusers or ultrasonic transducers. 
         [0004]    In general, health services under managed care guidelines require that medical procedures be more effective, faster, and inexpensive. Several promising medical diagnosis and treatment systems using light wave energy have failed to become commercially successful due to the high cost of the instruments. Most high energy light systems are expensive, large, and complex because they require an external light source, light conducting fibers, transducers, and connectors. 
         [0005]    The use of optical fibers to deliver light presents several problems. In order to transport an adequate amount of light energy from the light source to an internal tissue region, a significant amount of optical fibers must be included in an interventional device. An interventional device (e.g., catheter, endoscope, guide wire, needle or introducer), however, does not include a lot of space and higher quality optical fibers, which take up less space, are expensive. Optical fibers also lack mechanical properties necessary to be used with an interventional device. Optical fibers can break when flexed and have a relatively high stiffness as compared to conventional catheter materials. Therefore, it is difficult to design a flexible tip for a catheter that includes optical fibers. Overall flexibility of an interventional device that includes optical fibers is limited. Furthermore, optical fibers require an expensive terminating connector and must be properly coupled to afford adequate light throughput. Signal efficiency of fiber based devices depends greatly upon the ability of the device to couple sufficient light into the fibers at the desired wavelength, but it is a challenge to efficiently couple light from a lamp source into fibers with small diameters. 
         [0006]    Known high energy light systems also tend to cause undesirable side effects. The high intensity light, which is necessary for medical procedures, can cause thermal destruction of normal tissue regions, since the light signals have high intensity as well as long duration. 
       SUMMARY 
       [0007]    This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
         [0008]    The present invention relates to improved high energy light systems for use in interventional devices for medical applications. The high energy light systems according to the invention include miniature light sources capable of generating high intensity modular light waves and capable of being placed at or near the tips of various interventional devices (e.g., a catheter, endoscope, guide wire, needle or introducer). The present invention, therefore, eliminates the need for expensive proximally located light sources, transducers, fibers, and connectors. The present invention further provides light sources that generate modular light output in a spectrum ranging from the ultraviolet to X-rays. The high output, short duration light waves allow safe operation without excessive heating effects. 
         [0009]    In general, in one aspect, the invention features an interventional device including a miniature light device for generating and delivering high energy modular photonic energy to an internal tissue region for diagnostic and/or therapeutic purposes. The light device is capable of being placed at or near a distal end of the interventional device, eliminating the need for light carrying conduits to deliver light generated by an external light source. The device may further include a feedback system and a light guide for supplying light output to the feedback system. 
         [0010]    In one embodiment, the light device is a sonoluminescent light module. The sonoluminescent light module includes a housing, an acoustic transducer and an acoustic conducting medium. The acoustic conducting medium is positioned inside the housing adjacent the acoustic transducer. The acoustic transducer comprises a piezoelectric material and a wave matching layer. The sonoluminescent light module is capable of generating light spectrum in the X-ray region. 
         [0011]    In another embodiment, the light device is an arc lamp. The arc lamp comprises a housing and a first and a second electrode positioned inside the housing in relation to each other to strike an arc. The second electrode is formed on an inner surface of the housing by flash metallization. The electrodes are sealed inside the housing. The housing may be shaped for collecting and redirecting light generated by the arc lamp. 
         [0012]    In yet another embodiment, the light device is a fluorescent light source. The fluorescent light source comprises a flash tube coated with a phosphorescent or fluorescing material. The fluorescent light source may comprise equipotential flash tube shaped to uniformly discharge light. A dielectric material surrounds the equipotential flash tube and a pair of electrodes contact opposite sides of the dielectric material. Alternatively, the fluorescent light source may comprise a Gunn-effect diode, a dielectric resonator disposed adjacent the diode and a gas tube comprising a gaseous substance that fluoresce when subjected to RF energy. 
         [0013]    In still another embodiment, the light device is a spark gap module. The spark gap module comprises two electrodes positioned in relation to each other for generating a spark across a gap between the two electrodes. A transparent housing seals the electrodes. 
         [0014]    The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]    The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
           [0016]      FIG. 1  is a schematic representation of a medical apparatus comprising an energy source, a signal conduit, and an energy emitter inserted in an interventional device; 
           [0017]      FIG. 2A  is a diagram of an embodiment of an arc lamp for placement inside a body; 
           [0018]      FIG. 2B  is a diagram of an embodiment of an arc lamp in communication with a feedback system; 
           [0019]      FIG. 3A  is a diagram of an embodiment of a discharge tube placed at a distal end of an interventional device; 
           [0020]      FIG. 3B  is a diagram of an embodiment of a discharge tube in communication with a battery and a capacitor; 
           [0021]      FIG. 3C  is a diagram of the discharge tube of  FIG. 3A  placed inside a balloon catheter deploying a stent; 
           [0022]      FIG. 4  is a diagram of an embodiment of a sonoluminescent light source in communication with a pulse generator; 
           [0023]      FIG. 5A  is a diagram of an embodiment of a multi-electrode spark gap for placement inside an interventional device; 
           [0024]      FIG. 5B  is a diagram of an embodiment of an incandescent light source; 
           [0025]      FIG. 6  is a diagram of an embodiment of a laser diode driven light source placed at a distal end of an interventional device; 
           [0026]      FIG. 7A  is a diagram of an embodiment of a discharge lamp in communication with a transformer; 
           [0027]      FIG. 7B  is a diagram of an embodiment of a fluorescent lighting device driven by a Gunn diode; 
           [0028]      FIG. 8A  is a diagram of a catheter for use with a miniature light device; 
           [0029]      FIG. 8B  is a diagram of a needle for use with a miniature light device; 
           [0030]      FIG. 8C  is a diagram of a guide wire for use with a miniature light device; and 
           [0031]      FIGS. 8D and 8E  are diagrams of endoscopes for use with a miniature light device. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Referring to  FIG. 1 , a medical apparatus  2  includes an energy source  1 , a signal conduit  3 , a light device  5  and an interventional device  7  for introducing the light device  5  to an internal tissue region. The energy source, for example, may be an external battery, power supply, pulse generator or RF generator. The energy source  1  may be controlled by a computer or microprocessor. The energy source  1  delivers energy to a port  11 . The medical apparatus also includes a timer  9  for limiting the duration of the energy delivered to the port  11 . A signal conduit  3  extends along the length of the interventional device  7  and provides electrical communication between the port  11  and the light device  5 . The signal conduit  3 , for example, comprises an ordinary twisted wire, coaxial cable, metallized traces or other suitable signal carrying conduit. The signal conduit  3 , in bipolar mode, includes at least one signal wire and one return wire. Alternatively, the signal conduit  3  may operate in monopolar mode in certain instances. In one embodiment, where the interventional device  7  is a catheter, the signal conduit  3  is a wire, having a diameter ranging anywhere from about 0.005 inches to about 0.080 inches. A wire having a diameter in this range does not greatly impact the flexibility or size of the catheter  7 . In another embodiment, metal bodied catheters, guide wires, or needles provide the return path using the conductivity of the metal body. 
         [0033]    Still referring to  FIG. 1 , the medical apparatus  2  further includes a feedback loop conduit  13 . The feedback loop conduit collects and returns a small portion of the light energy generated by the light device  5 . In one embodiment, where the interventional device  7  is an optically transparent catheter, the catheter body conducts some of the light generated at a distal tip of the catheter  7  back to a proximal end of the catheter  7 , permitting an operator to observe or confirm the operation of the medical apparatus  2  simply by looking at the proximal end of the catheter  7 . In another embodiment, the returned energy is coupled to the energy source  1  to provide a controlling feedback in response to onset of illumination, intensity or spectral components. 
         [0034]    Referring to  FIG. 2A , the light device is an arc lamp  14 . An arc lamp is an electric lamp in which light is produced by an arc made when current flows through ionized gas between two electrodes. The arc lamp  14  includes a pair of electrodes  23 ,  27 . The electrodes  23 ,  27  are spaced from one another for striking an arc. A housing  15  surrounds the arc lamp  14 . In one embodiment, the housing comprises quartz  15 . The electrodes  23 ,  27  are sealed inside a cavity  20  defined by the housing  15 . A sintered metal  17  with a glass or epoxy  19  seal the arc lamp  14 . In one embodiment, the sintered metal  17  is copper. The sintered metal  17  absorbs some of the vapors generated from the operation of the arc lamp  14  and reduces clouding during operation. The glass or epoxy seal  19  yields at high pressure, preventing the housing  15  from fracturing. Sealing the arc lamp  14  prevents any debris or escaping gas generated by the arc lamp  14  from leaving the confines of the interventional device  7 . An insulator  21  isolates the first electrode  23  from the sealing material  17 ,  19 . In one embodiment, a distal end of the first electrode  23  has a hemispherical shape and comprises coating of a material such as carbon or tungsten. The second electrode  27  forms the return electrode. The second electrode  27  is formed along one side  16  of the housing  15 . A separator  29  protects the second electrode  27  and prevents current from the second electrode  27  from flowing through the sintered metal  17 . The inner surface of the housing  15  is coated with a conductive trace of aluminum  25 . In one embodiment, a vacuum metallizing process coats the inner surface. The thickness of the aluminum is enough to sustain an arc for a short period of time, while transmitting a useful amount of light energy. 
         [0035]    Still referring to  FIG. 2A , in one embodiment, the shape of the housing  15  permits collecting and redirecting some of the light energy generated by the arc lamp  14  to the proximal end of an interventional device in communication with the arc lamp  14 . The flat front surface  31  of the housing  15  may include additional lenses. Alternatively, masking may modify the shape of the housing  15 . In addition, the flat surface  31  may be coated with a reflective substance. In this embodiment, the thick wall of the housing  15  may be coupled to one or more light guides, comprising optical fibers, transparent cylindrical catheter bodies and the like, to conduct some of the reflected light energy to the proximal end of the interventional device for the purpose of providing a feedback system. 
         [0036]    In another embodiment, the housing  14  provides means for cooling the arc lamp  14 . The housing may include passages for a cooling fluid to flow. Alternatively, a jacket of water, air or other fluid may surround the housing  14 . 
         [0037]    Referring to  FIG. 2B , a light system  32  having an arc lamp  34 , illustrates the usefulness of a feedback mechanism. To “strike an arc,” one must either bring two electrodes close together and then separate them by a distance, or if that is not possible, raise the voltage applied to the electrodes gradually until an arc is struck and then, drop the voltage quickly. An ordinary current sensing circuitry may assist this process by sensing an increase in current flow as the arc is struck and sustained. While the current sensing circuitry may be useful, a better arrangement is to sample the actual light output, which is responsive to slight changes in applied power and erosion of the electrodes within. This capability is especially valuable, since the burning time of the arc may be in the order of a few milliseconds, short enough to prevent heating and destruction of the carrying member or the surrounding anatomy. 
         [0038]    Still referring to  FIG. 2B , the light system  32  includes an arc lamp  34  in communication with a feedback system  36 . The arc lamp  34  comprises a first metal electrode  37  disposed at the center of a cavity defined by a hemispherical quartz dome  35 . The electrode  37  is held stationary by copper wool  39 , tightly packed to seal the arc lamp  34 . The copper wool  39  absorbs the fumes emitted by the arc. The light system  32  includes a second electrode  43  or a return path for the arc. A flash metallization  43  process may form the return path  43 . The return path  43  formed by flash metallization is sufficient for a short duration emission of an extremely bright output of wide spectral bandwidth including infrared (IR), visible and ultraviolet (UV) components. In one embodiment, the dome surface has a layer  41  of mercury, which enhances certain spectral wavelengths. The feedback system  36  includes a light guide  33 , which is in communication with the arc lamp  34  at a distal end and a sensor  45  at a proximal end. The sensor  45  supplies light output to the current controller  47 . 
         [0039]    Referring to  FIG. 3A , the light device is a discharge lamp  57 . In a discharge lamp, light is produced by an electric discharge between electrodes in a gas. A rod-like assembly  59  has a discharge tube  57  mounted on a distal end. The assembly  59  permits placement of the discharge tube  57  through various lumens including, for example, the lumen of a catheter with an optically clear structure or an endoscope. A transformer  61  disposed proximal to the discharge tube  57  provides a voltage step. The transformer  61 , for example, consists of a copper wire wound around a cylindrical form and tapped at various points along the length of the wire. A light system that generates short duration light waves permits the use of wire gages that would otherwise be too small to withstand heating effects in continuous service. The transformer  61  may use a wire as small as 0.005 inches in diameter, as long as it is capable of supplying adequate current at relatively high voltage. An example of a suitable wire is a common enamel-covered copper wire. The turns ratio between the transformer primary and the transformer secondary coil determines the step up ratio of the transformer  61 . The transformer  61  requires only one tapped coil, thus saving space. The coil may be wound around a metallic core such as iron, which improves its efficiency. The core diameter ranges from about 0.004 inches to about 0.080 inches. The core length ranges from about 0.093 inches to about 1.0 inch or even longer. In one embodiment, one or more layers of copper wire wraps around flexible cores of thin strips of iron to provide a flexible assembly that does not greatly interfere with the flexible characteristics of an interventional device. 
         [0040]    Still referring to  FIG. 3A , the discharge tube  57  includes a third wire or capacitively coupled electrode  71  placed adjacent the discharge tube  57 . The third wire  71  extends along an interventional device and communicates with the reference ground of a power discharge source. The third wire  71  improves the flash output of the discharge tube  57  by providing an approximately equipotential charge along the length of the discharge tube  57 , thereby improving reliability, while reducing the peak voltage needed for flash onset. 
         [0041]    In one embodiment, the discharge tube  57  is mounted directly at the distal end of the transformer  61 . In another embodiment, the discharge tube  57  is separated from the transformer  61  with wires  73 . A variety of materials can fill the discharge tube  57 . In one embodiment, the discharge tube is a flash tube filled with gas  75  such as xenon, argon or krypton, providing various spectral output. In another embodiment, combinations of gases with other substances, such as xenon and a chloride fill the flash tube  57 . The combination of xenon and chloride produces output with prominent spectral lines in the ultraviolet (UV) region at around 308 nm or shorter. It is difficult to deliver spectral output in the UV region through an ordinary optical fiber due to loss through attenuation. In one embodiment, the flash tube  57  is frosted or coated with a phosphorescent or fluorescing material such as borax. 
         [0042]    An interventional device may include an elongated discharge tube  77  or a series of tubes capable of being passed though a channel of an interventional device. The length of the intervention device, for example, may be 2 meters or more. The discharge tube  77  diameter, for example, may be approximately 0.125 inches and the discharge tube  77  length, for example, may be approximately 1 inch. In the embodiment of  FIG. 3A , a transparent sheath housing  85  surrounds the discharge tube  77  to protect the discharge tube  77  and to prevent the discharge tube  77  from contacting the wall of a bodily channel being illuminated. Examples of suitable housing  85  materials include polyethylene and polypropylene. UV absorption, however, can be high in such materials. Therefore, where generation of UV light is desired, these materials must be sufficiently thin walled (e.g., about 0.002 inches) to reduce the net loss of UV energy to a manageable level. The relative lack of rigidity of the sheath material can be compensated by stretching the material, which has been formed into a cylindrical sheath over the discharge tube  77  or by inflating a section of the discharge tube  77  so that it takes on a more rigid form. 
         [0043]    Referring to  FIG. 3B , an equipotential discharge tube  77  reduces the possibility of hot spot formation. An equipotential discharge tube  77  has a shape, which provides a more even voltage gradient across a section of the tube  77 , and therefore a more distributed discharge upon firing. A dielectric material  78  surrounds the tube  77 . A pair of electrodes  75 ,  76  formed by metallization contacts opposite sides of the dielectric material  78 . A suitable dielectric material  78 , for example, includes glass or polystyrene. In one embodiment, the voltage gradient across the electrodes  76  is made more uniform by reducing edge effects. Edge effects may be reduced by creating a local condition with greater amount of gas  75  in the tube and a smaller amount of the dielectric material  78 . In one embodiment, the discharge tube  77  is in communication with a current source  81  such as a battery and a capacitor discharge storage  79 . The battery  81  charges the capacitor  79  to store energy, and the stored energy is discharged and applied to the discharge tube  77  by opening a normally closed switch  83 . In another embodiment, an RF current of either a continuous waveform (CW) or a pulsed form effectively creates a high voltage at the electrodes  75 ,  76  of the discharge tube  77  to generate light output. 
         [0044]    In one embodiment, an endoscope provides means for introducing the light devices of  FIGS. 3A and 3B . Once the light device is properly positioned, the light device discharges a desired spectrum of light to perform a medical procedure. One medical procedure performed in this manner is destroying or ablating a thin layer of cells on the surface of an organ or the inner wall of a vessel such as the esophagus using ultraviolet energy. The broad spectrum of emission of a xenon type flash tube, which contains IR, visible and UV components, for example, may be used to ionize, heat and/or irradiate a surface. This action may also kill foreign cells such as bacteria or various viruses. This procedure is described in a commonly-owned U.S. provisional patent application, namely U.S. Provisional Patent Application Ser. No. 60/033,333. Another commonly-owned U.S. provisional patent application is U.S. Provisional Patent Application Ser. No. 60/033,334. The disclosures in these two provisional patent applications, and any regular U.S. patent applications, including U.S. Patent Application Publication Nos. 2001/0041887 A1 and 2002/0115918 A1, converted on the basis of one or both of these provisional patent applications, are hereby incorporated herein by reference. Another medical procedure performed with such a device is tissue spectroscopy. Short duration UV pulses can excite intrinsic fluorophores that may be present in a tissue region. For this application, the output of the discharge lamp may be filtered so that its radiation is restricted to the blue or UV region of the spectrum. Still another medical procedure performed with the light device of the present invention includes activation of a photo active drug. 
         [0045]    Referring to  FIG. 3C , a balloon catheter  90  includes the light device of  FIG. 3A . Air or fluid may inflate the balloon portion  92  of the catheter  90 . The balloon  92  includes a polymeric stent  92 . The discharge lamp  57  inside the balloon  93  hardens the distended polymeric stent  92  by irradiating the polymeric stent  91 . In one embodiment, the polymeric stent  91  comprises a UV-curable epoxy or adhesive to assist in hardening of the stent  91 . Loctite  3761  adhesive “Litetak” is an example of a UV-curable adhesive. A fibrous stent may be hardened by impregnating the stent with some of the UV-curable adhesive and illuminating it with the intense light output of the discharge tube in-vivo. The inflation lumen  95  may include a cooling fluid to cool the discharge tube  57 . An inner sliding member  96  may be used to adjust the position of the discharge tube  57  inside the balloon  93 . 
         [0046]    All of the light devices described thus far generate photonic energy in the infrared (IR), visible and ultraviolet range of the spectrum. Referring to  FIG. 4 , a sonoluminescent light device  101  provides light output in the X-ray spectrum region. The term “sonoluminescence” refers to luminescence produced by high frequency sound waves. The operation of the sonoluminescent effect is currently somewhat of a mystery; however, it has been shown that sufficiently high acoustic powers may be generated with practical ultrasonic transducers and the sound waves focused to a point in a sound conducting medium may emit a short pulse of light energy including the ultraviolet region to X-ray region. Therefore, it becomes possible to generate X-rays at the distal tip of a flexible catheter. 
         [0047]    Still referring to  FIG. 4 , the sonoluminescent light device  101  includes a housing  103 , an acoustic transducer  110 , and an acoustic conducting medium  105 . The housing  103  encloses the acoustic conducting medium  105 . The acoustic conducting medium  105  is disposed in the pathway of sound waves generated by the acoustic transducer  110 . The acoustic transducer  110  includes a piezoelectric material  113  and an integral matching layer  107 . Lead zirconate-titanate is an example of a piezoelectric material  113 , which can be used to form the acoustic transducer  110 . Other suitable piezoelectric materials  113  may also be used to convert electrical energy to mechanical energy. 
         [0048]    The sonoluminescent light device  101  further comprises a focusing lens  109 , which is curved to provide a sharp spot of focused sound waves in the acoustic conducting medium  105 . The focusing lens  109  sits in between the acoustic transducer  110  and the acoustic conducting medium  105 . The sonoluminescent light device  101  comprises two electrodes. The first electrode  111  attaches to the back of the piezoelectric material  113 . The second electrode attaches to the face of the acoustic transducer  110 . The thickness of the piezoelectric layer  113  determines the frequency of the operation. In one embodiment, the wave matching layer  107  is a ¼ wave matching layer  107  made of a material such as silver filled epoxy. The wave matching layer  107  serves as both an electrode and a matching layer. In another embodiment, the wave matching layer  107  is shaped into a focusing lens to concentrate the ultrasound beam. In one embodiment, the acoustic conducting medium  115  comprises water. In another embodiment, the acoustic conducting medium  115  comprises a solid substance or target, on which the sonoluminescent effect can be observed. A pulse generator  112  provides a high voltage pulse or pulses to the transducer  110  via cable lines  114 . A train of pulses may be employed to produce a series of light or X-ray output events, and the pulses may be stepped up or down in voltage using a transformer. 
         [0049]    Still referring to  FIG. 4 , in one embodiment, the distal end  117  of the housing  103  is shaped to permit further reflection and concentration of the acoustic waves. In another embodiment, the distal end of the housing  103  is open so that the focus of the acoustic signal may be pointed directly in the tissue. The acoustic signals, when insonified, may radiate photonic energy including X-rays. 
         [0050]    In one embodiment, the sonoluminescent light  101  is implanted inside a body. In another embodiment, the sonoluminescent light device  101  is inserted inside an interventional device and the focal point of the acoustic signals lies outside the light assembly and inside the interventional device. The interventional device may simply be a cap, cover, or needle. Alternatively, the sonoluminescent light may be placed within a catheter, guide wire, endoscope or introducer. 
         [0051]    The sonoluminescent phenomenon is currently under investigation and may affect matter and living tissue in previously unobserved ways, and the use of a medical device in conjunction with a transducer capable of generating the sonoluminescence may find uses that have not been anticipated. 
         [0052]    Referring to  FIG. 5A , a multi-electrode spark gap module  121  includes a pair of electrodes  123  held inside a housing  121 . The multi-electrode spark gap module  21  is capable of generating a spark across the gap of the electrodes  123 , in response to the application of electronic pulses. A spark is a short duration electric discharge caused by sudden breakdown of air or some other dielectric material separating two terminals. The electric discharge produces a flash of light. The spark gap module  121  operates in a way similar to the arc lamp of  FIG. 2A , except that the cap does not necessarily have to be conductive in order to generate an emission when the current flow is established at the onset of discharge. The spark gap module  121  provides certain advantages, such as lower heat generation during operation and ease of manufacturing. 
         [0053]    Still referring to  FIG. 5A , the spark gap module  121  includes electrodes  123  sealed in a glass envelope  125 , in a manner similar to conventional spark gaps used to control static discharge. Leads  126  supply electrical power to the electrodes  123 . An insulator  127  seals the module  121  and separates the leads  126  from each other. Examples of materials appropriate to form the insulator  127  include plastic, glass and other nonconductive materials. 
         [0054]    It is possible to use the light energy of this relatively small electrical discharge produced by a spark gap module  121  to excite a volume of nearby tissue and determine its colors and fluorescence. The spectrum of the light generated by a spark gap module  121  contains blue and UV portions of the spectrum. This range is particularly useful for exciting fluorophores which may be present in the tissue. A filter layer  128  disposed at the distal end of the spark gap module  121  enhances the output of the blue and UV region of the spectrum. The filter layer  128  may comprise an inexpensive dyed plastic dip coat or a more expensive dichroic coating. 
         [0055]    Referring to  FIG. 5B , an incandescent light source  122  provides high intensity short duration light output. The incandescent light source  122  has the same basic structure as the spark gap module of  FIG. 5A , except that the incandescent light source  122  includes a filament  129  (i.e., non-gap). In one embodiment, the incandescent lamp  122  includes two electrodes encased in a housing  121  and a tungsten filament  129  bridging the two electrodes. The incandescent light source  122  generates high intensity, short duration light without generating excessive heat. The incandescent light source  122  can generate emissions of less than 100 milliseconds with color temperature of about 5000 degrees Kelvin, which includes substantially blue and UV light energy. Other filaments, vacuum or gas-filled enclosures, including oxygen filled and oxidizing filaments like those used in flash bulbs may be used to generate light of various colors. 
         [0056]    Certain medical procedures such as photodynamic therapy (PDT) or tissue spectroscopy including fluorescence and Raman spectroscopy require monochromatic light output at high intensities. One method of generating a monochromatic output is to use a filter. This method, however, may be inefficient when highly attenuative filtering techniques are employed. Another method of generating a monochromatic light is to use a laser. Typical laser diodes, which are commonly found in laser pen pointers have outputs in the red region with power levels typically in the 1-7 mW range. Lasers can be made very small in size using semiconductor fabrication processes. A typical laser diode assembly is about 0.375 inches in diameter, but most of that size is attributed to the case and tabs for solder connections. The actual light generating portion of the diode is in the order of a few microns in thickness and a few tens of microns in width and length. Therefore it is reasonable to predict that laser diode fabrication in the range of 0.010 inches to 0.080 inches will be practical and economical for use in catheter based devices. One drawback of the laser diode is that it is available in only a few wavelengths mostly within the IR and red regions, and none currently in the UV regions. Advances in semiconductor processing and laser diode physics portend that UV laser diodes will exist in the future, but in the meantime a practical way to double the frequency of operation is by introducing a volume of an optically nonlinear material followed by a filter that doubles the frequency of the laser diode. 
         [0057]    Referring to  FIG. 6 , the light device  132  includes a laser diode  131  and a frequency multiplier  137 . The laser diode  131  is capable of producing coherent laser light, which emanates from a narrow gap  133  in the diode structure  131 . The frequency multiplier is a KDP crystal  137  placed distal to the laser diode  131 , and the laser diode  131  and the frequency multiplier  137  are held in proximity to the tip of a carrying body  139 . A high pass filter  141  is mounted on the opposite side of the laser diode  131  so that any light of the fundamental frequency is absorbed or reflected and only the multiplied waveform remains. A diode mount  143  and a lens holder  145  maintain the relationship of the elements within the carrying body  139 . A pair of wires  147  supply DC power to the diode  131  from a connector at the proximal end of the carrying body  139 . A heat sink  146  supporting the laser diode  131  prevents overheating of the laser diode  131 . In one embodiment, the laser diode  131  is cooled further by fluid flow in the interventional device. It should be pointed out that the efficiency of frequency doubling in this manner is extremely poor and that outputs greater than −40 dB relative to the source is expected. In the past, this feature has made most applications of frequency multiplying crystals to laser diode devices impractical. In the present invention, however, the efficiency is tolerable since the light loss functions of intervening materials may be negligible and the power requirements are low. In another embodiment, the light device  132  includes an ordinary light emitting diode, which generates a non-coherent output. 
         [0058]    A fluorescent lighting device can generate monochromatic or relatively narrow band light wave energy. The fluorescent lighting device may be gas filled tubes, which fluoresce at known wavelengths and produce output spectra composed of discrete lines. Referring to  FIG. 7A , an RF driven fluorescent lighting device  150  generates monochromatic light. The fluorescent light device  150  may be inserted inside an interventional device such as a catheter or a guide wire. The fluorescent light device  150  includes a tube  159  filled with argon gas  157 . The tube  159  is pressurized or partially evacuated and then sealed. A pair of signal wires  151  electrically connect a transformer  153  to the tube  159  through a pair of electrodes  155  located on opposite sides of the tube  159 . The transformer  153  may step up an ordinary 60 Hz AC voltage to a higher voltage. Higher frequencies ranging from about 60 Hz to about 200 GHz provide greater efficiencies and more stable light output. In one embodiment, an RF generator connects to a proximal end of an interventional device carrying the lighting device  150 . This embodiment provides even greater efficiencies, since there is no need to supply RF energy to the interventional device via external means. 
         [0059]    Referring to  FIG. 7B , a fluorescent light device  160  includes a Gunn-effect diode  161  placed adjacent a resonant dielectric resonator  163 . Materials suitable to form the resonator  163 , for example, include yttrium-iron-garnet (YIG) and other high dielectric materials. These materials provide useful tuning ability and high efficiency oscillation, which results from the diode  161  being used as a relaxation oscillator. In the embodiment of  FIG. 7B , the light device  160  includes an additional cavity resonator  165  to provide a higher RF voltage to a gas tube  167 . In one embodiment, the cavity resonator  165  is filled with glass micro spheres to improve strength of the assembly, which would otherwise be hollow. The gas  169  placed inside the gas tube  167  may be any gaseous substance that will not explode when excited with RF energy, will fluoresce when DC current is applied through wires  171  in electrical communication with the diode  161  and resonator  165 , causing the diode  161  to emit RF energy. 
         [0060]    The scope of the present invention includes other types of light generating systems not specifically described herein, such as electroluminescent panels, mechanical sparking, various incandescent and combustion generated light, chemical luminescence and others. The present invention permits numerous light sources to be placed at a distal end of an interventional device by a combination of miniaturization and use of short duration energy. 
         [0061]    Referring to  FIGS. 8A ,  8 B,  8 C,  8 D, and  8 E, an interventional device having at least a portion that is optically transmissive may include any of the aforementioned energy sources. The interventional device is sized to permit passage through at least one of its lumens. A portion of the interventional device may function as the housing for the various light devices. It should be understood that any of the features herein referred to as catheter or catheter sheath also refers to other interventional devices such as a guide wire, guiding catheter, endoscope and needle art. 
         [0062]    Referring to  FIG. 8A , a catheter  200  may be used to introduce a light device inside a body. The catheter  200  includes a catheter body  201 , a fluid port  203 , an optically transparent window  209  and an aperture  211  located at a distal end  207  of the catheter  200 . The catheter body  201 , for example, comprises an extruded plastic such as polyethylene, nylon, PET, or polyimide. The fluid port  203  located near a proximal end  206  of the catheter  200  allows introduction of various substances such as drugs, fluorescing agents, ultrasound transducers, pressure transducers, flush, cooling or irrigation fluids or optical coupling fluids. The fluid port  203  comprises a side arm and a Luer fitting, as commonly used in the catheter art. The proximal end  206  of the catheter  200  further comprises a connector  205  capable of electrical and/or optical connection. In the case of a closed loop feedback system as shown in  FIG. 2B , the catheter  200  includes both optical and electrical connection made simultaneously. The distal end  207  of the catheter  200  is fitted with an optically transparent window  209  and an aperture  211 , through which fluid or light wave energy may pass. The material for the transparent window  209  is chosen to efficiently transmit various emission wavelengths generated by the light system incorporated inside the catheter  200 . For example, where the light device generates UV light, compromise between strength of the window  209  and the thickness of the window  209  may be necessary, since UV spectrum tends to attenuate when passing through a plastic material. In the embodiment of  FIG. 8A , an aperture located adjacent the light source allows the generated light to reach an interior tissue region. In another embodiment, a low loss glass such as quartz is bonded to the distal tip  207  of the catheter  200 . In the embodiment of the X-ray generating sono luminescent light source of  FIG. 4 , the X-ray radiation may be emitted through a denser material such as a metal, which may serve to house and shield, redirect or focus the X-rays at the distal tip  207  of the catheter  200 . In still another embodiment, the energy producing transducer protrudes through an open end of the catheter  200 . 
         [0063]    Still referring to  FIG. 8A , in one embodiment, a light device placed inside the catheter  200  contacts the inner surface of the distal end  207  of the catheter  200  to affix the light device location. In another embodiment, the light device is located in registration with a window  209  or another location throughout the length of the catheter  200 . The placement of the light device is adjustable using a proximal holder, which allows the user to pre-position the light device inside the catheter  200  or to move the light device and the catheter  200  relative to each other during use. In one embodiment, moving the light device relative to the catheter  200  during use allows the light device to illuminate various regions of the anatomy without having to move the catheter. In another embodiment, the light device inside the catheter  200  creates an image either by rotating the catheter  200  or the light device inside the catheter  200 , or by sliding the light device relative to the catheter body  201  to effect a scanning action. 
         [0064]    Referring to  FIG. 8B , a hollow needle  210  is configured to introduce a light device of the present invention near an interior tissue region. The needle  200  includes a shaft  219 , a beveled tip  221  at a distal end of the needle  210  and an aperture  217  sized to accept the light device at a proximal end of the needle  210 . In one embodiment, the needle shaft  219  comprises stainless steel with a wall thickness of about 0.003 inches and a length of about 210 millimeters. The beveled tip  221  may be sharpened to permit easy insertion of the needle  210  and a pathway for the light device. 
         [0065]    An operator uses an external X-ray or ultrasound imaging technique to first locate an internal tissue region of interest. The operator then inserts the needle  210  inside the body under image guidance until the tip  221  reaches the region of interest. The needle  210  allows the light device to be inserted into the body through the aperture  217  of the needle  210  and be located near the tissue region. The operator may confirm the position of the light device using the aforementioned image guidance. Once satisfied that the light device is in the proper place, the operator applies power to the light device to generate light. 
         [0066]    Referring to  FIG. 8C , a guide wire  225  placed inside a preexisting channel may deliver a light device of the present invention near an internal tissue region. The guide wire  225  has a single central lumen  226  extending through the guide wire body  227  and a guide wire coiled tip  229 . The guide wire body  227 , for example, comprises hypo tube, plastic extrusion, or wound wires. The tip  229 , for example, comprises coiled stainless steel or platinum wires. The outside diameter of the guide wire  225  ranges from about 0.035 inches to about 0.010 inches. The inside diameter of the lumen  226  ranges from about 0.032 inches to about 0.004 inches. The guide wire  225  length ranges from about 100 cm to about 200 cm. The guide wire  225  with a length in this range is useful for reaching the GI tract, brain, heart and other remote internal tissues. In another embodiment, a shorter guide wire  225  introduces a light device to less remote areas such as the tear ducts or breast milk ducts. 
         [0067]    Referring to  FIG. 8D , an endoscope  235  may deliver a light device of the present invention near an internal tissue region through an access port  237 . The endoscope  235  further includes an eye piece  239  and a flush lumen  241  used to flush and guide the location of the tip of the endoscope. The access port  237  may be relatively large to allow a light device to easily pass through. In one embodiment, the access port  237  has a diameter up to about 0.187 inches. The endoscope  235  is useful for delivering high energy emission such as that afforded by the xenon flash tube module to an area of the body such as the esophagus. 
         [0068]    Referring to  FIG. 8E , an introducer  251  may deliver a light device of the present invention near an internal tissue region. The introducer  251  includes a Touhey-Borst fitting  253 , a side arm  255 , a single lumen plastic sheath  257 , and an open distal end. In one embodiment, the open distal end  259  of the introducer  251  is inserted into arteries or veins and another interventional device comprising a light device is introduced into the internal tissue region through the introducer  251 . The guide wire shown in  FIG. 8C , the catheter shown in  FIG. 8A  and the needle shown in  FIG. 8B  are examples of interventional devices, which may comprise a light device of the present invention and which may pass through the introducer  251  to be placed near an internal tissue region of interest. 
         [0069]    Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the invention is to be defined not by the preceding illustrative description but instead by the spirit and scope of the following claims. 
         [0070]    While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.