Abstract:
A catheter enables real-time light measurements, for example, without limitation, diffuse reflectance, fluorescence, etc., from biological materials, such as tissue (including blood), while performing RF ablation. The catheter tip design isolates illumination and collection paths within the tip electrode such that light for illuminating the tissue of interest (e.g., cardiac tissue or blood) is isolated within the tip electrode from light that returns from the tissue to the catheter tip, and vice versa. Such a design advantageously avoids saturation of the optical detector, and ensures diffusion of the illumination light within the medium of interest. The catheter has a catheter body and a tip electrode with a shell wall and a hollow cavity. The shell wall has at least an illumination opening and a collection opening. The catheter further includes a first fiber optic cable in communication with the illumination opening, and a second fiber optic cable in communication with the hollow cavity, wherein light emitted from the first fiber optic cable exits the tip electrode to reach tissue through the illumination opening in defining a first path and returns to the tip electrode from the tissue into the hollow cavity through the collection opening in defining a second path, the first and second paths being optically isolated from each other within the tip electrode. The invention also includes a method of making an ablation electrode tip defining isolated optical paths with in the tip electrode for light exiting the tip electrode and light returning to the tip electrode.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to ablation catheters, and in particular to ablation catheters with optical monitoring of tissue. 
       BACKGROUND 
       [0002]    For certain types of minimally invasive medical procedures, real time information regarding the condition of the treatment site within the body is unavailable. This lack of information inhibits the clinician when employing catheter to perform a procedure. An example of such procedures is tumor and disease treatment in the liver and prostate. Yet another example of such a procedure is surgical ablation used to treat atrial fibrillation. This condition in the heart causes abnormal electrical signals, known as cardiac arrhythmias, to be generated in the endocardial tissue resulting in irregular beating of the heart. 
         [0003]    The most frequent cause of cardiac arrhythmias is an abnormal routing of electricity through the cardiac tissue. In general, most arrhythmias are treated by ablating suspected centers of this electrical misfiring, thereby causing these centers to become inactive. Successful treatment, then, depends on the location of the ablation within the heart as well as the lesion itself. For example, when treating atrial fibrillation, an ablation catheter is maneuvered into the right or left atrium where it is used to create ablation lesions in the heart. These lesions are intended to stop the irregular beating of the heart by creating non-conductive barriers between regions of the atria that halt passage through the heart of the abnormal electrical activity. 
         [0004]    The lesion should be created such that electrical conductivity is halted in the localized region (transmurality), but care should be taken to prevent ablating adjacent tissues. Furthermore, the ablation process can also cause undesirable charring of the tissue and localized coagulation, and can evaporate water in the blood and tissue leading to steam pops. 
         [0005]    Currently, lesions are evaluated following the ablation procedure, by positioning a mapping catheter in the heart where it is used to measure the electrical activity within the atria. This permits the physician to evaluate the newly formed lesions and determine whether they will function to halt conductivity. It if is determined that the lesions were not adequately formed, then additional lesions can be created to further form a line of block against passage of abnormal currents. Clearly, post ablation evaluation is undesirable since correction requires additional medical procedures. Thus, it would be more desirable to evaluate the lesion as it is being formed in the tissue. 
         [0006]    A known method for evaluating lesions as they are formed is to measure electrical impedance. Biochemical differences between ablated and normal tissue can result in changes in electrical impedance between the tissue types. Although impedance is routinely monitored during electrophysiologic therapy, it is not directly related to lesion formation. Measuring impedance merely provides data as to the location of the tissue lesion but does not give qualitative data to evaluate the effectiveness of the lesion. 
         [0007]    Another approach is to measure the electrical conductance between two points of tissue. This process, known as lesion pacing, can also determine the effectiveness of lesion therapy. This technique, however, measures the success or lack thereof from each lesion, and yields no real-time information about the lesion formation. 
         [0008]    Thus, there is a need for a catheter that is capable of measuring lesion formation in real-time, if not monitoring tissue in general, and is adapted for use at most angles to the tissue. Moreover, where such measuring and detecting are accomplished through optical spectroscopy, there is a need for a catheter that can provide separate optical paths for illuminating the tissue and recapturing light from the tissue. The catheter should also be of a simplified but efficient design that allows for ease in manufacturing and reduced production labor and costs. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is directed to a catheter that enables real-time light measurements, for example, without limitation, diffuse reflectance, fluorescence, etc., from biological materials, such as tissue (including blood), while performing RF ablation. The catheter tip design is implied but maintains isolated illumination and collection paths within the tip electrode for light to exit the catheter tip and interact with, if not travel through, the tissue of interest (e.g., cardiac tissue or blood) before returning to the catheter tip. Such a design advantageously avoids saturation of the optical detector, and ensures diffusion of the illumination light within the medium of interest. 
         [0010]    The light recaptured by the catheter from the tissue conveys tissue parameters that can be evaluated using optical spectroscopy. These parameters include, without limitation, lesion formation, depth of penetration of lesion, and cross-sectional area of lesion, formation of char during ablation, recognition of char during ablation, recognition of char from non-charred tissue, formation of coagulum around the ablation site, differentiation of coagulated from non-coagulated blood, differentiation of ablated from healthy tissue, tissue proximity, evaluation of tissue health, status, and disease state, and recognition of steam formation in the tissue for prevention of steam pop. 
         [0011]    In accordance with the present invention, the catheter in one embodiment includes a catheter body and a tip electrode with a shell wall and a hollow cavity, where the shell wall has at least an illumination opening and a collection opening. The catheter also has a first fiber optic cable in communication with the illumination opening and a second fiber optic cable in communication with the hollow cavity, wherein light emitted from the first fiber optic cable exits the tip electrode to reach tissue through the illumination opening in defining a first path and returns to the tip electrode from the tissue into the hollow cavity through the collection opening in defining a second path. Advantageously, the first and second paths in the tip electrode are optically isolated from each other. 
         [0012]    In a more detailed embodiment, a catheter has a catheter body and a tip electrode adapted for ablating tissue. The tip electrode has a shell and a hollow cavity. The shell has multiple illumination openings into which light from emitting fiber optic cables is injected to illuminate tissue of interest. The illumination openings have a semi-spherical cross-section and may be filled with a material with optical scattering properties, e.g., a scattering agent-filled epoxy or plastic, to aid in the even distribution of light out of the openings. The shell also has multiple collection openings through which light recaptured from the tissue is collected in the hollow cavity. And one or more receiving fiber optic cables are provided to receive the light collected in the hollow cavity. Where the emitting fiber optic cables traverse the hollow cavity, a coating is provided on the cables to prevent light from leaking out of or into the cables for keeping the separate paths optically isolated within the tip electrode. 
         [0013]    As an omnidirectional illuminator and collector, the tip electrode in one embodiment has a first section that is generally perpendicular to a longitudinal axis of the tip electrode, a second section that is at an angle between about 0 and 90 degrees with the longitudinal axis, and a third section that is generally parallel with the longitudinal axis. The collection and illumination openings may be configured in any of the first, second and/or third sections. In one embodiment, the collection openings are configured in the first and third sections, and the illumination openings are configured in the second section. 
         [0014]    The tip electrode also includes an alignment plug that seals the hollow cavity. The plug has passages for the emitting and the receiving fiber optic cables extending therethrough, to stabilize the fiber optic cables and minimize stress that can cause breakage of the fiber optic cables. 
         [0015]    The present invention is also directed to a method of making an ablation tip electrode that also functions as an omnidirectional illuminator and collector. The method includes providing a shell with a hollow cavity, configuring at least one collection opening in the shell, configuring at least illumination opening in the shell, providing an emitting fiber optic cable adapted to emit light into the illumination opening, providing a receiving fiber optic cable adapted to receive light collected in the hollow cavity, and providing an optical barrier between the emitting fiber optic cable and the hollow cavity. 
         [0016]    The method may further include providing the illumination opening with a semi-spherical cross section and filling the illumination opening with a material having optical scattering property, for example, a scattering agent-filled epoxy or plastic, to aid in the even distribution of light out of the openings. The method may also further include forming a plug to seal with hollow cavity, wherein the plug is configured with passages for the fiber optic cables to extend through, and fixedly securing portions of the fiber optic cables in the passages to the plug. 
         [0017]    The present catheter and method are designed to use light in conjunction with irrigation and the technology of RF ablation. Advantageously, the light used to monitor and assess the tissue (or a lesion formed in the tissue) is generally not affected by the portion of the electromagnetic radiation used for ablation. Moreover, the bandwidth used for monitoring and assessing also transmits through blood with minimal attenuations. The fiber optics are used and disposed in the catheter in a manner that avoids contact with tissue, which can increase the operative lifetime of the catheter and minimize damages caused by abrasion to the fiber optics. Furthermore, the alignment plug in the tip electrode secures the fiber optic cables with minimal bend or strain but increased angular coverage, which can minimize fiber optics breakage during assembly and use, as well as reduce nonlinear optical effects caused by orientation of the fiber optics. In addition, the use of fiber optics to emit and receive light is a generally temperature neutral process that adds little if any measurable heat to surrounding blood or tissue. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
           [0019]      FIG. 1  is a side view of an embodiment of the catheter of the present invention. 
           [0020]      FIG. 2A  is a side cross-sectional view of an embodiment of a catheter body according to the invention, including the junction between the catheter body and intermediate section, taken along a first diameter. 
           [0021]      FIG. 2B  is a side cross-sectional view of an embodiment of a catheter body according to the invention, including the junction between the catheter body and intermediate section, taken along a second diameter generally perpendicular to the first diameter of  FIG. 2A . 
           [0022]      FIG. 3A  is a side cross-sectional view of an embodiment of a catheter body according to the invention, including the junction between the intermediate section and a tip section, taking along a first diameter. 
           [0023]      FIG. 3B  is a side cross-sectional view of an embodiment of a catheter body according to the invention, including the junction between the intermediate section and a tip section, taking along a second diameter generally perpendicular to the first diameter of  FIG. 3A . 
           [0024]      FIG. 4A  is a side cross sectional view of an embodiment of a catheter body according to the invention, including a junction between a plastic housing and a tip electrode, taken along a first diameter. 
           [0025]      FIG. 4B  is a side cross-sectional view of an embodiment of a catheter body according to the invention, including a junction between a plastic housing and a tip electrode, taken along the second diameter generally perpendicular to the first diameter of  FIG. 4A ; 
           [0026]      FIG. 5  is a longitudinal cross-sectional view of an embodiment of an intermediate section of  FIG. 3A , taken along line  5 — 5 . 
           [0027]      FIG. 6  is a perspective view of an embodiment of a tip electrode. 
           [0028]      FIG. 7  is a longitudinal cross-sectional view of the tip electrode of  FIG. 4A , taken along line  7 — 7 . 
           [0029]      FIG. 8  is a longitudinal cross-sectional view of the tip electrode of  FIG. 4A , taken along line  8 — 8 . 
           [0030]      FIG. 9  is a longitudinal cross-sectional view of the tip electrode of  FIG. 4A , taken along line  9 — 9 . 
           [0031]      FIG. 10  is a longitudinal cross-sectional view of the tip electrode of  FIG. 4A , taken along line  10 — 10 . 
           [0032]      FIG. 11A  is a side view of another embodiment of a tip section whose longitudinal axis is generally perpendicular to tissue surface. 
           [0033]      FIG. 1B  is a side view of another embodiment of a tip section whose longitudinal axis is generally at an angle between zero and 90 to tissue surface. 
           [0034]      FIG. 11C  is a side view of another embodiment of a tip section whose longitudinal axis is generally parallel to tissue surface. 
           [0035]      FIG. 12  is a longitudinal cross-sectional view of the plug within the tip electrode of  FIG. 4A , taken along line  12 — 12 . 
           [0036]      FIG. 12A  is a detailed cross-sectional view of an embodiment of a distal end of a lead wire anchored in a plug of a tip electrode. 
           [0037]      FIG. 12B  is a detailed cross-sectional view of an embodiment of distal ends of a thermocouple wire pair anchored in a plug of a tip electrode. 
           [0038]      FIG. 12C  is a detailed cross-sectional view of an embodiment of a distal end of a puller wire anchored in a plug of a tip electrode. 
           [0039]      FIG. 13  is a schematic drawing showing components of an embodiment of an optical processing system for use with the catheter of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0040]    The catheter  10  of the present invention is adapted to facilitate optically-based real-time assessment of ablation tissue characteristics, including without limitation, lesion formation, depth of penetration of the lesion, cross-sectional area of the lesion, formation of char during ablation, recognition of char during ablation, differentiation of char from non-charred tissue, formation of coagulum around the ablation site, differentiation of coagulated from non-coagulated blood, differentiation of ablated from healthy tissue, tissue proximity, and recognition of steam formation in the tissue for prevention of steam pop. These assessments are accomplished by measuring the light intensity at one or more wavelengths that is recaptured at the catheter resulting from the light radiated from the catheter tip onto ablated tissue. Fiber optic cables are provided in the catheter to transmit light to and from the catheter tip. 
         [0041]    As shown in  FIGS. 1-13 , catheter  10  of the present invention comprises an elongated catheter body  12  having proximal and distal ends, a deflectable (uni- or bi-directionally) intermediate section  14  at the distal end of the catheter body  12 , a tip section  36  at the distal end of the intermediate section, and a control handle  16  at the proximal end of the catheter body  12 . 
         [0042]    With additional reference to  FIGS. 2A and 2B , the catheter body  12  comprises an elongated tubular construction having a single, axial or central lumen  18 . The catheter body  12  is flexible, i.e., bendable, but substantially non-compressible along its length. The catheter body  12  can be of any suitable construction and made of any suitable material. A construction comprises an outer wall  22  made of an extruded plastic. The outer wall  22  may comprise an imbedded braided mesh of stainless steel or the like to increase torsional stiffness of the catheter body  12  so that, when the control handle  16  is rotated, the catheter body  12 , the intermediate section  14  and the tip section  36  of the catheter  10  will rotate in a corresponding manner. 
         [0043]    Extending through the single lumen  18  of the catheter body  12  are components, for example, wires, tubes and/or cables. A single lumen catheter body can be preferred over a multi-lumen body because it has been found that the single lumen body permits better tip control when rotating the catheter. The single lumen permits the various components to float freely within the catheter body. If such wires, tube and cables were restricted within multiple lumens, they tend to build up energy when the handle is rotated, resulting in the catheter body having a tendency to rotate back if, for example, the handle is released, or if bent around a curve, to flip over, either of which are undesirable performance characteristics. 
         [0044]    The outer diameter of the catheter body  12  is not critical, but is preferably no more than about 8 french, more preferably 7 french. Likewise the thickness of the outer wall  22  is not critical, but is thin enough so that the central lumen  18  can accommodate the aforementioned components. The inner surface of the outer wall  22  may be lined with a stiffening tube  20 , which can be made of any suitable material, such as polyimide or nylon. The stiffening tube  20 , along with the braided outer wall  22 , provides improved torsional stability while at the same time minimizing the wall thickness of the catheter, thus maximizing the diameter of the central lumen  18 . The outer diameter of the stiffening tube  20  is about the same as or slightly smaller than the inner diameter of the outer wall  22 . Polyimide tubing may be preferred for the stiffening tube  20  because it may be very thin walled while still providing very good stiffness. This maximizes the diameter of the central lumen  18  without sacrificing strength and stiffness. 
         [0045]    The catheter may have an outer wall  22  with an outer diameter of from about 0.090 inch to about 0.098 inch and an inner diameter of from about 0.061 inch to about 0.078 inch and a polyimide stiffening tube  20  having an outer diameter of from about 0.060 inch to about 0.077 inch and an inner diameter of from about 0.051 inch to about 0.069 inch. 
         [0046]    Referring also to  FIG. 5 , the intermediate section  14  distal the catheter body  12  comprises a shorter section of tubing  19  having multiple lumens. The tubing  19  is made of a suitable non-toxic material that is preferably more flexible than the catheter body  12 . A suitable material for the tubing  19  is braided or non-braided polyurethane. The outer diameter of the intermediate section  14 , like that of the catheter body  12 , is preferably no greater than about 8 french, more preferably 7 french. The size and number of the lumens are not critical. In an embodiment, the intermediate section  14  has an outer diameter of about 7 french (0.092 inch). The tubing  19  is multi-lumened, for example, with a first lumen  30 , a second lumen  32 , a third lumen  34  and a fourth lumen  35 . In the illustrated embodiment, the lumens  30 ,  32  and  35  all have approximately the same diameter of about 0.22 inch, whereas the lumen  34  has a larger diameter of about 0.44 inch. 
         [0047]    As shown in the embodiments of  FIGS. 2A and 2B , the catheter body  12  that may be attached to the intermediate section  14  comprises an outer circumferential notch  24  configured in the proximal end of the tubing  19  that receives the inner surface of the outer wall  22  of the catheter body  12 . The intermediate section  14  and catheter body  12  are attached by glue or the like. Before the intermediate section  14  and catheter body  12  are attached, the stiffening tube  20  is inserted into the catheter body  12 . The distal end of the stiffening tube  20  is fixedly attached near the distal end of the catheter body  12  by forming a glue joint  23  with polyurethane glue or the like. Preferably a small distance, e.g., about 3 mm, is provided between the distal end of the catheter body  12  and the distal end of the stiffening tube  20  to permit room for the catheter body  12  to receive the notch  24  of the intermediate section  14 . If no compression coil is used, a force is applied to the proximal end of the stiffening tube  20 , and, while the stiffening tube  20  is under compression, a first glue joint (not shown) is made between the stiffening tube  20  and the outer wall  22  by a fast drying glue, e.g. cyanoacrylate. Thereafter, a second glue joint  26  is formed between the proximal ends of the stiffening tube  20  and outer wall  22  using a slower drying but stronger glue, e.g., polyurethane. 
         [0048]    If desired, a spacer can be located within the catheter body between the distal end of the stiffening tube and the proximal end of the tip section. The spacer provides a transition in flexibility at the junction of the catheter body and intermediate section, which allows this junction to bend smoothly without folding or kinking. A catheter having such a spacer is described in U.S. patent application Ser. No. 08/924,616, entitled “Steerable Direct Myocardial Revascularization Catheter”, the entire disclosure of which is incorporated herein by reference. 
         [0049]    Extending from the distal end of the intermediate section  14  is the tip section  36  that includes a tip electrode  27  and a plastic housing  21 , as shown in  FIGS. 4A and 4B . The plastic housing  21 , as also shown in  FIGS. 3A and 3B , connects the tip electrode  27  and the tubing  19 , and provides housing and/or transitional space for the components that extend into or through its lumen, as discussed further below. The plastic housing  21  is preferably made of polyetheretherketone (PEEK) and may be about 1 cm long. Its proximal end receives the outer circumferentially notched surface  17  of the tubing  19  of the intermediate section  14 . The intermediate section  14  and the plastic housing  21  are attached by glue or the like. Components such as wires, cables and tubes that extend between the intermediate section  14  and the tip electrode  27  help keep the tip electrode in place. 
         [0050]    In accordance with the present invention, the tip electrode  27  is adapted to function as an omnidirectional illuminator and collector for recapturing light that is radiated from the catheter tip onto ablated tissue. As shown in  FIGS. 4A and 4B , the tip electrode comprises a shell wall  38  and a plug  44 . The shell  38  is configured with a distal dome end  31  and an open proximal portion  33  in communication with a hollow cavity  29 . In the illustrated embodiment, the shell wall  28  has a generally uniform thickness except at the distal dome end  31  where the thickness is greater and surrounds a distal dome cavity  73  extending from a rim region  37  of the hollow cavity  29 . The distal dome end  31  of the shell is atraumatic and adapted for contact with tissue. The open proximal end  33  is configured to receive the plug  44  which, among other functions, seals the hollow cavity  29 . 
         [0051]    The shell  38  and the plug  44  are formed from any suitable material that is opaque and/or reflective, and both thermally and electrically conductive which allows for radio frequency ablation using an RF generator. Such suitable materials include, without limitation, platinum-irridium, platinum, gold alloy, or palladium alloy. 
         [0052]    The tip electrode  27  has different sections relative to its longitudinal axis  99  in rendering the tip omnidirectional for optical tissue monitoring. As shown in  FIGS. 4A ,  4 B, and  6 , there are a distal section  100 , a mid-section  102  and a proximal section  104 . The shell wall  38  of the distal section  100  is generally perpendicular to the axis  99 . The shell wall of the mid-section  102  is generally at an angle ranging between zero and 90 degrees, preferably about 30 to 60 and more preferably about 45 degrees to the axis  99 . The shell wall of the proximal section  104  is generally parallel with the axis  99 . These differently-angled sections which have a generally smooth and atraumatic transition between each other enable the tip electrode  27  to operate as an illuminator and a collector for various angles between the tip section  36  and the tissue as shown in  FIGS. 11A-11C . 
         [0053]    The shell wall  38  has a plurality of holes or openings of various sizes, including illumination openings and collection openings for light to leave and re-enter the tip electrode  27 . As discussed further below, the tip electrode  27  provides optically-isolated paths for light intended to illuminate tissue and for light that is received through the collection openings. Each section  100 ,  102 ,  104  of the tip electrode can have any number of illumination and/or collection openings as desired or appropriate, although the number is dependent in part on the size of the tip electrode and the size and number of fiber optic cables housed therein. In the illustrated embodiment, the distal section  100  has a collection opening  87 ′ at the distal end of the tip electrode along the longitudinal axis  99  ( FIG. 7 ). The mid-section  102  has three illumination openings  89  that are equi-angular from each other at about 120 degrees radially about the axis ( FIG. 8 ). The proximal section  104  has three more collection openings  87  that are equi-angular from each other at about 120 degrees radially about the axis ( FIG. 9 ). The three collection openings  87  are offset radially by about 20 degrees from the three illumination openings  89  in the mid-section  102  Also in the proximal section  104  further proximal to the three collection openings  87  are an additional three collection openings  87 ″ ( FIG. 10 ) that are equi-angular from each other at about 120 degrees about the axis. These three collection openings  87 ″ are offset radially by about 40 degrees from the more distal collection openings  87  in the proximal section  104 . 
         [0054]    To efficiently illuminate the tissue of interest, each of the illumination openings  89  has a generally curved cross-section. In the illustrated embodiment of  FIG. 8 , the cross-section has a semi-spherical apex  93  where the overall cross-section can be described as parabolic. The semi-spherical apex efficiently reflects light out of the opening  89  for a more even distribution of light from the distal dome end  31  of the tip electrode  27 . 
         [0055]    With reference to  FIGS. 4A and 4B , light is delivered to the illumination openings  89  by one or more emitting fiber optic cables  43 E whose distal ends are received in passages  97  extending longitudinally from the rim section  37  of the hollow cavity  49 . The configuration of the passages further isolates the light from the cables  43 E from the cavity  29 , and vice versa. The illumination openings  89  may be filled with a material  150  with optical scattering properties, e.g., a scattering agent-filled epoxy or plastic to aid in the even distribution of light out of the openings  89 . Accordingly, light is emitted omnidirectionally onto the tissue of interest from the distal end of the tip electrode with minimal loss to absorption within the tip dome structure and the material  150  used to scatter the light. 
         [0056]    Light reentering the tip electrode from the tissue via the collection openings  87  is captured and reflected about in the hollow cavity  29 . The distal dome cavity  33  connecting the opening  87 ′ and the hollow cavity  29  is configured to optimize the amount of light received in the hollow cavity  29  through the collection opening  87 ′. At least one receiving fiber optic cable  43 R extends into the hollow cavity to collect the light. It is noted that because each of the emitting fiber optic cables  43 E traverses the hollow cavity  29  to reach the passage  97 , each cable  43 E has a coating  47  to optically isolate itself from the cavity, and vice versa. The coating can be an opaque but reflective buffer material, e.g., aluminum, gold and the like, so that light cannot penetrate the side wall of the fiber  43 E either into the cavity  29  or from the cavity. The coating may extend the length of the fibers  43 E throughout the catheter. 
         [0057]    The fiber optic cables  43 E and  43 R are protectively housed in the catheter from the control handle  16  to the tip section  36 . As shown in  FIGS. 2B and 5 , they extend through the central lumen  18  of the catheter  12 , the third lumen  34  of the intermediate section  14 , the plastic housing  21  and into the tip electrode  27 . 
         [0058]    In the disclosed embodiment, there are three illuminating cables  43 E and one receiving cable  43 R. The cables  43 E function as light emitters by transmitting light to the tip electrode  37  from a remote light source. The cable  43 R functions as a light receiver by collecting light from the hollow cavity  29  in the tip electrode  27 . It is understood by one of ordinary skill in the art that optical waveguides and fiber optic cables in general serve to transmit optical energy from one end to the other, although these are not exclusive. 
         [0059]    Formed of the same or comparable material as the shell  38 , the plug  44  has a generally elongated cylindrical configuration having a predetermined length, and a generally circular cross-section that matches the cross-section of the open proximal end  33  of the tip electrode  27 . A distal portion of the plug  44  is press fitted, or fixed with solder into the open proximal end  33  to seal the hollow cavity  29 , while a proximal portion of the plug  44  extends proximally from the tip electrode  27  for attachment to the housing  21 . 
         [0060]    In accordance with the present invention, blind holes and passages are provided in the plug  44  to allow components extending from the intermediate section  14  to be anchored to the plug or to pass through to the hollow cavity  29 . In the illustrated embodiment of  FIGS. 4A ,  4 B and  12 , there are blind holes  102 ,  104  and  106  formed in the proximal surface of the plug in which distal ends of a lead wire  40 , thermocouple wires  41  and  45  and a location sensor  72  are anchored, respectively. There are also passages  108 ,  112 ,  114 , and  116  through which the fiber optic cables  43 E and  43 R extend, and a passage  110  through which an irrigation tube  48  extends into the hollow cavity of the tip electrode  29 . The passages  108 ,  112  and  114  for three fiber optic cables  43 E are generally aligned with the passages  97  leading to the illumination openings  89  in the shell wall  38  of the tip electrode. The portions of the components extending through the passages in the plug  44  are securely fixed in the passages to the plug  44  by glue, adhesive or the like. As such, the passages and the plug help align, stabilize and secure the various components extending through the plug  44 . In particular, the passages help minimize stress on the cables  43 E and  43 R in their transition between the intermediate section  14  and the tip electrode  27 . 
         [0061]    In accordance with the present invention, illumination of tissue  111  and recapturing of the light from the tissue is accomplished by the omnidirectional tip electrode  27  whether the catheter  10  is generally perpendicular to the tissue ( FIG. 11A ), at an angle between about zero and ninety degrees ( FIG. 11B ), or generally parallel with the tissue ( FIG. 11C ). It is understood by one of ordinary skill in the art that the plurality and configuration of the sections  100 ,  102  and  104  and of the collection and illumination openings  87 ,  87 ′ and  87 ″ and  89  may be varied as appropriate or desired. The size and dimensions of each section may also be varied as appropriate or desired, as well as the shape of the openings, which can be round, ovular, square, polygonal, flat(slit), or any combination of these shapes. 
         [0062]    In operation, the catheter  10  emits light at its tip electrode  27  as provided by the fiber optic cables  43 E at their distal ends which emit light into the illumination openings  89 , where the semi-spherical apex  93  efficiently reflects light out of the opening  89  for a more even distribution of light from the distal dome end  31  of the tip electrode  27 . As lesion  113  forms in the tissue  111  from ablation carried out by tip electrode  27  of the catheter  10  (or by another catheter), its characteristics are altered as understood by one of ordinary skill in the art. In particular, as the lesion is illuminated by light, the light is scattered and/or reflected back toward the tip electrode  27 , where such light having interacted or otherwise having been affected by the lesion bears qualitative and quantitative information about the lesion  113  as it is recaptured by the hollow cavity  29  via the collection openings  87 ,  87 ′,  87 ″ of the tip electrode. Light recaptured from the tissue is collected in the hollow cavity  29  of the tip electrode. The receiving fiber optic cable  43 R receives the recaptured light which bears the qualitative and quantitative information and is transmitted to an optical processing system, as described below in further detail. 
         [0063]    In accordance with the present invention, the tip electrode  27  provides separate optical paths for the light that illuminates tissue and the light recaptured from the tissue which are optically isolated from each other by the shell wall  38 , the passages  97  and/or the coating  47  on the emitting fiber optic cables  43 E. The optical path from the tip electrode to the tissue begins with light that is injected into the illumination openings  89  via the fiber optic cables  43 E which is reflected by the semi-spherical apex  93  and diffusely scattered by the filler  150  into multiple angles and directions before exiting the illumination openings  89  of the tip electrode  37 . Exiting the tip electrode  27  from the illumination openings  89 , the light is incidental on the tissue of interest, interacts with the tissue and is reflected or scattered back to the tip electrode from the tissue. The separate optical path from the tissue back to the tip electrode begins with entry through the collection openings  87  and then collection in the hollow cavity  29  where the light is received by the fiber optic cable  43 E. 
         [0064]    It is understood that the fiber optic cables  43 E and  43 R may be any suitable optical wave guide wherein light introduced at one of the cable is guided to the other end of the cable with minimal loss. Each of the cables  43 E and  43 R may be a single fiber optic cable or fiber bundles. They may be single mode (also known as mono-mode or uni-mode), multi-mode (with step index or graded index) or plastic optical fiber (POF), depending on a variety of factors, including but not limited to transmission rate, bandwidth of transmission, spectral width of transmission, distance of transmission, diameter of cable, cost, optical signal distortion tolerance and signal attenuation, etc. Moreover, light delivery and collection may be accomplished with other devices, such as air-core fibers, hollow waveguides, liquid waveguides and the like. 
         [0065]    Included in the present invention is a method for manufacturing the tip electrode  27 . The method includes providing a rod of a suitable diameter and length, constructed of a suitable material that is thermally and electrically conductive which allows for radio frequency ablation using an RF generator. Such suitable material may include, without limitation, platinum-irridium, platinum, gold alloy, or palladium alloy. To form the shell  38 , the distal end of the rod is turned to form the distal dome end  31  and the interior is drilled in the longitudinal direction of the rod from the proximal end  33  to form the hollow cavity  29  and the distal dome cavity  73 . The term drilling as used herein includes mechanical drilling, chemical or laser etching, or the like. 
         [0066]    The passages  97  are also drilled in the rim region  37  from the proximal end  33  through the hollow cavity  29  toward the distal dome end  31 . The illumination openings  89  are drilled radially from outside the shell  38  through to the passages  97 . It is understood that the illumination openings  89  can be drilled before or after the drilling of the passages  97 , so long as the two structures connect and are in communication, and in turn, the hollow cavity  29  and the outside of the tip electrode are in communication with each other via the passages  97  and the illumination openings  89 . 
         [0067]    The collection openings  87 ,  87 ′,  87 ″ are also drilled radially from outside the shell  38  so there is communication between outside the tip electrode and the hollow cavity  29 . The openings  87  can be formed before or after the formation of the illumination openings  89  and passages  97 . 
         [0068]    To form the plug, a rod of the aforementioned suitable material with a suitable diameter and length is provided. The passages  108 ,  112 ,  114  and  116  for the fiber optic cables  43  are drilled. The plug is press-fitted or soldered into the proximal opening of the tip electrode, but preferably after the fiber optic cables  43 E and  43 R are received in the passages  108 ,  112 ,  114  and  116  and the fiber optic cables  43 E are inserted into the passages  97 . After the plug  44  is press-fitted or soldered into the shell  38 , glue, adhesive or the like is injected into the passages  108 ,  112  and  116  to fix the portions of the fiber optic cables extending through the passages. These fixed portions secure the fiber optic cables, particularly those of cables  43 E, stationary within the tip electrode as a measure against breakage in or detachment from the tip electrode. The blind holes and other passages in the plug can be drilled before or after the plug is press-fitted into the shell  38 . Methods for manufacturing a shell and a plug are disclosed in 11/058,434; filed Feb. 14, 2005, the entire disclosure of which is hereby incorporated by reference. 
         [0069]    The shell  28  of the tip electrode  27  may have an actual length, i.e., from its distal end to its proximal end, between about 2.0 mm to about 8.0. The plug  44  of the tip electrode may have an actual length, i.e., from its distal end to its proximal end, between about 1.0 mm to about 4.0 mm. The tip electrode as a combination of the shell and the plug may have an actual length, i.e., from its distal end to its proximal end, between about 2.5 mm to about 11 mm. Preferably the tip electrode  27  has a diameter about the same as the outer diameter of the tubing  19  of the intermediate section  14 . 
         [0070]    To keep the collection openings of the tip electrode  27  generally free from obstruction from blood or other bodily fluids and tissue encountered by the tip electrode  37 , the tip electrode is irrigated with fluid, e.g., saline, that is fed into the hollow cavity by an irrigation tube  48 , as shown in  FIG. 4A . The irrigation tube  48  extends through the cental lumen  18  of the catheter body  12  ( FIG. 2A ), the fourth lumen  35  of the intermediate section  14  ( FIG. 3 ), through the plastic housing  21  and passage  110  in the plug  44  ( FIG. 12 ). The tube  48  is anchored in the passage  110  and in the fourth lumen  35  by polyurethane glue or the like. The proximal portion of the tube  48  extends through the control handle  16  and terminates in a luer hub  90  ( FIG. 1 ) or the like at a location proximal to the control handle. In the disclosed embodiment, the irrigation tube  48  transitions from a smaller diameter at the distal end to a larger diameter at the proximal end. For example, a distal segment can be about 0.0155×0.0175 inches and a proximal segment can be about 0.024×0.28 inches. In practice, fluid may be injected by a pump (not shown) into the irrigation tube  48  through the luer hub  90 , and into the hollow cavity  29  in the tip electrode  27 , and out the collection openings. The infusion tube  48  may be made of any suitable material, and is preferably made of polyimide tubing. 
         [0071]    In accordance with a feature of the present invention, the pump maintains the fluid at a positive pressure differential relative to outside the hollow cavity  29  so as to provide a constant unimpeded flow or seepage of fluid outwardly from the hollow cavity  29  which continuously flushes the collection openings and minimizes obstruction so light can freely pass through for the aforementioned light collection purposes. In addition to the above, the irrigation adaptation of the catheter  10  may serve other typical functions such as cooling the tip electrode and/or the ablation site and increasing conduction for deeper and larger lesions. 
         [0072]    To energize the tip electrode  27  for RF ablation, the lead wire  40  is anchored in the plug  44 . With reference to  FIGS. 1 ,  2 A and  5 , the lead wire  40  extends through the second lumen  32  of intermediate section  14 , the central lumen  18  of the catheter body  12 , and the control handle  16 , and terminates at its proximal end in an input jack (not shown) that may be plugged into an appropriate monitor (not shown). The portion of the lead wire  40  extending through the central lumen  18  of the catheter body  12 , control handle  16  and distal end of the intermediate section  14  is enclosed within a protective sheath  52 , which can be made of any suitable material, preferably Teflon RTM. The protective sheath  52  is anchored at its distal end to the distal end of the intermediate section  14  by gluing it in the lumen  32  with polyurethane glue or the like. The lead wire  40  is attached to the tip electrode  27  by any conventional technique. In the illustrated embodiment, connection of the lead wire  40  to the tip electrode  27  is accomplished, for example, by welding the distal end of the lead wire  40  into the blind hole  102  ( FIGS. 12 and 12A ) in the plug  44  of the tip electrode  27 . 
         [0073]    A temperature sensing means is provided for the tip electrode  27  in the disclosed embodiment. Any conventional temperature sensing means, e.g., a thermocouple or thermistor, may be used. With reference to  FIGS. 12 . and  12 B, a suitable temperature sensing means for the tip electrode  27  comprises a thermocouple formed by a wire pair. One wire of the wire pair is the copper wire  41 , e.g., a number  40  copper wire. The other wire of the wire pair is the constantan wire  45 , which gives support and strength to the wire pair. The wires  41  and  45  of the wire pair are electrically isolated from each other except at their distal ends where they contact and are twisted together, covered with a short piece of plastic tubing  63 , e.g., polyimide, and covered with epoxy. The plastic tubing  63  is then attached in the hole  104  of the plug  44 , by epoxy or the like. As shown in  FIGS. 2A ,  3  and  5 , the wires  41  and  45  extend through the second lumen  32  in the intermediate section  14 . Within the catheter body  12  the wires  41  and  45  extend through the central lumen  18  within the protective sheath  52  along with the lead wires  40 . The wires  41  and  45  then extend out through the control handle  16  and to a connector (not shown) connectable to a temperature monitor (not shown). Alternatively, the temperature sensing means may be a thermistor. A suitable thermistor for use in the present invention is Model No. AB6N2-GC14KA143T/37C sold by Thermometrics (New Jersey). 
         [0074]    The embodiment of the catheter disclosed herein is uni-deflectional, having a single puller wire; however, it is understood by one of ordinary skill in the art that the catheter may be bi-directional with two puller wires. Referring to  FIG. 2B , the puller wire  42  for deflecting the intermediate section  14  extends through the catheter body  12  and is anchored at its proximal end to the control handle  16 . The puller wire is made of any suitable metal, such as stainless steel or Nitinol, and is preferably coated with Teflon.RTM. or the like. The coating imparts lubricity to the puller wire. The puller wire preferably has a diameter ranging from about 0.006 to about 0.010 inches. A compression coil  56  is situated within the catheter body  12  in surrounding relation to the puller wire. The compression coil  56  extends from the proximal end of the catheter body  12  to the proximal end of the intermediate section  14 . The compression coil is made of any suitable metal, preferably stainless steel, and is tightly wound on itself to provide flexibility, i.e., bending, but to resist compression. The inner diameter of the compression coil is preferably slightly larger than the diameter of the puller wire  42 . The Teflon.RTM. coating on the puller wire allows it to slide freely within the compression coil. If desired, particularly if the lead wire  40  is not enclosed by the protective sheath  52 , the outer surface of the compression coils can be covered by a flexible, non-conductive sheath, e.g., made of polyimide tubing, to prevent contact between the compression coils and any other wires within the catheter body  12 . 
         [0075]    As shown in  FIG. 2B , the compression coil  56  is anchored at its proximal end to the proximal end of the stiffening tube  20  in the catheter body  12  by glue joint  50  and at its distal end to the intermediate section  14  by glue joint  51 . Both glue joints  50  and  51  preferably comprise polyurethane glue or the like. The glue may be applied by means of a syringe or the like through a hole made between the outer surface of the catheter body  12  and the central lumen  18 . Such a hole may be formed, for example, by a needle or the like that punctures the outer wall  22  of the catheter body  12  and the stiffening tube  20  which is heated sufficiently to form a permanent hole. The glue is then introduced through the hole to the outer surface of the compression coil  56  and wicks around the outer circumference to form a glue joint about the entire circumference of the compression coil. 
         [0076]    With reference to  FIGS. 2B and 5 , the puller wire  42  extends into the first lumen  30  of the intermediate section  14 . In the illustrated embodiment of  FIG. 3B , the distal end of the puller wire  42  is anchored to the distal end side wall of the first lumen  30  of the tubing  19  of the intermediate section  14 . The distal end of the puller wire  42  is anchored by means of a T-bar anchor  109  created by a metal tube  120 , e.g., a short segment of hypodermic stock, that is fixedly attached, e.g. by crimping, to the distal end of the puller wire  42 . The tube has a section that extends a short distance beyond the distal end of the puller wire  42 . A cross-piece  121  made of a small section of stainless steel ribbon or the like is soldered or welded in a transverse arrangement to the distal end of the metal tube which is flattened during the operation. A notch is created in the side wall of tubing  19  resulting in an opening in the lumen  30  carrying the puller wire  42 . The cross piece  121  lies transversely within the notch. Because the length of the ribbon forming the cross-piece  121  is longer than the diameter of the opening into the lumen  30 , the anchor  109  cannot be pulled completely into the lumen  30 . The notch is then sealed with polyurethane glue  122  or the like to give a smooth outer surface. The glue flows into the lumen  30  to fully secure the anchor. A t-bar anchor is described in U.S. Pat. No. 6,468,260, the entire disclosure of which is hereby incorporated by reference. Other means for anchoring the distal end of the puller wire  42  would be recognized by those skilled in the art and are included within the scope of the invention. For example, another blind hole  101  ( FIG. 12C ) may be formed in the proximal surface of the plug  44  in which the metal tube  120  at the distal end of the puller wire may be fixed by soldering. Anchoring the puller wire  42  within the tip electrode  27  provides additional support, reducing the likelihood that the tip electrode  27  will fall off. Within the first lumen  30  of the intermediate section  14 , the puller wire  42  extends through a plastic, preferably Teflon.RTM., sheath  81 , which prevents the puller wire  42  from cutting into the wall of the intermediate section  14  when the intermediate section is deflected. Longitudinal movement of the puller wire  42  relative to the catheter body  12 , which results in deflection of the tip section  36 , is accomplished by suitable manipulation of the control handle  16 . Suitable control handles are described in U.S. Pat. No. 6,602,242, the entire disclosure of which is hereby incorporated by reference. 
         [0077]    In the illustrated embodiment, the tip section  36  carries an electromagnetic sensor  72 , and as mentioned, the electromagnetic sensor may be carried in the plastic housing  21 , with its distal end anchored in the blind hole  106  in the plug  44  as shown in  FIGS. 4A ,  4 B and  12 . The electromagnetic sensor  72  is connected to an electromagnetic sensor cable  74 . As shown in  FIGS. 2A and 5 , the sensor cable  74  extends through the third lumen  34  of the tip section  36 , through the central lumen  18  of the catheter body  12 , and into the control handle  16 . The electromagnetic sensor cable  74  then extends out the proximal end of the control handle  16  within an umbilical cord  78  ( FIG. 1 ) to a sensor control module  75  that houses a circuit board (not shown). Alternatively, the circuit board can be housed within the control handle  16 , for example, as described in U.S. patent application Ser. No. 08/924,616, entitled “Steerable Direct Myocardial Revascularization Catheter”, the disclosure of which is incorporated herein by reference. The electromagnetic sensor cable  74  comprises multiple wires encased within a plastic covered sheath. In the sensor control module  75 , the wires of the electromagnetic sensor cable  74  are connected to the circuit board. The circuit board amplifies the signal received from the electromagnetic sensor  72  and transmits it to a computer in a form understandable by the computer by means of the sensor connector  77  at the proximal end of the sensor control module  75 , as shown in  FIG. 1 . Because the catheter can be designed for single use only, the circuit board may contain an EPROM chip which shuts down the circuit board approximately 24 hours after the catheter has been used. This prevents the catheter, or at least the electromagnetic sensor, from being used twice. Suitable electromagnetic sensors for use with the present invention are described, for example, in U.S. Pat. Nos. 5,558,091, 5,443,489, 5,480,422, 5,546,951, 5,568,809, and 5,391,199 and International Publication No. WO 95/02995, the disclosures of which are incorporated herein by reference. An electromagnetic mapping sensor  72  may have a length of from about 6 mm to about 7 mm and a diameter of about 1.3 mm. 
         [0078]    With reference to  FIG. 13 , an optical processing system  126  for optically evaluating ablation tissue using the catheter  10  is illustrated. A light source  128  supplies a broadband (white; multiple wavelengths) light and/or laser light (single wavelength) radiation to the tip section  36  of the catheter  10  via cable  127  which is split by a beamsplitter  131  outputting to the emitting cables  43 E. The light bearing lesion qualitative information from the tip section is transmitted by the receiving cable  43 R to a detection component  130 . The detection component may comprise, for example, a wavelength selective element  131  that disperses the collected light into constituent wavelengths, and a quantification apparatus  140 . The at least one wavelength selective element  131  includes optics  132 , as are known in the art, for example, a system of lenses, mirrors and/or prisms, for receiving incident light  134  and splitting it into desired components  136  that are transmitted into the quantification apparatus  140 . 
         [0079]    The quantification apparatus  140  translates measured light intensities into an electrical signal that can be processed with a computer  142  and displayed graphically to an operator of the catheter  10 . The quantification apparatus  140  may comprise a charged coupled device (CCD) for simultaneous detection and quantification of these light intensities. Alternatively, a number of different light sensors, including photodiodes, photomultipliers or complementary metal oxide semiconductor (CMOS) detectors may be used in place of the CCD converter. Information is transmitted from the quantification device  140  to the computer  142  where a graphical display or other information is generated regarding parameters of the lesion. A suitable system for use with the catheter  10  is described in U.S. application Ser. No. 11/281,179 and Ser. No. 11/281,853, the entire disclosures of which are hereby incorporated by reference. 
         [0080]    The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. In that regard, the tip electrode may be configured with illumination and/or collection openings without regard to the configuration or location of the various sections of the tip electrode. Moreover, the tip electrode may be modified such that any type and number of openings can be placed anywhere on the tip electrode. For example, there could be multiple openings on the most distal section of the tip dome instead of a single opening, or there could be an illumination opening instead of a receiving opening. In addition, the openings can be of any shape, and are only limited by manufacturing methods available, such as laser drilling, photo-chemical etching, EDM machining, etc. 
         [0081]    Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.