Patent Publication Number: US-6663621-B1

Title: Systems and methods for steering a catheter through body tissue

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 08/890,630, filed Jul. 9, 1997 which is hereby incorporated by references now U.S. Pat. No. 6,013,072 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to medical catheters and, more particularly, to methods for steering, or guiding, medical catheters through body tissue. 
     BACKGROUND OF THE INVENTION 
     Atherosclerotic plaque is known to build up on the walls of arteries in the human body. Such plaque build up restricts circulation and often causes cardiovascular problems, especially when the build up occurs in coronary arteries. Accordingly, it is desirable to remove or otherwise reduce plaque build up. 
     Known catheters implement laser energy to remove plaque build up on artery walls. One known catheter includes a laser source and a catheter body. The catheter body has a first end and a second end, or head, and several optical fibers extend between the first end and the second end. The laser source is coupled to each of the optical fibers adjacent the catheter body first end and is configured to transmit laser energy simultaneously through the optical fibers. 
     To remove arterial plaque, for example, the catheter body is positioned in the artery so that the second end of the catheter body is adjacent a region of plaque build-up. The laser source is then energized so that laser energy travels through each of the optical fibers and substantially photoablates the plaque adjacent the second end of the catheter body. The catheter body is then advanced through the region to photoablate the plaque in such region. 
     While known laser catheters are generally acceptable in connection with removing plaque from a straight region of plaque build-up, such catheters are not optimal in connection with curved regions of plaque build-up. While advancing the energized laser catheter in the curved region, it is possible for the second end of the catheter body to contact the arterial wall adjacent the curve, which may result in perforation of the arterial wall. 
     Until now, it was believed that a guide wire must be used to facilitate steering a catheter through a curved region of plaque build-up without perforating the arterial wall. Particularly, a guide wire is advanced through the artery and region of plaque build-up so that it forms a path through the artery and plaque build-up. The catheter is then guided through the artery using, the guide wire. 
     While guide wires facilitate steering catheters through curved regions of plaque build-up, inserting guide wires is time consuming and tedious. In addition, it often is not feasible to insert a guide wire into an artery. For example, a guide wire typically can not be inserted into a totally occluded artery, which results in subjecting a patient to bypass surgery. 
     Accordingly, it would be desirable to provide a catheter which may be advanced through a curved region of plaque build-up without requiring a guide wire. It also would be desirable to provide such a catheter which may be advanced through a totally occluded artery by removing plaque in such region. 
     SUMMARY OF THE INVENTION 
     These and other objects are attained by an catheter which, in one embodiment, includes a catheter body having a first group of optic fibers and a second group of optic fibers. The first group of optic fibers is adjacent the second group of optic fibers, and each group of optic fibers includes at least one optic fiber having a first end and a second end. The second ends of the optic fibers form a substantially rounded and self-centering catheter head. 
     A control element is communicatively coupled to the first ends of the respective optic fibers and is configured to transmit energy through the optic fibers of each respective group. Particularly, the control element is configured to selectively transmit energy through either the first group of optic, fibers, or the second group of optic fibers, or both the first and second groups of optic fibers simultaneously. 
     The catheter is inserted into a body passage, e.g., an artery or other blood vessel, and advanced until the catheter head is adjacent a region of blockage, e.g., a region of plaque build-up. The catheter is then advanced through the region of blockage by selectively energizing one of the groups of optic fibers or both of the groups of optic fibers. Particularly, while the region of blockage is substantially straight, the catheter is advanced while the control element transmits energy through both the first and second groups of optic fibers to photoablate the blockage adjacent the catheter head. While the region of blockage is curved, for example, so that the arterial wall is adjacent the first group of optic fibers, however, the control element transmits energy solely through the second group of optic fibers. Alternatively, while the region of blockage is curved so that the arterial wall is adjacent the second group of optic fibers, the control element transmits energy only through the first group of optic fibers. Accordingly, while advancing the advancing catheter through a curved region, the catheter only photoablates blockage adjacent the respective energized group of fibers, e.g., blockage away from the arterial wall, to form a path through such blockage and the self-centering head facilitates maneuvering the head along such path. 
     The above-described catheter may be advanced through a curved region without requiring a guide wire. Such catheter also may be advanced through a totally occluded artery by removing plaque in the blockage region. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial illustration of a catheter in accordance with one embodiment of the present invention. 
     FIG. 1A is a side sectional view of a catheter head of the catheter. 
     FIG. 2 is a front cross section view of the catheter body shown in FIG.  1 . 
     FIG. 3 is a pictorial illustration of the control element shown in FIG.  1 . 
     FIG. 4 is a pictorial illustration of the catheter shown in FIG. 1 inserted into a blood vessel. 
     FIG. 5 is a front cross section view of a catheter body in accordance with another embodiment of the present invention. 
     FIG. 6 is a pictorial illustration of a control element coupled to the catheter body shown in FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is a pictorial illustration of a catheter  18  in accordance with one embodiment of the present invention. Catheter  18  includes a sensing system  20  having an imaging screen  22 , a control element  24 , and a catheter body  26 . Catheter body  26  has a first, or proximate, end  28  and a rounded, or substantially hemispherical, second end, or head,  30 , and includes at least two groups, or bundles, of optic fibers (not shown in FIG. 1) bundled in a housing  32 . Catheter head  30  may, for example, be substantially self-centering. 
     Sensors, or sensing elements,  34 , are coupled to catheter body  26  adjacent catheter head  30  and are configured to transmit sensing signals to sensing system  20 . Sensing elements  34  may, for example, be either laser interferometry sensors or ultrasonic sensors. Alternatively, sensing elements  34  may be optic fibers extending the length of catheter body  26  configured for visual, laser interferometry, or ultrasonic conductance measurement techniques. In addition, while sensing elements  34  are shown coupled to the exterior of housing  32 , sensing elements  34  may be coupled to the interior of housing  32 . 
     Control element  24  is communicatively coupled to first end  28  of catheter body  26 , and is configured to transmit an energy beam through each group of optic fibers in catheter body  26 . Particularly, control element  24  includes at least one laser source (not shown in FIG. 1) configured to emit an energy beam and at least one beam splitter (not shown in FIG.  1 ). The beam splitter is substantially aligned with the laser source and is positioned to split the energy beam emitted from the laser source into two substantially equal secondary energy beams so that one of the secondary energy beams is aligned with the first group of optic fibers and so that the other of the secondary energy beams is aligned with the second group of optic fibers. 
     Sensing system  20  is coupled to sensing elements  34  and is configured to generate an image utilizing sensing signals received from sensing elements  34 . Particularly, sensing system  20  utilizes the sensing signals to display an image on imaging screen  22 . Sensing system  20  may, for example, include a computer configured to receive the sensing signals, generate image data using the sensing signals, and transmit the image data for display on imaging screen  22 . Obtaining sensing signals and displaying corresponding images from sensing elements  34  is well known. 
     Sensing system  20  also is coupled to control element  24  and configured to transmit control signals to control element  24 . Particularly, sensing system  20  utilizes the sensing signals to generate control signals for selectively energizing various groups of optic fibers. For example, the sensing system computer may be configured to receive the sensing signals, generate control signals using the sensing signals, and transmit control signals to control element  24 , as is described in more detail below. 
     Referring to FIG.  1 A and FIG. 2, catheter body  26  includes two groups, or bundles,  36 A and  36 B of optic fibers  38 . Optic fibers  38  each include a first end (not shown in FIG. 2) and a second end  40 , and second ends  40  of optic fibers  38  form catheter head  30 . Particularly, second ends  40  of first group  36 A of optic fibers  38  define a first region of catheter head  30  and second ends  40  of second group  36 B of optic fibers  38  define a second region of catheter head  30 . While first and second groups  36 A and  36 B, respectively, of optic fibers  38  are shown including several optic fibers  38 , each group may include either fewer, e.g., one, or more optic fibers  38 . 
     As shown more clearly in FIG. 3, control element  24  includes a laser source  42  and one beam splitter  44 . Beam splitter  44  is substantially aligned with laser source  42  and is positioned to split an energy beam  46  emitted from laser source  42  into two substantially equal secondary energy beams  48 A and  48 B so that secondary energy beam  48 A is aligned with first group  36 A of optic fibers  38  and so that secondary energy beam  48 B is aligned with second group  36 B of optic fibers  38 . 
     Control element  24  further includes two shutters  50 A and  50 B. Shutter  50 A is configured to move between a first position (shown in FIG.  3 ), where shutter  50 A substantially prevents secondary energy beam  48 A from being transmitted through optic fibers  38  in first fiber group  36 A, and a second position. (not shown in FIG.  3 ), where shutter  50 A does not prevent secondary energy beam  48 A from being transmitted through optic fibers in first fiber group  36 A. Similarly, shutter  50 B is configured to move between a first position (shown in FIG.  3 ), where shutter  50 B substantially prevents secondary energy beam  48 B from being transmitted through optic fibers  38  in second fiber group  36 B, and a second position (not shown in FIG.  3 ), where shutter  50 B does not prevent secondary energy beam  48 B from being transmitted through optic fibers  38  in second fiber group  36 B. 
     In addition, shutters  50 A and  50 B each are coupled to sensing system  20  (not shown in FIG.  3 ). Particularly, shutters  50 A and  50 B are configured to move between their respective first and second positions in accordance with the control signals transmitted by sensing system  20 . 
     Referring now to FIG. 4, to remove blockage from a blood vessel  52 , e.g., an artery, catheter  26  is inserted into blood vessel  52  and advanced until catheter head  30  is adjacent a region of blockage  54 , e.g., a region of plaque build-up. To remove blockage from straight portion SP 1  of blockage region  54 , laser source  42  is activated, e.g., by sensing system  20 , to transport energy beams through first and second groups  36 A and  36 B, respectively, of optic fibers  38  and photoablate the blockage adjacent catheter head  30 . While advancing catheter head  30  through first straight portion SP 1  of blockage region  54 , imaging screen  22  displays an image of the area adjacent catheter head in accordance with the sensing signals transmitted by sensing elements  34 . 
     When catheter head  30  approaches a first curved portion CP 1  of blockage region  54 , shutter  50 B is positioned to block secondary energy beam  48 B to avoid photoablating blood vessel  52  adjacent second group  36 B of optic fibers  38 . Particularly, when the sensing signals indicate that catheter head  30  is adjacent curved artery wall W 1  sensing system  20 , e.g., the sensing system computer, transmits control signals to shutter  50 B so that shutter  50 B moves to block secondary energy beam  48 B. Catheter head  30  is advanced through blood vessel  52  and secondary energy beam  48 A continues to transmit through first group  36 A of optic fibers  38  to photoablate blockage adjacent second ends  40  of such fibers  38 . First group  36 A of optic fibers  38  photoablates a path through blockage away from artery wall W 1  and self centering catheter head  30  travels through such path, thus steering catheter head  30  through first curved portion CP 1  of blockage region  54 . 
     Once catheter head  30  enters a second straight portion SP 2  of blockage region  54 , sensing system  20  transmits control signals to shutter  50 B, and shutter  50 B is moved to the second position so that secondary energy beams  46 A and  48 B are again simultaneously transmitted through both first group  36 A and second group  36 B of optical fibers  38 . Catheter head  30  is then advanced through second straight portion SP 2  until catheter head  30  approaches second curved portion CP 2  of blockage region  54 . 
     Upon approaching second curved portion CP 2  of blockage region  54 , shutter  50 A is moved to the first position to block secondary energy beam  48 A from transmitting through first group  36 A of optic fibers  38  and to avoid photoablating blood vessel  52  adjacent first group  36 A of optic fibers  38 . Particularly, when sensing signals indicate that catheter head  30  is adjacent curved artery wall W 2 , sensing system  20  transmits control signals to shutter  50 A so that shutter  50 A moves to block secondary energy beam  48 A. Shutter  50 B is simultaneously positioned in the second position to allow secondary energy beam  48 B transmit through second group  36 B of optic fibers  38  and photoablate blockage adjacent second ends  40  of such optic fibers  38 . 
     Catheter head  30  is then advanced through second curved portion CP 2  of blockage region  54  until catheter head  30  is positioned in a third straight portion SP 3  of blockage region  54 . Upon reaching third straight portion SP 3  of blockage region  54 , sensing system  20  transmits control signals to shutter  50 A to return to its second position, so that secondary energy beams  48 A and  48 B again are simultaneously transmitted through optic fibers  38 . Catheter  18  is then advanced through third straight portion SP 3  until catheter head  30  emerges blockage region  54  and into a substantially clear region  56  or artery  52 . 
     After advancing catheter head  30  through blockage region  54 , catheter  18  may be used as a guide wire for other medical apparatus. For example, a catheter having a larger diameter than catheter  18  may be advanced through blockage region  54  utilizing catheter  18  as its guide wire. 
     Laser source  42  and shutters  50 A and  50 B may, for example, be remotely operated via sensing system  20 . Alternatively, laser source  42  and shutters  50 A and  50 B may be operated by hand. 
     Catheter head  30  may be advanced, for example, manually, e.g., by hand, or automatically. Specifically, sensing system  20  may further include a motor, e.g., a stepper motor, coupled to the sensing system computer. In such case, the stepper motor also is coupled to catheter head  30  and is configured to advance catheter head  30  within the artery. 
     The above-described catheter  18  may be advanced through curved regions of blockage without requiring a guide wire device. Such catheter also may be advanced through a totally occluded region while simultaneously removing plaque in such region. Of course, it is to be understood that modifications may be made to catheter  18  and still be within the scope of the invention. 
     For example, catheter  18  includes sensing system  20  for providing automatic feed back control of fiber groups  36 A and  36 B, e.g., to automatically control shutters  50 A and  50 B. However, sensing system  30  may be used merely to display images on imaging screen  22 , and an operator may selectively energize and de-energize fiber groups  36 A and  36 B by utilizing the displayed images. 
     Also, while catheter  18  was described in connection with a rounded catheter head  30 , catheter head  30  may have a different shape, e.g., conical, elliptical, or spherical. Moreover, while catheter head  30  was described as self-centering, catheter head  30  may not be self-centering. 
     In addition, catheter  18  was described in connection with shutters  50 A and  50 B for blocking, or unblocking, respective secondary energy beams  48 A and  48 B. In an alternative embodiment, mirrors are used for blocking such secondary energy beams. Specifically, one mirror is positioned between beam splitter  44  and respective fiber groups  36 A and  36 B, and each mirror is configured to move between a first position, where such mirror permits its respective secondary energy beam  48 A and  48 B to transmit through respective fiber group  36 A and  36 B, and a second position, where such mirror substantially prevents its respective secondary energy beam  48 A and  48 B from transmitting through respective fiber group  36 A and  36 B. The mirrors may either be remotely operated by sensing system  20 , e.g., by the sensing system computer, or manipulated by hand. 
     Moreover, while the catheter described above includes two groups of optic fibers, the catheter may include more than two groups of optic fibers. For example, the catheter may include three groups, four groups, five groups, six groups, seven groups, or eight groups of optic fibers. The catheter may, if desired, include more than eight groups, e.g., twelve groups, of optic fibers. 
     For example, and referring now to FIG. 5, a catheter  58  in accordance with another embodiment of the present invention includes a catheter body  60  having five groups, or bundles,  62 A,  62 B,  62 C,  62 D and  62 E of optic fibers  64 . Optic fibers  64  each include a first end and a second end (not shown in FIG.  5 ), and the second ends of optic fibers  64  form a self-centering catheter head (not shown in FIG.  5 ). The second ends of first group  62 A of optic fibers  64  define a first region, or portion, of the catheter head, the second ends of second group  62 B of optic fibers  64  define a second region, or portion, of the catheter head, the second ends of third group  62 C of optic fibers  64  define a third region, or portion of the catheter head, the second ends of fourth group  62 D of optic fibers  64  define a fourth region, or portion, of the catheter head, and the second ends of fifth group  62 E of optic fibers  64  define a fifth region, or portion, of the catheter head. 
     Each group  62 A,  62 B,  62 C,  62 D, and  62 E of optic fibers  64  includes one sensing optic fiber, or sensing element,  66 A,  66 B,  66 C,  66 D, and  66 E, respectively. Sensing fibers  66 A,  66 B,  66 C,  66 D, and  66 E are coupled to a sensing system (not shown in FIG.  5 ), e.g., sensing system  20 , and configured to propagate ultrasound signals therethrough for generating image signals and control signals. Particularly, each sensing fiber  66 A,  66 B,  66 C,  66 D, and  66 E includes a distal end (not shown in FIG.  5 ), and each distal end is configured to transmit and receive an ultrasound signal to tissue adjacent respective group  62 A,  62 B,  62 C,  62 D, and  62 E of optic fibers  64 . 
     Referring to FIG. 6, a control element  68  is communicatively coupled to catheter body  60  and includes a laser source  70  and four beam splitters  72 . Laser source  70  is configured to emit an energy beam  74 , and beam splitters  72  are positioned to split energy beam  74  into five secondary beams  76 A,  76 B,  76 C,  76 D, and  76 E, which are aligned with respective fiber groups  62 A,  62 B,  62 C,  62 D and  62 E. 
     Control element  68  further includes five shutters  78 A,  78 B,  78 C,  78 D, and  78 E, which are coupled to the sensing system. Shutter  78 A is configured to move between a first position, where shutter  78 A substantially prevents secondary energy beam  76 A from being transmitted through optic fibers  64  in first fiber group  62 A, and a second position, where shutter  78 A does not prevent secondary energy beam  76 A from being transmitted through optic fibers in first fiber group  62 A. Similarly, shutters  78 B,  78 C,  78 D, and  78 E are configured to move between a first position, in which such shutter  78 B,  78 C,  78 D and  78 E substantially prevents respective secondary energy beam  76 B,  76 C,  76 D and  76 E from being transmitted through optic fibers  64  in respective fiber groups  62 B,  62 C,  62 D and  62 E, and a second position, where such shutter  78 B,  78 C,  78 D and  78 E does not prevent respective secondary energy beam  76 B,  76 C,  76 D and  76 E from being transmitted through optic fibers  64  in respective fiber groups  62 B,  62 C,  62 D and  62 E. 
     Catheter  58  is then advanced through an artery in substantially the same manner as described above with respect to catheter  18 . Particularly, sensing fibers  66 A,  66 B,  66 C,  66 D, and  66 E, the sensing system, and control element  68  cooperate to selectively move shutters  78 A,  78 B,  78 C,  78 D, and  78 E, and to selectively energize and de-energize respective groups  62 A,  62 B,  62 C,  62 D, and  62 E of optic fibers  64 . 
     The above-described catheter  58  may be advanced through curved regions of blockage without requiring a guide wire device. Such catheter also may be advanced through a totally occluded region while simultaneously removing plaque in such region. 
     While the above-described catheters were described in connection with laser energy, it is to be understood that such catheters may be utilized in connection with other types of energy. For example, ultrasound or thermal energy may be transmitted through the groups of optic fibers to cavitate or otherwise bore through arterial plaque. 
     In addition, while such catheters are described in connection with an artery, such catheters may be inserted and steered through other body passages. Moreover, such catheters may be utilized to create a passage in body tissue. For example, such catheters may be inserted and steered through a liver to create a path to a tumor in the liver. The catheters may then photoablate the tumor, or another medical instrument may be extended through the path to remove the tumor. 
     From the preceding description of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not be taken by way of limitation. For example, while each group of optic fibers described above included more than one optic fiber, at least one group of optic fibers may include only one optic fiber. In addition, while the sensing elements were described above as ultrasound sensors, such elements may be optic fibers configured to apply laser interferometry. Further, while the catheter head described herein was hemispherical, the catheter head may have a different shape, e.g., conical. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the claims.