FIELD OF INVENTIONThis invention relates to catheters, and in particular, to catheters that accommodate more than one optical fiber.
BACKGROUNDCertain lipid-filled cavities that form within the wall of a blood vessel are known as "vulnerable plaques." These plaques, when ruptured, can cause massive clotting in the vessel. The resultant clot can interfere with blood flow to the brain, resulting in a stroke, or with blood flow to the coronary vessels, resulting in a heart attack.
To locate vulnerable plaques, one inserts a catheter through the lumen of the vessel. The catheter includes a delivery fiber for carrying infrared light that will ultimately illuminate a spot on the vessel wall and a collection fiber for carrying infrared light scattered from a collection area on the vessel wall.
The distal tip of such a catheter includes a stationary transparent jacket enclosing a rotatable housing that holds the delivery and collection fibers. In addition to these fibers, the housing encloses two mirrors: one to bend a beam exiting the delivery fiber so that it illuminates the wall; and another to gather scattered light from the wall and to direct that scattered light into the collection fiber.
A vulnerable plaque can be anywhere within the wall of the vessel. As a result, it is desirable to circumferentially scan the illuminated spot and the collection area around the vessel wall. One way to do this is to spin the multi-channel catheter about its axis. This requires providing a torque cable and coupling the housing to the torque cable.
The housing at the distal tip, which is already crowded with optical elements, must now accommodate a coupling element to enable torque transmitted by the torque cable to rotate the housing. One way to accommodate this additional element is to enlarge the housing. However, an enlarged housing at the distal tip of a catheter is undesirable because of the limited size of the blood vessels through which the catheter is intended to pass.
SUMMARYThe invention is based on the recognition that a side-by-side arrangement of fibers results in a more compact tip assembly for a catheter. Such an arrangement can readily accommodate a coupling element that enables the tip to rotate.
One aspect of the invention is a catheter tip assembly in which a recess in a housing receives an optical bench. The optical bench has a transverse dimension selected to accommodate adjacent first and second fibers. The bench holds the first fiber in optical communication with a first beam re-director. The first beam re-director is oriented to cause a beam to travel away from the optical bench. An engaging structure coupled to the optical bench provides torque coupling between the housing and an end of a torque cable extending axially along a catheter.
When measured relative to an axis of an optical catheter, a direction can have a radial component, which is perpendicular to the axis, an axial component, which is parallel to the axis, and a circumferential component, which is perpendicular to the radial component and the axial component. As used herein, the phrase "away from the optical bench" means a direction that includes a radial component. Thus, "away from the optical bench" includes directions that may also include axial or circumferential components, in addition to the radial component.
In another aspect, the invention includes a catheter having a rotatable torque cable through which first and second optical fibers extend. A distal tip assembly as described above is coupled to the torque cable.
Another aspect of the invention is a catheter tip assembly having an optical bench. A recess extending along a longitudinal axis of the optical bench has a transverse dimension selected to accommodate adjacent first and second fibers. The optical bench includes a first beam re-director in optical communication with the first fiber. The first beam re-director is oriented to cause a beam to travel away from the optical bench. An engaging structure coupled to the optical bench provides a torque coupling between the housing and an end of a torque cable extending axially along a catheter.
The invention also includes a method for receiving light by inserting a distal tip assembly into a blood vessel. The distal tip assembly encloses first and second fibers extending axially to a tip assembly. These fibers lie on a plane at the tip assembly. Light traveling on the first fiber is then directed away from the plane. Meanwhile, light incident on the plane is received into the second fiber.
The catheter tip assembly may include a second beam re-director in optical communication with the second fiber. The second beam re-director is oriented to cause a beam to travel in a direction having a second radial component. The magnitudes of the first and second radial components need not be the same, in which case beams re-directed by the first and second beam re-directors travel in different directions. In addition, a beam re-director can direct a beam in a direction having only a radial component, in which case the beam is essentially perpendicular to a plane containing the first and second fibers.
Either the first or second beam re-director can be a mirror. However, other beam re-directors, such as diffraction gratings, or prisms, are within the scope of the invention. In embodiments having both first and second beam re-directors, different types of beam re-directors can be used. For example, the first beam re-director could be a mirror while the second beam redirector is a prism.
The engaging structure can include an annular coupling mount disposed between the torque cable and the housing. The annular coupling mount has a first face coupled to the torque cable and a second face for engaging the housing.
The housing may include a proximally extending stem for inserting into an aperture in the annular coupling mount. Alternatively, the housing may include a tab extending proximally from a periphery thereof. In this case, the annular coupling mount includes a distal face having walls forming a slot for receiving the tab. Or, the annular coupling mount may include a tab extending distally from a periphery thereof, in which case the housing includes walls forming a slot for receiving the tab. In some embodiments, a hook extending proximally from the annular coupling mount and into a recess in the housing provides torque coupling.
The mirror may be coated with a reflective metal. The reflective metal may be selected from the group consisting of gold, silver, and aluminum. An optical fiber may be seated in the optical bench. The first beam re-director may comprise a distal end of the optical fiber. A distal end of the optical fiber may comprise a diagonal face oriented to direct a beam traveling through the fiber in a direction away from the fiber. The catheter tip assembly may further comprise a lens assembly disposed to provide optical communication between the first fiber and the first beam re-director. The lens assembly may comprise a GRIN lens. The optical fiber may comprise a lens integral with a distal end thereof.
Another aspect of the invention is a catheter comprising a rotatable torque cable; first and second optical fibers extending through the torque cable; and a catheter tip assembly according to any other aspect of the invention.
As used herein, term "light" includes not only visible light, but also electromagnetic radiation in the ultraviolet, infrared and the near infrared bands. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
The adjacent configuration of delivery and collection fibers results in a distal tip assembly having a small cross section. In addition, the adjacent configuration leaves space available for a torque coupling element within the housing. As a result, the diameter of the housing need not be enlarged to accommodate a coupling to the torque cable.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS- FIG. 1 is a schematic of a system for identifying vulnerable plaque in a patient.
- FIG. 2 is a cross-section of the catheter in FIG. 1.
- FIG. 3 is a view of an optical bench at the tip assembly of the catheter in FIG. 1.
- FIG. 4 is a view of an optical bench in which a fiber has a distal tip shaped to function as a beam re-director.
- FIG. 5 is an exploded view of the tip assembly in FIG. 3.
- FIG. 6 is a cross-section through the torque cable proximate to the tip assembly of FIG. 3.
- FIG. 7 is a housing having tabs for coupling to slots in a coupling mount attached to a torque cable.
- FIG. 8 is a housing having slots to receive tabs from a coupling mount attached to a torque cable.
- FIG. 9 is a housing coupled to a torque cable by a hook.
- FIG. 10 is a housing coupled to the torque cable by a catch feature.
- FIGS. 11-12 are cross-sections of a catheter sliding along a guide-wire.
- FIG. 13 is a cross-section of a guide wire mounted on a catheter.
DETAILED DESCRIPTIONSystem OverviewFIG. 1 shows a diagnostic system10 for identifying vulnerable plaque12 in an arterial wall14 of a patient. The diagnostic system features a catheter16 to be inserted into a selected artery, e. g. a coronary artery, of the patient. A delivery fiber18 and a collection fiber20 extend between a distal end21 and a proximal end23 of the catheter16.
As shown inFIG. 2, the catheter16 includes a jacket17 surrounding a rotatable torque cable 19. The delivery fiber18 extends along the center of a torque cable19, and the collection fiber20 extends parallel to, but radially displaced from, the delivery fiber18. The rotatable torque cable19 spins at rate between approximately 1 revolution per minute and 400 revolutions per minute.
At the distal end21 of the catheter16, a tip assembly22 coupled to the torque cable19 directs light traveling axially on the delivery fiber18 toward an illumination spot24 on the arterial wall14. The tip assembly22 also collects light from a collection area26 on the arterial wall14 and directs that light into the collection fiber20.
A multi-channel coupler28 driven by a motor30 engages the proximal end23 of the torque cable19. When the motor30 spins the multi-channel coupler28, both the coupler28, the torque cable19, and the tip assembly22 spin together as a unit. This feature enables the diagnostic system10 to circumferentially scan the arterial wall14 with the illumination spot24.
In addition to spinning the torque cable19, the multi-channel coupler28 guides light from a laser32 (or other light source such as a light-emitting diode, a super-luminescent diode, or an arc lamp) into the delivery fiber18 and guides light emerging from the collection fiber20 into one or more detectors (not visible inFIG. 1).
The detectors provide an electrical signal indicative of light intensity to an amplifier36 connected to an analog-to-digital ("A/D") converter38. The A/D converter38 converts this signal into digital data that can be analyzed by a processor40 to identify the presence of a vulnerable plaque12 hidden beneath the arterial wall14.
Optical BenchFIG. 3 shows an optical bench 42 in which are seated the collection fiber20 and the delivery fiber18. The optical bench42 is seated in a recess46 between first and second side walls44A-B of the distal end of a housing62 (best seen inFIG. 5). The housing62 is in turn coupled to the distal end of the torque cable19. The recess46 is just wide enough to enable the collection fiber20 and the delivery fiber18 to nestle adjacent to each other. A floor48 extending between the first and second side walls44A-B and across the recess46 supports both the collection and delivery fibers18, 20.
Just distal to the end of the delivery fiber18, a portion of the optical bench42 forms a frustum50. The frustum50 extends transversely only half-way across the optical bench42, thereby enabling the collection fiber20 to extend distally past the end of the delivery fiber18.
The frustum50 has an inclined surface facing the distal end of the delivery fiber18 and a vertical surface facing the distal end of the optical bench42. The inclined surface forms a 135 degree angle relative to the floor48. Other angles can be selected depending on the direction in which light from the delivery fiber18 is to be directed. A reflective material coating the inclined surface forms a beam re-director, which in this case is a delivery mirror52. When light exits axially from the delivery fiber18, the delivery mirror52 intercepts that light and redirects it radially outward to the arterial wall14. Examples of other beam re-directors include prisms and diffraction gratings.
The collection fiber20 extends past the end of the delivery fiber18 until it terminates at a plane that is coplanar with the vertical face of the frustum50. Just beyond the distal end of the collection fiber20, a portion of the optical bench42 forms an inclined surface extending transversely across the optical bench42 and making a 135 degree angle relative to the floor48. A reflective material coating the inclined surface forms a collection mirror54. This collection mirror54 reflects light incident from the arterial wall14 into the distal end of the collection fiber20.
In the embodiment ofFIG. 3, the fibers18, 20 are in direct optical communication with their respective mirrors52, 54, with no intervening optical elements. However, in some embodiments, a lens assembly is interposed between the distal end of the delivery fiber18 and the delivery mirror52. In other embodiments, a lens assembly is interposed between the distal end of the collection fiber20 and the collection mirror54. In yet other embodiments, a lens assembly is interposed between the distal end of the collection fiber20 and the collection mirror54 and also between the distal end of the delivery fiber18 and the delivery mirror52.
The lens assembly can include one or more discrete lenses. A suitable lens for use in a lens assembly is a GRIN (graduated index of refraction) lens. In addition, the lens assembly need not be composed of discrete lenses but can instead include a lens that is integral with the distal end of the fiber18, 20. Such a lens can be made by shaping the distal end of the optical fiber18, 20 so that it has the desired optical characteristics.
As shown inFIG. 3, the beam re-director is a separate element disposed in optical communication with a fiber18, 20. However, the beam re-director can also be integral with the delivery fiber18 in which case the delivery mirror52 is rendered unnecessary. Or, the beam redirector can be integral with the collection fiber20, in which case the collection mirror54 is rendered unnecessary. Or the beam re-director can be integral with both the collection fiber20 and the delivery fiber18, in which case both the collection mirror54 and the delivery mirror52 are rendered unnecessary.
FIG. 4 shows one example of the various ways in which a beam re-director can be integrated into a fiber. InFIG. 4, a fiber, which in this case is the delivery fiber18, has a distal end that has a diagonal cut forming a diagonal face. Light traveling axially along the fiber is reflected at the diagonal face and directed radially outward, toward the wall of the delivery fiber18. By orienting the delivery fiber18 with its diagonal face facing radially inward, this light is made to travel in a direction away from the optical bench42. As shown inFIG. 4, the angle of the diagonal cut is on the order of forty-five degrees. However, it will be appreciated that different angles will still direct the light away from optical bench42, but will introduce an axial component into the direction in which the light is directed.
AlthoughFIG. 4 shows a delivery fiber18 having a beam re-director integrated therein, it will be appreciated that a beam re-director can also be integrated into the distal end of the collection fiber20 using the same physical principles.
In the embodiment described herein, the collection fiber20 extends beyond the delivery fiber18. However, this need not be the case. In some embodiments, the delivery fiber18 extends beyond the collection fiber20. Alternatively, the delivery fiber18 and the collection fiber20 can end on the same plane. This is particularly useful when the distal tip assembly is intended to recover light scattered from very nearby regions, such as when information on features of the blood, rather than the vessel wall, is sought. In this case, the frustum50 is eliminated and the space freed by doing so is used to accommodate the additional length of delivery fiber18. Light entering the collection fiber20 and leaving the delivery fiber18 can both be incident on the same beam re-director. Alternatively, light entering the collection fiber20 and leaving the delivery fiber18 can be incident on separate beam re-directors.
The surfaces of the delivery and collection mirrors52, 54 can be coated with a reflective coating, such as gold, silver or aluminum. These coatings can be applied by known vapor deposition techniques. Alternatively, for certain types of plastic, a reflective coating can be electroplated onto those surfaces. Or, the plastic itself can have a reflective filler, such as gold or aluminum powder, incorporated within it.
A fiber stop56 molded into the optical bench42 proximal to the frustum50 facilitates placement of the delivery fiber18 at a desired location proximal to the delivery mirror52. A similar fiber stop58 molded into the optical bench42 just proximal to the collection mirror54 facilitates placement of the collection fiber20 at a desired location proximal to the collection mirror54.
The optical bench42 is manufactured by injection molding a plastic into a mold. In addition to being simple and inexpensive, the injection molding process makes it easy to integrate the elements of the optical bench42 into a single monolith and to fashion structures having curved surfaces. Alternatively, the optical bench can be manufactured by micro-machining plastic or metal, by lithographic methods, by etching, by silicon optical bench fabrication techniques, or by injection molding metal.
A breakaway handle60, shown inFIG. 5, is attached to the distal end of the optical bench42. This breakaway handle60 is used to insert the optical bench42 into a housing62 that couples to the torque cable19, as described below.
Materials other than plastics can be used to manufacture the housing62 and the optical bench42. Such materials include metals, quartz or glass, ceramics, liquid crystal polymers (LCPs), polyphenylsulfone, polyethersulfone, and polyetherimide.
The floor48 in the illustrated embodiment is integral to the housing62. However, the floor48 can also be made part of the optical bench42.
As described herein, the housing 62 and the optical bench42 are manufactured separately and later joined. However, the housing62 and the optical bench42 can also be manufactured together as a single unitary structure.
Coupling to Torque CableFIG. 5 is an exploded view of the distal tip assembly22 showing the manner of coupling to the torque cable19. As noted above, the distal end of the housing62 has walls44A-B forming an axially extending recess46 sized and shaped to accommodate the optical bench42. The optical bench42, with its breakaway handle60 still in place, is slid proximally into the recess46 from the distal end of the housing62. Once the optical bench42 is seated in the recess46, the breakaway handle60 is snapped off.
An axially extending stem66 having a square cross section extends proximally from the housing62. The stem66 is inserted into an annular mount68 whose proximal face is attached to the torque cable19 and whose distal face is exposed to engage the housing62.
The coupling between the torque cable19 and the housing62 can also be effected by, for example, providing a stem66 having a circular cross-section. In this case, an adhesive or interference bond is applied between the stem66 and the annular mount68). Such a stem66 can be provided with axial grooves to engage corresponding axial teeth circumferentially disposed in the interior wall of the annular mount68. Stems with alternative cross sections can also be used to effect coupling. For example, a stem66 having a semi-circular cross section can engage a corresponding semi-circular aperture in the annular mount68. Or, the coupling can be affected by providing matching threads on the stem66 and the annular mount68, in which case the stem66 can be screwed into the annular mount68. In the case of a metal housing62 and a metal annular mount68, the housing62 can be brazed, soldered, or welded directly to the annular mount68. All the coupling methods described herein can be augmented by applying an adhesive at the engagement surfaces of the housing62 and the annular mount68.
FIG. 6 is a cross-sectional view of the annular mount68 sliced to reveal an upper portion that contains the collection and delivery fibers18, 20 and a lower portion that accommodates the stem66 extending from the housing62.
The annular mount68 can also have an optional marker groove70 on its outer surface for accommodating a radio-opaque marker72. An example of such an annular mount, shown inFIG. 5, has a marker groove70 that aligns with a corresponding marker groove71 on the housing62.
The radio-opaque marker72 can be a strip, as shown, a band, or any other convenient shape. The marker72 can be any radio-opaque material such as gold, iridium, praseodymium, or platinum. Instead of, or in addition to the radio-opaque marker, either the housing62 or the optical bench42 (or both) can incorporate a radio-opaque material. For example, the plastic can be a compound plastic (such as polycarbonate, acrylonitrile butadiene styrene, or polyamide) with a powder from a radio-opaque material incorporated therein. Suitable radio-opaque materials include barium sulfate.
An alternative coupling structure, shown inFIG. 7, features a pair of axially extending tabs74 protruding from the housing62. These tabs74 mate with a corresponding pair of axial slots76 in the torque cable19. The axially extending tabs74 can instead protrude from the distal end of the annular mount68, as shown inFIG. 8, and mate with corresponding axial slots76 in the housing62.FIG. 9 shows another coupling structure in which a hooked tab78 extends proximally from the annular mount68 and fits into a tab-receiving slot80 on the housing62.FIG. 10 shows yet another coupling structure in which a catch feature82 is molded onto the stem66. The stem66 is inserted into the annular mount68 until the catch feature82 is completely inside. The distal end84 of the annular mount68 is then crimped, thereby securing the catch feature82. Alternatively, the coupling shown inFIG. 10 can be effected by snapping the catch feature into place proximal to a reduced diameter distal end portion of the annular mount68.
Using the catheterIn use, the distal tip assembly22 is inserted into a blood vessel, typically an artery, and guided to a location of interest. Light is then directed into the delivery fiber18. This light exits the delivery fiber18 at its distal tip, reflects off the delivery mirror52 in a direction away from the plane containing the delivery and collection fibers18, 20, and illuminates an illumination spot on the wall of the artery. Light penetrating the arterial wall14 is then scattered by structures within the wall. Some of this scattered light re-enters the blood vessel and impinges on the plane and onto the collection mirror54. The collection mirror54 directs this light into the collection fiber20.
Alternatively, light incident on the wall14 can stimulate fluorescence from structures on or within the wall14. The portion of this fluorescent light that is incident on the collection mirror54 is directed into the collection fiber20.
The distal tip assembly22 can be inserted into the blood vessel in a variety of ways. One method for inserting the distal tip assembly22 is to provide a channel86 that extends axially through the jacket17 for accommodating a guide wire88, as shown inFIG. 11. The guide-wire88 is first inserted into the artery by itself and guided to the region of interest. Once the guide wire is in place, the guide wire is threaded through the channel86. The jacket17 is then slid along the guide-wire until its distal end reaches the region of interest. Then, the torque cable19 with the distal tip assembly22 at its distal end is inserted through a lumen90 in the jacket17.
Alternatively, the jacket17 can have a channel86 extending only through a distal tip thereof, as shown inFIG. 12. The procedure for inserting the distal tip assembly22 is identical to that described in connection with FOG. 11. However, this configuration provides a smaller transverse cross-section than that shown inFIG. 11, in which the channel86 extends along the length of the jacket17.
An even smaller transverse configuration is provided by the configuration shown inFIG. 13, in which the channel is dispensed with altogether and the guide wire88 is attached to, and extends from, the distal tip of the jacket17. In this case, the jacket17 is inserted into the artery and guided to the region of interest by using the guide wire88 already attached to its tip.
OTHER EMBODIMENTSIt is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.