Note: Descriptions are shown in the official language in which they were submitted.
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1 Backaround of the Invention
2 1. Field of the Invention
3 This invention relates to catheters and similar devices
4 having a mechanism for aiming light transmitting fibers. Although
S particularly described with reference to laser angioplasty, the
6 invention has broad applicability to any medical instrument which
7 fires a laser at a target.
8 2. DescriDtion of the Related Art -
9 This invention relates to medical instruments and in ~ - -
particular to devices for performing laser surgery e.g., ~
11 angioplasty, the treatment of atherosclerosis and the like. ~;
12 Atherosclerosis is a disease which causes thickening and hardening
13 of artery walls. It is characterized by lesions of raised ~ ;
14 atherosclerotic plaque which form within arterial lumens and occlude
them partially or wholly. Coronary atherosclerosis is a leading ~
16 cause of death in the United States. Atherosclerosis tends to ~ ~;
17 increase progressively with age. The treatment of atherosclerosis
18 typically consists of drug therapy, surgery or percutaneous balloon
19 angioplasty.
In percutaneous balloon angioplasty, small balloon ~ -
21 tipped catheters were first developed which could be passed , ,
22 percutaneously into various arteries and then inflated to dilate
23 areas of partial obstruction. While this procedure has gained a
24 measure of acceptance as a less invasive alternative to surgery, in
most cases balloon angioplasty simply redistributes the
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1 atherosclerotic plaque. Frequency of recurrence or restenosis of
2 the plaque occlusions has caused some concern about the efficacy of
3 this technique.
4 Laser therapy has been suggested as another approach to
percutaneous angioplasty. One such technique utilizes laser
6 technology to emit radiation onto a light receiving surface of a
7 heat generating element. The light is converted by the element to ;~
8 heat. The element can then be contacted against material in a
9 patient's body, such as a clot, atherosclerotic deposit or tissue, ~- -
10 to alter the same by melting, removing or destroying it. ; -11 In another laser technique, laser radiation is applied
12 directly to the plaque deposit, clot or the like to vaporize or ~ -13 ablate it. It is this second technique to which the subject
14 invention is most particularly directed. This particular technique
of laser angioplasty provides the ability to remove the
16 atherosclerotic plaque and reopen even totally occluded vessels
17 without significant trauma to the vessel wall. It also offers the
18 potential of reduced restenosis rate. However, the current
19 technology for impinging laser radiation directly on a selected
discrete treatment area has its own problems. Most critical has
21 been the lack of ability to precisely aim laser radiation to
22 selected areas to be treated without accidental arterial
23 perforati~n. !.
24 Various attempts have been made to overcome the problem
of aiming the laser at the target, while avoiding damage to the
26 vessel wall.
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1 U.S. Patent No. 4,445,892 issued May 1, 1984 for a "Dual
2 Balloon Catheter Device" discloses a tubular structure carried
3 inside the catheter. Mounted on the outside of the tubular
4 structure is the optic system which includes light transmitting
fiberoptic bundles. The optic system is rotatably mounted on the
6 tubular structure, and may be axially displaced as well. The laser
7 beam is reflected using a prism, such that the beam is fired ~
8 directly at the vessel wall. A major problem with this embodiment ~ ~-
9 is in determining when the beam has penetrated the target and is ;
firing on bare vessel wall.
11 U.S. Patent No. 4,587,972 issued May 13, 1986 for a
12 nDevice for Diagnostic and Therapeutic Intravascular Intervention"
13 discloses a device which contains a bundle of optic fibers in the -
14 center of a catheter. The device is capable of firing one or more
of these laser fibers. However, the laser beam fires axially, which
16 limits the precision with which the physician may aim the laser
17 energy at targets close to the vessel wall.
18 U.S. Patent No. 4,627,436 issued Dec. 9, 1986 for a
19 ~Angioplasty Catheter and Method For Use Thereofn discloses another ; ~ `
20 device which fires a laser beam axially. An expansion balloon ~ -~
21 permits the distal end of the catheter to be tilted for more precise ;~
22 aiming. The problem with this design is that targets close to the
23 ~ vessel wal~l remain difficult to hit due to the axial firing of this
24 design.
U.S. Patent No. 4,648,892 issued Mar. 10, 1987 for a
26 nMethod For Making Optlcal Shield For A Laser Cathetern discloses a
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1 device which fires one or more laser beams axially. The device has
2 a shield which allows the distal end of the catheter to be put into
3 contact with the target, allowing viewing of the target without the
4 interference of any liquid, such as blood. Various types of
elements may be placed within the shield to reflect the laser light.
6 A problem with this design is that the distal end of the catheter
7 must be manipulated such that the distal end comes into contact with
8 the plaque. If the plaque is in a difficult to reach spot it may be
9 difficult to ablate it. One advantage of the present single fiber
invention over this multiple fiber device is that it allows for a
11 smaller diameter device.
12 Another approach was disclosed in U.S. Patent ~o.
13 4,672,961 issued June 16, 1987 for a ~Retrolasing Catheter and
14 Method~. This patent discloses a device which fires a group of
laser fiber bundles spaced around the perimeter of the catheter,
16 reflecting the laser beams backward through a window portion in the ~ -
17 catheter wall to aim at a target. The energy from each bundle of
18 fibers is focused on a different point around the perimeter of the
19 catheter. A problem with this design is that it is difficult to -
determine where each of the laser fibers is being aimed since no
21 imaging technique is used. This device also cannot be used in
22 vessels so severely occluded that the catheter cannot be advanced
23 through the obstruc~tion. Applicant's invention allows even totally
24 occluded vessels to be unblocked by carving away the plaque with the
laser beam.
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1 U.S. Patent No. 4,681,104 issued July 21, 1987 for an
2 "Apparatus For Focusing An Intravascular Laser Catheter" discloses a
3 device which fires an array of laser fibers spaced around the
4 perimeter of the catheter, angling the beams such that they focus at
a point on the longitudinal axis of the catheter. The problem with
6 this device are that it is only useful for targets which almost
7 totally clog the vessel, due to the location of the focal point of
8 the laser beams. If the laser beams are allowed to fire through the
9 focal point and spread in an attempt to reach a target off axis, the
vessel wall opposite the target may be damaged. This is true even
11 if a portion of the array of laser beams is in fact correctly aimed
12 at the target. In addition, the multiple fiber configuration
13 requires a larger diameter catheter than applicant's single fiber
14 catheter. - ~ ;
The invention disclosed herein overcomes these problems
16 by providing a catheter device which may be aimed at any point `
17 within the cross-section of a vessel. The present invention fires a
18 laser at an angle ~ at a target using a beveled optical fiber and
19 the refractive indices of glass and water or air. Rotation of the
optical fiber wh;ch carries the laser beam causes the laser beam to
21 describe a cone. The optical fiber may also be moved axially within
22 the catheter and may even extend beyond the distal end face of the
23 ~ catheter. Movement,of the fiber axially within thç vessel, and
24 movement of the catheter, combined with the rotation of the fiber
allows the physician to aim the laser at any point within the
26 cross-section of the vessel. Placement of the laser fiber
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1 off-center within the distal end portion of the catheter, with
2 respect to the longitudinal axis of the catheter, allows for the
3 ablation of plaque which is on the axis. It also allows the imaging
4 means (typically an optical fiber bundle) to be placed at the center
axis of the catheter, which may facilitate the aiming of the
6 catheter.
7 Various types of lasers may be utilized in the context
8 of the present invention. The pulsed dye laser is one that is often
9 preferred for cardiovascular use due to its superior ability in
avoiding damage to surrounding tissue. This is due in part because
11 the plaque tends to absorb the particular wavelength of light used
12 by pulsed dye lasers more readily than the surrounding tissue.
13 Pla~ue is ablated by using pulsed energy as brief as about .5 to 50
14 microseconds, although the pulse time can vary. The pulsed dye
15 laser is also preferred because more energy can be delivered through -
16 the relatively fragile fibers because of the longer pulse time.
17 Excimer lasers as well as other types of lasers could also be used ;
18 in the present invention.
19 Optical fibers and fiber bundles have also been used in
a variety of medical applications. An optical fiber is a relatively
21 flexible clad plastic or glass core wherein the cladding is of a
22 lower index of refraction than the core. When a plurality of such
23 / fibers are combined!~ a!fiber optic bundle is produced. Optical ; ~ `
24 fibers are flexible and are therefore capable of guiding light in a ~
25 curved path defined by the placement of the fiber. `
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1 Summarv of the Invention
2 The aiming arrangement of the ~nvention is specifically
3 described herein with reference to catheters for laser angioplasty
4 but has broad applicability to any medical instrument which fires a
laser at a target. The instrument may be used in both coronary and
6 peripheral percutaneous angioplasty, but may also be used in
7 intraoperative procedures, such as when the chest cavity or femoral
8 artery are exposed ;ncident to another procedure or as a primary
9 procedure.
10 In its most preferred form a device of the invention ~- ;
11 will comprise a fiber optic catheter suitable for performing medical
12 procedures in a vascular lumen or other cavity within a patient. ~ ;
13 The catheter will have a distal end to be inserted into a patient
14 and a proximal end including a control means for directing the
contemplated procedure. Such devices are typically constructed for
16 disposal after a single use. More specifically, the catheter
17 includes an elongated external tube containing a laser light
18 transmitting means, such as an optical fiber. The catheter may also
1-9 contain one or more fiber optic viewing bundles, one or more fiber
optic illumination fibers and may also be provided with one or more
21 fluid passageways through which gases or liquids may be evacuated or
22 transmitted. The catheter may also include a balloon at the distal
23 end to halt the flow of blood,for the duration of the procedure.
24 This balloon may not be needed for intraoperative procedures since
the blood may have been removed from the vessel in question, or may
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1 not be flowing. A guide wire may also be inserted through one of
2 these conduits or otherwise included in the catheter.
3 The distal end of the catheter is advanced through a
4 lumen to the area of the vessel where the procedure is to be
performed. The fiber optic viswing bundles along with various other
6 techniques such as fluoroscopy allow the physician to see what the
7 laser is aimed at. The laser beam is situated such that it fires at
8 an angle ~. The angle ~ is determined by the bevel angle o of the
9 optical fiber as well as the refractive indices of glass and water
or air. Angle ~ may vary among catheter designs to provide the
11 physician flexibility for the various procedures which must be
12 performed. Rotation of the optical fiber around its own axis causes
13 the laser beam to describe a conic section, where the conic section
14 is the projection of a circle or ellipse onto the surface of the
15 plaque. By a combination of rotation of the catheter, axial -
16 movement of the catheter, and rotation of the optical fiber around
17 its own axis, any point within the entire cross-section of the
18 vessel can be precisely aimed at by the laser. ;;~
19 Brief Description of the Drawings
20 Fig. 1 is an elevational view of a preferred embodiment -~
21 of the medical device of the invention;
22 Fig. 2 is an enlarged detail view of the distal end of -~
23 the device shown injlFig. 1;
24 Fig. 3 is an end elevational view of Fig. 2; ;~
25 F19. 4 shows simplified schematics of various stages of ~-
26 the procedure; ;- ~`~
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1 Fig. 5 shows s;mplified schemat;cs of how the laser spot
2 is kept in the field of view, and
3 Fig. 6 shows simplified schematics of how rotating the
4 catheter may result in a higher amount of energy being directed at
the target.
6 Description of the Preferred Embodiments
7 While this invention can be embodied in many different ~;
8 forms, there are shown in the drawings and described in detail
9 herein specific preferred embodiments of the invention. The present
disclosure is an exemplification of the principles of the invention
11 and is not intended to limit the invention to the particular
12 embodiments illustrated.
13 The present invention in preferred form comprises a
14 medical device for delivering and applying laser radiation to a site
in a vessel lumen of a patient. The radiation may be used to
16 vaporize atherosclerotic plaque. Such instruments oftentimes take
17 the form of microcatheters of extremely small diameter. Such -
18 instruments are usually readily available in various diameter sizes ~ -
19 to suit the particular work site in the particular lumen in which
they are to be located and used. Thus a physician will have a
21 number of various sized catheters at his disposal during any given
22 procedure. This may include a number of catheters which will fire
23 the laser beam at various angles. -
24 In some such devices, an elongated guide wire (not -~;
25 shown) may be selectively positioned within the lumen of the patient `~
26 in association with the catheter. To this end, the catheter may
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1 include an elon~ated channel such as a slot, bore or conduit through
2 which an external guide wire may slide longitudinally. The catheter
3 can then be slid along the guide wire untll a selected position in
4 close proximity to a lesion which partially or totally occludes a
vessel is reached. The aiming mechanism can be manipulated as
6 desired and the laser radiation can then be ~electively impinged on
7 any area selected for treatment within the cross-section of the
8 vessel.
9 Some versions of such catheters are desirably ~
10 constructed with at least a tip portion thereof including ~;
11 radio-opaque material (not shown). The radio-opaque material can
12 then be used to locate the catheter under fluoroscopy which in
13 combination with the image bundle aids in determining the location
14 of the catheter tip relative to the plaque and aids in verifying the
aiming.
16 Referring now particularly to Figure 1 of the drawings,
17 a catheter device of the present invention in one embodiment
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18 comprises an elongated catheter, generally designated 10, having a
19 working distal end generally designated 12. The device is adapted
to be inserted into a patient and remote control means 14 is
21 attached at a proximal end 13 for manipulation and control by a
22 physician. The catheter is flexible and generally comprises an `~
23 extruded sol-id plasticlbody 15.- Body 15 may consist of a;single, -~
24 soft, solid, extruded plastic material or it may consist of a
25 plastic composite reinforced with plastic or metal braided ~;
26 filaments, such as Dacron~ polyester fiber or stainless steel.
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1 Plastics such as polytetrafluoroethylene, polyester, polyethylene
2 and s~licone may be used.
3 When using the catheter in a vessel which contains an
4 opaque fluid such as blood, it is often necessary to remove the
opaque fluid and flush the area with a clear fluid such as saline
6 solution to provide a viewable work area. To accomplish this,
7 catheter body 15 may include conduits 18 and 19 (shown in Fig. 3),
8 which open at distal end 12 and which are respectively connected to
9 tubes 20 and 21 at the proximal end. Conduits 18 and 19 may be
formed during extrusion of body 15. Tubes 20 and 21 include
11 appropriate connector fittings 22 and 23, which will be familiar to
12 those of ordinary skill in the art. Conduits 18 and 19 may thus
13 function as suction tubes, fluid flushing tubes, supply tubes or for
14 receiving a guide wire, in the already known manner.
Referring now to Figures 1 and 2 together, provision is
16 made for delivering laser radiation to the distal end 12 of catheter
17 10 by provid~ng a laser light source, (not shown). The laser may be
18 coupled as is known in the art to control means 14 through an
19 optical coupling fitting 29. This arrangement in turn directs laser
.,
radiation through control means 14 and through a laser radiation
21 transmitting fiber 30, which may be located within an internal
22 conduit 31 in body 15. Preferably, a single glass or fused silica ~ ~-
23 fiber 30 or other optical fiber with a core diameter of about 50 to
24 about 600 microns is utilized for the laser radiation transmitting
fiber 30. These are typical sizes presently available and are not
26 critical; the smaller the fiber the better, as long as enough energy ~ -
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1 can be transmitted through the fiber without damage to the fiber.
2 Such fibers are known in the art. However, other fiber arrangements
3 may be used as they become available.
4 Additionally, a bundle of very flexible and very small
diameter optical fibers or 1maging bundle 32 lncluding a lens as
6 well as illumination fibers 33 (shown in Fig. 3) may be included and
7 will also extend through catheter 15. In the preferred embodiment -
8 bundle 32 runs down the center of catheter 15. The proximal end
9 thereof is appropriately connected to a fitting 33 to provide
imaging or viewing in the known manner. Imaging bundle 32 is
11 coherently packed, such that light at the proximal end is in the
12 same relationship to the fibers in the bundle as when the light
13 enters the imaging bundle 32 at the distal end. The illumination
14 fibers 33 are not arranged in a coherent bundle like the imaging
bundle. This is because the illumination fibers need only transmit
16 white light to allow the physician to see inside the vessel, and not ;~ ;~
17 receive and transmit an image in a coherent manner for viewing.
18 Placing the imaging bundle 32 in the center of the catheter aids in -
19 the viewing of the vessel and in aiming the laser energy. However, ;~
it is to be understood that the viewing bundle 32 could be placed
21 anywhere within catheter 15.
22 Referring now specifically to Figures 2 and 3 together,
23 it can bq~seen thatila$er transmitting fiber 30 running through! ~
24 conduit 31 terminates near or at the distal end of the catheter 12. -
The optical fiber 30 terminates in a bevel angle ~ which may be
26 adjusted along with the refractive indices of the silica fiber 30
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1 and the water or air near the distal end of the catheter to control
2 the angle ~ at which the laser beam is fired. This type of
3 arrangement is well known in the art. It is contemplatsd that other
4 arrangements which result in the laser being fired at an angle ~
could be used also, such as using a mirror to reflect the beam, or
6 other arrangements. The laser beam is directed out through opening
7 38 in distal end 12 of the catheter. The laser energy emerges from
8 opening 38 at a predetermined angle ~ shown at 40. Angle ~ shown at
9 40 is determined by the formula ~ - Sin-1 (nl / n2 Cos ~) + ~ - 90-
where ~ is the bevel angle shown at 42, n1 is the refractive index
11 of glass or fused silica shown at 44, and n2 is the refractive index
12 of water or air shown at 46. Angle ~ is determined by the
13 longitudinal axis 48 of laser fiber 30 and the longitudinal axis 50
14 of the laser cone 52. The laser beam spreads out into a cone 52 as
the beam moves further from the distal end of the catheter.
16 Reference numerals 54, 56, 58 and 60 represent conic sections of the ~ ~-
17 cone shaped laser beam 52. The corresponding distances Dl, D2, D3,
18 and Dn show the various locations of plaque which would be ablated
19 if the plaque intersects the laser beam at various distances from --~
20 the distal end 12. As the optical fiber 30 is rotated within -~
21 conduit 31 the cone 52 will rotate around the longitudinal axis 48 ~ :~
22 of the optical fiber 30, always at an angle ~. By moving the
23 catheteriaxially along the vesseljthe catheter may be placed the -~
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24 exact distance fro- the target such that the diameter of the cone at
25 that point will include the target, and the laser radiation will ~ ~ -
26 strike it. The conic sections also demonstrate that the diameter of
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1 the cone may exceed the diameter of the catheter if the vessel is
2 large enough to allow the laser rad;ation to travel far enough.
3 With axially firing prior art arrangements it was difficult to aim
4 at a target which was outside the diameter of the catheter. By a
combination of rotation of the catheter 10, axial movement of the
6 catheter 10, and rotation of the optical fiber 30 around its own ;~
7 axis 48, any point within the entire cross-section of the vessel can
8 be precisely aimed at by the laser.
9 Referring now to Figure 4, reference line 64 shows the
relative position of the distal end 12 of the catheter to the plaque
11 target shown at 66. The first portion of figure 4, shown generally
12 at 68, shows the laser beam 52 directed through opening 38 at an
13 angle ~ towards plaque target 66. The laser beam, as shown, would
14 strike the vessel wall 70, which is undesirable. The second portion ~
15 of figure 4, shown generally at 72, shows how advancing the distal ~ -
16 end 12 of catheter 10 forward will enable the laser beam 52 to
17 strike the plaque target 66 without damaging the vessel wall 70.
18 The last portion of figure 4, shown generally at 74, shows how the
19 same laser beam placement on plaque target 66 may be achieved by ;
advancing the laser fiber 30 out of opening 38 of the catheter's
21 distal end 12. Some of the advantages of moving the fiber 30
22 forward rather than moving the entire catheter forward include less
23 wear and tear on the vessel;wall and the ability to keep the distal
24 end of the optical fiber 30 in view of the viewing bundle 32
(discussed in figure 5 below).
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1 Referring now to Figure 5, reference line 64 shows the
2 relative position of the distal end 12 of the catheter to the plaque
3 target shown at 66. The viewing bundle 32 (shown in figure 3)
4 provides a field of view shown generally at 76 bounded by lines 78
and 80. In the first portion of figure 5, shown generally at 82,
6 the distal end of the catheter must be moved up to the reference ~ ~-
7 l;ne 64 to allow the laser beam 52 to strike the target 66. The
8 closeness of the catheter to the target however, causes the laser
9 beam 52 and the target 66 to be outside the field of view 76. The
10 second portion of figure 5, shown generally at 84, shows that by -~
11 advancing the laser fiber 30 instead of the distal end 12 of the
12 catheter the laser beam`52 still strikes the plaque target 66, with
13 both being in the field of view 76.
14 Referring now to Figures 6, reference line 64 shows the
15 relative position of the distal end 12 of the catheter to a target -16 point shown at 86. The first portion of figure 6, shown generally
17 at 88, shows laser beam 52 striking point 86. The second portion of
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18 figure 6, shown generally at 90, shows that the same point 86 may be
19 reached with the laser beam 52 traveling less distance by advancing -- -
the catheter 10 and rotating it so the laser beam originates on the
21 same side of the vessel as the target point 86. The closer the ;~
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22 laser fiber 30 to the plaque the less beam spread (the conic section
23 diameter of the cone is lesjs) therefore focusing mqre laser energy
24 on the target point 86. Also there is less attenuation in the laser
beam 52 caused by the beam moving through the medium in the artery.
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1 Th;s completes the description of the preferred and
2 alternate embodiments of the invention. Those skilled in the art
3 will recognize other equivalents to the specific embodiments
4 described herein which equivalents are intended to be encompassed by
the claims attached hereto.
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