Note: Descriptions are shown in the official language in which they were submitted.
wo 95/09571 2 1 ~ 4 9 o o PCT~S93,096~
OPTICAL WAVEGUIDE WITH FLEXIBLE TIPS
1 BACKGROUND OF THE INVENTION
2 1. Field of the Invention
3 The invention relates generally to the field of
4 interventional optical catheters and, more specifically, to a
flexible terminus or tip for transluminal surgical catheters and
6 the like.
7 2. Prior Art
8 The use of energy delivered from a light source, for
g example, a laser, for surgical and industrial applications is
well documented. Typically, optical waveguides such as silica
11 optical fibers (alternatively referred to herein as "fiber
12 optics") are used to deliver light energy to internal areas of
13 the human body not readily aCc~cc~ directly by the light source.
14 A growing number of procedures, such as laparoscopic
lS cholecystectomy, laparoscopic appendectomy, lithotripsy of
16 calculi of the biliary, salivary and urinary tracts, and a host
17 of other light energy surgeries require flexible fiber optics to
18 access and deliver substantial energy to the treatment sight.
19 Often, fiber optics which are flexible enough to access
deep, tortuous internal areas of the body are so small in
21 diameter that they lack the rigidity required to push them
22 through the lumen and/or excessive energy density in the fiber
23 causes damage to the fiber rendering such thin fiber optics
24 impractical. Moreover, transmitting higher powers, on the
order of 10 or more watts, is inefficient in small fibers due to
W095/0957~ 2 1 8 4 9 00 PCT~S93/096~6
1 the difficulty of coupling. Energy density at the fiber optic
2 tip is the total energy delivered divided by the cross sectional
3 area of the optical fiber.
4 High energy densities cause undesired damage to the tip of
the fiber. The solution to this problem, with present
6 technology, is either using larger core diameter optical fibers,
7 which while reducing the energy densi~y, substantially reduces
8 the flexibility (doubling the core size reduces the flexibility
9 fourfold), or using a bundle of small core diameter fiber optics
creating a large ~LU~O~ ~ion of dead space- Dead space, as used
11 herein, refers to the portion of the cross sectional area of a
12 fiber optic catheter which does not transmit light energy.
13 Large core fiber optics permit the relatively efficient
14 coupling of energy from an external source into the fiber; even
if the source is divergent. This is not true of small core
16 fibers. the coupling efficiency of large cores together with
17 their rigidity enables them to be readily advanced through a
18 straight lumen and conduct a large amount of light energy to the
19 tip. The disadvantage is that the tip lacks the flexibility to
follow a tortuous path.
21 With conventional laser catheter tips heat buildup is a
22 significant problem. Sapphire or another expensive heat-stable
23 material is frequently used at the tip of such catheters to
24 prevent heat-induced fracturing and subsequent disintegration.
Laser surgery is conveniently done by using a flexible quartz
woss/oss7~ 2 1 8 4 q U O PCT~S93/096~
1 fiber for transmitting the laser energy, usually from a Nd:YAG
2 laser source, to the tissue undergoing treatment. In a typical
3 laser surgery system the end or tip of the silica fiber optic
4 serves as the probe for radiating the tissue to effect incision
or coagulation thereof. With some fiber optic tips it is
6 desirable to hold the tip away from direct contact with the
7 tissue to avoid fouling of the fiber and, importantly, to avoid
8 heat damage to the fiber end. Non-contact laser systems
g employing a light transmitting member at the output end of the
fiber to focus or otherwise alter the radiation characteristics
11 of the fiber have also been ~pG~ed, for example, by Enderly in
12 U.S. Patent 4,273,109, and by Daikuzono in U.S. Patent 4,736,743.
13 Microlenses may also be employed to distribute the light exiting
14 the catheter. The problem with the foregoing termini for laser
catheters is that they lack the flexibility to enter small
16 tortuous tubular members such as blood vessels, vas deferens,
17 ureters and so forth.
18 SU~MA~Y OF THE lNv~:Nl~loN
19 It is an object of this invention to provide a minimally
invasive medical, light transmitting catheter having the light
21 transmitting capability of a large core conventional silica fiber
22 dimensioned to fit within very small tubular members but having
23 much greater flexibility at the distal end that a comparable
24 silica fiber optic.
It is yet another object of this invention to provide a tip
woss/0957~ 2 1 8 4 q 00 PCT~S93/096~6
1 having substantially the same light transmitting capabilities as
2 silica tips having a much larger diameter while exhibiting
3 greater flexibility at the tip than can be achieved with silica.
4 It is still another object of this invention to provide a
transluminal catheter for conducting light from a source to a
6 distal target which has the advantages of a large core silica
7 fiber for coupling light from a source into the fiber and
8 permitting advancement of the catheter through the lumen and
9 having a tip which has the flexibility of a small core silica
fiber.
11 It is yet another object of this invention to provide a
12 flexible tip for a medical light delivery catheter of a
13 composition amenable to being formed in many different geometries
14 or configurations.
These and other objects of the invention will soon become
16 apparent as we turn now to the descriptions of the preferred
17 embodiment.
18 BRIEF DESCRIPTION OF THE DRAWINGS
19 Figure 1 is a perspective view of the tip of the catheter
of the present invention.
21 Figure 2 is a partially cutaway view of the tip of Figure
22 1.
23 Figure 3 is a longitll~; nA 1 cutaway view of the catheter of
24 the present invention with a first preferred embodiment of the
tip in place.
woss/0957~ 2 1 8 4 ~ O O PCT~Sg3/096~fi
1 Figure 4 is a longitudinal cutaway view of the catheter of
2 the present invention with a second preferred embodiment of the
3 diffuser tip in place.
4 Figure 5 is another longitudinal, cross sectional view of
an embodiment of the catheter of the current invention with the
6 core of the flexible tip spaced from the core of the optical
7 fiber.
8 Figure 6 is the same as Figure 5 except a cladding surrounds
9 the core material of the tip.
Figure 7 is a partially cutaway schematic view of an
11 embodiment of the invention used with a divergent light source.
12 Figure 8 shows the embodiment of Figure 7 with the flexible
13 tip fitted with a terminus configured as (a) a pointed probe, (b)
14 a rounded smooth terminus, and (c) a focusing lens.
DESCRIPTION OF THE PREFERRED EMBODIMENT
16 A flexible tip for use with the invasive catheter of the
17 present invention is shown in Figure 1, generally indicated at
18 10. The central core 11 of the flexible tip 10 is made from an
19 optically transmissive material such as silicone, silicone
copolymer, or any variety of elastomers. Surrounding the central
21 core 11 is a cladding layer 12, again fabricated from silicone,
22 silicone copolymer or elastomer. The cladding layer 12 and the
23 core 11 are specifically chosen for their refractive indices.
24 The refractive index of the cladding 12, which may be a length
of tubing, is preferably less than the refractive index of the
woss/0957~ 2 1 8 4 9 00 PCT~S93/096~
1 core 11. Correctly choosing the refractive indices of the
2 materials will insure total internal reflection of the light
3 energy while also controlling the solid angle of the exiting
4 light energy (not shown). The tip 10 shown in Figure 1 is
abutted to a single fiber (not shown) or fiber bundle (not shown)
6 to receive the light from the optical fiber(s) (not shown) and
7 ultimately to deliver the light energy to the treatment site.
8 The tip core 11 and the cladding 12 are held in position relative
g to the fiber optic (not shown) by a structural tube 13 made with
flexible elastomeric material such as Teflon~ or polyurethane.
11
12 Figure 2 is a cut away view of the tip of Figure 1. It is
13 clear that the optically transmissive tip core 11 is suLLouded
14 by a cladding layer 12 which in turn is ~LLoul.ded by a
structural tube 13 made of flexible elastomeric material. The
16 outer tube 13 may, of course, be made from a variety of flexible
17 elastomers including Teflon~ and polyethylene. The catheter of
18 the present invention, showing the flexible tip abutted to the
19 terminus of the fiber optic is shown in Figure 3. The catheter,
generally indicated at numeral 30, has a fiber optic portion 34
21 abutted to the flexible tip portion 10. The fiber optic portion
22 34 of the catheter 30 comprises a fiber central core 31
23 surrounded by a cladding 32. The core 31 and cl~;ng 32 are
24 enclosed in a jacket 33. The distal tip, or terminus, 35 of the
optical fiber portion 34 is abutted against the tip core 11 of
-
woss/0957~ 2 1 8 4 ~ o o PCT~S93~96~6
1 the flexible tip 10. The tip core 11 is surrounded by tip an
2 outer sheath 13. Treatment light (not shown) exits the tip of
3 the catheter 30 in Figure 3 in the forward direction towards the
4 right. The flexible tip 10 may also include a cladding 12
surrounding the tip core 11 as shown in emhoAiment 40 in Figure
6 4.
7 A second preferred embodiment of the catheter of the present
8 is generally indicated at 50 in Figure 5. In this embodiment the
9 distal tip 35 of the optical fiber portion 34 is spaced from the
flexible tip core 11 of the tip portion 10 by means of a liquid
11 or gas-filled space 51. The fluid gap 51 allows greater power
12 handling capabilities by substantially reducing the power density
13 of the transmissive core 11/fluid gap 51 interface compared to
14 the transmissive core 11/fiber optic 31 interface. The fluid
space 51 may be filled with a gas or a fluid.
16 Figure 6 shows yet another emhoAiment 60 of the catheter
17 shown in Figure 5 except that the flexible tip has a cladding
18 material 12 surrolln~inq the flexible tip core ll of the flexible
19 tip 10.
It is important that the fiber optic core 31 retain its
21 cladding 32 during fabrication of the catheter. If the cladding
22 32 is stripped from around the core 31 of the fiber optic 34, the
23 catheter will be vulnerable to breakage at the point where the
24 cladding has been stripped from the core. The material chosen
for the fiber optic core is less elastic of flexible than the
W095/0957~ 2 1 8 4 ~ 00 PCT~S93/09656
1 material chosen for the core of the flexible tip.
2 The advantage of combining a large core silica fiber with
3 an elastomer tip is seen by looking now to Figure 7. Divergent
4 light 70 from a divergent source such as a diode laser 71 readily
enters the large core 75 of the silica fiber 72 which conducts
6 the light to the core 78 of the flexible elastomeric tip 74.
7 optically transparent silicone rubber is preferably employed as
8 a material of choice for the tip 74 due to its biocompatibility.
g The index of refraction of the material comprising the flexible
tip 74 is preferably close to that of the core 75 of the fiber
11 optic. Alternatively, the space 51 in the embodiment shown in
12 Figures 5 and 6 may be filled with a optically transparent
13 material having an index of refraction between the index of the
14 tip core 74 and the fiber core 75. The relative stiffness of the
large diameter silica core 75, enh~ceA by the presence of
16 cladding jacket 76 and outer sheath 77, permits advancement of
17 the catheter through constricted tubular tissue but has a large
18 minimum radius of curvature A. The silicone core tip 74, being
19 relatively short compared to the silica core fiber optic 72
portion, is pushed ahead of the fiber portion 72 during
21 advancement. The silicone core tip, being more flexible, has a
22 much smaller minimum radius curvature, shown at B in Figure 7,
23 enabling it to track sharp turns, guiding the silicone core
24 portion 72 during advancement. The silicone core tip 74 and the
silica core 75 of the fiber optic portion 72 of the waveguide
wo 9s/09s7~ 2 1 8 4 9 00 PCT~S93109656
1 form a high coupling efficiency union 73. This union 73 can
2 conveniently be made by ext~nAing the sheath (not shown) surround
3 the silica core portion beyond the silica core portion and
4 filling the sheath with uncured silicone followed by curing.
Figure 8 shows the emh~iment of the flexible tipped
6 waveguide of Figure 7 with a variety of flexible tip terminus
7 configurations. Since the flexible tip 74 is elastomeric, it
8 readily bonds to various other plastics. Figure 8(a) shows the
9 flexible tip 74 with a pointed terminus 81 suitable for
interstitial use. A rounded or beveled terminus 82 (Figure 8(b)
11 is useful for intraluminal use. Figure 8(c) shows a focusing
12 lens 83 affixed to the flexible tip 74. The termini 81-83 may
13 be fabricated from any transparent material or they may be opaque
14 if the light reaching the flexible tip 74 tip need not exit the
tip in the forward direction.
16 It will be appreciated that, while a preferred emho~iment
17 of the invention has been described herein, various modifications
18 will suggest themselves to those skilled in the art. For
19 example, variations in materials may be required for certain
industrial applications. The essential feature of the invention
21 is the placement of a flexible tip on a relatively rigid, large
22 core optical fiber to confer the advantages of both materials to
23 a combination product while minimizing their disadvantages.
24 Rigid, large core fibers having relatively inflexible cores
comprising a transparent material other than silica such as a
wogs/09571 2 1 8 4 9 ~ PCT~S93/09656
1 plastic may be used. Flexible elastomers other than silicone may
2 also be used for the tip. These and other modifications that may
3 suggest themselves to those skilled in the art are considered to
4 be within the spirit and scope of the present invention as set
forth in the following claims.
