AU1471499A - Optical waveguide with flexible tips - Google Patents

Description

4, DI Ii JJ64

AUSTRALIA

Patents Act 1990 COMPLETE

SPECIFICATION

FOR A STANDARD PATENT Name of Applicant: Actual Inventors: Address for Service: Invention Title: MIRAVANT SYSTEMS, INC.

Daniel R DOIRON and Hugh L NARCISO CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, QId. 4000, Australia.

OPTICAL WAVEGUIDE WITH FLEXIBLE-

TIPS

Y

The following, statement is a full description of this invention, including the best method of performing iR known to us OPTICAL WAVEGU.IDE WITH FLEXIBLE

TIPS

1 BACKGROUND OF THE INVENTION 2 1. Field of the Invention 3 The inVention relates generally to the field of '1 initervenitional optical catheters and, more specifically, to a flexible terminus or tip for transluininal surgical catheters and the like.

7 2. Prior Art The use bf energy delivered from a light source, for 9 example, a laser, for surgical anid industrial applications is well documenlted. Typically, optical waveguides such as siliua 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 accessed directly by the light source.

14 A growing number of procedures, such as laparoscopic cholecystectomy, laparoscopic appendectomy, lithotripsy of X6 calculi of the biliary, salivary and urinary tracts, and a host of other light energy surgeries require flexible fiber optics to access and deliver gubstantial energy to the treatment sight.

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 Z. through the lumen and/ or eicsve energy density in the fiber 23 causes damage to the f iber rendering such thin fiber optics impractical. Moreover, transmitting higher powers, on, the *order of 10 or more watts, is inefficient in small fibers due to la bl 3229 3384 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 density, 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 proportion of dead space. Dead space, as used 11 herein, refers to the portion of the cross sectional area of a S 12 fiber optic catheter which does not transmit light energy.

13 Large core fiber optics permit the relatively efficient 24. coupling of energy from an external source into the fiber; even if the source is divergent. This is not true of small core n 37! their rigidity enables them to be readily advanced through a 18 straight lumen and conduct a large amount of light energy to the S 1: tip. The disadvantage is that the tip lacks the flexibility to follow a tortuous path.

With conventional laser catheter tips heat buildup is a 22 significant problem. Sapphire or another expensive heat-stable .33: material is frequently used at .the tip of such catheters to '*24 prevent heat-induced fracturing and subsequent disintegration.

S 25 Laser surgery is conveniently done by using a flexible quartz 2 1 fiber for transmitting the laser energy, usually from a Nd:YAG 2 laser source, to the tissue undergoing treatmenlt. 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 inlcison or coagulation thereof. With some fiber optic tips it is b desirable to hold the tip away from direct contact with the 7 tissue to avoid fouling of the fiberand, importantly, to avoid 8 -heat damage to the fiber end. Non-contact laser .systems 9 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 proposed, for example, by Endecly in -a12 U.S. Patent 4,273, 1u9, and-by Daikuzono in U.S. Patent 4,736,743.

13 Hicrolenses 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 *w tortuous tubular members such as blood vessels, vas deferens, LT 7 ureters and so, forth.

.1,9:SUJMARY OF THE INVENTIONI 1 9 It is an object of this 1flv~ntjon to provide a rninimqlly invasive medical, light transmitting catheter having the light 21 transmitting capability of a large core conventional silica fiber dimnsinedto fit within very small tubular members but having 23 much greater flexibility at the distal end that a comparable silica fiber optic-.

29. it is yet another object of this invention to provide a tip 3 f- I 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 b distal target which has the advantages of a large core silica 7 fiber for coupling light from a sburce into thle 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.

AThese and other objects of-the invention will soon become apparent as we turn now to the descriptions of the preferred *17 ebdmn.

M:-BRIEF DESCRIPTION OF THE DRAWINGS 19 Figure 1 is a perspective vi~w of the tip of the catheter of the present invention.

21 Figure 2 is a partially cutaway view of the tip of Figure Figure 3 is a longitudinial cutaway view of the catheter of the present ir rention with a first preferred embodiment of .the -tip in place.

71 7 4

A

A UI I JLLJ JJU4 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 G core of the flexible tip spaced from the core of the optical 7 f ibera Figure 6 is the same as Figure 5 except a cladding surrounds 9 the core material of the tip.

Figu~re 7 is a partially cutaway schematic view of an 11 embodiment of the invention used with a divergent light source.

12 Figure B shows the embodiment of Figure 7 with the flexible .13 tip fitted with a terminus configured as a pointed probe, (b) li a rounded smuooth terminus, and a focusing lens.

DESCRIPTION OF THE PREFERRED EMBODIMENT- 1L6 A flexible tip for use with the invasive catheter of the 17 present invention is shown in Figure 1, generally indicated at 3.B 0. The central core 11 of the flexible tip 10 is made from an ig optically transmissive material -,such as -gllicone, silicone copolymer, or any variety of P-lastoner.. Surrounding the central 21 core 11 is a cladding layer 12, again fabricated from silicone, Z2 silicone copolymer or elastomer. The cladding layer 12 and the I -3 core 11 are specifically. chosen- for their refractive indices.

-24 The refractive index of the cladding 12, which may be a len~gth .of tubing, is preferably less than the refractive index of the 1 Core 11. Correctly choosing thle refractive indices of the 2 materials, will ingure 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 fromn the optical fiber(s) (not shown) and 7 ultimately to deliver the light energy to the treatment site.

9 OThe tip core 11 and the cladding 12 are held in position relative 9 to the fiber optic (not shown) by a structural tube 13 made with flexible elastoineric material such as Tefloniw or polyurethane.

12 Figure 2 is a out away vie of the tip of Figure 1. It is 13 clear that the optically transmnissive tip core 11 is surrounded 4 by a cladding layer 12 which in turn is surrounded by a structural tube 13 made of flexible elastomeric material. The 6 outer tube 13 may, of course, be made from a variety of flexible 11elastoniers including Teflon m and polyethylene. The catheter of the present invention, showing the flexible tip abutted to the v l terminus of the fiber optic is shoirn in Figure 3- The catheier, f210 generally indicated at numeral 30, has a fiber optic portion 34 21l abutted to the flexible tip portion 10. The fiber optic portion 22 34 of the catheter 30 comprises a f iber central core 31 surrounded by a cladding 32. The core 31 and cladding j2 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 6 DI jjL jj3q 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 ini embodiment 40 in Figure *6 4.

7 A second preferred embodiment of the cathater 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 of the transmissive core li/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 5 shows yet another embodiment 60 of the catheter 1-7 shown in Figure 5 except that the flexible tip has a cladding material 12 surrounding the fl~exible tip core 11 of the flexible 1 19 tip 20 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 tile 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 care is less elastic of flexible than the

AA

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 wnich conducts 6 the, light to the core 7u of the flexcible elastomeric tip 74.

7 optically transparent silicone rubber Is preferably employed as 8 material of choice for the tip 74 due to itg biecompatibility.

9 The index of retraction 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 f illed with a optically transparent -11* material having an index of refractionl between the index of the .14* tip core 74 and the fiber core 75. The relative stiffness of the large diameter silica core 75, enhanced by the presenlce of 16~ cladding jacket 76 and outer sheath 77, per-nits advancement of 17 the catheter through constricted tubular tissue but has a large Minimum radius of curvature The silicone core tip 7i4, being 1relatively short compared to the; silica core fibcr optic 1 ,72 portion, is pushed ahead of the fiber portion 72 during 21advancement. The silicone core tip, being ma-re flexible, has a 2much smaller minimuum radffiis 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 01 1 3L~j J304 ~*2 3 4 7 6 9 .11 "1;7 21 23 24 form a high coupling effickfty-UnliX'f 73. This union 73 can conveniently be made by extending the sheath (not Shown) -surround the silica core portion beyond the silica core portinn and filling the sheath with uncured silicone followed by curing.

F'igure 8 shows the embodiment of the flexible tipped waveguide of Figure 7 with a variety of flexible tip terminus configurations. Since the flexible tip 7 4 is elastomeric, it -'readily bonds to various other plastics. Figure 8(a) shows the flexible tip 74 with a pointed terminus 81 suitable for interstitial use. A rounded or beveled terminus 82 (Figure 8(b) is useful for intralumiflal use. F~igure 8(c) shows a focusing lens 83 affixed to the flexible tip 74. The termnini 81-23 may be fabricated from any transparent material or they may be opaque if the light reaching the f lexib-le tip 74 tip need not exit the tip in the forward direction.

It will be appreciated that, while a preferred embodiment of the invention has been described herein, various modifications will suggest themselves to those skilled in the art. F'or example, variations in mmateria-s;.XaY be-requiired for oertLai industrial applications- The essential feature of the invention is the placement of af lexible tip on a relatively rigid, large core optical fiber to confer the advantages of both materials to a combination product while minimizing their disadvaitqes- Rigid,, large core-fibarg hAving-relatively inflexible cores comprising a transparent material other than silica guch as a 9

K-

~i1I 1 plastic may be used. Fleib-e elastoiners other than silicone may also be used for the tip. These and other modification~s that may suggest them~selves to those Skcilled in the art are considered to beo within the spirit and scope of the present invention as set forth in the following claims-

I,

Claims (5)

1. A medical catheter for conveying light energy from a source of said light energy to a tissue undergoing light treatment, the catheter comprising: a fiber optic portion having a first proximal and a first distal Lnd and a light- transmitting first core having a first flexibility coextensive with said fiber optic portion; and a tip portion, located at said first distal end said tip portion comprising a light- transmitting second core having a second proximal and second distal end, said second core consisting of a light-transmitting elastomer having a second flexibility greater than said first flexibility, the second proximal end of said second core being in optical communication with said first distal end of said first core, and wherein said second proximal end of said tip portion is affixed to said first distal end of said optical fiber portion of said catheter. 25 2. The medical catheter of claim 1 further comprising an outer sheath surrounding said second core.

3. The medical catheter of claim 2 further comprising a layer of cladding interposed between said 30 second core and said outer sheath.

4. The medical catheter of claim 3 wherein said cladding consists of silicone elastomer. 35 5. The medical catheter of claim 1 wherein said elastomer comprises optically transparent silicone. a I' 8~ a K ir The medical catheter of claim 1 further 01 I j~JL 3f 12 comprising a point terminus affixed to said second distal end of said tip portion.

7. The medical catheter of claim 1 further comprising a rounded terminus affixed to said second distal end of said tip portion. S. The medical catheter of claim 1 further comprising a focusing lens affixed to said second distal end of said tip portion.

9. A medical catheter for conveying light energy from a source of said light energy to a tissue undergoing light treatment, the catheter comprising: a fiber optical portion having a first proximal and first distal end and a light transmitting first con coextensive with said fiber optical portion; and a tip portion located at said first distal end comprising a light-transmitting .second core, said second core consisting of a i light-transmitting elastomer, said second core having a second proximal and second distal end, said second proximal end of said second core i 25 being in optical communication with at least a portion of said first distal end, and wherein a space is interposed between said second proximal end of said tip portion and the first distal end of said optical fiber portion of said catheter. The medical catheter of claim 1 or claim 9 wherein said first core has ,a first index of refraction and said second core has a second index of refraction and I- S 35 wherein said space is -fille with a light-transmitting material, said light-transmitting material having a third index of refraction, said third index of refraction being -intermediate to said first index of refraction and said i i J 01 f 4 ,4 j o 13 second index of refraction. DATED this 1st day of Vebruary 1999 PDT SYSTEMS, INC. By their Patent Attorneys CULL 4 EN CO. If I