WO1991006251A1

WO1991006251A1 - Optical fibre assembly for medical lasers

Info

Publication number: WO1991006251A1
Application number: PCT/GB1990/001620
Authority: WO
Inventors: Mark Jeffrey Taggart
Original assignee: Surgilase Inc.
Priority date: 1989-11-06
Filing date: 1990-10-22
Publication date: 1991-05-16
Also published as: GB8925004D0

Abstract

An optical fibre assembly (2) includes an end assembly (10) having telescopically co-operating parts (14, 16). Assembly (2) includes an optical fibre (12) adapted at one end for receiving laser radiation from a source and adapted at its other end (13) for delivering radiation to a site. End (13) is shaped to provide a conical tip to the core of the fibre and a short length of the core is freed of its cladding and protective coating. This short length of core is either protruding from the end assembly (10) or shrouded by the end assembly (10) depending upon the telescopic condition of the parts (14, 16). The core tip has a roughened surface which is provided by cold grinding and the exposed core length is free from micro-grooves or cracks due to careful peeling of the cladding from the core.

Description

OPTICAL FIBRE ASSEMBLY FOR MEDICAL LASERS

The present invention relates to an optical fibre assembly for use with lasers in medical/surgical operations and to a method of manufacturing the fibre assembly.

In the field of medical science it is known to conduct high energy laser radiation from a laser by means of an optical fibre assembly to an area of a patient which is to be irradiated. However, until fairly recently it has always been necessary to maintain a slight gap between the end of the single optical fibre which forms part of the optical fibre assembly and the tissue of the patient during laser surgery to avoid the fibre end being damaged by burning and losing its radiation transmitting qualities. In order to simplify matters for the surgeon it has more recently become known to include as part of the fibre assembly a contact member, usually made of artificial sapphire, located in front of the end of the optical fibre which allows the assembly to be used in contact with the tissue being irradiated. The use of artificial sapphire as a contact member renders the optical fibre assembly expensive to manufacture

It is one object of the present invention to provide an optical fibre assembly including an optical fibre end which can be used in contact with tissue without the use of a separate contact member.

It is also an object of the present invention to provide a method of manufacturing an optical fibre assembly.

It is a further object of the present invention to provide an optical fibre assembly which has a mechanism for shrouding the optical fibre end when not in use in order to minimise the possibility of damage to the end and to provide means of cleaning the sides and tip of the fibre of adhering tissue, mucus or other matter during the procedure.

The ppresent invention provides a method of manufacturing an optical fibre assembly comprising an optical fibre with an end which can be used in contact with tissue without the use of a separate contact member, the method comprising stripping the fibre end of its protective coating whilst leaving the cladding on the fibre core, carefully peeling the exposed cladding from the core in a manner which avoids introduction of micro grooves or cracks in the core, and thereafter shaping the tip of the exposed core by a cold working method which avoids embrittling of the core and which leaves the shaped tip with a roughened surface.

The present invention also provides an optical fibre assembly for transmitting all appropriate levels of laser radiation includes an end assembly having two parts which together co-operate in a telescopic manner such that in a first position an optical fibre end is exposed ready for use and in a second position the optical fibre end is shrouded by the distal end of the end assembly, the protrusive fibre end comprising a fibre core freed of cladding and coating and provided with a shaped tip having a roughened surface.

This so called shroud or protective mechanism provides three functions:

a) to protect the fibre end from damage

b) to act as a cleaning device for the sides of the fibre

c) to act as a thermal pressure instrument to help seal larger blood vessels which cannot be coagulated by the laser and thermal energy of the fibre alone.

An embodiment of the invention will now be described by way of example, reference being made to the Figures of the accompanying diagrammatic drawings in which:-

Figure 1 illustrates an optical fibre assembly having a portion shown in cross-section to illustrate a detail;

Figure 2 is a further view of the cross-sectionalised detail of the Figure 1 assembly;

Figure 3 illustrates another part of the Figure 1 assembly in cross-section;

Figure 4 shows a modification of a detail in the Figure 3 part;

Figure 5 illustrates apparatus used in the manufacture of the Figure 1 assembly; and

Figure 6 illustrates a detail of the Figure 5 apparatus.

As is shown in Figure 1 an optical fibre assembly 2 comprises a tubular moulded plastics handle 4 to which is fitted at one end a metallic termination 6 for secural to and accurate alignment with the laser output of a laser light source in the manner particularly described in U.K. Patent Specification No. 2177518.

A length of plastics tubing 8 (or catheter) is fitted to the opposite end of the handle 4 in a manner known per se and at the distal or opposite end of the tubing 8 there is fitted an end assembly 10.

Within the tubing 8 and extending between the handle 4 and end assembly 10 there is a plastics-coated (e.g. PTFE) glass-cored optical fibre 12 having a soft plastics cladding, preferably a silicone plastics in order to render the fibre 12 inexpensive. The optical fibre 12 is secured to the handle 4 in a manner known per se (for example, as described in U.K. 2177518) such that its core end is located within a chamber formed in the metallic termination 6 to act as a receptor for laser radiation emitted by the laser source (not shown) .

The optical fibre 12 extends completely through the tubing 8 and the end assembly 10 and terminates with a free fibre end 13 having a shaped tip 20 (see Figure 3 inparticular) which, as will be explained, can either protrude from the assembly 10 or can be shrouded by the assembly 10 by virtue of assembly 10 being formed by co-operating telescopic parts 14, 16.

The end assembly 10 includes elongate tubular member 14 which is secured at end 14A to the tubing 8 whilst its other end 14B receives therein, in a telescopic manner with a sliding fit, a tail member 16 securely fitted as by crimping or other means to a main body part 18 which functions as a hand piece for a surgeon or other operator. Tubing 8 is a sliding fit within a central bore formed along the length of tail member 16 and main body 18 so that sliding movement of the tail member 16 within the tubular member 14 from the position shown in Figure 1 to the position shown in Figure 2 will cause the end 13 of the optical fibre 12 to become exposed (as illustrated in dotted lines in Figure 3) and ready for use.

When the optical fibre assembly 2 is to be stored or to be cleaned or is otherwise inactive or is to be used for vessel coagulation the tail member 16 is slid along the tubular member 14 to the position shown in Figure 1 such that the end 13 is shrouded within and shielded by the distal end of the body part 18 as shown in Figure 3 in solid lines.

The telescopically co-operating parts of items 14, 16, in addition to end stops which limit the extent of the telescopic movement, preferably also provide forreleasable retention of items 14, 16 at the two limits ofthe telescopic movement. This can be achieved by, manufacturing the items 14, 16 to close tolerances so that their sliding fit is almost an interference fit, or more simply, by providing detent protrusions on the co-operating parts of item 14, 16. With this arrangement items 14, 16 can be maintained in the Figure 2 condition with the end 13 of the fibre 12 protruding from end assembly 10 which is its normal "in-use" condition.

The optical fibre 12 is between 400 and 1000 microns in core diameter and its free end 13 is provided with a cone-shaped tip 20 as illustrated in Figures 3 and 4.

The tip 20 is shaped by various cold-working methods one of which is grinding using a silicon carbide paper disc having a grit size of in the range 400 to 1500, and a grit size of approximately 600 is preferred.. The coned angle as illustrated is 40° but may lie anywhere in the range 25° to 60°. The fibre 12 at end 13 is initially stripped of its hard plastic outer protective coating 12C, for example by use of a wire stripper tool, to leave the core 12A and its soft plastic cladding 12B. Shaped tip 20 is formed thereafter by a cold working method which avoids embrittling of the core 12A and the worked surface of the tip 20 is not polished but is left rough. The soft plastic cladding 12B surrounding the core 12A is thereafter carefully stripped from the core 12A to a distance of approximately 5 or 6 mm by careful peeling of cladding 12B in a manner which avoids introduction of micro grooves or cracks in the core 12A. The resultant fibre end 13 is thereafter useable directly in contact with human tissue and without any requirement to have an artificial sapphire contact member. Furthermore the method of manufacturing tip 20 is inexpensive, involves work bench practises and avoids hot working of the fibre 12.

The preferred method of shaping tip 20 comprises use of the grinding apparatus 30 shown in Fig. 5 which comprises a solid base plate 31 on which is mounted a grinding wheel 32 rotatable about a horizontal axis 33 and presenting a planar grinding surface 32A which extends in a vertical plane. A tubular positioning arm 35. is supported in a horizontal plane by a vertical pillar mounting 36 which is adjustable in azimuth so that the longitudinal axis of arm 35 can be set and clamped at any desired angle to axis 33. This setting is denoted on a calibrated marker scale 37 and effectively denotes the cone angle for tip 20. Arm 35 is disposed relative to wheel 32 such that when a 2.5 mm length of fibre protrudes from the end of arm 35 it engages surface 32A essentially in the vertical plane which contains axis 33 and vertically below that axis by a distance lying within the range 0.2R to 0.8R where R is the radius of the surface 32A. Pillar mounting 36 is adjustable vertically to permit selection of position within this range.

As is shown in Fig. 6 arm 35 comprises an inner guide tube 35A the bore of which is carefully dimensioned to be a sliding fit over the outer diameter of the fibre 12 including its hard plastic outer protective coating 12C. The outer surface of tube 35A acts as a rotatable bearing surface for a collet tube 35B which internally supports a resiliently collapsable collet element 35C and externally carries, by way of a screw thread, a collet clamp ring 35D. The collet element 35C has a bore which is dimensioned to be a sliding fit over the soft plastic cladding 12B of the fibre 12 and when ring 35D is tightened the element 35C is caused to grip cladding 12B. Thus, due to the collet arrangement the fibre 12 is rotatable about its longitudinal axis whilst being held with respect to grinding surface 32A at the angular disposition imposed on it by the arm 35.

In order to shape tip 20 a short length of core 12A is completely exposed and a further short length of outer coating 12C removed. The prepared fibre is then fitted to the collet arrangement and the latter then fitted to the inner tube 32A. Arm 35 is then clamped at the selected angle and height on the mounting 36 with the end of the fibre 12 adjacent the grinding surface 32A. The wheel 32 is rotated at a fixed speed in the range 3000 to 3500 revs/min. and in an anticlockwise direction as viewed from the fibre 12. The end of the fibre is pressed against the surface 32A (by axial sliding movement of tube 35B over tube 35A) with a force in the range 1.0 to 1.5 Newtons and at the same time the collet arrangement is rotated on tube 35A at a steady and even rate of about 2 revs/min. This procedure is maintained for a maximum time interval of 5 minutes which is normally sufficient to grind the tip 20 but insufficient to polish the tip. If further grinding is required the arm 35 is vertically adjusted on mounting 36 by a distance greater than the diameter of the fibre core 12A and grinding recommenced.

The radiation power density emitted by the cone tip 20 when in contact with tissue is high giving improved cutting characteristics whilst maintaining coagulation. However, a large beam divergence in the order of 90° included angle ensures that lower power densities are achieved even a few millimetres away from the tip and about 60-70% of the laser power is radiated out of the tip 20 with the remainder being back scattered into and absorbed by the end assembly 10. To accommodate this backscattered power it is preferred that in its in-use position the length of end 13 of fibre 12 which protrudes from assembly 10 is of the order of 16 mm (about 10 mm of which is plastic coated) and that the adjacent end 18A of main body part 18 is formed by a stainless steel tube 19 of sufficient capacity and axial length to function as a heat sink. Tube 19 is itself tapered at its free end to enable the surgeon or other operator to see the exposed fibre end 13 and is bonded at its other end to the main plastic body of part 18 in a manner which leaves an annular chamber for axial movement of tubing 8 within mainbody part 18. In this connection it will be appreciated that the telescopic movement of items 14, 16 effectively means that tube 19 moves towards and away from the end of plastic tubing 8. Furthermore the axial bore of tube 19 is dimensioned to be a sliding fit over the plastic coating 12C of fibre 12 and thereby acts as a mechanical guide and support for fibre end 13 when the assembly is in its Figure 2 condition.

It is preferred that the completed assembly be subjected to a mechanical stress test of the fibre end 13 prior to the assembly 2 being sold. This test involves moving items 14, 16 to their Figure 2 condition so that end 13 is protruding. Placing the tip 20 against a rigid support and applying, manually, lateral pressure omnidirectionally to the body part 18 in order to bend fibre end 13 through an angle of at least 45°. The existence of micro cracks or grooves on core 12A leads to fracture of the end 13 during this test.

The optical fibre assembly 2 as illustrated in Figures 1 to 3 or with a tip 20 as illustrated in Figure 4 and comprising a toughened cylindrical portion 20A can be used to cut tissue at powers from 1 to 100 watts. The life of the tip will clearly depend on the type of procedure and therefore the type of tissue with which it is interacting.

It should be further noted in respect of the optical fibre assemblies of the invention that:-

i) The 'rough⁷ surface of the conical tip 20 permits adhesion of very small carbonised tissue particles at low powers (2-6W) . This leads to heating of the tip 20 as the carbonised tissue absorbs laser radiation. The tip temperature therefore quickly reaches a temperature greater than 100°C. At this temperature vaporisation of tissue in contact with the tip occurs and tissue cutting is performed with minimal power levels.

ii)The fibre tip is fragile and hence must not be subjected to impact forces. Extending the fibre 16 mm from the tube 19 distal end allows the fibre to flex during use, thereby reducing the possibility of tip breakage by impact forces. In addition, extending the fibre from the tube 19 increases the absorption of backscattered laser energy by the tube 19, thereby limiting the temperature rise of the tip 20 during use.

iii)Interstitial application of the conical tip - by inserting the fibre tip into a tumour mass for treatment by hyperthermia, a 'cooked⁷ volume approximating to a sphere can be formed. As described before, carbonised tissue builds up around the tip at low powers due to the high beam divergence and the surface 'roughness⁷. Because the tip is stationary in the tissue no cleaning of the tip occurs and in a short time all the laser power delivered to the tip is absorbed by the carbonised tissue. This power is then re-emitted by the carbon as thermal radiation in all directions hence a spherical ball of treated tissue results. Generally speaking, the diameter of the ball is a function of the total energy applied for a given tissue type.

Claims

1. A method of manufacturing an optical fibre assembly comprising an optical fibre with an end which can be used in contact with tissue without the use of a separate contract member, the method comprising stripping the fibre end of its protective coating whilst leaving the cladding on the fibre core, carefully peeling the exposed cladding from the core in a manner which avoids introduction of micro grooves or cracks in the core, and thereafter shaping the tip of the exposed core by a cold working method which avoids embrittling of the core and which leaves the shaped tip with a roughened surface.

2. The method as claimed in Claim 1, wherein the tip is shaped into a cone by grinding.

3. The method as claimed in Claim 1, including the further step of stress-testing the optical fibre end by bending the fibre end omnidirectionally through an angle of at least 45°.

4. The method as claimed in Claim 2, wherein a portion of the cylindrical core adjacent the shaped tip is provided with a roughened surface by cold grinding.

5. An optical fibre assembly for transmitting all appropriate levels of laser radiation includes an end assembly having two parts which together co-operate in a telescopic manner such that in a first position an optical fibre end is exposed ready for use and in a second position the optical fibre end is shrouded by the distal end of the end assembly, the protrusive fibre end comprising a fibre core freed of cladding and coating and provided with a shaped tip having a roughened surface.

6. An assembly as claimed in Claim 5, wherein the shaped tip is conical.

7. An assembly as claimed in Claim 5, wherein the distal end of the end assembly is made of a thermally conductive material to act as a heat sink for the assembly when in use.