WO1990000914A1

WO1990000914A1 - Light delivery system

Info

Publication number: WO1990000914A1
Application number: PCT/GB1989/000822
Authority: WO
Inventors: Adrian Charles Rowland; James Todd Allardice; Christopher Paul Swain
Original assignee: Adrian Charles Rowland; James Todd Allardice
Priority date: 1988-07-18
Filing date: 1989-07-17
Publication date: 1990-02-08
Also published as: AU4032389A; GB8817032D0

Abstract

A light delivery system for illuminating a flexible stricture in a tube, e.g. on oesophyal tumour, comprising a dilator (1) including a transparent window (7) which is used to dilate the stricture so that it is in contact with the transparent window (7). The transparent window (7) is adapted so that it contacts a known pre-determined area of stricture so that the illumination of the stricture can be measured. This is achieved either by the transparent window being cylindrical and terminated by opaque end caps (3, 5) flush with the outer surface of the window or by the dilator and window being inflatable to a pre-determined size. The dilator (1) has a hollow central core (9) to allow it to be threaded along a wire and to allow an optical fibre to be used to deliver light to it.

Description

LIGHT DELIVERY SYSTEM

This invention relates to a device for delivering light to a stricture in a tube and in particular for allowing a defined quantity of light to be delivered to the stricture. It is particularly useful in medical applications for the treatment of tumours e.g. in the oesophagus.

It has been found that photodynamic therapy can be used to successfully treat cancer. This is a technique in which a tumour containing a light activated agent, usually hae atoporphyrin derivative (or HPD), is illuminated with, e.g. light from an argon dye laser. The light causes the HPD to release oxygen radicals which destroy the surrounding tissue. Since HPD tends to concentrate in tumour tissue rather than healthy tissue, if HPD is administered to the patient some time, e.g. about three days, before the illumination of the tumour with laser light, it is the tumour tissue which is preferentially destroyed. The time between the administration of HPD and the laser treatment may, however, vary depending on the type of tumour to be treated.

At present, tumours are usually illuminated by shining light onto the tumour using a simple flat-ended optical fibre, although it has been proposed to add diffusing tips to the ends of the optical fibres in order to try and achieve a more uniform illumination. However, even with these devices uniform illumination is difficult to achieve, particularly when, as is often the case, the size of the tumour is greater than the area of the spot of light from the fibre as achieving a uniform illumination of the whole tumour then relies on the surgeon scanning the spot evenly across the whole tumour. The problems are particularly great with tumours around the oesophagus - circumferential endoluminal tumours - as parts of the tumour are at different angles to the incident light thus affecting the illumination per unit area. An alternative technique in which the end of the optical fibre is introduced into the tumour to transmit light directly into the interior of the tumour has also been proposed, but it is difficult to calculate how much tissue is illuminated and this technique also causes haemorrhage of the tumour. Furthermore thermal effect at the tip of the fibre can affect the treatment, and tissue tends to become caked onto the end of the fibre thus impeding the light delivery.

According to the present invention there is provided a device for delivering light to a flexible stricture in a tube, which dilates the stricture so that a known area of the stricture is in contact with a transparent window in the device through which the stricture can be illuminated. - 3 - "Transparent" as used in this description is intended to include translucent as well as specular-transparent windows.

The invention also provides a method of illuminating a stricture with light comprising the step of causing the stricture to be dilated into contact with a transparent window through which the stricture is then illuminated by the light.

The invention also provides apparatus for illuminating a structure in a tube comprising a device according to any one of the preceding claims and including a plurality of replaceable dilator bodies of different sizes whereby the size of dilator body to be used can be chosen in relation to the size of the tube and/or stricture and/or area to be illuminated. Preferably the light source for illuminating the stricture is positioned in the middle, i.e. on a longituderal axis, of the device including the transparent window.

In a first embodiment of the invention the structure is dilated with a rigid dilator body comprising a cylindrical transparent window having an opaque end cap on each end. Thus when the stricture is dilated by the body, the opaque end caps precisely define the ends of the cylindrical area being illuminated and prevent any light escaping beyond that area. Thus the area of the tumour being illuminated corresponds to the area of the transparent - 4 - window. Light is delivered to the dilator body by an optical fibre provided with a diffusing tip, which provides a uniform circumferential distribution, e.g. a PTFE cylinder or, fibre optic cylindrical diffuser, positioned on the axis and near the middle of the cylindrical window. Conveniently the body is provided with a central bore and is attached at its trailing end to a hollow flexible introducer shaft so that it may be fed down the tube over a guide wire previously positioned in the tube. The bore may also be used to house the optical fibre carrying the light to the dilator. The body may be provided with a flexible tip at its leading end to assist guiding the dilator body round any curves in the tube.

The second embodiment of the invention comprises an inflatable dilator body which can be inflated to a known size and shape. The inflatable part includes a transparent window through which the stricture can be illuminated.

Conveniently, the device has a central bore so that it may be threaded over a guide wire previously positioned in the tube; the same bore may also be used for an optical fibre delivering light to the inflatable body. Conveniently the device comprises a hollow cylindrical transparent core defining the bore and which, in use, contains the optical fibre and a light diffusing material, e.g. intralipid fluid, or cylindrical diffuser. The inflatable body may be formed by a flexible envelope around the outside of the central core and may be inflated by e.g. intralipid fluid or water supplied via an inflation passage communicating with the envelope. Preferably the end of the central core is filled with a light diffusing medium, e.g. intralipid fluid, so that a uniform illumination can be achieved. Conveniently the end of the core is open so that during treatment a small flow of light diffusing fluid down the central channel can be maintained. In use the device in its deflated state is guided down the tube over the guide wire and when in position in the stricture is inflated to the predetermined size and shape by pressing intralipid fluid or water down the inflation passage. Then the guide wire is removed and the optical fibre connected to a laser is passed down the central bore and positioned so that the tip of the optical fibre is within the transparent window. Subsequently the optical fibre is gradually moved while illumination is being carried out so that the tip moves axially in the cylindrical window to illuminate the whole stricture. Since the size and shape of the inflated envelope and the window are known, the area of the stricture under illumination can also be calculated and so the amount of light delivered can be determined.

Both embodiments are particularly suited for medical applications e.g. the treatment of tumours in the oesophagus or bowel by photodynamic therapy using, for example, HPD.

In medical applications the device according to the second embodiment is preferably of such a size that in its deflated state it can be passed down an endoscope used to view the tumour and inflated when in position in the tumour.

Either of the first or second embodiments of the device may be provided with radio opaque markers on the dilator body so that their position in the tube can be checked.

The present invention will be further described by way of non-limitative example with reference to the accompanying drawings in which:

Figure 1 is a schematic, cross-sectional view of one part of a first embodiment of the invention;

Figure 2 is a schematic cross-sectional view of another part of the first embodiment of the invention;

Figure 2A shows and alternative arrangement which can be used in an embodiment of the invention;

Figure 3 is a schematic cross-sectional view of the second embodiment of the invention.

Figures 1 and 2 show a first embodiment of the invention suitable for use in medical photodynamic therapy. It comprises a relatively rigid dilator body 1 which, in use, is passed down the oesophagus of a patient and inserted into the stricture caused by the tumour under treatment. The dilator body 1 includes a transparent hollow cylindrical window 7 made from e.g. Perspex (Trade Mark), terminated at each end by a stainless steel end-cap, 3 and 5. The external diameter of the end-caps is equal to the external diameter of the cylindrical window. The dilator body 1 is attached, preferably detachably so that different sized dilator bodies can be used as appropriate, to the end of a hollow, flexible, introducer shaft 11 and is provided with a flexible tip 13 which helps guide the dilator down the oesophagus. Each end-cap has an axial bore or aperture 8 and the flexible tip 13 has an axial bore 14 so that a passage 9 is formed through the introducer shaft 11, the dilator body 1 and flexible tip 13. This passage is used to house the optical arrangement which delivers light to the dilator body and also allows the device to be guided down the oesophagus into the stricture by threading it along a quide wire previously positioned in the oesophagus e.g. with the aid of an endoscope. The use of a guide thread or fibre allows the device to be safely passed down the oesophagus, which may be obstructed by bends or other strictures, without puncturing it.

The optical arrangement for delivering light from the light source e.g. Argon dye laser to the dilator body is shown in Figure 2 and comprises an optical fibre 15 housed by a PTFE sleeve 17. The optical fibre 15 projects slightly - 8 - beyond the end of the sleeve into a cylindrical PTFE diffusing tip 19. The PTFE diffuser is fixed to the PTFE sleeve by means of a diameter-reduced portion 18 inserted into the sleeve 17. The diffuser may either be held to the sleeve by friction alone or may be glued or welded to the sleeve. The diffuser causes the light to be emitted substantially uniformly circumferentially of the diffuser. Figure 2A shows another diffuser arrangement where the diffuser is formed on the optical fibre itself by removal of the outer sheath so to leave an exposed area of glass 51 which has an etched surface. The effect of this is that light escapes from the fibre and is emitted from the etched area.

It will be noted that the transparent window 7 is cylindrical and that the steel end-caps 3 and 5 have exactly the same external diameter as the window. This is important in order that the area of the stricture under illumination is accurately determined as will be explained below.

In the illustrated embodiment the diffusing tip projects about 1cm from the end of the sheath 17 and has a full diameter of about 2.5 mm. The optical fibre is positioned so that its tip is on the axis of and approximately in the middle of the diffusing tip. Typically the dilator body has a length of about 4 cm and a diameter of about 1 cm but different sizes are provided for treating - 9 - different sized strictures.

In use the dilator is passed down the oesophagus of a patient by threading it over a guide wire into position. Usually, the guide wire will be removed and then the light delivery part 2 may be passed down the introducer shaft 11 until the diffusing tip 19 is in position in the transparent window 7. Alternatively the dilator may be passed over the guide wire in the oesophagus with the light delivery part already fitted. The dilator body 1 produces a mild dilation of the stricture so that the stricture is in contact with the transparent window 7. Assuming that a dilator body 1 with the correct length has been chosen, the contact patch with the stricture will also overlap onto the end caps 3 and 5 adjacent to the window. Thus only a precisely defined length of stricture exactly equal to the length of the transparent window 7 can be illuminated. Assuming the stricture extends wholly circumferentially around the inside of the oesophagus, the surface area of stricture which will be illuminated is simply the area of the transparent window. This means that if a known power is delivered by the light delivery system for a known time, the exact amount of light which reaches the stricture can be calculated. The illumination may be carried out with the diffusing tip held still in the middle of the window, or it may be moved axially of the window during illumination. Where the stricture can be sensitized to the light so that it preferentially absorbs light as compared with the rest of the tube, so that it is less critical that light is confined to the stricture, the transparent window can be chosen to be longer than the stricture so that the ends of the stricture are illuminated.

In order to cope with strictures of different sizes, dilator bodies 1 of different lengths and diameters are provided and the appropriate one fitted to the introducer shaft 11. The tumour would therefore be inspected using an endoscope and the size of dilator which is required would be determined, and this dilator would be then fitted to the introducer shaft 11.

Figure 3 show a second embodiment of the invention which also allows a precise determination of the area under illumination of a stricture in a tube by dilating the stricture so that it adopts a known surface geometry. In the case of the second embodiment of the invention this is achieved by passing an inflatable body down the tube e.g. oesophagus of a patient, into the stricture and inflating the body to a known size and shape. The inflatable body includes a transparent window and the size of the inflatable body and degree of inflation are chosen so that a known surface area of the stricture is in contact with the transparent window and the surface geometry is also known thus eliminating uncertainties caused by oblique illumination.

The device is shown in more detail in Figure 3. The device comprises an inner transparent, hollow cylindrical guide 38 made from e.g. a plastics material such as polyethylene and defining a central channel 39. Just as in the first embodiment, the central channel 39 not only houses the light delivery system 32, but also allows the device to be passed over a guide wire previously positioned in the oesophagus. The inflatable body 40 is formed by a flexible envelope made from a non-elastic transparent material, e.g. a well cross linked polymer mounted on the inner guide 38. A typical size of envelope is 12-15mm in diameter and 6 to 10cm in length, though the dimensions will be chosen according to the particular application. The envelope is either completely transparent or includes a transparent window through which the tumour is illuminated. The use of a window, with the rest opaque, helps in preventing escape of light and thus improves the accuracy of the dosage. The envelope is in fluid communication with a passage 41 down which a medium is passed to inflate the envelope. The medium used can be a low absorption scattering medium, conveniently intralipid fluid, which is easily available in most hospitals, is used. The passage 41 runs alongside or surrounds the inner guide 38 and terminates in an inflation - 12 - fluid inlet 44. An inner channel inlet port 42 is also provided for, in use, allowing a light scattering medium to be passed down the inner channel. The light scattering medium may, conveniently, also be intralipid fluid. The use of the light scattering medium achieves a substantially uniform circumferential light output. The end 46 of the inner channel 38 is not closed in use and a small flow of intralipid fluid may be maintained down the inner channel 39.

In an alternative arrangement a diffuser area as in Fig 2A can be provided on the optical fibre itself and light scattering media may not need to be used in conjunction with this.

The device is introduced into the tumour by passing it down an endoscope placed in the oesophagus of the patient and over a guide wire extending from the endoscope through the tumour. Conventionally, the size of channel available in the endoscope for passing the device down is usually either 2.8 or 3.5mm and so it is necessary that the device should be smaller than this when it is in its deflated state.

Then the guide wire is removed and the optical fibre passed down the central guide 38. The optical fibre is typically between 100 and 1000 micrometers diameter for use with a lw, 630nm laser. The optical fibre is positioned with its tip near one end of the inflatable part and laser light is passed down the optical fibre while withdrawing it gradually so that the tip moves along the length of the inflatable part illuminating the surface of the tumour. The envelope is held by friction in a fixed position in the tumour as the fibre is withdrawn.

The device may also be provided with a radio opaque marker so that its position in the body can be checked. A typical complete operation procedure is as follows:

1. The area to be illuminated is cleaned pre- rea ment.

2. The endoscope is introduced to visualise the proximal stricture.

3. The inflatable illuminator is passed down the biopsy channel of the endoscope and introduced into the stricture. Alternatively, the system is passed alongside the endoscope and introduced this way. Via the endoscope would be preferable as steerage control would be finer.

4. The system is guided through the stricture either by pushing directly or with the use of an introducer, or with a guide wire.

5. The position of the system is checked radiologically if necessary.

6. The envelope is inflated with intralipid or other fluid in the correct position. 7. The inner channel is filled with intralipid or other fluid and a small head of pressure applied; no fluid may be necessary with some types of diffuser, e.g. the etched diffuser on the optical fibre.

8. The quartz fibre is introduced into the system to a predetermined position.

9. The laser irradiation is commenced.

10. The quartz fibre is drawn slowly back at a predetermined rate to give the required energy dose.

11. Laser irradiation completed, fibre withdrawn, envelope deflated and system withdrawn from patient.

The central guide 38 maintains the fibre tip a constant distance from the window thus aiding uniform illumination.

Thus it will be appreciated that with both embodiments of the invention the surface geometry of the part of the tumour or stricture being illuminated is known - because it is forced into a known shape by the dilator - and so the illumination per unit area and the area of illumination are also known. The light dosage can therefore be determined accurately without the uncertainties caused by parts of the tumour being illuminated obliquely, or light escaping to either side of the tumour. Furthermore, both embodiments achieve circumferentially uniform illumination patterns by the use of diffusing media or areas, for example the tip 19 or the intralipid fluid in the central passage 39 - which also increases the accuracy of the dosage.

This device can be used in areas outside medical treatment for the delivery of light or other forms of electromagnetic radiation. By delivering electromagnetic radiation into a tube in a circumferential fashion, the device of this invention finds application in the irradiation of photosensitive compositions used for example in pipe joints. The device also finds application, for the same reason, in systems requiring illumination for inspection purposes, either where the light is used as the sensing medium e.g. holography or as illumination for other visual techniques.

Claims

1. A device for illuminating a flexible stricture in a tube, comprising an illuminator body provided with a transparent window and adapted to be passed down the tube and a light source in the illuminator body, for illuminating the window the illuminator body being so adapted that a known quantity of light can be directed onto the stricture.

2. A device according to claim 1 wherein the illuminator body is adapted to dilate the flexible stricture so that a known area of the stricture is exposed to the known quantity of light emitted from the light source through the transparent window.

3. A device according to claim 2 wherein the transparent window is so treated on the illuminator body that the entire exterior surface of the window is adapted to contact the dilated stricture whereby the area of stricture illuminated equals the exterior area of the transparent window.

4. A device according to claim 3 wherein the transparent window extends completely circumferentially of the illuminator body and is terminated at each end by opaque end caps to prevent leakage of light at the ends of the window.

5. A device according to claim 4 wherein the - 17 - transparent window is cylindrical and the end caps are flush with the exterior of the window.

6. A device according to any one of claims 1 to 4 wherein the illuminator body is inflatable to dilate the stricture so that a known, pre determined area of the stricture can be expanded into contact with the transparent window.

7. A device according to claim 6 comprising a central core surrounded along at least part of its extent by a transparent inflatable sheath to form said body.

8. A device according to claim 7 including an inflation duct for delivering fluid to the sheath to inflate it.

9. A device according to any one of the preceding claims wherein the illuminator body has a core through its centre and is connected to a flexible introducer shaft to allow it to be threaded along a wire to guide it down the tube.

10. A device according to any one of the preceding claims wherein the dilator body is provided with a flexible tip to help guide it down the tube.

11. A device according to any one of the preceding claims wherein the light source is positioned on a longitudinal axis of the dilator body. to be on a central axis of the dilated stricture.

12. Apparatus according to any preceding claims wherein - 18 - the light source comprises a diffuser connected to the end of a light quide which extends with said body.

13. Apparatus for illuminating a stricture in a tube comprising a device according to any one of the preceding claims and including a plurality of replaceable dilator bodies of different sizes whereby the size of dilator body to be used can be chosen in relation to the size of the tube and/or stricture and/or area to be illuminated.

14. A method of illuminating a flexible stricture in a tube iri which the stricture is dilated with an illuminator body having a transparent window through which the stricture is illuminated, and which includes the step of reflecting an illuminator body such that the transparent window is so dimensioned and configured that all of the light passing through the window is incident upon the structure.

15. A method according to claim 14 wherein the illuminator body transparent window is terminated by opaque end caps and is flush with its perpphery of its end caps .

16. A method according to claim 14 where in said illuminator body is inflatable and which includes the step of inflating the body to a predetermined size and shape to bring its outer surface of the transparent window into contact with the stricture.

17. A method of treating a tumour where its tumour causes a stricture which is illuminated using the method of any one of claims 14 to 16.