WO2000077446A2

WO2000077446A2 - Optical apparatus

Info

Publication number: WO2000077446A2
Application number: PCT/GB2000/002273
Authority: WO
Inventors: Douglas Alastair Stewart; James Oscar Molloy
Original assignee: Tissuemed Limited
Priority date: 1999-06-12
Filing date: 2000-06-12
Publication date: 2000-12-21
Also published as: CA2376608A1; WO2000077446A3; GB9913597D0; JP2003502690A; EP1234143A2; AU5544600A

Abstract

Optical apparatus for the delivery of high intensity light to a location remote from the source of said light comprises a source (21) of polychromatic non-laser light, fibre optic means (12) for transmitting said light to said location, and an ellipsoidal reflector (22) arranged to focus light from said source onto the input end of said fibre optic means (12). The clear aperture of the ellipsoidal reflector (22) is at least 100 times greater than the effective size of the source (21) of said light. The source (21) is preferably a Xe arc lamp, particularly such a lamp of the 'short arc' type. One important application of such apparatus if for directing light to a photo-activatable tissue adhesive with sufficient intensity to bring about polymerization of the adhesive. Numerous other applications in the medical, scientific and industrial fields also exist.

Description

Title: Optical Apparatus

This invention relates to an optical apparatus, and in particular to apparatus for the delivery of high intensity light to a location remote from the source of said light. One important application of such apparatus is for directing light to a photo-activatable tissue adhesive with sufficient intensity to bring about polymerization of the adhesive. Another application of such apparatus is photodynamic therapy (PDT) in which light is used to excite a previously administered photosensitive reagent. Numerous other applications in the medical, scientific and industrial fields also exist.

Sealants and adhesives for the in vivo bonding of living tissues are known. Typically such adhesives comprise protein solutions which are cross-linked by heating. Heat energy can be transferred to the proteins by incorporating into the adhesive a photon-absorbing material and exposing the adhesive to light of sufficiently high intensity. The amount of energy required to reach temperatures high enough for curing of the adhesive to occur necessitates the supply of a large number of photons of radiation within the absorption spectrum of the photon- absorbing material. It is also generally the case that the light beam which is used in such applications must be of very small dimensions. Hitherto, in order to satisfy these requirements it has been necessary to use lasers, which are very intense monochromatic sources.

The use of lasers, whilst acceptable for some applications, is less satisfactory in some cases, usually due to the extreme monochromaticity of such light sources. Lasers are difficult to tune and it may therefore be difficult or impossible for the wavelength of the laser source to be matched precisely or adequately to the absorption wavelength of the photon-absorbing material.

For other applications involving the delivery of light to a remote location white light sources have been used. However, the light intensity which can be achieved with such sources has hitherto been severely restricted and inadequate for many applications. There has now been devised apparatus which overcomes or substantially mitigates the above- mentioned disadvantages.

According to a first aspect of the present invention, optical apparatus for the delivery of high intensity light to a location remote from the source of said light comprises a source of polychromatic non-laser light, fibre optic means for transmitting said light to said location, and an ellipsoidal reflector arranged to focus light from said source onto the input end of said fibre optic means, wherein the clear aperture of the ellipsoidal reflector is at least 100 times greater than the effective size of the source of said light.

The apparatus of the invention is advantageous primarily in that the use of the ellipsoidal reflector enables very high levels of irradiance at the input end of the fibre optic means. The use of a polychromatic, non-laser light source has other attendant advantages, such as lower cost, greater compactness, safety and ease of maintenance. In addition, polychromatic light provides greater flexibility of application. If desired, appropriate wavelength bandwidths can be selected relatively easily. The intensity of the light introduced into the fibre optic means may be sufficient for applications in which the fibre optic means forms part of an endoscopic apparatus. The apparatus according to the invention may also enable particularly fine (small diameter) fibre optic means to be used, such fibre optic means being of high mechanical flexibility and hence particularly suitable for applications (such as endoscopic applications) in which high flexibility is advantageous.

By the term "clear aperture" of the reflector is meant the maximum dimension (in the case of a reflector which is of circular or part-circular cross-section, the diameter) of the open mouth of the reflector.

By the "effective size" of the light source is meant the largest physical dimension of the element or component of the light source at which the light is generated. In the preferred case in which the light source is an arc lamp this is the size of the arc gap. Various sources of polychromatic light may be used in the performance of the invention, provided that they have the desired spectral range and sufficient intensity. However, as mentioned above, the most preferred form of light source is an arc lamp, most preferably a Xenon arc lamp, and in particular such lamps of the so-called "short arc" type. Such lamps have continuous and nearly line free spectral output and high intensity.

The arc lamp preferably has an arc gap of less than 0.6mm, more preferably in the range 0.2 to 0.5mm, eg 0.4mm. The power output of the arc lamp is preferably in the range 100 to 200W. Using such lamps beams having suitable dimensions and sufficient power for surgical, or other, applications can readily be produced.

The light from the light source (most preferably the Xe-arc lamp) is collected and focused by the ellipsoidal reflector. The reflector should be of such a form as to gather the optimum amount of light energy within the 400-700nm spectrum and concentrate the light into a spot, and should be of such a design as to minimise aberrations. In order to achieve this the clear aperture of the ellipsoidal reflector is very large in relation to the size of the arc gap. More particularly the clear aperture of the ellipsoidal reflector is at least 100 times greater than the size of the arc gap, more preferably at least 200 times greater, eg about 250 times greater.

In practice, the optimum form of the ellipsoidal reflector (ie the form which maximises the collection of light) may be determined by the geometry of the arc lamp electrodes and by the maximum acceptance angle of the fibre optic means. In general, the form of the reflector will be such as to optimise magnification of the light intensity and maximise the light energy input to the fibre optic means, and to minimise aberrations. The arc lamp is most preferably mounted with the arc co-axial with the optical axis of the ellipsoidal reflector. Light is emitted from such an arc over a range of solid angles which is limited by the geometry of the lamp electrodes, which generally have tapered ends. In particular, the shape of the electrode which is nearer to the fibre optic means (which is preferably the cathode) influences the shape of the ellipsoidal reflector. Typically, the tip of the cathode is tapered at an angle of 50° or so to the optical axis. Light is preferably focussed by the ellipsoidal reflector directly onto the input end of the fibre optic means. By this is meant focussing of the light without the use of intervening refractive, reflective or diffractive optical elements. Nonetheless, it may be necessary or desirable for one or more filters or the like to be positioned in the light path, as is described below.

The light source (ie in the preferred case the arc lamp) is preferably removably mounted within the apparatus, separately from the ellipsoidal reflector. To facilitate this, the reflector is preferably provided with an opening through which the lamp may be inserted (or by which the ellipsoidal reflector may be mounted about the lamp). Separate mounting of the lamp and the reflector has a number of advantages, not least that the lamp can be exchanged or replaced without removing the reflector.

The arc lamp is essentially a white light source, and for many applications it may be necessary or desirable to restrict the output beam to a particular range of wavelengths. An appropriate range of wavelengths (bandwidth) can be selected by means of filters interposed in the light path. Filters of the type referred to as "hot mirrors" and "cold mirrors" may be included, in order to eliminate low wavelengths and to dissipate heat from the system. In general, any filters may be used which exhibit sufficient transmission of the waveband of interest and which can tolerate the large amount of energy which they must reject. Dichroic filters are preferred. Absorbing coloured glass filters may be used, but for many applications may not be suitable as they may not be capable of absorbing the relatively large amounts of energy which must be dissipated within the filter.

An example of an application in which the output beam must be restricted to a particular bandwidth is the activation of tissue adhesive. In this case, the lower wavelength limit of the bandwidth is generally chosen to protect from any unwanted absorbance by material such as blood adjacent the tissue adhesive, since this would cause unwanted heating of the target area. The upper wavelength limit of the bandwidth will eliminate infra-red radiation which could cause direct heating of the target area. The optimum bandwidth of the radiation which is employed in such an application will depend on the absorption spectrum of the material to which the light is to be delivered. In one example, in which the adhesive incorporates methylene blue (which absorbs strongly between 620 and 670nm) the bandwidth is typically approximately 1 OOnm centred around 650nm. In general, the bandwidth is most commonly between 10 and 200nm. The output spectrum may be in a single band, or may comprise two or more bands, to match the absorbance characteristics of the adhesive.

The fibre optic means will generally be arranged with its endplate disposed in the exit plane of the optical train such that the output spot is focused on it. The fibre will generally be of sufficient length that the light source can be positioned a convenient distance from the patient and is readily manipulable by a user. Typically the fibre has a length of 1 to 3m, eg about 2.5m.

The fibre may have a diameter in the range 0.01 to 1mm, or greater. For certain applications, such as intravascular illumination, the fibre diameter will be at the lower end of this range, typically around 0.2mm.

In order to maximise energy input into the fibre optic, the fibre preferably has a relatively high numerical aperture NA=sinθ, where θ is the semi-angle of the acceptance cone at the fibre optic end plate. Preferably, the numerical aperture is in the range 0.20 to 0.52.

The fibre optic means may comprise a single fibre or a bundle of fibres. In the latter case, the input ends of the fibres in the bundle are preferably fused together, rather than being bonded together with adhesive, as the high light intensity may melt or destroy such adhesive and such adhesive could absorb some of the light energy. Alternatively, the bundle of fibres can be butted up to a short length of glass rod. Where a bundle of fibres is used, the output ends of the fibres in the bundle can be arranged in any desired configuration, eg to produce a shaped beam appropriate to a particular application.

The fibre optic means is preferably contained within a protective sheath, which will most commonly be of plastics material. For medical applications, it may be desirable or necessary for the fibre optic means to be sterilizable (as may also be the case for some or all of the other components of the system). In such a case, the protective sheath should be of a material which is capable of withstanding sterilization processes.

The light emerging from the fibre optic means is most preferably projected onto the target by means of a handpiece fitted to the end of the optical fibre and adapted to be held by a user. Such a handpiece will preferably contain optical elements arranged to focus the output light beam at a distance to suit the particular application being undertaken. In addition, the handpiece may form the beam into a particular shape to suit the application. Such a shape could be a small diameter circular spot, or it may be a rectangle or any other desired shape.

Although described above principally in relation to the curing of tissue adhesive, the apparatus according to the invention may be used in a variety of other applications. Other medical applications include endoscopy and other applications in which lasers or other intense light sources are conventionally used, such as biostimulation, photodynamic therapy and curing of dental materials. Other applications include curing of materials such as semiconductor photoresists and industrial adhesives, and research applications in photochemistry, spectroscopy and microscopy.

The invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings, in which

Figure 1 is a schematic view of apparatus according to the invention; and

Figure 2 is a side view (partly in section) of a light source which forms part of the apparatus of Figure 1.

Referring first to Figure 1 , apparatus for delivering polychromatic light to the site at which two living tissues are to be bonded together comprises generally a light source unit 10, an optical fibre tube 12 and a hand piece 14. The apparatus is used to direct light of sufficient intensity onto tissue adhesive applied to the junction of two living tissues. In use, a surgeon holds the handpiece 14 and uses it to apply light to the adhesive. The light source unit 10 includes, in front of the input end of the optical fibre tube 12, a so-called "hot mirror" 15 and a filter pack 16 comprising one or more wavelength-selective filters. The hot mirror 15 effectively blocks infrared radiation from approximately 780 to 1 lOOnm, and also inhibits ultraviolet transmission below 380nm. The effect of the filter pack 16 is to eliminate from the light beam wavelengths less than 585nm. The waveband of the transmitted radiation is thus approximately 585 to 700nm. This waveband is appropriate for use with a tissue adhesive which absorbs wavelengths in that range. An example of such an adhesive is an adhesive containing a chromophoric dye such as methylene blue which absorbs wavelengths of 620 to 670nm.

Figure 2 shows a light source which is used in the apparatus of Figure 1. This comprises a 150W, 0.4mm gap Xe arc lamp 21 and an ellipsoidal reflector 22. The lamp 21 extends through a central opening 23 in the reflector 22 such that the lamp 21 is disposed on the optical axis of the reflector 22, with the lamp cathode 24 disposed towards the input end of the optical fibre tube 12.

The tips of the cathode 24 and of the anode 25 are tapered and spaced apart by 0.4mm to define a 0.4mm arc gap. The tip of the cathode 24 is tapered at an angle of 50° which limits the range of angles at which light is emitted from the arc. The reflector 22 has a clear aperture D of 118mm, this being sufficiently large to capture all the light from the arc. The form of the reflector 22 is also dictated by the maximum acceptance angle (in this case 31 °) of the optical fibre tube 12.

The lamp 21 is releasably mounted in the light source unit 10 such that it can be removed without removing the reflector 22.

After passing through the filter pack 16, the light is focussed onto the end plate of a glass optical fibre which is housed within the optical fibre tube 12. The optical fibre itself has a diameter of approximately 1mm and a numerical aperture of 0.51. The optical fibre tube 12 comprises a protective outer sheath of plastics material, and has an overall external diameter of 6.5mm and a length of 2.5m.

The light is transmitted along the optical fibre tube 12 to the handpiece 14 by which it is directed by the user onto the target area. The end piece 14 contains near its output end a pair of aspheric lenses (not visible in the drawings) which focus the beam into a spot of 1mm diameter at a distance of a few centimetres from the end of the handpiece 14.

The effect of the optical arrangement described above is to transmit a high optical power density into the optical fibre. The intensity is such that the output light is converted at the site of action to heat, thereby causing the tissue adhesive material to polymerise and bond the tissues together. The output power of the device is comparable to that of laser devices.

Thus, in use, a surgeon will apply adhesive to the tissues which are to be bonded, and bring those tissues into contact. The surgeon then aims the light from the handpiece 14 at the adhesive and, by operation of the foot pedal, increases the light intensity to full power. Application of high intensity light is continued for sufficient time to effect curing of the adhesive. Sufficient application of light may be indicated by a colour change (as described in International patent application number WO 96/22797).

Claims

1. Optical apparatus for the delivery of high intensity light to a location remote from the source of said light comprises a source of polychromatic non-laser light, fibre optic means for transmitting said light to said location, and an ellipsoidal reflector arranged to focus light from said source onto the input end of said fibre optic means, wherein the clear aperture of the ellipsoidal reflector is at least 100 times greater than the effective size of the source of said light.

2. Apparatus as claimed in Claim 1, wherein the source of said light is an arc lamp and the effective size of said source is the size of the arc gap.

3. Apparatus as claimed in Claim 2, wherein the arc lamp is a Xenon arc lamp.

4. Apparatus as claimed in Claim 2 or Claim 3, wherein the arc lamp has an arc gap of less than 0.6mm.

5. Apparatus as claimed in Claim 4, wherein the arc lamp has an arc gap in the range 0.2 to 0.5mm.

6. Apparatus as claimed in any one of Claims 2 to 5, wherein the power output of the arc lamp is in the range 100 to 200W.

7. Apparatus as claimed in any preceding claim, wherein the clear aperture of the ellipsoidal reflector is at least 200 times greater than the effective size of the source of said light.

8. Apparatus as claimed in Claim 2, wherein the arc lamp is mounted with the arc coaxial with the optical axis of the ellipsoidal reflector.

9. Apparatus as claimed in any one of the preceding claims, wherein light is focussed by the ellipsoidal reflector directly onto the input end of the fibre optic means.

10. Apparatus as claimed in any preceding claim, wherein the light source is removably mounted within the apparatus, separately from the ellipsoidal reflector.

11. Apparatus as claimed in Claim 10, wherein the reflector is provided with an opening through which the light source may be inserted or by which the ellipsoidal reflector may be mounted about the lamp.

12. Apparatus as claimed in any preceding claim, which is further provided with one or more filters interposed in the light path between the source and the fibre optic means in order to select a range of wavelengths.

13. Apparatus as claimed in Claim 12, wherein the range of wavelengths has a bandwidth of between lOnm and 200nm.

14. Apparatus as claimed in Claim 13, wherein the bandwidth is approximately 1 OOnm centred around 650nm.

15. Apparatus as claimed in any preceding claim, wherein the fibre optic means has a length of 1 to 3m.

16. Apparatus as claimed in any preceding claim, wherein the fibre optic means has a diameter in the range 0.01 to 1mm.

17. Apparatus as claimed in any preceding claim, wherein the fibre optic means has a numerical aperture in the range 0.20 to 0.52.

18. Apparatus as claimed in any preceding claim, wherein the fibre optic means is contained within a protective sheath of plastics material.

19. Apparatus as claimed in any preceding claim, wherein light emerging from the fibre optic means is projected onto a target by means of a handpiece fitted to the end of the fibre optic means and adapted to be held by a user.