WO1998052645A1

WO1998052645A1 - Light producing apparatus

Info

Publication number: WO1998052645A1
Application number: PCT/IB1998/000896
Authority: WO
Inventors: Morgan Gustafsson
Original assignee: Morgan Gustafsson
Priority date: 1997-05-22
Filing date: 1998-05-22
Publication date: 1998-11-26
Also published as: AU7669398A; GB9710627D0

Abstract

A lamp is provided for the treatment of the human or animal body. It comprises a source of non-coherent light, means for attenuating ultra violet light emitted by the source, and means for attenuating infra-red light emitted by the source so that the resulting light does not cause thermal tissue damage. The lamp may comprise a closed reflective cavity, a source of non-coherent light in said cavity, means for leading the light to the skin of the human or animal body, and means for leading a flow of cooling fluid past the source to cool it. The reflective cavity may be divided into first and second spaces, the first space surrounding the source and arranged for turbulent flow of cooling fluid through it, and the second space comprising the remainder of the space from the reflective cavity and being fed with cooling fluid from the first space. Means may be provided for cooling the recirculating fluid and/or a waveguide to below ambient temperature by means of a heat exchanger and/or a Peltier cooling element.

Description

LIGHT PRODUCING APPARATUS FIELD OF THE INVENTION

The present invention relates to a lamp for the treatment of human or animal body by light . Embodiments of the present lamp can be used for removal and prevention of regrowth of hair, for the treatment of pigmented lesions or vascular lesions, for coagulating blood, for the treatment of superficial virus infections e.g. warts or herpes infection, or for the treatment of tumour cells.

BRIEF DESCRIPTION OF THE PRIOR ART

Treatment of the human body by light is known e.g. from US patent 3327712 (Kaufman), US patent 5320618 (Gustafsson) and US patent 5405368 (Eckhouse). Apparatus for treatment of the human body by means of laser light is also well known.

One problem associated with these existing designs is that they have to be used under medical supervision because there is a serious risk of tissue damage in the event of misuse. Furthermore, the pulse widths which are available from laser lamps are in practice limited to about 2.5 ms which is too short for many clinical applications. A further problem with prior art machines is that because of problems associated with heat control it is impossible to achieve a high pulse repetition rate.

SUMMARY OF THE INVENTION One problem with which the invention is concerned, therefore, is to provide a lamp for the treatment of the human or animal body in which it is possible to achieve a high pulse repetition rate without damage to the optical components of the equipment. A further aspect of the invention provides a lamp for the superficial treatment of the human or animal body in which the risk of causing serious or permanent damage to the skin is reduced or eliminated.

In one aspect the present invention provides a lamp for the treatment of the human body e.g. for one of the medical indications set out above, which works by a combination of filtered and fluorescent light.

In a further aspect of the invention there is provided a lamp for the treatment of the human body comprising a source of pulsed non-coherent light, means for filtering the light to remove an infra-red component thereof, and a solid-state fluorescent plate through which the light is arranged to pass and which serves to adjust the wavelength of at least a portion of the emergent light to a value desired for treatment.

The invention further provides a lamp for the treatment of the human body comprising a source of non-coherent pulsed light, and a reflective cavity containing the light source and provided with means for circulating cooling fluid for cooling the light source.

It may be desirable to provide means for cooling the fluid and/or the waveguide to below ambient temperatures. Such cooling means may comprise a heat exchanger for cooling the circulation of cooling fluid and a cooling element e.g. a Peltier element for cooling at least a proximal region of the waveguide .

The waveguide may be of two portions . A first portion which is contact with the liquid in the cavity may be of glass, and a second portion which extends away from the first portion may be of a different material such as sapphire which_. has good heat conductivity.

DESCRIPTION OF PREFERRED FEATURES The lamp also advantageously contains a filter for removing a major proportion of UV light emitted by the light source.

The light which is produced by the present is the result of two processes. The first of these is a passive filtering technique which uses water and/or optical materials to remove unwanted wavelengths such as ultraviolet and infra-red parts of the spectrum. In conventional hair removal or other skin treatment processes the infra-red part of the spectrum is insufficiently filtered out with the result that it is absorbed by the water in the skin and can give rise to tissue damage. Filtration by water or other optical media is arranged to reduce the infra-red component to a level at which accidental burning is unlikely. The filtered light then preferably passes via a waveguide in which it is multiply internally reflected to a fluorescent material where light in the range 450 to 920nm (green to red) is adjusted to have a greater intensity in the range 600-920nm (yellow to red).

The light from the lamp may penetrate to about 2-3mm below the skin surface, which is deep enough to affect those hair cells which induce growth but does not affect other tissues such as nerves or blood vessels. The wavelength of light selected is most absorbed by hair cells, with any remaining light being absorbed through the dermis with no effect. The mechanism for interruption of hair growth is not fully understood, but it is at present believed that the growth cells found at the base of the hair shaft are denatured which leads to the death of the hair. The results obtained depend on the individual, and in some people permanent hair removal can be achieved relatively easily, whereas in other it is difficult to prevent regrowth.

The use of a fluorescent plate attenuates unwanted wavelengths, and if it is omitted, the patient may notice more heat in the skin, and there may be some slight blistering or reddening of the treated area from the infra-red component or some slight tanning as a result of the ultraviolet component. The effectiveness of the lamp is, however, retained.

The light produced is incoherent and resembles that from a light bulb or a camera flash bulb except that it is more powerful and is adapted for the purpose of hair removal or one of the other treatments mentioned above. Laser light is potentially harmful if aimed at the wrong target, whereas the light from the present lamp is much less likely to give rise to tissue damage if abused and does not require medical supervision for its safe use.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Fig 1 is a diagrammatic side view of apparatus according to the invention.

Fig 2 is a diagram showing the optical components of a hand piece forming part of the apparatus together with a turbine, reservoir, pump and filter forming part of a power unit, but with the electrical supply to the lamp not shown .

Fig 3 is a diagrammatic side view of apparatus according to a second embodiment of the invention .

Fig 4a is a diagrammatic side view of apparatus according to a third embodiment of the invention, Fig 4b is a detailed view of a waveguide showing its junction to the body of the apparatus, and Fig 4c is a detailed view of a gusset piece forming part of the apparatus.

Fig 5 is a diagrammatic side view of apparatus according to a fourth embodiment of the invention.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In Fig 1, a light source 10 is provided within a semi- cylindrical cavity 12 of glass or other transparent material provided with a layer 13 of silver or other reflective material on its exterior surface. Silver is advantageous compared to e.g. aluminum because of its high reflectance to visible light. The silver layer may be protected by a backing layer of an epoxy resin or of lacquer. The semi-cylindrical cavity is closed by reflective end plates which are also silvered as aforesaid. Typically the radius of the cavity 12 is 24mm and the lamp 10 is of internal diameter about 5mm and is offset about 1mm behind the centre of the semi- cylindrical reflective surface. A front face of the optical cavity is closed off by a plate 14 of UV and low- visible absorption glass having a cut off of about 380nm. The outer face of the glass plate 14 is silvered as aforesaid except for a window 16 which in this embodiment is rectangular and corresponds in dimension and position to a working part of the lamp 10. The height of the window 16 can be up to twice the diameter of the lamp 10 in order to maximise the amount of light which is fed to the waveguide whilst also preserving the maximum energy density. In practice about 25 to 50 % of the light emerging through the window 16 is direct from the lamp 10, and the balance is multiply reflected within the cavity defined by the cylindrical surface, the end walls and the front plate 14.

The lamp 10 may be Xenon arc lamp of internal diameter 5mm and of length 20mm and it advantageously has an internal pressure of about 700 torr to improve efficiency. The lamp 10 is preferably operated as spectral partial volume emitter so that when it is fired, the plasma formed within it is opaque to infra-red light but in at least a partial region is transmissive to the visible light.

The tubing of the lamp 10 is of clear fused quartz in order to minimise the amount of heat which is absorbed by the walls of the lamp, and is of wall thickness preferably about 0.5mm which is a relatively low value adopted with the intention of reducing thermal gradients within the lamp itself . The central or working region of the lamp 10 is surrounded by a flow tube 11 of borosilicate glass (Pyrex or Duran) which is absorbent to UV light and transmits visible and IR light. The operation of the lamp 10 as a spectral partial volume emitter is arranged so that the lamp absorbs internally about 45% of the IR output, the combination of driving voltage and pulse width being selected to achieve this result. In an arc lamp as aforesaid, the driving voltage typically about 90 to about 125 volts, and the lamp is driven with pulses about 2ms in duration and separated by intervals of about 0.2ms. The current density within the lamp 10 should be preferably about 1000 amps per cm² and not above 1800 amps per cm², as at this value the lamp is almost totally transparent to the therapeutic and the polymer pumping light i.e. 500 - 920nm and 450 - 590nm, the latter light being the light which serves to activate the fluorescent plate subsequently described.

The pulses can occur in bursts of 0.5 to 50msec, typically 10 to 20msec depending on the medical application required. The lamp can be driven continuously rather than with the 0.2ms intervals, but if so its lifetime may be shortened. Other similar mark and space lengths may be used instead of those above. The use of a train of pulses with a relatively long mark-space ratio as aforesaid is advantageous from the standpoint of improvement of the lamp life, and the value of the overall length of the train of pulses may be selected depending on the medical application required and the requirements of a particular patient.

The lamp can be arranged to produce on the patients skin a power of 4-80J/cm² typically about 40J/cm² depending upon the patient and the treatment to be given e.g. in the case of hair removal the nature and colour of the hair to be removed. In the case of hair removal, the light energy is transmitted through the skin to the cells adjacent the hair shaft and the hair shaft itself, which are destroyed so that the hair does not subsequently regrow. A ruby laser which produces a light output pulse of 2.5ms does not achieve sufficient pulse length to easily give this result.

For the treatment of hair the present lamp should preferably produce a majority of its output light at a wavelength 595-920nm, depending upon to some extent upon the skin type of the individual being treated. For the treatment of pigmented lesions or vascular lesions the wavelength can be about 455-595nm.

The cavity within which the lamp 10 is housed is filled with de-ionised water. This water absorbs infra-red light and since it is de-ionised is of low electrical conductivity (and hence electrically of low risk) and avoids deposition of solids on the glass of the lamp. The de-ionised water is recirculated through the cavity and is arranged to cool the lamp e.g. by a first pass where it makes a turbulent flow through a narrow cylindrical region between the sleeve 11 and the lamp 10 adjacent the lamp before it then re-enters the body 17 of the cavity via ports 19, 21. The water recirculation circuit advantageously incorporates a de-ionisation filter and heat exchanger.

A waveguide 18 is of high refractive index glass and typically has a refractive index of about 1.7 to 1.8. It is attached to the window 16 by an optically clear cement e.g. a UV curable acrylate adhesive so as to receive the light therefrom and it is typically of width 6-7mm and of length 20-25mm. With this waveguide the treatment spot size may be 20 x 5mm, but it is possible that the size may be increased to e.g. 25 x 7mm. The spot of light produced on the patients skin is conveniently rectangular, but other shapes e.g. square, elliptical, oval or circular may be employed. A spot of at least 3mm across is desirable for adequate skin penetration. At the distal end of the waveguide 18 there is preferably provided a detachable fluorescent plate 20 of plastics film which may contain an appropriate fluorescent dye or pigment, for example, 1,2,3,5,6,7- hexamethyl-8-cyanopyrromethane difluoroborate complex ( Pyrromethene 650) or 4-dicyanomethylene-2-methyl-6-(p- dimethylaminostyryl ) -4-N-pyran (CAS No 51325-91-8). The fluorescent dye or pigment is a solid solution in the plastics film which may be a polymethyl methacrylate based polymer and may typically have a thickness of about 0.5mm. It may be adhered to the end of the waveguide 18 by a relatively weak adhesive so that it may be treated as disposable item which can be removed and replaced at each treatment. It also may be provided in differently coloured sets or grades for the treatment of different categories of patients or different conditions.

The light emerging from the fluorescent plate 20 may be coupled to the skin by means of an index matching gel or by means of water. A suitable gel is Carbopol 980. Alternatively a transparent oil such as a vegetable oil, mineral oil or silicone oil could be used.

The lamp of the invention has the following significant features. It comprises a source of non-coherent pulsed light, for example from a Xenon or Krypton arc lamp which is held within a water-filled reflective cavity. A significant proportion of the light emitted by the lamp is multiply internally reflected within the cavity and therefore takes a long path through the water which acts as a UV filter, as advantageously does the filter sleeve 11 of borosilicate glass placed around the lamp and a wall defining an exit path from the cavity. The filter sleeve and the wall 14 defining the exit path may serve to filter out part of the UV light. Light from the cavity is transmitted direct to the skin via a waveguide 18 of relatively high refractive index which may apply the light direct to the skin or optionally through a replaceable fluorescent plate. The present combination of filtration of UV visible and IR filtration in a lamp of the present kind is believed to be new, as also is the combination of filtered and fluorescent elements for control of the light spectrum applied to the body.

The optical components may be contained within a hand piece which is connected to a power supply unit via a conduit housing the power and water cooling cables . A flexible connecting cable is provided which permits recirculation of water through the cavity and supply of lamp power. The output may be direct to the patients skin. The hand piece may comprise a body of plastics material having a cavity containing an aluminum housing for the optical components and flash lamp, and the waveguide leading from it together with controls e.g. a trigger for initiation of pulses. The hand piece may be made small enough to be truly hand held, precluding the need for an optical fibre delivery system or an articulated arm support system. The machine may therefore be provided in two parts , a hand piece and a power unit. The power unit may be approximately the same size as a desk top computer. It is therefore not demanding of space and is easy to transport if desired. Because of the effective cooling of the optical components within the cavity, pulse repetition rates of about 1Hz can be achieved in practice.

The invention also provides methods of skin-resurfacing of the human or animal body which comprises treating the human body with light from a lamp as aforesaid.

A second form of lamp and waveguide assembly is shown in Fig 3. A body 15 is formed with a semi-cylindrical water-filled cavity 12a as before, with a reflective silver coating 13a. A xenon arc light source 10a in a clear fused quartz envelope is surrounded by a flow tube 11a of cerium doped quartz. The forward face of the cavity 12a is closed by means of a cover plate 14a which is formed on its inner surface with a reflective coating of gold to permit heat dissipation into the cooling water within the cavity 12a and resistance to corrosion from contact with the cooling water. The cover plate 14a may be of glass as in the preceding embodiment, but may be of other material. A waveguide 18a is provided which is made out of sapphire on account of the good thermoconductivity of that material. Sapphire can remove heat from a fluorescent polymer filter 20a attached by tape (not shown) to the distal end of the waveguide 18a. The waveguide 18a is adhered to a window in the cover plate 14a by means of a glue seam 22 on all four sides of the window. Instead of sapphire, the waveguide 18a can also be of glass, e.g. Schott SF6, SFL6 or glass with n_d«8. The waveguide is supported where it extends out of the cover plate 14a by means of gusset pieces 24.

The combination of a sapphire waveguide and a gold reflective coating on the cover plate 14a makes it desirable to cool the water to below room temperature, and this may be done by a heat exchanger alone, a Peltier cooling device (electrical cooling device) alone, or both a heat exchanger and a Peltier cooling device.

A third form of the lamp and waveguide assembly is shown in Fig 4a, and has a body 15b having a lamp 10b, flow tube lib and cover plate 14b arranged as previously described. The window in the cover plate 14b is plugged by a glass member 19 which provides a proximal region of the waveguide and desirably has a refractive index of about 8, for example Schott SF6 or SFL6. The member 19 serves to separate the balance of the waveguide from contact with the water within the cavity 12b. The waveguide extends forwardly of the glass member 19 as a sapphire waveguide 18b, and the two parts are coupled by oil 25 or other suitable coupling medium.

The proximal end of the waveguide 18b is formed to either side with mirror-coatings 27. The protective gussets 24b for the waveguide 18b carry on their inner faces one or more Peltier elements, which are in close proximity with the waveguide each to one or more sides of the waveguide. The Peltier elements enable the waveguide to be cooled e.g. to -20°C.

Fig 5 shows a further embodiment of the lamp and waveguide assembly which is similar to that of Fig 4a except that the Peltier elements 28c are located on the outer face of the cover plate 14c beneath the protective gusset pieces 24c.

The waveguide 18b can have a greater or smaller cross- section than in the first embodiment to give a larger or smaller treatment spot. At present, it is feasible to carry out treatments with spot sizes 20mm by 20mm, but considerably larger spot sizes may be treatable. The spot size can be adjusted by attaching a waveguide extension of increasing or decreasing size to the distal end of the waveguide 18b, and the shape can be square or rectangular as in the preceding embodiments .

Claims

1. A lamp for^" the treatment of the human or animal body comprising a source of non-coherent light, a means for attenuating ultra violet light emitted by the source, and means for attenuating infra-red light emitted by the source so that the resulting light does not cause thermal tissue damage.

2. The lamp of claim 1, wherein the light source is a flash lamp.

3. The lamp of claim 1 or claim 2, arranged to produce an output which is a train of light pulses of pulse length 1 to 10ms with intervals of about 0.1 to 1ms.

4. The lamp of claim 3, arranged to produce an output in which the train is of pulse length 0.5 to 50msec.

5. The lamp of claim 3, arranged to produce an output in which the train of pulses is of length 10 to 20msec.

6. The lamp of any preceding claim, arranged to produce on the patients skin a power of about 4-80J/cm².

7. The lamp of any of claims 1 to 5 , arranged to produce on the patients skin a power of about 40J/cm².

8. The lamp of any preceding claim, wherein the means for attenuating ultra violet light comprises a body of glass through which the light from the source is arranged to pass.

9. The lamp of claim 8, wherein the glass is borosilicate glass.

10. The lamp of any preceding claim, wherein the infrared light is arranged to be at least partly attenuated in the source.

11. The lamp of any preceding claim, wherein the infra red light is arranged to be at least partly attenuated by water surrounding the source .

12. The lamp of any preceding claim, further comprising a fluorescent element arranged to attenuate relatively high frequency visible light.

13. The lamp of any preceding claim, having a waveguide of transparent solid material for leading light from the source to the patients skin.

14. The lamp of claim 13, wherein the waveguide is of refractive index at least 1.7.

15. The lamp of claim 13, wherein the waveguide is of a refractive index of 1.7-1.85.

16. The lamp of any preceding claim, wherein the source is contained within a closed reflective cavity, and means is provided for circulating cooling water through the cavity.

17. The lamp of claim 16, wherein the circulating means comprises a deionization filter for removing ionic materials from the water.

18. The lamp of any preceding claim, wherein there is provided a plate through which the light is caused to pass through the body, said plate containing at least one fluorescent dye or pigment.

19. The lamp of claim 18, wherein the plate is of a plastics material and is adhesively attached to the lamp.

20. A lamp for the treatment of the human or animal body comprising a closed reflective cavity, a source of noncoherent light in said cavity, means for leading the light to the skin of the human or animal body, and means for leading a flow of cooling fluid past the source to cool it.

21. The lamp of claim 20, wherein the cooling fluid is arranged to flow turbulently past the source to effect cooling thereof .

22. The lamp of claim 20 or 21, wherein the reflective cavity is divided into first and second spaces, the first space surrounding the source and arranged for turbulent flow of cooling fluid through it, and the second space comprising the remainder of the space from the reflective cavity and being fed with cooling fluid from the first space.

23. The lamp of any of claims 20 to 22, wherein the cooling fluid is water.

24. The lamp of claim 23, wherein ther water is de- mineralised water.

25. A lamp according to claim 20, further comprising means for cooling said means for leading light to the skin of the human or animal body.

26. The lamp of claim 25, wherein said cooling means is a Peltier cooling element.

27. The lamp of claim 25 or claim 26, further comprising a heat exchanger for cooling the recirculating fluid returning to the reflective cavity to below ambient temperatures .