WO2005009267A1

WO2005009267A1 - Device for delivering electromagnetic radiation to human tissue

Info

Publication number: WO2005009267A1
Application number: PCT/IB2004/051267
Authority: WO
Inventors: Bernardus L. G. Bakker; Robbert A. M. Van Hal; Michiel E. Roersma; Jozef J. M. Janssen; Willem Hoving
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2003-07-29
Filing date: 2004-07-21
Publication date: 2005-02-03

Abstract

The present invention discloses a device for delivering electromagnetic radiation (3) to human tissue. The device comprises a treatment head with a duct (5) that is fillable with liquid (6). Radiation is coupled into the liquid. The liquid is ejected through a nozzle (13) as a jet (14), guiding the radiation through total internal reflection. The device allows a safer guidance of the radiation towards the skin etc., and furthermore allows a much larger depth of field, i.e. the distance over which the radiation may be delivered effectively.

Description

Device for delivering electromagnetic radiation to human tissue

The present invention relates to a device for delivering electromagnetic radiation to human tissue, comprising a treatment head with a duct which is fillable with a liquid, and coupling means for coupling electromagnetic radiation into the duct, wherein the duct ends in an aperture for emitting the electromagnetic radiation in an emission direction.

The document US 5,112,328 describes an apparatus for laser surgery. The apparatus comprises a handpiece with a tubular terminal portion with an open distal end, means for introducing a laser beam into the handpiece for focussing said beam to a focus spot. Furthermore the tubular terminal portion may be filled with a saline solution through which the laser beam is guided, and which saline solution may be made to flow out of the terminal end portion. This known apparatus is designed to perform surgery, i.e. cutting human tissue, by means of a focussed laser beam. To this end the apparatus comprises one or more lenses for focussing the beam, and the apparatus must be positioned at a certain distance from the body part to be treated in order to direct the focussed spot to the intended position. In fact, in order to obtain a stable position, in most cases the apparatus will engage the body part to be treated. The saline solution is made to flow across the body part to be treated and hence across the focus in order to wash away debris. The known apparatus has the disadvantage that it is very sensitive to correct positioning. When the position is incorrect, either the apparatus does not function because the beam is out of focus, or a wrong part of the tissue is cut with the laser beam. Hence said apparatus needs professional supervision in order to be operated safely. Furthermore, since a focussed laser beam is used, only a very small area of tissue may be treated.

Hence an object of the present invention is to provide an apparatus of the kind mentioned above which is safer to use and less sensitive to the distance for use. The object is achieved with an apparatus of the kind mentioned in the preamble, which is characterized in that the device further comprises ejection means for ejecting said liquid in a jet from the aperture in the emission direction, wherein the jet guides at least a portion of the electromagnetic radiation via total internal reflection. The apparatus uses the property of a jet of liquid that it will guide radiation via total internal reflection, i.e. at least radiation whose entrance angle lies within a certain range. Since apart from absorption in the liquid, the transport of the radiation within the jet of liquid may continue over an indefinite distance, the device may deliver the radiation at any distance from the aperture. No spacers etc. are needed to set a correct distance. Moreover, since no optical elements are used, the intensity losses can be made very low, especially if the absorption in the liquid is very low. The losses are reduced even further because there are less reflection losses due to different indices of refraction between air (n= ±1) and e.g. skin (n= ±1.5). By selecting a liquid with refractive index which is matched to that of skin, or some other tissue to be treated, these losses can be made close to zero. Furthennore, since the radiation is guided in the jet of liquid, at least for a substantial part, it is clear to an operator of a device where the radiation will be delivered, even if the radiation itself is invisible to the human eye. In other words, there is a well defined treatment area. Furthermore the radiation is confined to the jet of liquid and will not escape therefrom, which is an inherent safety feature. Obviously, when the jet of liquid hits the surface or tissue to be treated, the liquid will start to swirl across the surface, but the radiation will have entered the tissue and have brought about its effect on the tissue. It is to be noted that in the apparatus of US 5,112,328 the saline solution flows out of the apparatus, but only in a direction perpendicular to the direction of the laser beam. To that end, separate channels are provided. Another important aspect of the jet of liquid is that the liquid may be used to cool the tissue that is being treated in order to prevent burns or other injuries. The liquid acts as a coolant, without any other means being necessary for cooling, such as cooled optical windows, separate sprays or gels, etc. A preferred embodiment of the device according to the invention comprises a plurality of apertures. It goes without saying that in this embodiment the device is adapted to emit radiation through the plurality of apertures, in each case through ejection of a jet of liquid through said apertures. To this end each of the plurality of apertures may be formed in separate ducts, or the plurality of apertures may be formed in parallel in one duct. The same holds for the coupling means and ejection means, which may be formed as separate means for every aperture, or may be combined into a single coupling means or ejection means. In a preferred embodiment, the liquid comprises water. This is not only a very simple solution, but it also has an inherent safety feature since water is completely harmless to the human body as to toxicity etc. Furthermore, use may be made of the fact that certain kinds of possibly unwanted radiation may be filtered out by means of the water, in particular medium wave and long wave infrared radiation. Of course the water may comprise additives such as disinfectants, detergents, etc. Preferably, additives are used that have a beneficial effect on the skin, such as skin conditioners, perfumes, and advantageously filtering additives for filtering out e.g. ultraviolet radiation etc. In an advantageous embodiment, the device comprises liquid conditioning means. The liquid conditioning means may be cooling means or heating means to bring the liquid to a desired temperature, such as a low temperature of between 0 and 10 °C. The liquid conditioning means may comprise a heater, a heat exchanger, a Peltier element, a block of ice and so forth. Advantageously, the device further comprises connection means for connecting an external source of liquid to the duct. In this embodiment, it is possible to have a constant supply of fresh liquid. Advantageously, the connection means are meant for connecting the duct to a water pipe or e.g. a water hose. This offers the possibility to connect the device to the mains water supply of a house or hospital, etc. Any other external source of liquid may also be used, such as an oil, etc. with an appropriate refractive index. In an advantageous embodiment, the device further comprises drainage means for draining off ejected liquid through a drainage opening near the aperture. The drainage means will comprise some kind of tubing with a drainage opening and pump means for pumping away drained liquid. These pump means may be provided separately, but in many cases it will be preferable for the ejection means and pump means to be combined into a single pump means. The advantage of providing drainage means is that ejected liquid can be drained off in order to avoid problems with too large a quantity of liquid. Furthermore, any dirt, debris, etc. that is washed away with the ejected liquid will automatically be disposed of together with the liquid. Preferably the drainage opening surrounds the aperture. In this case it is possible to effectively drain off all of the ejected liquid. In principle, the type of electromagnetic radiation is not subject to limitations. However, depending on the properties of the liquid used, it is advantageous for the electromagnetic radiation to have a wavelength between 300 and 1500 nanometer. These types of electromagnetic radiation may be used safely by non-professional users. Even more preferably, the wavelength is between 380 and 1500 nanometer. This limits the type of electromagnetic radiation to visible optical radiation and short-wave infrared radiation. Advantageously, the electromagnetic radiation is non-coherent radiation (i.e in particular no laser radiation). This offers not only an inherent safety feature, because after having left the liquid non-coherent radiation will quickly decrease in intensity upon hitting a surface, except for very specific cases of near point sources and converging optics. Also, in the case of e.g. malfunction of the device, caused by no ejection of liquid, the emitted radiation will not have a dangerous intensity, except at the shortest distances. Furthermore, because of total internal reflection back and forth within the jet of liquid, the intensity profile within the jet of liquid will become very homogeneous, which improves the quality of treatment with the device according to the invention. It is to be noted, however, that the use of laser radiation is not excluded. Preferably, the laser radiation will not be focussed. Although even focussed radiation would be confined to the liquid for not too acute angles, said focussing might become dangerous for an operating person and is not intended for use at home, etc. In a preferred embodiment of the device according to the invention, a power density of the electromagnetic radiation in a cross-section of the jet of liquid is less than 10 kW/cm2, more preferably less than 1 kW/cm2. By limiting the power density to 10 kW/cm2 or less, a device is obtained which, at the hands of reasonably well trained personnel, is very unlikely to inflict injury upon a person being treated. By limiting the power density to 1 kW/cm2 or less, an even safer device is obtained, which may be used by non- professional users without much risk. In particular, unintended cutting of human tissue is avoided. In another advantageous embodiment, the electromagnetic radiation is continuous radiation, and a power density of the electromagnetic radiation in a cross -section of the jet of liquid is between 1 kW/cm2 and 150 W/cm2. At such a low power density the safety of a device is ensured even better. It is to be noted that in the case of continuous radiation a treatment may comprise the application of the device, switching on the device and, after a certain amount of the radiation, switching off the device. This may be considered a single (long) pulse. It is also possible to move the device over the skin etc. at a certain speed, with continuous emission of radiation. By selecting the right speed, depending on the intensity of the emitted radiation, the right amount of radiation that will hit a certain area may be set. In this respect the notion of 'dwell time' is to be mentioned, which is equal to the time during which a point on the skin receives radiation. It is also equal to the time during which the emission window "passes" said point, thus equal to the dimension of the emission window as seen in the direction of movement of the device, divided by the velocity of said movement. Although it is not necessary to have continuous electromagnetic radiation, said type of radiation is advantageous in that the peak density more or less equals the average density, which will help avoid overloading the tissue. However, non-continuous radiation, e.g. a pulsed laser or a discontinuously operated broad band radiation source may also be preferable in certain circumstances, although in that case it is preferable to limit the peak power density to 10 kW/cm2 and preferably to 1 kW/cm2, as mentioned above. In principle, for the device according to the invention it suffices to have coupling means for coupling electromagnetic radiation into the liquid. To this end, e.g. a condenser lens or some other kind of optical window may be used at an end of the duct opposite the aperture. Alternatively, one or more optical fibers etc. may be used. However, preferably, the device according to the invention further comprises a source of the electromagnetic radiation. This not only offers the advantage of a possible compact design of the device, but it also diminishes the risk of radiation being emitted unintendedly, e.g. not via the jet of liquid. On the other hand, providing a separate source of electromagnetic radiation may be advantageous if said source is rather bulky. In that case it is preferable to separate the source from the device and use e.g. optical fibers as coupling means for the electromagnetic radiation. The device itself, in particular that part of the device that will emit radiation and eject liquid, will then be much easier to use. In the case that the device comprises a source of electromagnetic radiation, this source is preferably a flash lamp or a laser. The former is a very convenient source for broad band optical radiation, which may be made very small and yet have a high peak power. The latter is a very well defined monochromatic light source, with even higher peak power, which is very controllable. A laser may be embodied as a cw laser or a pulsed laser. A pulsed laser has the advantage that the action on the skin may be controlled and checked after each pulse or after a number of pulses. Other types of sources however are not excluded, such as halogen incandescent lamps, (high pressure) gas discharge lamps and LEDs. Advantageously, the source is coolable by the liquid, for example because the liquid can be made to flow along the source or a reflector combined with the source. In this way, the liquid will carry off part of the heat of a reflector (if present) or of the heat generated PH-ML030917 PCT/IB2004/051267 6 by the source. This may also serve as a filter means for unwanted parts of the spectrum of the radiation emitted by the source, e.g. infrared radiation above ±1200 n-m in the case of water. In an advantageous embodiment of the device according to the invention, the device further comprises control means disabling emission of electromagnetic radiation during a predetermined period of time after the start of the ejection of the jet of liquid. This embodiment offers a safety feature, in that the device will not emit radiation until after a certain predetermined period of time after the start of the ejection of liquid. Suppose, for example, that unintendedly the device is aimed at a person's eye. In that case, as soon as the jet of liquid hits the eye, the person will close his eyes in a reflex, without the eyes having been irradiated with the radiation. Hence it follows that it would suffice for the predetermined period of time to be equal to or slightly longer than the response time of humans. For safety reasons one second would suffice. Another reason for using such a period of time would be to allow the jet of liquid to become a stable jet. In another advantageous embodiment of the device, in addition to the duct, a second path for the electromagnetic radiation is present in the treatment head, which second path is not connected to the aperture and is of such design that, when the duct is not filled with liquid, the electromagnetic radiation will travel along said second path. This is also a safety feature which prevents emission of radiation in the absence of liquid. In the absence of liquid, the radiation may be directed to the second path not connected to the aperture. To this end, e.g. the coupling means are such that they will guide radiation towards the ejection opening only in the presence of liquid. This may be easily realized through simple laws of optics, e.g. refraction of liquid which causes a shift in the direction of an oblique beam of radiation, which shift is different in the absence of liquid. For example, a beam of light directed, at an angle of 45°, to a cell with two parallel walls at a distance of 2 cm will hardly shift when the cell is empty. When the cell is filled with water (n = 1.33), the beam will undergo a shift of about 0.5 cm. This difference may be used to redirect the beam. Although the above-mentioned safety feature may be used in combination with any type of electromagnetic radiation and any type of source therefor, the electromagnetic radiation and/or source therefor preferably is laser radiation/a laser. Especially in the case of laser radiation this safety feature may become important because a parallel laser bundle which would be emitted in the absence of liquid may cause harm at large distances, which should be avoided. Also in the case of invisible radiation, such as ultraviolet or infrared radiation, the advantages will be obvious. Embodiments of a device for delivering electromagnetic radiation to human tissue in accordance with the invention will be explained in detail hereafter with reference to the appended drawing, in which: Fig. 1 is a schematic representation of a basic embodiment of a device according to the invention, Fig. 2 shows a detail of a second embodiment of a device according to the invention, Figs. 3a and 3b show two examples of methods for coupling electromagnetic radiation from a source into a duct of a device according to the invention, Fig. 4 shows a detail of a device according to the invention, and Fig. 5 schematically shows a safety feature for a device according to the invention.

The drawings are all schematic and not to scale. Similar parts are denoted with the same reference numerals throughout the drawings. Fig. 1 is a schematic representation of a basic embodiment of a device according to the invention. In Fig. 1, 1 is a source of electromechanic radiation in a housing 2. A beam 3 of electromagnetic radiation is emitted and, via an optical window 4, coupled into a duct 5. The duct 5 is filled with a liquid 6 which is fed through a feeding tube 7. A pump 8 pumps the liquid 6 which is taken in from a water mains connection 9. Reference numeral 10 denotes control means for controlling pump means 8 via first connector 11, and for controlling the source 1 via second connector 12. The liquid 6 is ejected through a nozzle 13 as a jet 14 towards a surface 15 to be treated. The source 1 of electromagnetic radiation is for example a laser, a halogen incandescent lamp, a gas discharge lamp, one or more LED s etc. The source 1 may emit continuous electromagnetic radiation, but may also be operated intermittently. In particular, source 1 may be a flash lamp. The housing 2 may be any appropriate housing for the source 1. Preferably the housing 2 comprises a reflector or other means for forming a bundle of radiation. The beam 3 of electromagnetic radiation which is emitted by the source 1 travels through the housing 2 and through an optical window 4. The optical window 4 may be a piece of material which is transparent to the beam of electromagnetic radiation, or at least to a part thereof. In the latter case, the optical window 4 may comprise filter means for filtering out a desired portion of electromagnetic radiation. For example, if the beam of electromagnetic radiation 3 comprises broad band electromagnetic radiation with wavelengths between e.g. 300 and 3000 nanometer, then optical window 4 may comprise a band pass filter which is transparent to radiation between e.g. 400 and 800 nanometer only. Optical window 4, also referred to as coupling means, may also comprise a simple convex lens which may serve as a condensor in order to obtain a more favorable beam 3. Optical window 4 may furthermore comprise shutter means (not shown) which may block the beam 3 if desired. The duct 5 which is filled with liquid 6 may be a simple box, preferably having a shape which is convenient for manual operation of the device as a treatment head. The duct 5 is connected to feeding tube 7 for receiving the liquid 6. The liquid 6 leaves the duct 5 through a nozzle 13 opposite the optical window 4. The duct 5 may be made from a material which is transparent to the electromagnetic radiation, but preferably it is made of an opaque material. In another advantageous embodiment, the duct 5 may be coated on the inside with a reflective material, e.g. like a mirror, in order to guide as much electromagnetic radiation as possible towards the nozzle 13, which serves as the aperture of the device. In another advantageous embodiment, the duct 5 is made of a material with a refractive index which is lower than that of the liquid. In the case of the liquid 6 being water, this is very difficult to achieve, but in the case of the liquid 6 being some kind of oil or the like, many kinds of plastics will satisfy this requirement. In this case, the duct 5 as a whole will guide the electromagnetic radiation by means of total internal reflection, and in any case the efficacy will be higher than in the case that the refractive index of the material of the duct 5 is higher than that of the liquid 6. The pump means 8 serve to pressurize the liquid 6 in order to eject the liquid 6 from the duct 5. In some cases, notably when use is made of the water pressure of the water mains, the pump 8 may be omitted. In another advantageous embodiment, the pump may be replaced by some kind of valve or other closing means, which may be controlled by the control means 10. On the other hand, if the water mains connection 9 is replaced by a connection to some kind of liquid storage (not shown) then an external pressure source may be required. Control means 10 serve to control pump 8. For this reason the pump 8 and the control means 10 are connected through first connector 11, which may be e.g. any kind of cable permitting data traffic or for example a simple power supply cable to the pump 8, which power supply may be switched by control means 10. Control means 10 may also be connected to source 1 by means of a second connector 12. Again, this may be any kind of cable permitting data traffic or a simple power supply cable. It is to be noted that control means 10, as well as the first 11 and second connector 12 are optional, although a simple on/off switch may be regarded as a minimum control means. Control means 10 may be used to switch on and off source 1, either in a continuous or pulsed mode. In particular, control means 10 may comprise a computer that may also be used to enter specific data of the object under treatment. Specifically, the device according to the invention will be used to treat human body parts, notably skin and the surface of teeth. Some uses of the device according to the invention are in the field of photo hair removal by administering light to hair follicles etc., skin-photo rejuvenation and dental care by removing plaque. Many other possible uses may be contemplated. In all cases, the spectrum of the electromagnetic radiation in the jet of liquid 6 may be optimized for the specific use. For example, for hair removal the source of electromagnetic radiation may be a diode laser (e.g. 808 nanometer, pulse duration 10-100 ms, optical intensity 5-50 J/cm²), or a flash lamp system (550-1100 nm broad band spectrum, pulse duration 10-100 ms, optical intensity 5-50 J/cm²). If the device is to be used for dental cleaning, it may be used in combination with a special photo-sensitive toothpaste. Details relating to such toothpaste may be found in US 6,056,548. As the jet 14 is ejected from the nozzle 13 it will hit the surface 15, thereby administering the bundle 3 of electromagnetic radiation to the surface 15, while the surplus liquid 6 will flow sidewards, where it may be collected in a (bath) tub, etc.. Fig. 2 shows a detail of a second embodiment of a device according to the invention. The detail shows the lower part of the duct 5 with a nozzle 13 ejecting a jet 14 of liquid 6. The nozzle 13 is surrounded by a sleeve (or collar) 17. In the jet 14 there are shown two rays of radiation, 16a and 16b. In the embodiment shown in Fig. 2, the internal surface of the duct 5 has a reflective coating. This coating ensures that the rays 16a and 16b inside the duct will be reflected off the wall of the duct 5. As soon as the liquid 6 is ejected as jet 14, and the radiation with it, it will depend on the specific direction of the rays of radiation whether they will be totally internally reflected at the surface of the jet 14. For instance, ray 16a travels at such an angle with respect to the surface of jet 14 that it will not be totally reflected; instead it refracted and leave the jet 14. The maximum angle between the ray and the normal to the surface of the jet 14 at which total internal reflection still takes place depends on the refractive index. The other ray 16b travels at an appropriate angle and will be reflected totally, as shown in the figure. To prevent rays like rays 16a from escaping from the jet 14, or more particularly to prevent any harm since they are emitted in an uncontrolled direction, they need to be absorbed. To this end, an absorptive sleeve 17 is present around and at a certain distance from the nozzle 13. The dimensions of the sleeve 17 will have to fulfil minimum requirements, which may be determined in a very simple way. Figs. 3a and 3b show two examples of methods for coupling electromagnetic radiation from a source into a duct in a device according to the invention. Fig. 3 a shows a duct 5 with liquid 6 into which a beam 3 is coupled in through an optical window 4 after having gone through a lens 18 and a shutter 19. The beam 3 of radiation may originate from any source and may be redirected by means of a positive, converging lens 18. Lens 18 may also symbolize a beam expander in the case of a laser beam. Shutter 19 may be used, i.e. closed, in order to shut off the beam 3 when it is no longer needed or e.g. when it would be dangerous to emit radiation. Shutter 19 may also be used to produce a pulsed beam from a continuous source. Moreover, shutter 19 may also symbolize some kind of diaphragm in order to adjust the total amount of energy in the beam. In Fig. 3b, liquid 6 flows around source 1 and through duct 5. Reference numeral 4 is an optical window and 20 denotes an optical fiber. The liquid is made to flow around source 1 in order to cool the source or e.g. filter the radiation emitted by the source. In this respect use may be made of the property of e.g. water that it filters out medium and longer wave infrared radiation, which may be advantageous to prevent overheating of the skin. Additionally, in or surrounding the duct 5 heater means or cooler means may be provided (not shown) to further bring the liquid to a desired temperature. The cooler means may be for instance a block of ice or a heat exchanger. The optical window 4 may e.g. be a piece of glass or other transparent material or a lens etc. The optical window 4 is used to couple the radiation from source 1 into the optical fiber 20. The optical fiber 20 may be made of an appropriate plastic, e.g. PMMA or of glass or quartz. At a certain distance from the optical window 4, the optical fiber 20 enters the duct 5, still carrying the electromagnetic radiation inside it. Said radiation is emitted as a beam 3 at an end of the fiber 20 opposite the optical window 4. An advantage of coupling by means of an optical fiber 20 is that it is much easier for the duct 5 to be made flexible while the radiation can still be transported substantially loss-free. Obviously, instead of a single optical fiber 20, a bundle of optical fibers may be used. It is to be noted that the embodiment according to Fig. 3b is an example in which the liquid supply and the electromagnetic radiation "supply" are more or less decoupled. It is not necessary that the duct 5 with liquid 6 passes the source 1. If the source 1 and the duct 5 are separate it is possible for the source 1 to be rather heavy, bulky etc. without the treatment head, i.e. the part of the device held in the hand of the operating person and comprising the end of the duct with the nozzle, being less convenient. More generally, the treatment head may comprise a connection to a base station (also referred to as an

"umbilical") comprising one or two liquid tubes, i.e. one supply tube and one drainage tube, and e.g. an optical fiber and wiring for control means. One of the liquid tubes may for example be a hose connected to a water means, in which case the other tube may be a drainage tube connected to a sink or sewer. The embodiment with two liquid tubes will be elucidated in Fig. 4. Fig. 4 shows a detail of a device according to the invention, in which 5 denotes the duct with the nozzle 13, which is surrounded by an outer duct 21. The whole is positioned on a skin surface 15. The liquid flows through the duct 5, out of the nozzle 13 and into the outer duct 21, as indicated by the arrows. The liquid can be made to flow into the outer duct 21 by means of suction means (not shown) which drain the liquid into the outer duct 21. This drainage ensures that the ejected liquid will not cause any problems. Furthennore, this controlled flow of liquid will help remove any debris, dirt etc. from the surface being treated. In this case, the skin surface 15 could be cleansed by the flow of liquid in order to remove cut hair, small flakes of skin, bacteria etc. The drainage means or suction means may be separate, but may also be combined with the pump means. One part of the pump means may pump liquid towards the nozzle, while another part of the pump means may drain liquid through the outer tube 21. Outer tube 21 may also be a separate tube not surrounding duct 5, but merely extending parallel to it. Fig. 5 schematically shows a safety feature for a device according to the invention. Herein, 5 denotes (a part of) the duct through which liquid is guided. Reference numeral 3 is a laser beam. Reference numeral 22 is a block of optical material with an outer surface 23. Reference numeral 24a is a resultant laser beam in the presence of liquid, while

24b denotes a resultant laser beam in the absence of liquid. In this case the laser beam 3 is made to enter the block 22 perpendicularly so it will not be refracted at the boundary between air and the optical material. The duct 5, which may also be a separate fluid duct, will be filled with a liquid when the device is operative.

The block of optical material 22 and the liquid may be selected such that there refractive indices do not differ very much, although the main criterion will be that the refractive index of the liquid is substantially higher than that of air, which is always the case. In Fig. 5, the refractive index of the liquid is only very slightly lower than that of the optical material of the block 22. This means that when the laser beam 3 crosses the duct 5 with the liquid at an oblique angle, the beam will not be shifted very much. This is clearly shown in that the resultant beam 24a almost coincides with the original laser beam 3. In the absence of liquid however, there is a large difference between the index of refraction of the material of the optical block 22 and the air in the duct 5. This means that there will be a large range of angles for which total internal reflection within the optical block

22 will occur. Hence in the absence of liquid, resultant ray 24b will travel in a completely different direction towards the surface 23 of the block 22. By making the surface 23 absorptive except for the intended entrance and exit areas, it is very easy to block any unwanted emission of radiation in the absence of liquid. It is to be noted that the safety feature shown in Fig. 5 is not limited to the device according to the invention, but may in fact be used in any device in which light travels through liquid. The present invention has been illustrated by means of preferred embodiments shown in the drawings. However, the invention is not to be construed as limited thereby. The scope of the invention is determined by the appended claims.

Claims

CLAIMS:

1. A device for delivering electromagnetic radiation to human tissue, comprising a treatment head with a duct which is fillable with a liquid, and coupling means for coupling electromagnetic radiation into the duct, wherein the duct ends in an aperture for emitting the electromagnetic radiation in an emission direction, characterized in that the device further comprises ejection means for ejecting said liquid in ajet from the aperture in the emission direction, wherein the jet guides at least a portion of the electromagnetic radiation via total internal reflection.

2. A device according to claim 1, comprising a plurality of apertures.

3. A device according to any of the preceding claims, wherein the liquid comprises water.

4. A device according to any of the preceding claims, further comprising connection means for connecting an external source of liquid to the duct.

5. A device according to any of the preceding claims, further comprising drainage means for draining off ejected liquid through a drainage opening near the aperture.

6. A device according to any of the preceding claims, wherein the electromagnetic radiation has a wavelength between 300 and 1500 nanometer.

7. A device according to any of the preceding claims, wherein the electromagnetic radiation is non-coherent radiation.

8. A device according to any of the preceding claims, wherein a power density of the electromagnetic radiation in a cross-section of the jet of liquid is less than 10 kW/cm2, more preferably less than 1 kW/cnA

9. A device according to any of the preceding claims, wherein the electromagnetic radiation is continuous radiation, and a power density of the electromagnetic radiation in a cross-section of the jet of liquid is between 1 kW/cm² and 150 W/cm^.

10. A device according to any of the preceding claims, further comprising a source of the electromagnetic radiation.

11. A device according to claim 10, wherein the source is a flash lamp or a laser.

12. A device according to any of the preceding claims, further comprising control means disabling emission of electromagnetic radiation during a predetermined period of time after the start of the ej ection of the j et of liquid.

13. A device according to any of the preceding claims, wherein in addition to the duct, a second path for the electromagnetic radiation is present in the treatment head, which second path is of such design that, when the duct is not filled with liquid, the electromagnetic radiation will travel along said second path.

14. A device according to claim 13, wherein the electromagnetic radiation is laser radiation.