WO2011161126A1

WO2011161126A1 - A system for providing insertable probes

Info

Publication number: WO2011161126A1
Application number: PCT/EP2011/060384
Authority: WO
Inventors: Pär H. Henriksson
Original assignee: Clinical Laserthermia Systems Ab
Priority date: 2010-06-21
Filing date: 2011-06-21
Publication date: 2011-12-29
Also published as: SE1050655A1; SE537342C2

Abstract

The present invention relates to probe tips for laser light emitting probes. Each probe tip comprises a probe tip body made of a first material with a first refractive index, which probe tip body has a smooth outer surface and contains internal light diffusing means.

Description

A SYSTEM FOR PROVIDING INSERTABLE PROBES

Field of the Invention

This invention pertains in general to the field of insertable probes devices and methods for emitting diffused light. More particularly the invention relates to using into tissue insertable probes for thermal treatment of tissue using electromagnetic radiation and even more particularly for avoiding undesirable overheating of tissue or causing hot spots.

Background art

The treatment of tissues by electromagnetic radiation in the form of laser beams is known. Typically a laser source produces a beam of laser light which is fed via a waveguide, for example an optical fibre, though the body of an insertable probe to a light- transmissive probe tip from which the light can leave the probe and heat up the tissue in the vicinity of the probe tip. Different types of probe tips are known which can have the purpose of diffusing the light leaving the probe tip so that the energy is more or less evenly distributed into the surrounding tissue. EP 404968 describes a probe with a tapered light transmissive tip which is provided with a surface which scatters the exiting laser light. The light-scattering surface can be achieved by making the surface rough or by attaching light-scattering particles made of a material having a higher refractive index than that of the material of the tip to the surface.

An issuewith such light-scattering probe tips is that in practice the rough surface or light-scattering particles may cause the surrounding tissue to adhere to the surface. The adhering tissue can negate the light-scattering effect of the rough surface or light-scattering particles and cause the laser energy to be concentrated into the area where the tissue is attached leading to undesirable overheating of the tissue so-called "hot spots". Another objection of the invention is to provide an alternative solution to create emitted diffused light from a probe tip.

Summary of the invention

Accordingly, embodiments of the present invention preferably seek to mitigate, alleviate or eliminate one or more deficiencies, disadvantages or issues in the art, such as the above-identified, singly or in any combination by providing a system and a method, according to the appended patent claims. An object of the present invention is to provide probes which overcome the drawbacks of the prior art probe tips.

The present invention achieves the above object by providing a probe with a probe tip which reduce the risk that tissue can adhere to the probe tip and which also, in the event that tissue does adhere to the probe tip, reduce the risk that local overheating of the tissue occurs.

According to a first aspect of the invention a laser light emitting probe is disclosed comprising an elongated probe tip body made of a first material with a first refractive index. The probe tip body has a smooth outer surface. Further the elongated probe tip body contains an internal conical portion has a second refractive index. The second refractive index differ from the first refractive index and an inner light reflective contact surface is created between the elongated probe tip and the internal conical portion. The surface reflects at least a portion of incident light from a light source, wherein internal reflections in said probe tip is obtained and causes said laser light to leave said probe tip as diffused light.

In a further embodiment of the present invention this is achieved by providing a probe tip with means for indicating when a control temperature has been achieved.

In another embodiment, the invention provides the use of a probe tip for emitting diffused light for thermal treatment of tissue.

In yet another embodiment, the invention provides the use of a probe tip for emitting diffused light for avoiding undesirable overheating of a tissue or causing hot spots

According to a second aspect of the invention, a method is disclosed for obtaining emitted diffused light from a probe tip. The method comprises providing an elongated probe tip body made of a first material with a first refractive index; providing an internal conical portion with a second refractive index, said second refractive index differ from said first refractive index; creating an inner light reflective contact surface between said elongated probe tip and said internal conical portion, said surface reflects at least a portion of incident light from a light source; and causing said laser light to leave said probe tip as diffused light by obtaining internal reflections in said probe tip.

According to a third aspect, a use of a probe tip according to the first aspect is provided for emitting diffused light for thermal treatment of tissue.

According to a fourth aspect, a use a method according the second aspect is provided for emitting diffused light for thermal treatment of tissue. Some embodiments of the invention provide for emitting diffused light to tissue while avoiding undesirable overheating of the tissue.

Some embodiments of the invention provide for emitting diffused light to tissue while avoiding the causing of hot spots.

Further embodiments of the invention are defined in the dependent claims, wherein features for the second and subsequent aspects of the invention are as for the first aspect mutatis mutandis.

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Brief Description of the Drawings

These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which

shows schematically a side view of a prior art probe with a shows schematically a side view of a prior art probe with a tapered shows schematically a side view of a prior art probe with a rounded shows schematically a side view of a probe with a cylindrical probe first embodiment of the present invention;

shows schematically an enlarged perspective view of the probe tip of shows schematically a side view of a probe with a cylindrical probe second embodiment of the present invention;

shows schematically an enlarged perspective view of the probe tip of shows schematically a side view of a probe with a cylindrical probe third embodiment of the present invention; Figure 4b) shows schematically an enlarged perspective view of the probe tip of figure 4a);

Figure 5a) shows schematically a side view of a probe with a cylindrical probe tip in accordance with a fourth embodiment of the present invention; and

Figure 5b) shows schematically an enlarged perspective view of the probe tip of figure 5 a):

Figure 6a) shows schematically a side view of a probe with a cylindrical probe tip in accordance with a fifth embodiment of the present invention; and

Figure 6b) shows schematically an enlarged perspective view of the probe tip of figure 6a),

Figure 7a) shows schematically a side view of a probe with a cylindrical probe tip in accordance with a sixth embodiment of the present invention; and,

Figure 7b) shows schematically an enlarged perspective view of the probe tip of figure 7a).

Description of the Invention

Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

Figures la), lb) and lc) show examples of prior art insertable probes with different shapes of probe tips.

Figure la) shows a probe 1a with a cylindrical body 3a surrounding a waveguide 5a. The proximal end 2a of the waveguide 5a is connectable to a source of laser radiation 7a. The distal end 4a of waveguide 5a leads to a probe tip 9a attached to the distal end 6a of cylindrical body 3 a. Probe tip 9a is made of a laser light transmissive material such as quartz or, sapphire. Probe tip 9a is cylindrical and the surface 11 a of it is roughened to give a matt, frosted surface structure which acts as a light diffuser. When a beam of laser radiation is emitted from the laser radiation source 7a it travels though the waveguide 5a to probe tip 9a whereupon it is refracted by the rough surface of probe tip 9a and emitted from the probe tip in many directions, thereby producing a diffuse laser light which covers a large area. Figure lb) shows a probe lb with a cylindrical body 3b surrounding a waveguide 5b. The proximal end 2b of the waveguide 5b is connectable to a source of laser radiation 7b. The distal end 4b of waveguide 5b leads to a probe tip 9b attached to the distal end 6b of cylindrical body 3b. Probe tip 9b is made of a laser light transmissive material such as quartz, or sapphire. Probe tip 9b is conical with the widest end 13b of the cone nearest the distal end 4b of the waveguide and the surface 1 lb of it is roughened to give a matt, frosted surface structure which acts as a light diffuser.

Figure lc) shows a probe lc with a cylindrical body 3 c surrounding a waveguide 5c. The proximal end 2c of the waveguide 5c is connectable to a source of laser radiation 7c. The distal end 4c of waveguide 5c leads to a probe tip 9c attached to the distal end 6c of cylindrical body 3 c. Probe tip 9c is made of a laser light transmissive material such as quartz or sapphire. Probe tip 9c is hemi-spherical with the flat surface 13c of the hemisphere nearest the distal end 4c of the waveguide and the surface 1 1 c of the hemisphere intended to be in contact with tissue is roughened to give a matt, frosted surface structure which acts as a light diffuser.

Figures 2a) and 2b) shows a first embodiment of a probe 201 with a probe tip 209 in accordance with the present invention, where figure 2b) is an enlarged view of the probe tip shown in figure 2a). Probe 201 has an elongated body 203 surrounding a waveguide 205. The proximal end 202 of the waveguide 205 is connectable to a source of laser radiation 207. Preferably the laser radiation is in the form of a beam with a wavelength between 800 nm and 1300 irai, more preferably between 1000 and 1100 nm and most preferably 1060 nm. The distal end 204 of waveguide 205 leads to a substantially transparent probe tip 209 attached to the distal end 206 of elongated body 203. Probe tip 209 is made of laser light transmissive materials such as quartz, sapphire, polymers, glass or the like. Probe tip 209 is cylindrical with a diameter Dpt which is preferably the same as the outer diameter Dtb of elongated body 203 (and therefore Dpt is greater than diameter Dwg of waveguide 205) in order to allow the join between the probe tip and probe body to pass through tissue without catching on it. Probe tip 209 has a smooth and/or low friction surface 211 which prevents tissue adhering to it. The term "smooth" in this application the means that a surface is substantially free of scratches or defects which would cause light passing through it to be diffused, in particular that preferably the surface has a surface roughness (Ra) of less than 25 pm, more preferably an Ra of less than 10 pm, even more preferably an Ra of less than 1 μηι and most preferably a Ra of less than 0.1 pm. Probe tip 209 is made of two or more materials with different refractive indexes. Probe tip 209 comprises internal light diffusion means in the form of an elongated probe tip body 217 and a conical probe tip proximal portion 215.

Proximal portion 215 is of length Lcpp with the widest end 213 (preferably of diameter Dpt) of the conical portion 215 nearest the distal end 204 of the waveguide. Proximal portion 215 is made of a material with a first refractive index. An elongated probe tip body 217 of length Lptb (which in this embodiment is shown as being substantially equal to Lcpp but may conceivably be longer than Lcpp) which has a longitudinally extending concave cavity 218, of the same size and shape as proximal portion 215, is mounted on, and encloses, proximal portion 215. Elongated probe tip body 217 is made of a material with a second refractive index which is not the same as the first refractive index. The second refractive index can be lower than the first refractive index. Alternatively the second refractive index can be higher than the first refractive index. The use of two materials with different refractive indexes means that the contact surface between the two materials acts as to reflect some of the incident light and to transmit some of the incident light. This causes some of the incoming laser beam A, which is highly collimated, to be internally reflected before leaving the probe tip 209. Different portions of the laser beam will be reflected a different number of times and will leave the probe tip at different positions which causes the laser light leaving the probe tip to be diffuse. Alternatively or additionally the outer surface of conical proximal portion 215 and/or the inner surface of elongated probe tip body may be partly mirrored to cause internal reflection in the probe tip. The total surface area of the cylindrical surface of the transparent portion probe tip which is intended to emit a portion of the diffuse laser beam has a surface area of X square millimetres and the, in this embodiment circular, surface area of the distal end of probe tip 209 which is intended to emit the remaining portion of the diffuse laser beam (such an emitting area may be less than the total surface area of the distal end of probe tip 209 - see below for an example where an end cap is used to reduce the surface area of the emitting area) has a surface area of Y square millimetres. In a preferred example of this embodiment of the present invention it is intended that the incoming laser beam is emitted as a diffuse beam with substantially equal intensity (and thus substantially equal warming effect) in the longitudinal direction and lateral directions of the probe tip. In order to achieve this the angle of the slope of the side of the conical proximal portion 215, its length, refractive index and any mirroring of the probe tip are selected so that the proportion of diffused laser light which is emitted through the end surface of the probe tip is Y/(X + Y) of the total emitted light. The remaining emitted light X/(X +Y) is intended to be emitted through the transparent cylindrical surface of the probe tip. While it is preferable that the intensity of the emitted diffused light is substantially the same over the whole of the emitting surface, it is also possible to have some variations in the intensity of the distributed of light without causing hot spots where the tissue is overheated, as once the tissue in the vicinity of the probe starts to heat up due to the diffused laser light, any temperature differences in the heated tissue will tend to be reduced by conduction of heat energy from the hotter areas to cooler areas.

Optionally the distal end of probe tip 209 may be covered by an end cap 219 of diameter Dec which is substantially the same as that of the probe tip body 217 and a length which is less than that of the probe tip body Lptb. The surface of end cap 219 which faces the waveguide is preferably arranged to reflect light - this can be achieved by surface treatment so that it has a mirror finish or by making end cap 219 of a material which has a different refractive index to the material used for the probe tip body 217. The reflective surface end cap reflects light back into the probe tip body which helps it become more evenly dispersed and at the same time prevents light being emitted in the axial direction of the probe tip - something which is desirable in some applications. However, in the event that it is desirable that some light be emitted in the axial direction of the probe tip then the end cap can be omitted or, as shown by dotted lines, a light-transmissive portion 221 of the end cap (in this example the centre portion but any other portion is also conceivable, e.g. an annular portion or one or more segments) can be made non-reflective or less than 100% reflective to allow light to pass through it.

Figures 3a) and 3b) shows a second embodiment of a probe 301 with a substantially transparent probe tip 309 in accordance with the present invention, where figure 3 b) is an enlarged view of the probe tip shown in figure 3 a). Probe 301 has an elongated body 303 surrounding a waveguide 305. The proximal end 302 of the waveguide 305 is

connectable to a source of laser radiation 307. The distal end 304 of waveguide 305 leads to a probe tip 309 attached to the distal end 306 of elongated body 303. Probe tip 309 is made of laser light transmissive materials such as quartz, sapphire, polymers, glass or the like. Probe tip 309 is cylindrical with a diameter Dpt which is preferably the same as the outer diameter Dtb of elongated body 303 (and therefore Dpt is greater than diameter Dwg of waveguide 305) in order to allow the join between the probe tip and probe body to pass though tissue without catching on it. Probe tip 309 has a smooth or low-friction surface 31 1 which prevents tissue adhering to it. Probe tip 309 is made of two or more materials with different refractive indexes. Probe tip 309 comprises internal light diffusing means comprising a conical distal portion 316 and an elongated probe tip body 317. Conical distal portion 316 has length Lcdp with the widest end 313 (preferably of diameter Dpt) of the conical portion 316 furthest from the distal end 304 of the waveguide. Conical distal portion 316 is made of a material with a first refractive index. A elongated probe tip body 317 of length Lptb (which may substantially equal to Lcdp but in this embodiment is shown to be longer than Lcdp) which has a longitudinally extending concave cavity 318, of the same size and shape as conical distal portion 316, is mounted on, and encloses, conical distal portion 316. Elongated probe tip body 317 is made of a material with a second refractive index which is not the same as the first refractive index. The use of two materials with different refractive indexes means that the contact surface between the two materials acts as a mirror and the incoming laser beam is internally reflected a plurality of times before leaving the probe tip 309. This causes the laser light leaving the probe tip to be diffuse. Alternatively or additionally the outer surface of conical distal portion 316 and/or the inner surface of elongated probe tip body may be partly mirrored to cause internal reflection in the probe tip.

Optionally the distal end of probe tip 309 may be covered by an end cap 319 of diameter Dec which is substantially the same as that of the probe tip body 317 and a length which is less than that of the probe tip body Lptb. The end cap 319 may be part of the internal laser diffusing means. The surface of end cap 319 which faces the waveguide is preferably arranged to reflect light - this can be achieved by surface treatment so that it has a mirror finish or by making end cap 319 of a material which has a different refractive index to the material used for the distal portion 316. The end cap reflects light back into the probe tip body which helps it become more evenly dispersed and at the same time prevents light being emitted in the axial direction of the probe tip - something which is desirable in some applications. In the event that it is desirable that some light be emitted in the axial direction of the probe tip then the end cap can be omitted or, as shown by dotted lines, a light-transmissive portion 321 of the end cap (in this example the centre portion but any other portion is also conceivable, e.g. an annular portion or one or more segments) can be made non-reflective or less than 100% reflective to allow light to pass through it.

Figures 4a) and 4b) shows a third embodiment of a probe 501 with a substantially transparent probe tip 509 in accordance with the present invention, where figure 4b) is an enlarged view of the probe tip shown in figure 4a). Probe 501 has an elongated body 503 surrounding a waveguide 505. The proximal end 502 of the waveguide 505 is

connectable to a source of laser radiation 507. The distal end 504 of waveguide 505 leads to a probe tip 509 attached to the distal end 506 of elongated body 503. Probe tip 509 is made of laser light transmissive materials such as quartz, sapphire, polymers, glass or the like. Probe tip 509 is cylindrical with a diameter Dpt which is preferably the same as the outer diameter Dtb of elongated body 503 (and therefore Dpt is greater than diameter Dwg of waveguide 505) in order to allow the join between the probe tip and probe body to pass though tissue without catching on it. Probe tip 509 has a smooth or low-friction surface 51 1 which prevents tissue adhering to it. Probe tip 509 comprises internal light diffusing means. Probe tip 509 is made of two or more materials with different refractive indexes. Probe tip 509 comprises a rounded (shown here as substantially hemispherical) proximal portion 515 of length Lcpp with the widest end 513a (preferably of diameter Dpt) of the conical portion 516 closest to the distal end 504 of the waveguide and a conical distal portion 516 of length Lcdp with its widest end 513b (preferably of diameter Dpt) furthest away from the distal end 504 of the waveguide. Rounded proximal portion 515 and conical distal portion 516 may be made of the same material with a first refractive index or of different materials with different refractive indices. A elongated probe tip body 517 of length Lptb (which may substantially equal to Lcpp + Lcdp but in this embodiment is shown to be longer than Lcpp + Lcdp) which has two longitudinally extending concave cavities 518a and 518b, of the same size and shape respectively as hemispherical proximal portion 515 and conical distal portion 516, is mounted on, and encloses, hemispherical proximal portion 515 and conical distal portion 516.

Elongated probe tip body 517 is made of a material with a refractive index which is not the same as that of the material(s) used for the rounded proximal and conical distal portions 515, 516. The use of materials with different refractive indexes means that the contact surface between the materials acts as a partial mirror or light deflecting surface and the incoming laser beam is internally reflected a plurality of times before leaving the probe tip 509. This causes the laser light leaving the probe tip to be diffuse. Alternatively or additionally the outer surface of rounded proximal portion 515 and/or conical distal portion 516 and/or the inner surface of elongated probe tip body may be partly mirrored to cause internal reflection in the probe tip.

Optionally the distal end of probe tip 509 may be covered by an end cap 519 of diameter Dec which is substantially the same as that of the probe tip body 517 and a length which is less than that of the probe tip body Lptb. The surface of end cap 519 which faces the waveguide is preferably arranged to reflect light - this can be achieved by surface treatment so that it has a mirror finish or by making end cap 519 of a material which has a different refractive index to the material used for the distal portion 516. The end cap reflects light back into the probe tip body which helps it become more evenly dispersed and at the same time prevents light being emitted in the axial direction of the probe tip - something which is desirable in some applications. In the event that it is desirable that some light be emitted in the axial direction of the probe tip then the end cap can be omitted or, as shown by dotted lines, a light-transmissive portion 521 of the end cap (in this example the centre portion but any other portion is also conceivable, e.g. an annular portion or one or more segments) can be made non-reflective or less than 100% reflective to allow light to pass through it.

While the invention has been illustrate with examples where 515 has a rounded shape and 516 has a conical shape it is conceivable that both 515 and 516 may have a rounded shape or 515 a conical shape and 516 a rounded shape.

Figures 5a) and 5b) shows a fourth embodiment of a probe 601 with a substantially transparent probe tip 609 in accordance with the present invention, where figure 5b) is an enlarged view of the probe tip shown in figure 5 a). Probe 601 has an elongated body 603 surrounding a waveguide 605. The proximal end 602 of the waveguide 605 is

connectable to a source of laser radiation 607. The distal end 604 of waveguide 605 leads to a probe tip 609 attached to the distal end 606 of elongated body 603. Probe tip 609 is made of laser light transmissive materials such as quartz, sapphire, polymers, glass or the like and contains laser light diffusing means. Probe tip 609 is cylindrical with a diameter Dpt which is preferably the same as the outer diameter Dtb of elongated body 603 (and therefore Dpt is greater than diameter Dwg of waveguide 605) in order to allow the join between the probe tip and probe body to pass though tissue without catching on it. Probe tip 609 has a smooth or low-friction surface 611 which prevents tissue adhering to it. Probe tip 609 comprises a hollow tubular probe tip body 617 of length Lptb and inner diameter Di made of a material with a first refractive index.

The distal end of probe tip 609 is covered by an end cap 619 of diameter Dec which is substantially the same as that of the probe tip body 617 and a length which is less than that of the probe tip body Lptb. The surface of end cap 619 which faces away from the waveguide is preferably arranged to reflect light - this can be achieved by surface treatment so that it has a mirror finish or by making end cap 619 of a material which has a different refractive index to the material used for the probe tip body 617 and, as mentioned below, different to that of the first material which fills hollow probe tip body 617. The material used for end cap 619 is luminescent (i.e. fluorescent or phosphorescent) so that when excited by incident laser light of a certain wavelength λ; it emits light at emitted wavelength λ_β and its reflective surface reflects some of this light back into the probe tip body and to wave guide 605. Waveguide 605 guides this emitted light to a light detector 625 which produces a signal which is dependent on the strength of emitted light detected by it and the wavelength of the reflected light λ_ε may depend on the surrounding temperature.

Hollow probe tip body 617 is substantially filed with a first material 627 with a melting point temperature which is the same as a desired temperature. Preferably the desired temperature is a temperature that is over nonnal body temperature and is also a temperature at which a desired effect on surrounding tissue takes place. For example, the melting point temperature can be set at a temperature which would be expected to cause tissue at a distance of 1 -20 mm more preferably 10 mm from the surface of the probe tip body to achieve a temperature at which damage to cells occurs. Preferably this is a steady-state temperature between 42° C and 48° C, more preferably a steady-state temperature of between 43° C and 47° C, and even more preferably between 45° C and 46° C. This melting point temperature is dependent on thermal conductivity of the tissue that the probe tip body is inserted into and it may need to be as high as 98° C to achieve the necessary steady-state temperature at a distance from the probe tip body. However in order to avoid damaging a patient the melting point temperature preferably be low enough to prevent boiling or burning of the tissue in contact with the probe tip body. This first material contains light-blocking material 629 which prevents light passing through the particles or reduces the amount of light which passes through the particle. The particles can be (semi-)light-reflectingor (semi-)light-absorbing particles in the form of grains or pieces of foil or nanowires. The light-blocking material causes incident laser light to be reflected and/or absorbed and as the material is randomly distributed the laser light will be reflected randomly which will result in it becoming diffused. When the probe is below the melting point of the first material the light-blocking material is immobilised and the amount of light which reaches the luminescent end cap is substantially constant if the incident laser light is kept at constant power. The light-blocking material prevents some of the laser light from reaching the luminescent material and also prevents some of the light emitted from the end cap from reaching the light detector. This means that the amount of light which is emitted from the end cap at λ_β and reflected back into the probe tip body and to wave guide 605 is substantially constant and therefore the signal from light detector 625 is substantially constant. However when the probe is heated and the first material melts then the light-blocking material is able to move about in the melted first material and both the amount of laser light reaching the end cap and the amount of light emitted from the end cap reaching the light detector 625 will change as the light-blocking material moves. By monitoring changes in the signal from the light detector it is possible to detect when the first material melts and thereby determine the temperature in the probe is the same as, or higher than, the melting point temperature. This information can be used in a feedback system to control the temperature of the probe tip body, for example by reducing the intensity of the incident laser light when melting of the first material has been detected, and increasing the intensity when solidification of the first material has been detected.

It is conceivable to provide a probe tip body with two or more sealed compartments arranged along the axial direction of the probe tip body and to provide light- blocking material and a first material with a first melting point temperature e.g. 50° C in a first compartment, light-blocking material and a second material with a second melting point temperature, e.g. 90° C in a second compartment and light-blocking material and, subsequent materials with different melting point temperatures in subsequent compartments. This will lead to one change in the amount of reflected light once the probe tip has passed the first lowest melting point temperature and further changes in the amount of reflected light when the temperature of the probe tip passes subsequent melting point temperatures. These changes in the amount of reflected light can be used to determine if the temperature of the probe tip body has passed the predetermined melting point temperatures.

Other embodiments of probe tips provided with material which melts at a predetermined temperature are also possible. For example, a probe tip may be provided with a solid rounded or conical distal portion (a conical distal portion is shown in dotted lines as 616 by way of example) or the solid conical or rounded proximal/distal portions of a probe tip described above can be replaced by hollow conical or rounded probe portions containing a material which melts at a predetermined temperature. This material can completely or partly fill the hollow probe portions, any remaining space being filled with a fluid. In place of, or in addition to, light-blocking material it is also conceivable that the material which melts at a predetermined temperature could be opaque when in the solid state and transparent in the liquid state, such as for example, waxes or fats. If an opaque material is used then it will disperse incident laser light and act as an internal diffuser.

Figure 6a) and 6b) show a fifth embodiment of a probe 701 with a probe tip 709 in accordance with the present invention, where figure 6b) is an enlarged view of the probe tip shown in figure 6a). Probe 701 is similar to the third embodiment and has an elongated body 703 surrounding a waveguide 705. The proximal end 702 of the waveguide 705 is

connectable to a source of laser radiation 707. The distal end 704 of waveguide 705 leads to a probe tip 709 attached to the distal end 706 of elongated body 703. Probe tip 709 is made of laser light transmissive materials such as quartz, sapphire, polymers, glass or the like. Probe tip 709 is cylindrical with a diameter Dpt which is preferably the same as the outer diameter Dtb of elongated body 703 (and therefore Dpt is greater than diameter Dwg of waveguide 705) in order to allow the join between the probe tip and probe body to pass though tissue without catching on it. Probe tip 709 has a smooth or low- friction surface 71 1 which prevents tissue adhering to it. Probe tip 709 is made of two or more materials with different refractive indexes. Probe tip 709 comprises a rounded (shown here as substantially hemispherical) proximal portion 715 of length Lcpp with the widest end 713a (preferably of diameter Dpt) of the conical portion 716 closest to the distal end 704 of the waveguide and a conical distal portion 716 of length Lcdp with its widest end 713b (preferably of diameter Dpt) furthest away from the distal end 704 of the waveguide. Rounded proximal portion 715 and conical distal portion 716 may be made of the same material with a first refracti ve index or of different materials with different refractive indices. A elongated probe tip body 717 of length Lptb (which may substantially equal to Lcpp + Lcdp but in this embodiment is shown to be longer than Lcpp + Lcdp) which has two longitudinally extending concave cavities 718a and 718b, of the same size and shape respectively as hemispherical proximal portion 715 and conical distal portion 716, is mounted on, and encloses, hemispherical proximal portion 715 and conical distal portion 716. Elongated probe tip body 717 is made of a material with a refractive index which is not the same as that of the material(s) used for the rounded proximal and conical distal portions 715, 716. The use of materials with different refractive indexes means that the contact surface between the materials acts as a partial mirror or laser light deflecting area and the incoming laser beam is internally reflected a plurality of times before leaving the probe tip 709. This causes the laser light leaving the probe tip to be diffuse.

Alternatively or additionally the outer surface of rounded proximal portion 715 and/or conical distal portion 716 and/or the inner surface of elongated probe tip body may be partly mirrored to cause internal reflection in the probe tip.

Optionally the distal end of probe tip 709 may be covered by an end cap 719 of diameter Dec which is substantially the same diameter as that of the probe tip body 717 and a length which is less than that of the probe tip body Lptb. The surface of end cap 719 which faces the waveguide is preferably arranged to reflect light - this can be achieved by surface treatment so that it has a mirror finish or by making end cap 719 of a material which has a. different refractive index to the material used for the conical distal portion 716 which it is in contact with. The end cap reflects light back into the probe tip body which helps it become more evenly dispersed and at the same time prevents light being emitted in the axial direction of the probe tip - something which is desirable in some applications. In the event that it is desirable that some light be emitted in the axial direction of the probe tip then the end cap can be omitted or, as shown by dotted lines, a light-transmissive portion 721 of the end cap (in this example the centre portion but any other portion is also conceivable, e.g. an annular portion or one or more segments) can be made non-reflective or less than 100% reflective to allow light to pass through it.

Additionally the distal end of probe tip 709, or end cap 719, if present is provided with electrical temperature sensor such as a thermistor 731 which produces a signal dependent on the temperature in its vicinity and which signal is sent along a conductor 732 to a temperature monitoring and/or displaying means 734. Preferably each temperature sensor has a diameter of less than 0.5 mm or, if it has a quadratic shape, it has no dimension which is greater than 0.5 mm It is of course possible to attach such an electrical temperature sensor to any embodiment of the present invention. Preferably each electrical temperature sensor is shielded from direct exposure to the laser light in order to prevent the direct laser light from wanning the temperature sensor.

Additionally it is possible to provide any probe in accordance with the present invention with one or more additional electrical temperature sensors 733, 735 and conductors 736, 738 as shown by dotted lines. The use of additional temperature sensors provides more precise temperature sensing and allows thermal mapping of the temperature distribution in the target area. Preferably each temperature sensor is positioned 5-15 mm, more preferably 8-12 mm, in the axial direction of the probe from any neighbouring sensor.

In the event that it is required to measure the impedance or other electrical property of the tissue surrounding the probe, a probe in accordance with the present invention can be provided with one or more electrically conducting surfaces 741, 743, 745 (shown by dotted lines) each connected by its own conductor 751, 753, 755 (shown by dotted lines) to an impedance sensing circuit 761 (shown by dotted lines). Preferably an electrically conducting surface can be in thermal contact with an electrical temperature sensor, such as electrically conducting surface 733 and electrical temperature sensor 743, in order to make it possible to determine the temperature at which the impedance or other electrical property reading was measured.

Figures 7a) and 7b) show an embodiment of the invention similar to that shown in figures 6a) and 6b). The conductors 751 753, 755 are opaque and cause shadowing, i.e. they prevent laser light that is leaving the probe tip from reaching the tissue which lies in their shadow or they attenuate the laser light. In order to prevent this shadowing from affecting the treatment of the tissue the conductors can be arranged in spirals around the probe so that the shadowing is distributed around the probe and not concentrated into one area. Preferably the conductors are equally spaced around the circumference of the probe, e.g. if there are 2 conductors then they are can be spaced at intervals of 180°, if there are 4 conductors then they can be spaced at intervals of 90°. Preferably the spirals are wound in the same direction and with the same pitch so that the conductors are mutually parallel. Such an arrangement of conductors can be used as appropriate with any embodiment of the present invention.

Typically the diameter Dpt of a probe tip body in accordance with the present invention preferably will be less than 5 mm and more preferably is less than 3 mm. The length Lptb of the probe tip body will be preferably be less than 15mm and more preferably is less than or equal to 10mm. The end cap of a probe tip body preferably will be less than 2 mm thick and more preferably is less than 1 mm thick.

While the invention has been illustrate with examples of rotationally symmetrical probe tip proximal and distal portions it is conceivable to have non-symmetrical or irregular shaped probe tip proximal and distal portions in order to produce a desired special diffusion pattern. It is also conceivable to use more than two different materials for the probe tip in order to achieve different amounts of internal reflection as this amount is dependent on which two materials are present at the interfaces between materials that the laser beam passes through. It is conceivable that probe tip components such as proximal portions and/or distal portions and/or probe bodies may be hollow bodies which are filled with material, solid, liquid or gas which has a further refractive index which is different to the refractive index of the material which the probe tip component is made from. In such cases laser light passing through the wall of the hollow component will be refracted twice - once on entering the material of which the wall is made and once on leaving it.

The present invention has been described above with reference to specific embodiments. However, other embodiments than the above described are equally possible within the scope of the invention. Different method steps than those described above, performing the method by hardware or software, may be provided within the scope of the invention. The different features and steps of the invention may be combined in other combinations than those described. The scope of the invention is only limited by the appended patent claims.

Claims

1. A probe tip (209, 309, 509, 609, 709) for a laser light emitting probe characterised in that it comprises an elongated probe tip body (217, 317, 517, 617, 717) made of a first material with a first refractive index, which probe tip body has a smooth outer surface (21 1 , 311, 51 1, 61 1 , 71 1); said elongated probe tip body contains an internal conical portion (215, 316, 516, 616, 716) that has a second refractive index, said second refractive index differs from said first refractive index; wherein an inner light reflective contact surface is created between said elongated probe tip and said internal conical portion, said surface reflects at least a portion of incident light from a light source (207, 307, 507, 607, 707); wherein internal reflections in said probe tip is obtained and causes said laser light to leave said probe tip as diffused light.

2. A probe tip (209, 309, 509, 609, 709) according to claim 1, wherein said elongated probe tip body is transparent.

3. A probe tip (309, 509, 609, 709) according to claim 1 or 2, wherein said internal conical portion (316, 516, 616, 716) is distally positioned in said elongated probe tip body, and is longitudinally extended towards an incident laser light.

4. A probe tip (209) according to claim 1 or 2, wherein said internal conical portion (215) is proximally positioned in said elongated probe tip body, and is longitudinally extended in a same direction as an incident laser light.

5. A probe tip (209, 309, 509, 609, 709) according to any of the preceding claims, wherein said laser light in operation of said probe tip leaving said probe tip is diffuse and is leaving said probe tip with substantially equal intensity in a longitudinal direction and a lateral directions of said probe tip.

6. A probe tip (209, 309, 509, 609, 709) according to any of the preceding claims, wherein said elongated probe tip has an end cap positioned at a distal end (219, 319, 519, 619, 719) made of a material with a third refractive index and wherein said end cap at least partially covers said distal end.

7. A probe tip (209, 309, 509, 609, 709) according to claim 6, wherein said end cap has a light-transmissive portion (221, 321 , 521 , 721).

8. A probe tip (209, 309, 509, 609, 709) according to any of the preceding claims, wherein a surface of said conical portion ( 316) and/or a inner surface of said elongated probe tip body is at least partially mirrored to cause internal reflection in said probe tip.

9. A probe tip (209, 309, 509, 609, 709) according to claims 6 or 7, wherein a surface of said end cap (219, 319) faces said elongated probe tip body is arranged to reflect light.

10. A probe tip (209, 309, 509, 609, 709) according to claim 9, wherein said surface of said end cap is treated with a mirror finish.

1 1. A probe tip (509, 709) according to any of the preceding claims, wherein said probe tip comprises a rounded proximal portion (515, 715).

12. A probe tip (509, 709) according claim 11, wherein said rounded proximal portion has a refractive index which differ from the refractive index of said elongated probe tip body.

13. A probe tip (509, 709) according claim 1 1 or 12, wherein an outer surface of said rounded proximal portion is at least partly mirrored to cause internal reflection in said probe tip.

14. A probe tip (209, 309, 509, 609, 709) according to any of the preceding claims, wherein said elongated probe tip body has a longitudinally extending concave cavity (218, 318, 518b, 718b).

15. A probe tip (209, 309, 509, 609, 709) according to claim 14, wherein said concave cavity has same size and shape as a proximal (215) or distal (316, 516, 616, 716) portion of said elongated probe tip body and is mounted on, and encloses, said proximal or distal portion.

16. A probe tip (209, 309, 509, 609, 709) according to any preceding claims, wherein an angle of the slope, a length and refractive index of said conical portion of said probe tip are selected to determine the proportion of diffused laser light emitted in a longitudinal direction and a lateral directions of said probe tip.

17. A probe tip (209, 309, 509, 609, 709) according to any preceding claims, wherein said outer surface of said probe tip has low friction.

18. A probe tip (209, 309, 509, 609, 709) according to any preceding claims, wherein said elongated probe tip body has at least two sealed compartments arranged along a longitudinal direction of said elongated probe tip body.

19. A probe tip according to any preceding claims, wherein a luminescent end cap and a hollow portion containing light-blocking material immobilised in a material with a melting point temperature greater or equal to 42° C and less than or equal to 98° C.

20. A probe tip according to any of claims 1-18, wherein a luminescent end cap and a hollow portion containing light-blocking material immobilised in a material which is solid below 42°

C.

21. A probe tip according to any of claims 1-18, wherein a luminescent end cap and a hollow portion containing light-blocking material immobilised in a material which is solid below 98°

C.

22. A method for obtaining emitted diffused light from a probe tip comprising:

providing an elongated probe tip body (217, 317, 517, 617, 717) made of a first material with a first refractive index; providing an internal conical portion (215, 316, 516, 616, 716) with a second refractive index, said second refractive index differ from said first refractive index; creating an inner light reflective contact surface between said elongated probe tip and said internal conical portion, said surface reflects at least a portion of incident light from a light source (207, 307, 507, 607, 707); causing said laser light to leave said probe tip as diffused light by obtaining internal reflections in said probe tip.

23. Use of a probe tip according to any of claims 1-21, or a method according to claim 22, for emitting diffused light for thermal treatment of tissue.

24. Use of a probe tip according to any of claims 1 -21 or a method according to claim 22, for emitting diffused light for avoiding undesirable overheating of a tissue or causing hot spots.