Laser system and method for the treatment of body tissue

Abstract

A laser system for body tissue treatment has laser source, control device, scanner, and handpiece with treatment head transparent to the laser beam. An incoming laser beam section enters the treatment head longitudinally. The treatment head has a conical output surface with a minimum and a maximum surface radius and a half opening angle for total reflection of the incoming beam section. The reflected beam section is refracted radially into an emerging beam section away from the treatment head through the output surface. The incoming beam section has at the output surface a mean diameter that is a difference of maximum surface radius and minimum scanning radius. A conical scanning surface as a part of the conical output surface extends from the minimum scanning radius to the maximum surface radius. The control device controls the scanner for scanning the conical scanning surface with the incoming beam section.

Claims

1. A laser system (1) for the treatment of body tissue (2) on an inner circumferential tissue surface (3), the laser system comprising: a laser source (4) adapted to generate a laser beam (5), a handpiece (6) with a treatment head (7), a control device (8), and a scanner (9), wherein the treatment head (7) extends along a longitudinal axis (10) and is made of a material transparent to the laser beam (5) and has a first refractive index, wherein, during operation of the laser system, an incoming beam section (11) of the laser beam (5) enters the treatment head (7) in a direction of the longitudinal axis (10), wherein the treatment head (7) has a conically shaped output surface (12) disposed around the longitudinal axis (10) and having an apex (13) facing away from an origin of the incoming beam section (11), wherein the conically shaped output surface (12) has a minimum surface radius (r) and a maximum surface radius (R), wherein the conically shaped output surface (12) has a half opening angle () adapted to provide total reflection of the incoming beam section (11) into a reflected beam section (14) within the treatment head (7) and adapted to provide refraction of the reflected beam section (14) into an emerging beam section (15) emerging radially from the treatment head (7) through the output surface (12), wherein a minimum scanning radius (R.sub.in) is derived from the minimum surface radius (r) and the half opening angle () according to:
R.sub.in=r(tg(2)+tg())/(tg(2)tg()), wherein the incoming beam section (11) has at the location of the output surface (12) a mean diameter (d) that is a difference of the maximum surface radius (R) and the minimum scanning radius (R.sub.in), wherein, as a part of the conically shaped output surface (12), a conically shaped scanning surface (38) is defined extending from the minimum scanning radius (R.sub.in) to the maximum surface radius (R), wherein the control device (8) is adapted to control the scanner (9) for scanning at least a portion of the conically shaped scanning surface (38) with the incoming beam section (11).

2. The laser system according to claim 1, wherein the first refractive index of the material of the treatment head (7) is >1.28, wherein air surrounding the treatment head (7) has a second refractive index of 1.0, wherein an optimal half opening angle (.sub.opt) of the conically shaped output surface (12) is derived from the first refractive index and the second refractive index, and wherein the half opening angle () of the conically shaped output surface (12) is at least approximately equal to the optimal half opening angle (.sub.opt).

3. The laser system according to claim 1, further comprising a liquid-tight protective sleeve (16) that covers the treatment head (7) and is made of a material that is transparent to the laser beam (5), wherein the conically shaped output surface (12) is surrounded by a circumferential wall (17) of the protective sleeve (16), and wherein a free space (18) between the conically shaped output surface (12) and the circumferential wall (17) is filled with gas.

4. The laser system according to claim 1, wherein the treatment head (7) is adapted for immediate access to the body tissue (2) on the inner circumferential tissue surface (3), and wherein the first refractive index of the material of the treatment head (7) >1.64.

5. The laser system according to claim 4, wherein the laser source (4) is selected from the group consisting of an Er:YAG laser source, an Er:YSGG laser source, an Er,Cr:YSGG laser source, and a CO.sub.2 laser source, and wherein the control device (8) is adapted to control the laser source (4) and the scanner (9) such that the emerging beam section (15) has a fluence of at least 1.0 J/cm.sup.2 at the conically shaped output surface (12).

6. The laser system according to claim 1, wherein the material of the treatment head (7) is YAG, and wherein the half opening angle () of the conically shaped output surface (12) is in a range from 33 to 39, with 33 and 39 included in the range.

7. The laser system according to claim 1, wherein the conically shaped output surface (12) extends to the apex (13) and has a minimum surface radius (r)=0.

8. The laser system according to claim 1, wherein the material of the treatment head (7) has a laser beam transmission above 80% within a treatment head beam path length.

9. The laser system according to claim 1, wherein the control device (8) is adapted to control scanning of the conically shaped output surface (12) by the incoming beam section (11) of the laser beam (5) on circles around the longitudinal axis (10) of the treatment head (7) such that the emerging beam section (15) is subjected to a circular feed about the longitudinal axis (10).

10. The laser system according to claim 1, wherein the control device (8) is adapted to control scanning of the conically shaped output surface (12) by the incoming beam section (11) of the laser beam (5) in a radial direction relative to the longitudinal axis (10) of the treatment head (7) such that the emerging beam section (15) is subjected to an axial feed parallel to the direction of the longitudinal axis (10).

11. The laser system according to claim 1, wherein the control device (8) is adapted to control scanning of the conically shaped output surface (12) by the incoming beam section (11) of the laser beam (5) in a random pattern.

12. The laser system according to claim 1, wherein the control device (8) is adapted to control scanning of the conically shaped output surface (12) by the incoming beam section (11) of the laser beam (5) such that at least one certain and predefined portion (35) of the output surface (12) is excluded from irradiation or is subjected to a reduced irradiation by the incoming beam section (11).

13. A method for operating a laser system (1) for the treatment of body tissue (2) on an inner circumferential tissue surface (3), wherein the laser system (1) comprises: a laser source (4) adapted to generate a laser beam (5), a handpiece (6) with a treatment head (7), a control device (8), and a scanner (9), wherein the treatment head (7) extends along a longitudinal axis (10) and is made of a material transparent to the laser beam (5) and has a first refractive index, wherein, during operation of the laser system, an incoming beam section (11) of the laser beam (5) enters the treatment head (7) in a direction of the longitudinal axis (10), wherein the treatment head (7) has a conically shaped output surface (12) disposed around the longitudinal axis (10) and having an apex (13) facing away from an origin of the incoming beam section (11), wherein the conically shaped output surface (12) has a minimum surface radius (r) and a maximum surface radius (R), wherein the conically shaped output surface (12) has a half opening angle () adapted to provide total reflection of the incoming beam section (11) into a reflected beam section (14) within the treatment head (7) and adapted to provide refraction of the reflected beam section (14) into an emerging beam section (15) emerging radially from the treatment head (7) through the output surface (12), wherein a minimum scanning radius (R.sub.in) is derived from the minimum surface radius (r) and the half opening angle () according to:
R.sub.in=r(tg(2)+tg())/(tg(2)tg()), wherein the incoming beam section (11) has at the location of the output surface (12) a mean diameter (d) that is a difference of the maximum surface radius (R) and the minimum scanning radius (R.sub.in), wherein, as a part of the conically shaped output surface (12), a conically shaped scanning surface (38) is defined extending from the minimum scanning radius (R.sub.in) to the maximum surface radius (R), the method comprising: positioning during operation of the laser system (1) the longitudinal axis (10) of the treatment head (7) at least approximately parallel to the inner circumferential tissue surface (3), controlling with the control device (8) the scanner (9) to scan at least a portion of the conically shaped scanning surface (38) with the incoming beam section (11) such that: the incoming beam section (11) is subjected to total reflection at the conically shaped scanning surface (38) into a reflected beam section (14) within the treatment head (7), and the reflected beam section (14) is refracted at the conically shaped output surface (12) into an emerging beam section (15) radially emerging from the treatment head (7) through the output surface (12), scanning the inner circumferential tissue surface (3) at least partially by the emerging beam section (15).

14. The method according to claim 13, wherein the inner circumferential tissue surface (3) of the body tissue (2) is accessed by the treatment head (7), the method further comprising: selecting the material of the treatment head (7) to have a first refractive index of >1.28, covering the treatment head (7) with a liquid-tight protective sleeve (16) such that the conically shaped output surface (12) is surrounded by a circumferential wall (17) of the protective sleeve (16), filling a free space (18) between the conically shaped output surface (12) and the circumferential wall (y) with gas.

15. The method according to claim 13, wherein the inner circumferential tissue surface (3) of the body tissue (2) is immediately accessed by the treatment head (7), further comprising: selecting the material of the treatment head (7) to have a first refractive index of >1.64, and using the treatment head (7) in an environment in which water is present.

16. The method according to claim 13, wherein the inner circumferential tissue surface (3) of the body tissue (2) is immediately accessed by the treatment head (7), further comprising: selecting the material of the treatment head (7) to have a first refractive index of >1.75, and using the treatment head (7) in an environment in which blood is present.

17. The method according to claim 13, further comprising: selecting the laser source from the group consisting of an Er:YAG laser source, an Er:YSGG laser source, an Er,Cr:YSGG laser source, and a CO.sub.2 laser source, and applying parameters of the laser beam (5) to provide a fluence of the emerging beam section (15) at the conically shaped output surface (12) of at least 1.0 J/cm.sup.2.

18. The method according to claim 13, wherein, in the step of controlling, the scanner (9) is controlled such that at least one certain and predefined portion of the circumferential tissue surface (3) is excluded from irradiation or is subjected to a reduced irradiation by the emerging beam section (15).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An example of the inventive device and method will be explained in the following in more detail referring to the drawings.

(2) FIG. 1 shows a schematic cross sectional view of a body cavity with an inserted inventive treatment head providing total reflection followed by refraction of the laser beam at a conically shaped output surface of the treatment head.

(3) FIG. 2 shows an enlarged view of the treatment head of FIG. 1 with details of its geometric layout and the resulting laser beam path.

(4) FIG. 3 shows a schematic top view of the treatment head of FIG. 1 with details of the related scanning pattern.

(5) FIG. 4 is a schematic cross sectional side view of the treatment head of FIG. 1 surrounded by a protective sleeve.

DESCRIPTION OF PREFERRED EMBODIMENTS

(6) FIG. 1 shows in a schematic cross sectional view a cavity in body tissue 2, wherein said cavity forms an inner circumferential tissue surface 3. For the treatment of the body tissue 2 on the inner circumferential tissue surface 3 an inventive laser system 1 and related inventive operation method is provided. The inventive laser system 1 is depicted in a schematic block diagram.

(7) The laser system 1 comprises a laser source 4 for the generation of laser beam 5, a hand piece 6 with a treatment head 7, a control device 8, and a scanner 9. The scanner 9 comprises two mirrors 24, 27, which are rotationally movable about two perpendicular axes 26, 28. The rotational movement of both mirrors 25, 27 is controlled by the control device 8. Alternatively, the scanner 9 may comprise of only one mirror, 25 or 27, which is rotationally movable about two perpendicular axes. The control device 8 further controls the operation of the laser source 4 in terms of intensity and pulse sequences. Upon entering the scanner 9, the laser beam 5 subsequently impinges on both mirrors 25, 27, and is afterwards deflected by an optional bending mirror 29 such that the laser beam 5 enters the treatment head 7 of the hand piece 6 from an input side generally parallel to a longitudinal axis 10 along which the treatment head 7 extends. The portion of the laser beam 5 entering the treatment head 7 generally parallel to the longitudinal axis 10 defines an incoming beam section 11. In the shown embodiment, the incoming beam section 11 that is disposed generally parallel to the longitudinal axis 10 has its origin at the optional bending mirror 29. However, said origin may be located at the scanner 9 in case that the scanner 9 is directly disposed on the input side of the treatment head 7 and the longitudinal axis 10. In any case, the origin of the incoming beam section 11 is located at the input side of the treatment head 7. By controlling the rotational position of both mirrors 25, 27, the exact position of the laser beam's 5 incoming beam section 11 within the treatment head 7 relative to the longitudinal axis 10 can be adjusted. Generally parallel means in the present context that a mean course of the incoming beam section 11 is parallel to the longitudinal axis 10 and that the deviations from said parallelism as caused by the scanning action of the scanner 9 are included. The rigid treatment head 7 is made of a solid material which is transparent to the laser beam 5, having a laser beam transmission within the treatment head beam path length above 80%. On its free or distal end, the treatment head 7 has a conically shaped output surface 12 which provides a total reflection of the laser beam 5 followed by a subsequent refraction such that the laser beam 5 emerges from the treatment head 7 substantially radial to the longitudinal axis 10. In operation, the treatment head 7 is inserted into the body cavity such that the longitudinal axis 10 is substantially parallel to the inner tissue surface 3. In consequence, the emerging laser beam 5 impinges on the inner circumferential tissue 3 substantially perpendicular.

(8) FIG. 2 shows in an enlarged schematic view the treatment head 7 according to FIG. 1 with details of its geometric layout and the resulting laser beam path. The rigid, solid and massive treatment head 7 comprises a base body 22 and an output body 23, which form a unitary one-piece (monolithic) construction. The base body 22 is cylindrically shaped. However, any other suitable shape with a longitudinal extension may be useful as well. The output body 23 is conically shaped with its cone base adjacent to the base body 22 and its apex 13 facing away from both the base body 22 and the origin of the incoming beam section 11, while the apex 13 is positioned on the longitudinal axis 10. Thereby, the conically shaped output surface 12 is formed on the output body 23.

(9) At the cone base adjacent to the base body 22, the conically shaped output surface 12 has a maximum surface radius R corresponding to the radius of the base body 22. The conical output body 23 could be a truncated cone with a bottom 30 facing away from the base body 22, as schematically indicated by a dotted line. At the location of the bottom 30, the conically shaped output surface 12 has a minimum surface radius r. Both maximum and minimum surface radii R, r are measured perpendicular and relative to the longitudinal axis 10. In the shown longitudinal section, the conically shaped output surface 12 extends from the minimum surface radius r to the maximum surface radius R. In other words, any point on the output surface 12 has a local radius relative to the longitudinal axis 10 that is the minimum surface radius r and the maximum surface radius R. In the circumferential direction, the output surface 12 preferably extends 360 about the longitudinal axis 10. For certain applications however, a circumferential extension of less than 360 might be advisable within the scope of the invention. In the shown preferred embodiment, the conically shaped output surface 12 extends from the base body 22 to the apex 13 resulting in a minimum surface radius r=0. The geometric layout of the conically shaped output surface 12 is further defined by a half opening angle relative to the longitudinal axis 10. A further optical property of the treatment head is a first refractive index n.sub.1 of the material from which the treatment head 7 is made. As can be seen in both FIGS. 1 and 2, the treatment head 7 is used in a surrounding environment medium having a second refractive index n.sub.2.

(10) From the minimum surface radius r and the half opening angle , a minimum scanning radius R.sub.in is derived based on Eq. 1. From the fact that the conically shaped output surface 12 has an apex facing away from the origin of the incoming beam section 11, it follows and is required that the minimum scanning radius R.sub.in is <the maximum surface radius R. A specific part or portion of the conically shaped output surface 12, which extends from the minimum scanning radius R.sub.in to the maximum surface radius R, is defined as a conically shaped scanning surface 38. In other words, any point on the scanning surface 38 has a local radius relative to the longitudinal axis 10 being the minimum scanning radius R.sub.in and the maximum surface radius R.

(11) In operation, the laser beam 5 enters the treatment head 7 from the treatment head's 7 input side as said incoming beam section 11. The incoming beam section 11 first impinges with its centerline on the output surface 12 at a point P.sub.1. At said first impingement point P.sub.1, the incoming beam section 11 is totally reflected on the output surface 12, thereby forming a reflected beam section 14 crossing the longitudinal axis 10 within the output body 23 of the treatment head 7. At the location of total reflection the inventive laser system and method meet three requirements: Firstly, the incoming beam section 11 is adjusted to have at the location of the output surface 12, specifically at the first impingement point P.sub.1, a mean beam diameter d being the difference of the maximum surface radius R and the minimum scanning radius R.sub.in. Secondly, the scanner 9 is controlled such that the incoming beam section 11 impinges on the first impingement point P.sub.1 within the conically shaped scanning surface 38. Thirdly, the scanner 9 is controlled such that the first impingement point P.sub.1 has sufficient distance to both the maximum surface radius R and the minimum scanning radius R.sub.in for providing total reflection of the incoming beam section 11 substantially throughout its entire mean beam diameter d. In other words, measured in the radial direction relative to the longitudinal axis, the first impingement point P.sub.1 has a radial distance to both the maximum surface radius R and the minimum scanning radius R.sub.in substantially half of the mean beam diameter d.

(12) After crossing the longitudinal axis 10, the reflected beam section 14 of the laser beam 5 impinges again on the conically shaped output surface 12 on a point P.sub.2 lying opposite the first impingement point P.sub.1 relative to the longitudinal axis 10. At said second impingement point P.sub.2, the reflected beam section 14 passes the output surface 12 to the outside of the treatment head 7, thereby being refracted into an emerging beam section 15 of the laser beam 5. By meeting the above mentioned three requirements at the location of total reflection, the scanning pattern is limited to a ring-shaped area, defined by an outer ring radius which is equal to the maximum surface radius R and an inner ring radius R.sub.in which can be mathematically calculated from Eq. 1. Thereby it is made sure, that the reflected beam section 14 is refracted into the emerging beam section 15 throughout its entire beam diameter or cross section, without irradiation the apex 13 or the bottom 30, if present, and without emitting a significant portion of, or even the entire, laser energy in the longitudinal direction. The emerging beam section 15 emerges radially from the treatment head 7, i.e. at an angle of 90 with a tolerance of 10, preferably with a tolerance of 3 relative to the longitudinal axis 10.

(13) FIG. 3 shows in a schematic cross sectional top view the arrangement of FIG. 2. It can be seen that, due to the curvature of the output surface 12, the reflected beam section 14 is focussed onto the longitudinal axis 10. On the other hand, as shown in the side view of FIG. 2, the beam height of the reflected beam section 14 remains constant within the treatment head 7. As a result, the reflected beams section 14 forms a focal line 32 being disposed on the longitudinal axis 10. After having crossed the focal line 32, the beam width of the reflected beam section 14 widens again until reaching the second impingement point P.sub.2, as shown in FIG. 3. Since said second impingement point P.sub.2 is closer to the longitudinal axis 10 and the focal line 32 compared to the first impingement point P.sub.1, the emerging beam section 15 has a beam width w being smaller than the beam diameter d of the incoming beam section 11 (FIG. 2). As a result, the emerging beam section 15 meets the circumferential tissue surface 3 in the form of an elliptical laser spot 31. The closer the second impingement point P.sub.2 is disposed to the longitudinal axis 10 or the apex 13, the smaller the beam width w will be, resulting in an increased laser intensity and fluence. It is to be appreciated that FIG. 3 depicts what happens with a water-absorbed laser beam, where a water vapor bubble channel is formed immediately upon the laser light exiting the treatment head and entering the water, effectively facilitating propagation of a water-absorbed laser light through water over relatively very long distances without any significant broadening of the beam diameter. In order to avoid laser energy overload of the material of the treatment head 7, scanning of the conical output surface 12 is further desired such that a certain radial distance between both impingement points P.sub.1, P.sub.2 and between the first impingement point P.sub.1 and the apex 13 is maintained such that the immediate vicinity of the apex 13 is excluded from irradiation by the reflected beam section 14.

(14) Furthermore, according to the invention, a certain scanning pattern is performed by the scanner 9 and the control device 8 (FIG. 1), as shown in FIG. 3: According to the treatment requirements, the conical output surface 12 is scanned by the incoming beam section 11 on circles around the longitudinal axis 10 of the treatment head 7, as indicated by arrow 33, such that the emerging beam section 15 is subjected to a circular feed about the longitudinal axis 10, as indicated by arrow 34. Alternatively, the conically shaped output surface 12 is scanned by the incoming beam section 11 in a radial direction relative to the longitudinal axis 10, as indicated by arrow 36, as a consequence of which the emerging beam section 15 is subjected to an axial feed parallel to the direction of the longitudinal axis 10. Both circular and radial scanning patterns may be combined.

(15) Scanning can be performed continuously or in the form of a discrete dot pattern. The dot pattern might be a regular one or a random one. For certain applications it is advisable to scan the output surface 12 such that at least one certain and predefined portion 35 of the output surface 12 is excluded from irradiation or is subjected to reduced irradiation intensity by the incoming beam section 11, which can be controlled by the control device 8 (FIG. 1). This results in a skipped or reduced irradiation of a certain portion of the tissue surface 3; this might be required e.g. in a vaginal treatment for protecting the urethra.

(16) In order to achieve the described path of the laser beam 5 including the incoming beam section 11, the reflected beam section 14 and the emerging beam section 15 of the invention require a certain half opening angle of the conically shaped output surface 12 adapted to the first refractive index n.sub.1 of the treatment heads 7 material and the second refractive index n.sub.2 of the medium immediately surrounding the output surface 12 of the treatment head 7. The adjustment of the half opening angle is performed by meeting both aforementioned equations 1 and 2, thereby adjusting the half opening angle to be at least approximately equal to the optimal angle .sub.opt. Dependent on the required application, the adjustment of the half opening angle can be based on any surrounding medium having a second refractive index n.sub.2. However, preferably a half opening angle is chosen based on a second refractive index n.sub.2=1.0. As long as it is made sure that such treatment head 7 is operated in air only having such second refractive index n.sub.2=1.0, any optical material for forming the treatment head 7 having a first refractive index n.sub.1>1.28 will allow for adjusting the half opening angle to be the optimum angle .sub.opt. However, in case that the conically shaped output surface 12 come into contact with other media like water and/or blood, the conditions for total reflection and subsequent 90 refraction might not be met. In such cases, a treatment head material is chosen having a first refractive index n.sub.11.64 for working in contact with water, or even having a first refraction n.sub.11.75 for working in contact with water and/or blood.

(17) Preferably, the treatment head 7 is made of YAG having a first refractive index n.sub.1 of approximately 1.8, while the half opening angle is in a range from 33, inclusive, to 39, inclusive, and is in particular 36 as shown in FIG. 2. Said half opening angle =36 is equal to the optimal angle .sub.opt as derived from both aforementioned equations 2 and 3, resulting in an angle =90 when immersed in air having a second refractive index n.sub.2=1.0, as shown in FIG. 2. In case of contact with water and/or blood the conditions for total reflection at the first impingement point P.sub.1 are maintained, while the refraction at the second impingement point P.sub.2 leads to an angle only slightly deviating from the preferred 90 angle within the aforementioned tolerances. The half opening angle of 36 as a preferred example, based on aforementioned equation 1, leads to a minimum scanning radius R.sub.in being 1.62 the minimum surface radius r.

(18) The first preferred embodiment according to FIGS. 1, 2 and 3 is adapted for and used in immediate access to the body tissue 2 on the inner circumferential tissue surface 3. This means that no protection of the output surface 12 against treatment site media having the second refractive index n.sub.2 is provided and that the output surface 12 might come into contact with said media.

(19) In a first scenario, such laser system 1 including its treatment head 7 might be used for a non-ablative treatment of the tissue surface 3. In such case, the laser source 4 is chosen to provide a wavelength of the laser beam 5 which is not much absorbed by water. Preferably, the laser source 4 is a Nd:YAG laser source providing a laser beam 5 with a wavelength of 1,064 nm. Such laser beam 5 passes from the treatment head 7 to the tissue surface 3 even in cases when the medium in between is water and/or blood. Any desired laser parameters like pulse sequences, pulse durations, energy levels, and fluences can be chosen to perform the desired non-ablative treatment of the tissue surface 3.

(20) In an alternative scenario, an ablative treatment of the tissue surface 3 might be required. In such cases, a laser source 4 is chosen to provide a laser beam 5 having a strongly water-absorbable wavelength. Preferably, such laser source is selected from an Er:YAG, an Er:YSGG, an Er,Cr:YSGG, and a CO.sub.2 laser source. In case of air being the surrounding medium, such laser beam 5 reaches unhindered the tissue surface 3. In case of water and/or blood being the surrounding medium, the water content absorbs a significant amount of the laser energy when emerging from the output surface 12. In such cases, it is preferable to control the laser source 4 and the scanner 9 by means of the control device 8 such that the emerging beam section 15 has at the second impingement point P.sub.2 of the conically shaped output 12 a fluence of at least 1.0 J/cm.sup.2. By applying such a fluence level, the emerging beam section 15 causes vaporisation of the water containing surrounding medium. Thereby a so-called tunneling effect is achieved, by which the emerging beam section 5 passes through vapour bubbles to the tissue surface 3 as required.

(21) The shown embodiment can be used for post treatment of drilling holes in hard bone material e.g. in implantology. In such a case, the treatment head 7 preferably has a diameter in a range from 2.0 mm to 6.0 mm corresponding to a maximum surface radius R in a range from 1.0 mm to 3.0 mm. The preferred laser source 4 is an Er:YAG laser source being operated in a pulse mode with pulse durations in a range from 10 s to 1,000 s, with pulse energies in a range from 5 mJ to 2,000 mJ, and with mean diameters of the laser spots 31 in a range from 0.2 mm to 1.5 mm.

(22) The shown embodiment can also be used for thermally treating soft tissue in body cavities such as vagina and anus. In gynecology, the method and device can be used to treat stress and mixed stress urinary incontinence, vaginal atrophy, and vaginal relaxation syndrome. In such cases the treatment head 7 preferably has a diameter in a range from 8.0 mm to 50.0 mm corresponding to a maximum surface radius R in a range from 4.0 mm to 25.0 mm. The preferred laser source 4 is an Er:YAG laser source being operated in a pulse mode with pulse duration, in a range from 10 s to 2,000 s, with pulse energies in a range from 5 mJ to 2,000 mJ, and with mean diameters of the laser spots 31 in a range from 0.2 mm to 20 mm.

(23) FIG. 4 shows in a schematic cross-sectional side view a second preferred embodiment of the inventive hand piece 6 as part of the laser system 1 according to FIG. 1. The hand piece 6 comprises a grip 20 for manual movement, to which the treatment head 7 is attached. Unless explicitly mentioned otherwise, the treatment head 7 is identical to the treatment head 7 according to FIGS. 1, 2 and 3. The hand piece 6 further comprises a liquid-tight protective sleeve 16, which is attached to the grip 20 and which entirely covers the treatment head 7. The liquid-tight protective sleeve 16 is made of a material transparent to the laser beam 5 and comprises a circumferential wall 17, which is closed at its free distal end by a spherical end portion 37. The circumferential wall 17 is generally cylindrically shaped. However, any other longitudinally extending shape with e.g. a polygonal cross section might be usable as well. The circumferential wall 17 extends in the direction of the longitudinal axis 10 across the output body 23 of the treatment head 7, thereby leaving a free space 18 between the conically shaped output surface 12 at the circumferential wall 17. The free space 18 is filled with gas, preferably with air. However, any other gas fill or even a vacuum will do, as long as the medium within the free space 18 has a second refractive index n.sub.2 that is at least approximately 1.0.

(24) The hand piece 6 is inserted with its treatment head 7 and its surrounding protective sleeve 16 into a schematically sketched woman's vagina for treatment of the inner circumferential tissue surface 3 of the body mucosa tissue 2. The entire treatment head 7 including its conically shaped output surface 12 is shielded from any treatment site's water-containing and/or blood-containing liquid by means of the protective sleeve 16. Total reflection and refraction conditions of the laser beam 5 are maintained under the conditions of a surrounding medium having a second refractive index n.sub.2 of approximately 1.0. After emerging from the output body 23, the laser beam 5 passes unhindered through the free space 18 and the circumferential wall 17, until it reaches the target site on the tissue surface 3.

(25) On the outer surface of the treatment head 7 a depth scale 21 is provided, which allows for an exact axial positioning of the handpiece 6 relative to the treatment site. Said optional depth scale 21 may be incorporated into the embodiment according to FIGS. 1, 2, and 3 as well. In the embodiment of FIG. 4 the depth scale 21 may be alternatively positioned on the outer surface of the protective sleeve 16.

(26) The hand piece 6 according to FIG. 4 is part of a laser system 1 as described with the aid of FIGS. 1, 2, and 3. All related features and process steps may be applied with the hand piece 6 of FIG. 4. However, since the protective sleeve 16 allows for excluding the optical influence of water, blood and other surrounding media, any desired treatment process can be applied. This includes both ablative and non-ablative treatments with any suitable laser beam wavelength, fluence and energy levels, pulse sequences and so forth. The treatment of the vagina as disclosed is an exemplary non-limiting embodiment only. Any other circumferential tissue surface 3 of a body opening can be treated including urinal, rectal, ENT (ear, nose and throat) and implantology applications.

(27) The specification incorporates by reference the entire disclosure of European priority document EP 13 003 273.3 having a filing date of Jun. 27, 2013.

(28) While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.