METHOD FOR OPERATING A DEVICE FOR TREATMENT OF A TISSUE AND DEVICE FOR TREATMENT OF A TISSUE

Abstract

A method of operating a device (1) for treatment of a tissue (6) of a living being and such a device (1) including a transducer (2) comprising at least two subtransducers (2, 2), each for emitting a sub-beam (8) of ultrasound waves, preferably high intensity focused ultrasound waves, for irradiating the tissue (6). Each of the sub-beams (8) is focused on or focusable onto a focal point (F). In order to reduce skin burns, the intersection Area (A.sub.si) of a skin surface (7) for each sub-beam (8) is evaluated and a power (P.sub.si) and/or a duration (t.sub.si) of the irradiation, for every sub-transducer (2, 2), is determined as a rate of the total power (P.sub.total) or duration (t.sub.total) depending from the evaluated intersection area (A.sub.si).

Claims

1-16. (canceled)

17. A method of operating a device for treatment of a tissue of a living being, the device comprising: a transducer comprising at least two sub-transducers, each for emitting a sub-beam of ultrasound waves for irradiating the tissue, and each of the sub-beams being focused on or focusable onto a focal point; wherein the method includes the following steps: positioning the transducer such that at least one focal point of a sub-beam is located within the tissue to be treated; defining a total power and a duration of the irradiation to be delivered to the tissue; evaluating an intersection area of a skin surface with each sub-beam; and determining at least one of the power and the duration of the irradiation for every sub-transducer as a rate of the total power or duration depending from the evaluated intersection area.

18. The method according to claim 17, wherein the intersection area is evaluated taking into consideration a sub-beam area at a sub-transducer surface and a distance between skin surface and the sub-transducer surface.

19. The method according to claim 18, wherein the distance between skin surface and the sub-transducer surface is determined by means of A-mode echography.

20. The method according to claim 17, wherein if the intersection area is below a given value, at least one of the power and the duration of the corresponding sub-transducer is set to zero.

21. The method according to claim 17, wherein after the step of determining at least one of the power and the duration of the irradiation, every sub-transducer is triggered to emit a sub-beam of ultrasound waves.

22. A device for treatment of a tissue of a living being comprising: a transducer comprising at least two sub-transducers, each for emitting a sub-beam of ultrasound waves for irradiating the tissue, and each of the sub-beams being focused on or focusable onto a focal point, wherein the device further comprises: means for determining an intersection area of a skin surface with each sub-beam, and control means for controlling the device, and the control means being able to determine, based on a total power and a duration of the irradiation to be delivered to the tissue, at least one of a power and a duration of the irradiation for every sub-transducer as a rate of the total power or a duration, depending from the evaluated intersection area.

23. The device according to claim 22, wherein the transducer has a transducer surface which is substantially a sector of a hemispherical surface.

24. The device according to claim 22, wherein every sub-transducer has substantially at least one of the same sub-transducer surface and sub-transducer shape.

25. The device according to claim 22, wherein the transducer has 8 sub-transducers.

26. The device according to claim 22, wherein each sub-transducer has a fixed focal point, the focal point of one sub-transducer being coincident with the focal point of the at least one other sub-transducers.

27. The device according to claim 22, wherein every sub-transducer comprises an A-mode echography element for evaluating a distance between the skin surface and the sub-transducer surface.

28. A method of operating a device for treatment of a tissue of a living being, the device comprising: at least one transducer for emitting a beam of ultrasound waves for irradiating the tissue, and the beam being focused on or focusable onto a focal point; and an imaging device having at least an imaging plane intersecting the focal point; wherein the method includes the following step: positioning the at least one transducer such that the focal point is located within the tissue to be treated; orienting the at least one transducer such that the distance between the focal point and the skin surface intersected by the beam is as constant as possible throughout the whole skin surface, whereby the focal point is not moved.

29. The method according to claim 28, wherein the at least one transducer is rotated around an axis contained in the imaging plane of the ultrasonic imaging device for orienting.

30. The method according to claim 28, wherein the at least one transducer is rotated around an axis which does not cross the focal point for orienting.

31. The method according to claim 28, wherein a three-dimensional representation of the skin surface, obtained by the imaging device, is taken into consideration for determining the distance between the focal point and the skin surface.

32. A device for treatment of a tissue of a living being, the device comprising: at least one transducer for emitting a beam of ultrasound waves for irradiating the tissue, and the beam being focused on or focusable onto a focal point; an imaging device having at least an imaging plane intersecting the focal point; wherein the device further comprises: means for positioning the at least one transducer such that the focal point is located within the tissue to be treated; means for orienting the at least one transducer such that a distance between the focal point and the skin surface intersected by the beam is as constant as possible throughout an entire skin surface, whereby the focal point is not moved.

Description

[0053] The invention will be now described according to a preferred embodiment of the present invention in connection with the drawings, which show:

[0054] FIG. 1: a schematic view of a device according to the present invention;

[0055] FIG. 2: a schematic arrangement of the sub-transducers of the device according to FIG. 1;

[0056] FIG. 3: a schematic arrangement of a sub-transducer of the device according to FIG. 1; and

[0057] FIG. 4: a schematic comparison between a method and a device according to the prior art (left) and the present invention (right).

[0058] FIG. 1 schematically shows a device 1 comprising a transducer 2 with a fixed focal point divided in eight sub-transducers. In FIG. 2 the arrangement of the sub-transducers is shown schematically, whereby for sake of clarity, only six sub-transducers are shown in total and only two sub-transducers 2 and 2 are provided with reference numerals.

[0059] The transducer 2 has a transducer surface 3 which is a sector of a spherical surface, with every sub-transducer having a sub-transducer surface A.sub.tr as shown in FIG. 3.

[0060] The device 1 further includes an imaging device 4, in this case an A-mode echography device, with an imaging plane 5.

[0061] The sub-transducers of the transducer 2 are focused on a common focal point F, which also lies within the imaging plane 5 of the imaging device 4. The distance between the transducer surface and the focal point D.sub.tf (which is represented schematically in FIG. 3) is therefore the same for each sub-transducer.

[0062] The transducer is arranged such that the focal point F is located within a tissue to be treated, schematically represented by a body 6.

[0063] The body 6, which in this case is a breast tumour, is not located superficially but is surrounded by healthy tissue which must not be treated. The breast skin is also schematically represented by the skin surface 7.

[0064] Regarding FIG. 2, the surfaces of the sub-transducers are also represented schematically. The converging structure 8, represented schematically by the dashed lines and of which only one is shown for sake of clarity, represents the beam emitted by the respective sub-transducer 2.

[0065] Every sub-transducer 2, 2 comprises a distance measuring means, shown schematically by the reference numeral 9, which is placed roughly at the centre of the sub-transducer surface and is used for determining the distance between the sub-transducer surface and the skin surface 7 in order to perform the method according to the present invention.

[0066] The imaging device 4 is arranged in a gap 10 between neighbouring sub-transducers represented schematically.

[0067] After defining the total power (P.sub.total) and duration (t.sub.total) of the irradiation to be delivered to the body 6, the distance between the sub transducer surface and the skin surface 7 D.sub.ts is measured by the distance measuring means 9 for every sub-transducer.

[0068] An intersection area A.sub.si (also shown schematically in FIG. 3) of each sub-beam generated by each sub transducer is then evaluated by control means of the device 1 (not shown) according to:

[00003]$A_{\mathrm{si}}=A_{\mathrm{tr}}*{\left(\frac{D_{\mathrm{sf}}}{D_{\mathrm{tf}}}\right)}^2$

[0069] The area of the sub-transducer surface A.sub.tr and the distance between sub-transducer surface and focal point F D.sub.tf (which is equal to the radius of the surface of the transducer 2) are known parameters of the device 1. Therefore the distance between the skin surface 7 and the focal point F D.sub.sf can also be calculated.

[0070] Once every intersection area has been evaluated for every sub-transducer, the control means also determine the power P.sub.si of the irradiation for every sub-transducer as a rate of the total power P.sub.total proportional to the evaluated intersection area A.sub.si according to:

[00004]$P_{\mathrm{si}}=P_{\mathrm{total}}*\frac{A_{\mathrm{si}}}{\underset{i=1}{\overset{n}{.Math.}}.Math..Math.A_{\mathrm{si}}}$

[0071] The control means are then used to trigger the respective sub-transducers in order to irradiate the tissue to be treated located within the body 6.

[0072] After irradiation, the transducer 2 is oriented for treating tissue of the body 6 which has not (or not with the desired power) been treated during the preceding irradiation. The distance between the surface of the sub-transducers and the skin surface 7 is measured again, the intersection area A.sub.si is evaluated and the power P.sub.si is determined as described above. This process is repeated until the whole body 6 has been irradiated and hence treated.

[0073] FIG. 4 shows schematically on the left an arrangement according to the prior art, wherein a focal point F of a beam emitted or emittable by a transducer 2 with a transducer surface 3 is focused on a tissue to be treated. The beam intersects a skin surface 7. A distance D.sub.ts between the transducer surface 3 and the skin surface 7, which is represented schematically by the double-headed arrows, of which only one is provided with a reference sign for sake of clarity, varies throughout the whole skin surface intersected by the beam.

[0074] According to the present invention, the transducer 2 is oriented as shown schematically on the right of FIG. 4, such that the distance D.sub.ts between the transducer surface 3 and the skin surface 7 is as constant as possible throughout the whole skin surface.