Therapeutic device for treating tissue by emission of remote cross-focused ultrasound - Patent 733636

Abstract

To provide a therapy apparatus for treating tissue by the emission of focused ultrasound waves.SOLUTION: A creation surface of a pressure field of focused ultrasound waves is divided into at least N sectors having segments of asymmetrical concave curve with centres of curvature. Centres of curvature (c1, c2, ...) are asymmetrical where the centres of curvature are situated at different distances from a plane of symmetry A1 or from an axis of symmetry S and / or at different depths taken according to the axis of symmetry. Individual axes (a1, a2, ...) intersect between focal zones (Zc1, Zc2, ...) and the creation surface or beyond the focal zones such that a plurality of beams originating from the sectors create a focal coverage zone Zr which is off-axis relative to the plane of symmetry A1 or to the axis of symmetry S. The sectors of this creation surface creates energy deposit zones with profiles corresponding to the focal coverage zones.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to the technical field of an apparatus or device comprising an ultrasound probe formed by a plurality of ultrasound transducer elements, adapted to emit high intensity focused ultrasound (HIFU).

[0002] The object of the invention applies particularly advantageously in the field of therapeutic treatment with focused ultrasound. [Background technology]

[0003] In particular, from the publication "Kennedy, JE, High-intensity focused ultrasound in the treatment of solid tumours. Nat Rev Cancer, 2005. 5(4): p.321-7" it is known that treatment with focused ultrasound creates biological lesions in tissues by a combination of thermal and acoustic cavitation effects. To perform such a treatment, it is necessary to control the applied energy and to perform lesions of a suitable size in the tissue to be treated in a minimum time. Also, moving the probe requires motion sensing, which not only increases the treatment time but also reduces the accuracy of manual operations or requires the introduction of robotic systems that allow millimeter-level movements. Therefore, it is necessary to plan this treatment with as few probe movements as possible. Furthermore, depending on the tissue being treated, the acoustic window available for treating the tissue may be very limited, so moving the probe is not always practical (Reference: "Aubry, JF, et al. The road to clinical use of high-intensity focused ultrasound for liver cancer: technical and clinical consensus. J Ther Ultrasound, 2013. 1: p. 13").

[0004] The shape of such tissue damage is directly derived from the shape of the surface of the emitting face of the ultrasound probe used. For example, the natural geometric focus of a conventional spherical HIFU ultrasound transducer becomes elliptical due to diffraction. Also, the prior art has proposed various solutions to increase the size of the treated area without having to move the ultrasound probe.

[0005] EP 0214782 describes a solution for an ultrasonic transducer with a lens to obtain an annular focus from a spherical transducer geometry. This special configuration not only expands the focal area to the size of a ring, but also creates a focal range area resulting from the intersection of multiple ultrasonic beams at a location on the central axis of the transducer beyond the focal plane of the transducer. This document provides a system for reducing the pressure field in this focal range area to overcome the risk of secondary damage.

[0006] WO 2011 / 092683 describes a high-intensity focused ultrasound probe comprising a first network of ultrasound transducers for focusing a first beam on a target volume located at a lesion and a second network of ultrasound transducers for forming a second ultrasound beam focused on the same target volume, such that interference between said first and second beams results in an asymmetric ultrasound field in the target volume. In this document, various embodiments of this probe are described. The main drawback is that the two ultrasound beams are formed at different frequencies, which requires more expensive electronics, more complex dephasing calculations and causes the appearance of secondary pressure lobes outside the target volume.

[0007] It should be noted that an ultrasound therapeutic probe can be used in conjunction with an imaging probe, as proposed in EP 0 661 029. In the same vein, US Patent No. 5,522,869 describes an ultrasound energy therapeutic device with a cylindrical probe having a ring-shaped transducer.

[0008] Non-patent document XP55009820 describes a therapeutic probe that includes a rotating radiation surface formed by rotating a concave curved section with a center of curvature located away from the axis of symmetry around the axis of symmetry. In a cross section, this radiation surface shows two concave curved sections that are symmetrical about the axis of symmetry, each of which has an acoustic axis passing through the center of curvature and the center of the concave curved section. Such a transducer forms, on the one hand, a ring of ultrasonic foci bounded by a focal plane, and, on the other hand, a crossing area of ​​multiple ultrasonic beams. As can be seen from this document, the crossing area of ​​multiple ultrasonic beams corresponding to the secondary pressure peaks is located behind the focal plane.

[0009] EP 2035091 describes a toric HIFU transducer in which a ring-shaped focal region is formed in the center where a central focus is located.

[0010] EP 2 691 154 describes a therapeutic probe in which an ultrasound emitter includes an emission surface configured to form a first focal region defined in the focal plane and a second focal region located locally between the first focal region and the emission surface, the second focal region corresponding to the application region of a plurality of ultrasound beams.

[0011] The article "Vincenot, J., et al., Electronic beam steering used with a toroidal HIFU transducer substantially increases the coagulated volume. Ultrasound Med Biol, 2013. 39(7): p.1241-54" describes a technique of electronic focusing that introduces a minimal degree of freedom along an axis perpendicular to the acoustic axis, and consequently moves the lesion by a few millimeters along this axis. This solution allows the imaging of large areas (50 cm 3 ) can be treated in a very short time (2 minutes).

[0012] WO 2011 / 024074 proposes a solution to accommodate the large number of emitter elements and current generators employed in conventional expensive and complex electronic focusing techniques. The solution aims to effectively reduce the number of current generators by coupling the emitter elements through packets so that the current generator can supply multiple emitter elements in parallel. Such coupling can be modified electrically to move the focal spot to the shape of the area to be treated. Although this solution can reduce the cost of the control electronics, it cannot reduce the cost of transducers containing hundreds of emitter elements. The production of this type of transducer requires the use of digital micromachining machines, and the problem of electro-acoustic coupling between the elements requires multi-element cutting, which is difficult to implement with conventional ceramic transducers.

[0013] WO 2016 / 144931 likewise discloses a system and process of ultrasound radiation for tissue regeneration, which performs defined scanning cycles. Summary of the Invention

[0014] Analyzing various solutions of the prior art, it is considered that the treatment of complex-shaped tissue regions away from the acoustic axis is difficult. In fact, the treatment of complex shapes with focused ultrasound in the broad sense requires a large number of elements (and associated electronics) and long treatment times. In the case of focused ultrasound treatment with a toric transducer, the pressure is maximum along the acoustic axis, which suggests that it is difficult to increase the treatment area relative to the acoustic axis and treat complex shapes that do not have rotational symmetry.

[0015] This is especially true for the tissue targeted for breast cancer treatment. This organ is cone-shaped, with a ring-like appearance at its apex, and although it varies in size, there is almost always one possible position where the probe can treat the tumor. From this unique position, not only must the entire target area containing the tumor be treated, but also a certain amount of healthy surroundings. To do this, the energy must not only be applied deeply, but also in such a way that the final damage extends along an axis perpendicular to the acoustic axis, as well as this axis itself.

[0016] This is also the case for target regions with asymmetric volumes along the acoustic axis, with the distance along an axis perpendicular to the acoustic axis increasing along the acoustic axis. This target region may, for example, conform to complex shaped tumors or complex shaped organs (prostate, kidney, thyroid, etc.). Another shape of target region relates to hollow volumes extending around non-linear sections, for example to treat tumors along arteries or veins, tumors along the digestive tract, tumors along bones, Wilson's duct of the pancreas, tumors along the urethra or bile duct.

[0017] The object of the present invention is to remedy the shortcomings of various prior art solutions by proposing a novel low-cost treatment device configured to obtain a biological lesion volume adapted to the complex shape of the tissue to be treated, in particular when the acoustic treatment window is limited.

[0018] To achieve this objective, a therapeutic device for treating tissue by emitting focused ultrasound comprises a therapeutic probe having a transducer including a plurality of ultrasound emitters driven by signals transmitted by a signal generator constituting part of a control circuit so as to define a generation plane of a focused ultrasound pressure field.

[0019] According to the present invention, The generation surface is divided into at least N sectors (N is between 2 and 32) so that the ultrasound waves are focused in a focal region defined by a focal plane, and the sectors of the generation surface have, in a cross section, a concave curved portion (concave curved segment) of finite length that is asymmetric with respect to a symmetry plane or axis; the centres of curvature (of the concave curved portion) are asymmetric with respect to the plane of symmetry or the axis of symmetry such that the centres of curvature are located at different distances from the plane of symmetry or the axis of symmetry and / or at different depths along the axis of symmetry; Each of the concave curved portions has an individual axis passing through a center of curvature of the concave curved portion and a center of the concave curved portion; the individual axes intersect between the focal region and the generation surface or across the focal region such that a plurality of beams originating from the sector intersect between the focal region and the generation surface or across the focal region to form a focal coverage zone that is off-axis with respect to the plane or axis of symmetry and spaced apart from the focal plane; the sector of the generation surface is formed by rotating the concave curved portion 2π / N around the axis of symmetry or by moving the concave curved portion along a direction perpendicular to the cross section including the concave curved portion, such that the sector forms an energy deposition region having a profile corresponding to the focal range region, The concave curved portions of the generation surface extend in the cross section on either side of the axis of symmetry or the plane of symmetry and are spaced apart from one another such that the focal range regions are spaced apart from the generation surface.

[0020] According to a preferred implementation feature, the generating surface is divided into two sectors.

[0021] Advantageously, at said generating surface, an inner end defines a housing for mounting an ultrasound imaging probe.

[0022] According to a first variant embodiment, the generated surface originates from a surface defined by transducer elements arranged in a circular geometric arrangement, the circular geometric arrangement being formed by rotating a concave curved portion around the axis of symmetry to describe arcs of intersecting and non-coincident circles, the intersecting and non-coincident circles intersecting such that the focal region has the shape of a portion of a circle.

[0023] According to a practical feature, said surface has a shape that is cut symmetrically about said axis of symmetry.

[0024] According to a second variant embodiment, the generation surface originates from a surface defined by the transducer elements arranged in a cylindrical geometric arrangement, the cylindrical geometric arrangement being formed by moving two of the concave curved portions a finite length along a direction perpendicular to the cross section including the concave curved portions so that the focal region has a linear shape.

[0025] According to one embodiment, the ultrasound emitters of the transducer define an emission surface which corresponds to the production surface of a focused ultrasound pressure field.

[0026] According to another embodiment, the signal generator, which forms part of the control circuit, is controlled to transmit signals to drive the ultrasonic emitters arranged in segments using a delay law or a phase law so that the generation surface of the focused ultrasonic pressure field is formed.

[0027] According to an advantageous variant embodiment, during the exposure phase, the ultrasound emitters forming part of a sector and a sector symmetrically opposite said sector with respect to said axis of symmetry are driven by signals transmitted by the signal generator forming part of the control circuit, such that corresponding energy deposition areas are formed.

[0028] According to one feature of the invention, during the exposure phase, the ultrasound emitters forming part of a sector and a sector symmetrically opposite said sector about said axis of symmetry are driven by signals transmitted by the signal generator forming part of the control circuit, such that corresponding energy deposition areas are formed on one side of the plane of symmetry.

[0029] According to another feature of the invention, in a subsequent exposure stage, the ultrasound emitters forming a sector and a part of the sector opposite said sector symmetrically with respect to said plane of symmetry are driven by a signal transmitted by the signal generator forming part of the control circuit, such that a corresponding energy deposition area is formed on a side opposite to the side on which the energy deposition area was formed in the previous exposure stage.

[0030] Advantageously, the ultrasound emitters are arranged along a plurality, in particular several, sectors perpendicular to the plane of symmetry, and in successive exposure phases the ultrasound emitters of the sectors are driven by signals transmitted by the signal generator constituting part of the control circuit, such that energy deposit zones are formed on either side of the plane of symmetry.

[0031] According to the invention, in each successive exposure stage, in which the centre of curvature for each exposure stage is located at a different distance from the plane or axis of symmetry and / or at a different depth along its perpendicular axis, the ultrasound emitter is driven by a signal transmitted by the signal generator forming part of the control circuit so as to obtain off-axis energy deposit zones.

[0032] According to one embodiment, in successive exposure stages, in which the centre of curvature is located at different distances from the plane or axis of symmetry and / or at different depths along the normal axis for each exposure stage, the ultrasound emitter is driven by signals transmitted by the signal generator forming part of the control circuit so as to obtain differently positioned off-axis energy deposition areas having the same or different sizes in these successive exposure stages.

[0033] According to another embodiment, the energy application regions can be concentric and / or symmetrical and / or asymmetrical and / or overlapped along their vertical axis, in successive exposure stages, by the ultrasound emitters being driven by signals transmitted by the signal generator constituting part of the control circuit, such that the distance and / or the depth of the centre of curvature is varied from one exposure stage to another.

[0034] According to an additional embodiment, at least one Supplementary During the exposure phase, the ultrasonic emitter is driven by a signal transmitted by the signal generator, which forms part of the control circuit, so as to focus the ultrasonic waves at a focal region and obtain a focal range region that is centered with respect to the plane or axis of symmetry and located between the focal region and the emission plane, spaced apart from the focal plane or beyond the focal region.

[0035] The present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a schematic diagram of a treatment device including a treatment probe shown according to a first variant embodiment, having a shape of revolution about an axis of symmetry. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a generation surface of a pressure field of focused ultrasound implemented in accordance with the first modified embodiment, which is regarded as a virtual generation surface. [Diagram 3] FIG. 3 is a diagram for explaining a guideline for forming a surface for generating a pressure field of the focused ultrasonic wave shown in FIG. [Figure 4] FIG. 4 is an elevational view in cross section of a first example of a surface where a pressure field of focused ultrasound is generated, which can be implemented in accordance with the first and second modified embodiments of the probe, and has a quasi-cylindrical shape. [Diagram 5] FIG. 5 is an elevational view in a cross section of a second example of a surface where a pressure field of focused ultrasound is generated, which can be implemented in accordance with the first and second modified embodiments of the probe. [Figure 6] FIG. 6 is an elevational view in a cross section of a third example of a surface where a pressure field of focused ultrasound is generated, which can be implemented in accordance with the first and second modified embodiments of the probe. [Figure 6A] FIG. 6A is an elevational view in cross section of a fourth example of a surface where a pressure field of focused ultrasound is generated, which can be implemented in accordance with the first and second variant embodiments of the probe. [Figure 7A] FIG. 7A is a rear view of a probe implemented in accordance with a first alternative embodiment, showing that the face of the probe is divided into four sectors. [Figure 7B] FIG. 7B is a diagram showing a surface where a pressure field of focused ultrasound is generated by the probe shown in FIG. 7A. [Figure 7C] FIG. 7C is a diagram showing a surface where a pressure field of focused ultrasound is generated by the probe shown in FIG. 7A. [Figure 8A] FIG. 8A is a cross-sectional view of a probe implemented according to a first alternative embodiment in the form of a toroidal transducer having a central opening. [Figure 8B] FIG. 8B is a cross-sectional elevational view showing the central natural focusing pointer implemented by a probe according to a first alternative embodiment implemented in the form of a toric transducer as shown in FIG. 8A. [Figure 8C] FIG. 8C is a cross-sectional elevation view obtained following the central natural focusing guidelines shown in FIG. 8B and taken perpendicular to the axis of symmetry along plane Pr, showing the shape of the focal range region of multiple ultrasound beams at their centers. [Figure 9A]FIG. 9A is a schematic diagram showing an embodiment of a virtual plane for forming a pressure field of focused ultrasound, implemented according to a first variant embodiment and obtained by a transducer as shown in FIG. 8A. [Figure 9B] FIG. 9B is a cross-sectional elevation view in section showing the focusing guideline of the transducer shown in FIG. 8A to form a virtual plane for forming the pressure field of the focused ultrasound shown in FIG. 9A to obtain a focal range area that is off-axis of multiple ultrasound beams shown relative to the focal range area of ​​multiple ultrasound beams obtained according to the natural focusing guideline. [Figure 9C] FIG. 9C is a cross-sectional elevation view taken perpendicular to the axis of symmetry along plane Pr, illustrating the shape of the off-axis focal range region of multiple ultrasound beams obtained according to the teachings of the present invention and the shape of the focal range region of multiple ultrasound beams obtained according to the teachings of natural focusing. [Figure 9D] FIG. 9D is a perspective view illustrating the shape of off-axis focal range regions of multiple ultrasound beams obtained in accordance with the teachings of the present invention. [Figure 10A] FIG. 10A is a schematic diagram showing another embodiment of a virtual surface for forming a pressure field of focused ultrasound obtained by a transducer as shown in FIG. 8A, implemented according to a first variant embodiment. [Figure 10B] FIG. 10B is a cross-sectional elevation view in cross section showing the focusing guideline of the transducer shown in FIG. 8A to form a virtual plane for creating the pressure field of focused ultrasound shown in FIG. 10A to obtain a focal range area that is off-axis of multiple ultrasound beams shown relative to the focal range area of ​​multiple ultrasound beams obtained according to the natural focusing guideline. [Figure 10C] FIG. 10C is a cross-sectional elevation view taken perpendicular to the axis of symmetry along plane Pr illustrating the shape of the off-axis focal range region of multiple ultrasound beams obtained according to the teachings of the present invention and the shape of the focal range region of multiple ultrasound beams obtained according to the teachings of natural focusing. [Figure 10D]FIG. 10D is a perspective view showing the shape of the off-axis focal range regions of multiple ultrasound beams obtained by following the focusing guidelines shown in FIG. 10B. [Figure 10E] FIG. 10E is a perspective view showing the combined geometry of off-axis focal range regions of multiple ultrasound beams obtained in two successive ultrasound exposure steps corresponding to the guidelines shown in FIGS. 9B and 10B. [Figure 10F] FIG. 10F is a plan view showing the combined geometry of off-axis focal range regions of multiple ultrasound beams obtained in two successive ultrasound exposure steps corresponding to the guidelines shown in FIGS. 9B and 10B. [Figure 11A] FIG. 11A is a plan view showing concentric and asymmetric off-axis focal range regions at successive exposure stages. [Figure 11B] FIG. 11B is a perspective view showing concentric, symmetric, and superimposed off-axis focal range regions in successive exposure steps. [Figure 11C] FIG. 11C is a perspective view showing concentric, symmetric, and superimposed off-axis focal range regions in successive exposure steps. [Figure 11D] FIG. 11D is a perspective view showing a central natural focal range region combined with concentric, symmetrical, and superimposed off-axis focal range regions in successive exposure stages. [Figure 11E] FIG. 11E is a plan view showing, in successive exposure stages, a natural focus range region surrounded by a focus ring having two concentric off-axis focus range regions, which is itself surrounded by a focus ring having four concentric off-axis focus range regions. [Figure 12] FIG. 12 is a perspective view showing an example of a transducer having a pseudo-cylindrical shape according to a second modified embodiment for implementing the present invention. [Figure 12A] FIG. 12A is a perspective view showing the shape of the focal range regions of multiple ultrasound beams obtained in an exposure stage according to the central natural focusing guideline implemented by a transducer having a pseudo-cylindrical shape shown in FIG. [Figure 12B] FIG. 12B is a perspective view showing the shape of the off-axis focal range regions of multiple ultrasound beams obtained by a transducer having a quasi-cylindrical shape as shown in FIG. 12 during an exposure stage. [Figure 12C] FIG. 12C is a perspective view showing the symmetric shape of the off-axis focal range regions of multiple ultrasound beams obtained with a transducer having a quasi-cylindrical shape shown in FIG. 12 at a later exposure stage. [Figure 13A] FIG. 13A is a perspective view showing an example of a second alternative embodiment of the transducer having a pseudo-cylindrical shape shown in FIG. [Figure 13B] FIG. 13B is a perspective view showing symmetrical off-axis focal range regions of multiple ultrasound beams obtained by the transducer shown in FIG. 13A in two successive exposure steps. [Figure 13C] FIG. 13C is a perspective view showing the shape of the off-axis focal range regions of multiple ultrasound beams obtained by the transducer shown in FIG. 13A in successive exposure steps. [Figure 13D] FIG. 13D is a perspective view showing the shape of the off-axis focal range regions of multiple ultrasound beams obtained by the transducer shown in FIG. 13A in relation to the areas of ultrasound preserved in successive exposure steps. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] As can be seen in more detail from FIG. 1, the object of the invention relates in a general sense to a treatment device I comprising a treatment probe 1 adapted to perform a treatment of tissue of a living body using high intensity focused ultrasound (HIFU). In particular, the treatment probe 1 comprises a transducer 2 including a number of ultrasound emitters 3, for example piezo elements, which define an emission surface 4 of focused ultrasound waves. These ultrasound emitters 3 are connected by a coaxial cable 5 and via an amplifier stage 6 to a control circuit 7 which transmits signals for driving the ultrasound emitters 3. A detailed description of the control circuit 7 will not be given, since the implementation of the control circuit 7 is part of the technical knowledge of the person skilled in the art. This control circuit 7 typically includes a control signal generator, which is connected to the ultrasound emitters via the amplifier stage 6. Thus, each of the ultrasound emitters 3 is connected to a respective signal generator.

[0038] The signal generator of the control circuit 7 drives the ultrasonic emitters 3 arranged in segments, more precisely in curved or straight sections, so as to define a surface 8 for forming the pressure field of the focused ultrasound. According to a first advantageous embodiment, the signal generator forming part of the control circuit 7 is controlled to send signals for driving the ultrasonic emitters 3 of the transducer 2 using a delay or phase law, so as to define a generation surface 8 of the pressure field of the focused ultrasound. This generation surface 8 is considered as a virtual generation surface different from the emission surface 4 of the transducer (FIGS. 2, 9A and 10A). According to a second embodiment, the generation surface 8 of the pressure field of the focused ultrasound corresponds to the surface 4 of the transducer.

[0039] In other words, the generation surface 8 of the pressure field of the focused ultrasound corresponds to a physical transducer, more precisely to the surface 4 of the transducer 2, or to a virtual generation surface 8 by applying a phase to the command channel of the transducer 2.

[0040] The driving of the ultrasonic emitter 3 using the delay or phase law is well known to those skilled in the art, but the following provides a guide for completeness.

[0041] The total pressure P(r) at each point in the region of interest is defined as follows (Chavrier et al. 2000):

[0042]

number

[0043] P(r) is the pressure (Pa) at point r, dS is the set of elementary sources, ρ is the volumetric mass of the propagation medium, c is the speed of ultrasound in the propagation medium, λ is the wavelength, N is the number of driving elements of the transducer, S is the surface area of ​​each of the radiation sources, u n is the normal velocity of element n, φ n is the phase applied to element n, α medium is the attenuation coefficient of the medium, f is the frequency of use of the transducer, and finally k is the wave number. According to a method known as "maximal response" (Curiel et al. 2002), the phase due to each transducer element at the preferred focus is expressed as φ in the line integral above. n = 0.

[0044] Therefore, to obtain a maximum signal at the preferred point, the phase applied to each element is given by:

[0045]

number

[0046] Im[P(n,m)] and Re[P(n,m)] are the imaginary and real parts, respectively, of the pressure field at point M transmitted by transducer element n. Thus, for each element n, the delay time τ n is defined as follows:

[0047]

number

[0048] Another way to calculate this is to define for each element n the path difference radiated between the natural focus and the desired focus. The delay of each element is then defined as the distance between element n and its natural focus, d nat , the distance between element n and the desired focus is d foc , where c is the speed of ultrasound in the medium,

number

number

[0049] Another calculation method is to define a virtual ultrasonic emitter divided into N elements having different geometric shapes, and spatially match the center of the first element of the real emitter with the center of the first element of the virtual emitter. The distance d between each element is n calculates the applied delay,

number

number

[0050] As will be better understood herein, the shape of the generating surface 8 will vary, in particular depending on the application of the treatment device. It may therefore be advantageous to arrange a probe with a surface 4 of a given shape that is easy for a person skilled in the art to form (for example as in FIG. 1 ) and to form from this surface 4 a generating surface 8 that has a complex shape to form and that differs from the shape of the surface 4 (for example as shown in FIG. 2 ). However, it is also possible to manufacture a transducer 2 with a surface 4 of a shape that corresponds to the generating surface 8 of the pressure field of focused ultrasound, as shown in FIG. 2 .

[0051] It should be noted that according to the first modified embodiment (FIGS. 1, 2, 3, 7A-7C, 8A-8C, 9A-9D, 10A-10F, and 11A-11E), the generation surface 8 has a shape of revolution about the axis of symmetry S. It should also be noted that according to the second modified embodiment (FIGS. 12, 12A-12C, and 13A-13D), it has a tubular pseudo-cylinder shape, or a form consisting of two cylinder parts having a symmetry plane A1. It should be noted that FIGS. 4, 5, 6, and 6A are cross-sectional views for explaining the generation surface 8 according to the first modified embodiment and the generation surface 8 according to the second modified embodiment. The symmetry axis S defined along the vertical direction Z corresponds to the symmetry axis or acoustic axis of the transducer surface 4 formed in the shape of a surface of revolution. The symmetry plane A1 is defined in a plane determined by the vertical direction Z and the lateral direction Y. This plane of symmetry is perpendicular to the plane Pp defined by the axes X, Z of the references X, Y, Z. This plane of symmetry A1 is the plane of symmetry or acoustic plane of face 4 of the transducer.

[0052] According to a feature of the invention, which is shown in more detail in the figures, the generation surface 8 is divided into at least N sectors 81, 82, ..., which contain the acoustic axis S and extend by radial cuts in the acoustic axis S or in a mirror position relative to the acoustic plane A1. According to a first variant embodiment, the sectors are radial sectors relative to the acoustic axis S, which contain, per sector, the ultrasound emitters 3 arranged in a ring. Meanwhile, in a second variant embodiment, the sectors are mirror-image sectors relative to the acoustic plane A1, which contain the ultrasound emitters 3 arranged in a straight section. According to the first variant embodiment, an advantageous number N of radial sectors is between 2 and 8, preferably equal to 2 (Fig. 2), while in the second variant embodiment, the number N of sectors perpendicular to the acoustic plane A1 is between 2 and 32 (Figs. 12 and 13A). Thus, according to these advantageous variant embodiments, the ultrasound emitters 3 of the transducer are limited in number and the cost of such a transducer is reduced. For example, in the preferred two sector variant, each sector may contain 32 ultrasound emitters 3. For simplicity of explanation, in the remainder of the specification only the term sector will be used.

[0053] The generation surface 8 is divided into N sectors 81, 82, ... so that the ultrasound waves are focused in respective focal regions Zc1, Zc2, .... The focal regions Zc1, Zc2, ... are defined in the focal planes Pf1, Pf2, ..., respectively. Figures 2 to 6, 9A, 10A and 12 show a preferred embodiment in which the generation surface 8 is divided into two sectors 81, 82. Figure 1 shows another embodiment in which the emission surface 4 is advantageously divided into two sectors 41, 42 to form a generation surface 8 divided into two symmetrically opposed sectors.

[0054] Figure 7A shows another embodiment in which the emission surface 4 is advantageously divided into four sectors 41, 42, 43, 44 to form a generation surface 8 which is itself divisible into four sectors 81, 82, 83, 84. Advantageously, the emission surface 4 is divided into four sectors to form a generation surface 8 which is divided into two sectors each by two orthogonal planes (Figures 7B and 7C).

[0055] As can be seen more precisely from Fig. 4, in a cross section Pp determined by the axes X and Z of the references X, Y, and Z, each sector 81, 82, ... of this generating surface 8 shows a concave curved portion (concave curved segment) S1, S2, ... of finite length. As can be seen from the figure, the concave curved portions S1, S2 of the sectors 81, 82 are delimited by respective ends 8a1, 8b1 and respective ends 8a2, 8b2. In the cross section Pp, the two concave curved portions S1, S2, ... are located on either side of the symmetry plane A or the symmetry axis S.

[0056] The concave curved portions S1, S2, ... are asymmetric with respect to the symmetry axis S of the transducer 2 in a first modified embodiment in which the generating surface 8 has a shape that rotates around the symmetry axis (FIGS. 1, 2, 3, 7A to 7C, 8A to 8C, 9A to 9D, 10A to 10F, and 11A to 11E). Alternatively, the concave curved portions S1, S2, ... are asymmetric with respect to the symmetry plane A1 of the transducer in a second modified embodiment in which the generating surface 8 has a pseudo-cylindrical shape (FIGS. 12, 12A to 12C, and 13A to 13D).

[0057] According to Figs. 4, 5, 6 and 6A showing the generation surface 8 according to the first modified embodiment and the generation surface 8 according to the second modified embodiment, each of the concave curved sections S1, S2, ... has a center of curvature c1, c2, ... corresponding to the ultrasound focal region Zc1, Zc2, ..., respectively. According to the present invention, the concave curved sections S1, S2, ... of the sectors are asymmetric with respect to the symmetry plane A1 or the symmetry axis S. Also, the centers of curvature c1, c2, ... are asymmetric with respect to the symmetry plane A1 or the symmetry axis S, and are asymmetric with respect to the symmetry plane A1 or the symmetry axis S, in that the centers of curvature c1, c2, ... are located at different distances from the symmetry plane A1 or the symmetry axis S and / or are located at different depths along the vertical direction Z.

[0058] According to the example shown in FIG. 4, including a first sector 81 and a second sector 82, the distance from the center of curvature c1 of the first sector 81 to the symmetry axis S or symmetry plane A1 is greater than the distance from the center of curvature c2 of the second sector 82 to the symmetry axis S or symmetry plane A1. These distances are taken along a direction X perpendicular to the symmetry axis S or symmetry plane A1. It should be noted that in the example shown in FIG. 4, the centers of curvature c1 and c2 are located at the same depth along the vertical direction Z (or the symmetry axis S). That is, it should be noted that the centers of curvature c1 and c2 are located along the same straight line perpendicular to the symmetry axis S or symmetry plane A1. In other words, the centers of curvature c1 and c2 are located along the combined focal planes Pf1 and Pf2.

[0059] 5 shows another embodiment in which not only the distance from the center of curvature c1 to the axis of symmetry S or plane of symmetry A1 is different from the distance from the center of curvature c2 to the axis of symmetry S or plane of symmetry A1, but also the depth of the center of curvature c1 along the axis of symmetry S is different from the depth of the center of curvature c2 along the axis of symmetry S. Thus, according to the example shown in FIG. 5, the focal plane Pf2 containing the center of curvature c2 is further away from the transducer along the axis of symmetry S than the focal plane Pf1 containing the center of curvature c1. In other words, the centers of curvature c1, c2 are located in different focal planes Pf1, Pf2, respectively.

[0060] Of course, the centers of curvature c1, c2 are also considered asymmetric if they have different depths along the axis of symmetry S, while the distances from the centers of curvature c1, c2 to the axis of symmetry S or plane of symmetry A1 are the same. Figure 6 shows this embodiment, where the depth of the center of curvature c1 along the axis of symmetry S is different from the depth of the center of curvature c2 along the axis of symmetry S, while the distance from the center of curvature c1 to the axis of symmetry S or plane of symmetry A1 is the same as the distance from the center of curvature c2 to the axis of symmetry S or plane of symmetry A1. According to this example, the centers of curvature c1, c2 are located in different focal planes Pf1, Pf2, respectively.

[0061] Each of the concave curved portions S1, S2, . . . of a sector has an individual axis a1, a2, . . . passing through the centre of curvature c1, c2, .

[0062] According to another feature of the invention, the individual axes a1, a2, ... of the concave curved portions intersect to form a focal range region Zr off-axis with respect to the plane of symmetry A1 or with respect to the axis of symmetry S. This focal range region Zr corresponds to the focal range region of the multiple ultrasound beams originating from sectors 81, 82, ... of the generation surface 8. In the embodiment shown in Figures 4 to 6 and 6A, in the cross section Pp, the focal range region Zr shows a four-sided cross section in the shape of a parallelogram defined by the multiple beams originating from each end 8a1, 8b1 and each end 8a2, 8b2 of each of the concave curved portions S1, S2. This focal range region Zr of ultrasound is advantageously used to create voluminous biological lesions. Independently of the use of the focal range region Zr as a treatment region, the geometry of the lesions created is controlled by the combination of the focal range regions Zc1, Zc2, ... and the focal range region Zr. In the present invention, the energy deposition region corresponds to the focal range region Zr, independently of the energy that may be deposited in the other focal regions.

[0063] This focal range region Zr is off-axis in the sense that the individual axes a1, a2, ... intersect at a common intersection point I located outside the plane of symmetry A1 or outside the axis of symmetry S. The individual axes a1, a2, ... either intersect at a depth located between the focal regions Zc1, Zc2, ... and the generation surface 8, as shown in Figures 3 to 6 and 12, or intersect beyond the focal regions Zc1, Zc2, ... as shown in Figure 6A. The beams originating from sectors 81, 82, ... intersect such that the focal range region Zr is located at a distance from the focal planes Pf1, Pf2, ... along the vertical direction Z.

[0064] According to a feature of an advantageous embodiment, the curved portions S1, S2, ... extend in the cross section Pp on either side of the axis of symmetry S or the plane of symmetry A1 and are spaced apart from one another so that the focal range region Zr lies away from the generation plane 8. Thus, as is evident from Figures 4 to 6 and 6A, the ends 8a1, 8a2 of the curved portions, referred to as the inside, are spaced apart from the axis of symmetry S or the plane of symmetry A1.

[0065] As a result of such an arrangement, the generating surface 8, and subsequently the surface 4, presents an opening 10 centered on the symmetry axis S or plane A1. The ends, called inner 8a1, 8a2, of the curved portion located in the cross section Pp are spaced apart from each other by an inner distance Di along the axis X ranging from 10 mm to 120 mm. The selection of the distance between these ends changes the position of the focal range region Zr relative to the generating surface 8 (FIGS. 3, 4, 5, 8B, 9B and 10B), or the associated configuration changes the shape of the focal range region Zr and its extent along the axis Z (FIG. 6A). Advantageously, this opening 10 serves as a housing for an ultrasound imaging probe.

[0066] It should be noted that in the cross section Pp, the ends 8b1, 8b2 of the sectors referred to as outer are spaced apart from each other by an outer distance Ds in order to place the focal range region Zr away from the focal planes. In other words, the focal range region Zr does not contact the focal planes Pf1, Pf2, .... In this way, the focal range region Zr and the focal regions Zc1, Zc2, ... are different from each other or spaced apart from each other.

[0067] According to another feature of the invention, according to a first variant embodiment, the sectors 81, 82, ... of the generating surface 8 are formed by rotating the concave curved sections S1, S2, ... by 2Π / N around the axis of symmetry S. Alternatively, according to a second variant embodiment, the sectors 81, 82, ... of the generating surface 8 are formed by moving (translating) the curved sections S1, S2, ... along a direction Y perpendicular to the cross section Pp including the curved sections S1, S2, ..., where N is the number of sectors. The sectors 81, 82, ... extend along an angular range or length of substantially the same value. Thus, if the generating surface 8 is a surface of revolution divided into two sectors, each sector 81, 82 extends along an angular range of 180° (FIG. 2).

[0068] The sectors 81, 82, ... located in mirror image positions with respect to the symmetry axis S or symmetry plane A1 form energy deposition areas with contours corresponding to the focal range area Zr and the focal area Zc. According to a first variant embodiment, the sectors of the generation surface 8 are formed by rotating a concave curved section around the symmetry axis S, and the focal areas Zc1, Zc2, ... have the shape of a part of a circle. If the generation surface 8 is divided into two sectors 81, 82, the focal areas Zc1, Zc2 are semicircular extending along an angular range of 180° (FIG. 3). According to a second variant embodiment, the sectors 81, 82, ... are formed by moving a concave curved section along a direction Y perpendicular to the cross section Pp including the curved section, and the focal areas Zc1, Zc2, ... extend along straight lines located in the focal planes Pf1, Pf2, ... parallel to the direction Y (FIG. 12). If the generation plane 8 is divided into two sectors 81, 82, the focal regions Zc1, Zc2 extend along two straight lines located in the focal planes Pf1, Pf2 parallel to the direction Y (FIG. 12).

[0069] The generation surface 8 of the focused ultrasound pressure field is obtained or implemented by a transducer having a surface 4 configured to obtain the characteristics of the generation surface 8 described above.

[0070] According to a first variant embodiment, the generating surface 8 is a body of revolution. This generating surface 8 originates from a surface 4 defined by the transducer elements, advantageously arranged in a toric geometric arrangement. The toric geometric arrangement is formed by rotating a concave curved section around an axis of symmetry S, describing mutually intersecting and non-coincident circular arcs, such that the focal regions have the shape of portions of a circle.

[0071] The face 4 of the transducer corresponds to a truncation of the envelope of a crossed torus along two planes perpendicular to the axis of symmetry S, as shown in FIG. 8A.

[0072] According to a second variant embodiment, the generating surface 8 exhibits a pseudo-cylindrical or tubular shape. The surface of this generating surface 8 originates from the surface 4 defined by the transducer elements, which are arranged in a cylindrical geometry. The cylindrical geometry is formed by displacing two curved sections by a finite length along a direction perpendicular to the cross section containing them, so that the focal region has a linear shape.

[0073] FIG. 8A shows a preferred exemplary embodiment of a face 4 of a transducer 2 defined by concave curves based on an intersecting torus geometry.

[0074] As can be seen from FIG. 8B, in the cross section Pp, the radiation surface 4 includes two concave curved portions S'1, S'2 that respectively describe an arc of a first circle E'1 having a center c'1 and a second circle E'2 having a different center c'2 different from the center c'1 of the first circle E'1. The first circle E'1 and the second circle E'2 intersect with each other without coinciding. One of the two concave curved portions, S'1 (right side of FIG. 8B), describes an arc of the first circle E'1, and the arc of the first circle E'1 is located inside the second circle E'2. Similarly, the other concave curved portion S'2 (left side of FIG. 8B) describes an arc of the second circle E'2, and the arc of the second circle E'2 is located inside the first circle E'1.

[0075] In the cross section Pp, the radiation surface 4 presents two finite length concave curved portions S'1, S'2 that are symmetrical about the symmetry axis S. Each of the concave portions S'1, S'2 of the radiation surface 4 thus focuses ultrasound waves at a circle centre c'1, c'2 in a respective ultrasound focal region Zc'1, Zc'2. Each ultrasound focal region Zc'1, Zc'2 is located across the symmetry axis S with respect to the corresponding radiation surface 4S'1, S'2. These ultrasound focal regions Zc'1, Zc'2 are defined in the focal plane Pf'.

[0076] According to a first variant embodiment, the individual axes of the concave curved sections S'1, S'2 cross the axis of symmetry S at a common intersection I' located on this axis of symmetry S. The common intersection of the individual axes is located between the emission surface 4 and the focal regions Zc'1, Zc'2 or beyond the focal plane Pf'. The beams of the emission surface 4 therefore cross to form a range region Z'r of the multiple ultrasound beams that is symmetrical about the axis of symmetry S. The focal range region Z'r of the multiple ultrasound beams is called natural and is centered on the axis of symmetry S.

[0077] According to a first variant embodiment, the transducer presents a shape of revolution. This radiating surface 4 is obtained by rotating a concave curved section, represented by S'1 and S'2, around the axis of symmetry S, whose centre of curvature, when considering the intersection, is located on the opposite side of the axis of symmetry S to said concave curved section. In the plane XY, FIG. 8C shows the natural shape of the focal range area Z'r obtained by such a transducer of revolution. It should be noted that in the case of a toric transducer, the transducer also exerts pressure on the focal surface in the shape of a circle, represented by the focal areas Zc'1, Zc'2 (FIG. 8B).

[0078] According to a first variant embodiment, the radiation surface 4 is a surface of revolution. This radiation surface 4 comprises, for example, a series of ultrasonic transducer elements 3 mounted concentrically with respect to each other and with respect to the axis of symmetry S. Of course, it is possible to cut the radiation surface 4 symmetrically about the axis of symmetry S, so that the transducer is limited to a portion of an intersecting torus, for example having a width of 5 mm to 250 mm, as shown in FIG. 8A. According to this embodiment, the transducer 2 comprises a series of ultrasonic transducer elements 3 mounted concentrically with respect to each other and with respect to the axis of symmetry S, so that the transducer elements 3 are arranged in the shape of a ring-like portion.

[0079] According to a second variant embodiment, the transducer 2 presents an emission surface 4 that includes two portions (parts) of a cylinder. This emission surface 4 is obtained by forming concave curves S'1, S'2 of finite length that are symmetrical with respect to the plane of symmetry A1, according to the guidelines mentioned above, and by moving these two concave curves S'1, S'2 along a direction Y perpendicular to the cross section Pp that includes them. Each of the portions of the emission surface 4 is thus focused in front of, behind or on the plane of symmetry A1, along a straight line extending in a focal plane parallel to the direction Y. The respective axes of the concave curves S'1, S'2 cut the plane of symmetry A1 at a cross axis I'' contained in the plane of symmetry A1 (FIG. 12A). As described above for the first variant embodiment, during the natural exposure phase, the beams of the emission surface 4 intersect to form a range area Z'r of multiple ultrasound beams that is symmetrical with respect to the plane of symmetry A1. This focal range area Z'r of multiple ultrasound beams is called natural and is centered on the plane of symmetry A1.

[0080] A generation surface 8 is created by the present invention, the characteristics of which have been described above, using a probe 1 with an emission surface 4. In the following description, the generation surface 8 is divided into two sectors 81, 82 as a preferred embodiment, but the object of the present invention can also be applied to a generation surface 8 including more sectors. It should be noted that the transducer 2 corresponds to a physical or real transducer held in the user's hand. It should also be noted that the generation surface 8 is formed by two virtual half-transducers, which are simulated by dividing the two sectors into several emitter elements and then applying a phase to each of the channels of the physical transducer. To determine these phases, it is only necessary to calculate for each emitter element the propagation time of the ultrasound between the transducer 2 and the generation surface 8. According to the present invention, two virtual transducers are formed in order to move the focusing elements without moving the geometrically arranged elements specific to the physical transducer, such as the acoustic axis or the axis of symmetry. The following description describes an advantageous embodiment in which a signal generator forming part of the control circuit 7 is controlled using a delay law or a phase law to send signals that drive ultrasonic emitters 3 arranged in a ring shape so that a pressure field generation surface 8 of focused ultrasonic waves is formed.

[0081] As an example, Figures 9A to 9D and Figures 10A to 10F show the operation of the ultrasonic emitter 3 of the transducer shown in Figures 8A to 8C so that a generating surface 8 of the type of a first variant embodiment is formed, which includes two sectors 81, 82.

[0082] A signal generator forming part of the control circuit 7 is controlled to transmit signals to activate ultrasonic emitters 3 forming part of sector 41 and sector 42 symmetrically opposite sector 41 about the axis of symmetry S, so that a corresponding energy deposition area is formed during the exposure phase.

[0083] In the exposure phase, the ultrasonic emitters 3 of the two sectors 41, 42 are driven so that a generation surface 8 of the pressure field of the focused ultrasonic waves is obtained, and the generation surface 8 forms two radiation surfaces. Each of the two radiation surfaces is obtained by rotating different concave curved portions s1, s2 around the symmetry axis S. In this way, the centers of curvature c1, c2 can be located on the opposite side or the opposite side of the curved portion with respect to the symmetry axis for each sector 81, 82 independently. Accordingly, as shown in Figures 9B and 9C, an energy deposition area Zr1 off-axis with respect to the rotation axis can be formed. By driving the ultrasonic emitters 3 forming a part of the sector 81 and the symmetrically opposite sector 82, an energy deposition area Zr1 with an arched shape having a contour corresponding to the energy deposition area, in particular the focal range area, is formed. This guideline is applied to the entire sector constituting the transducer, and effectively improves the shape of the pressure deposition area.

[0084] In a second exposure phase, more precisely shown in Figures 10A-10D, the ultrasonic emitters 3 of the two sectors 41, 42 are driven to form an arched energy deposition area Zr2 having a contour corresponding to the focal range area, symmetrical to the arched energy deposition area Zr1 shown in Figure 9D. To perform this second exposure phase, the control circuit again drives the entire transducer face by inverting the phase applied between the sectors according to the guidelines described above.

[0085] It should be noted that the signal generator forming part of the control circuit 7 is controlled to transmit signals to activate the ultrasonic emitters forming part of each of the sectors and the sectors symmetrically opposed to the axis of symmetry, such that in successive exposure steps a corresponding energy deposition area is formed for each set of sectors. In the example shown (FIGS. 10E-10F), two successive ultrasonic exposures allow the formation of a coagulation crown.

[0086] 10E-10F, the coagulation crown exhibits a constant profile or width. Of course, the profile or width of the arcuate energy application regions may vary from one exposure stage to another in terms of their position relative to the axis of symmetry S, as well as their height along the direction Z.

[0087] Thus, in general, a signal generator forming part of the control circuit 7 is controlled to transmit signals to drive the ultrasound emitters in each successive exposure stage such that the centres of curvature c1, c2, ... are located at different distances from the plane of symmetry A1 or axis of symmetry S and / or at different depths along the vertical axis Z in each exposure stage, so as to obtain off-axis energy deposition regions.

[0088] Thus, the signal generator, which forms part of the control circuit 7, is controlled to transmit signals to activate the ultrasound emitters in successive exposure stages in order to obtain off-axis energy deposition areas at different positions having the same or different sizes in the successive exposure stages, and in each exposure stage the centres of curvature c1, c2, ... are located at different distances from the plane of symmetry A1 or the axis of symmetry S and / or at different depths along the vertical axis Z.

[0089] In the example shown in Figures 10E-10F, the entire ultrasonic emitter of the two sectors 81, 82 undergoes two driving phases whose phase is calculated so that the focal range areas Zr1, Zr2 are symmetrical about the symmetry axis S. During the second driving cycle, the area of ​​the generation surface 8 is reflected by transforming the concave curved portion S1 to S2 and the concave curved portion S2 to S1.

[0090] 11A shows an embodiment in which, in one exposure cycle, the entire ultrasound emitter of two sectors 81, 82 undergoes two actuation stages, the phases of which are calculated such that the focal range areas Zr1, Zr2 are asymmetric about the symmetry axis S. According to this example, the two actuation stages are carried out with the centers of curvature c1, c2 positioned in an adapted manner to obtain asymmetric focal range areas Zr1, Zr2.

[0091] The centers of curvature are spaced apart from each other. or at different distances from the plane of symmetry A1 or the axis of symmetry S, but at the same depth, or at the same distance from the plane of symmetry A1 or axis of symmetry S, but at different depths, or at different distances from the plane of symmetry A1 or the axis of symmetry S and at different depths relative to the plane of symmetry A1 or the axis of symmetry S, It is contemplated that the exposure steps may be carried out sequentially, from one exposure step to another.

[0092] It is therefore envisaged that by driving the ultrasound emitters in successive exposure steps such that the distance and / or depth of the centre of curvature is changed from one exposure step to another, the focal range regions can be made concentric and / or symmetric and / or asymmetric and / or overlapped about the vertical axis Z. Thus, "infinitely" combinations of exposure steps can be made according to a more or less complex shape of the volume to be treated.

[0093] 11B shows an embodiment in which the signal generator forming part of the control circuit 7 controls the entire ultrasonic emitter of the two sectors 81, 82 to undergo two actuation phases, the phases of which are calculated so that the focal range areas Zr1, Zr2 are symmetrical about the axis of symmetry S. These two actuation phases form an exposure cycle that is repeated at different depths along the vertical axis Z so as to obtain a superimposed crown of energy deposition. This crown forms a cylinder with the same width and height from one exposure phase to the other.

[0094] FIG. 11C shows another embodiment in which a signal generator forming part of the control circuit 7 is controlled to transmit signals that drive the ultrasound emitters 3 such that the focal range regions Zr are located at different distances and different depths along the vertical axis Z in order to obtain overlapping focal range regions of variable width and / or height.

[0095] In the above example, the volume of energy application is hollow, i.e. not bounded by the axis of symmetry S. Of course, the signal generator forming part of the control circuitry may include at least one Supplementary In the exposure stage, the ultrasonic emitter can be controlled to transmit signals to drive the ultrasonic emitter so that the ultrasonic waves are focused in the focal region and a focal range region Z'r is obtained that is centered with respect to the symmetry plane A1 or symmetry axis S and is located away from the focal plane between the focal region and the emission plane or is located beyond the focal region. Therefore, it is called natural according to the guidelines described in Figures 8A and 8B. supplementary Multiple exposure steps may be performed for one or each exposure step to complete the volume of energy deposition. supplementary Such an exposure step may be performed for one and / or the other of the embodiments described herein. Thus, FIG. 11D illustrates a variation of the embodiment shown in FIG. 11B. supplementary This shows the implementation of a detailed exposure phase.

[0096] FIG. 11E shows in plan view a natural focal range region Z′r centered with respect to the axis of symmetry S surrounded by a focal crown K formed by two successive ultrasonic exposures as previously described. It should be noted that this figure shows that four successive ultrasonic exposures embodied by a generating surface 8 divided into four sectors to form four focal range regions Zr1-Zr4 generate the formation around the focal crown K, an additional focal crown.

[0097] By way of example, the following description illustrates the implementation of the generation surface 8 according to a second variant embodiment. According to this example, shown in Fig. 12, the first focal region has a double-line shape. The conditions for implementing the invention explained in relation to Figs. 10A-10F and 11A-11E for the first variant embodiment apply analogously to a pseudo-cylindrical generation surface 8.

[0098] According to the invention, the ultrasound emitter 3 is cut parallel to the plane of symmetry A1 and is driven with a delay or phase law so as to form a generation plane 8. The ultrasound emitter is arranged along at least two sectors, and according to the example shown in Fig. 12 has two sectors 81, 82 arranged symmetrically with respect to the plane of symmetry A1.

[0099] Thus, a signal generator forming part of the control circuit is controlled to transmit signals for activating ultrasonic emitters forming a sector located on one side of the symmetry plane A1 and a part of the symmetrically opposite sector during the exposure phase to form a corresponding energy deposition area. Thus, on one side of the symmetry plane A1, a volume of energy deposition Zr1 (or a focal range area Zr1) can be formed at a distance from this symmetry plane (FIG. 12B). In the same way, on the other side of the symmetry plane A1, a volume of energy deposition Zr2 (or a focal range area Zr2) can be formed at a distance from this symmetry plane A1 (FIG. 12C).

[0100] According to another advantageous embodiment, the ultrasonic emitters are arranged along sectors perpendicular to the plane of symmetry A1 and arranged oppositely with respect to the plane of symmetry A1. In the example shown in FIG. 13A, nine sectors are located on either side of the plane of symmetry A1, each sector on one side facing a sector on the other side. Thus, a signal generator forming part of the control circuit is controlled in the exposure phase to transmit signals that activate the ultrasonic emitters forming part of the sector and the opposite sector, using a delay or phase law, so that a corresponding energy deposition area is formed on one side of the plane of symmetry (FIG. 13A). The ultrasonic emitters of the opposite sectors can form an energy deposition volume on either side of the plane of symmetry A1. FIG. 13B shows the implementation of two energy deposition volumes located on either side of the plane of symmetry A1. The thickness of the energy deposition volume corresponds to the width of one sector of the transducer.

[0101] As explained above, each of the energized volumes can vary in shape, size, and location, particularly by exploiting the location of the center of curvature. Sequential actuation of different sectors of the transducer creates hollow energized volumes of variable thickness (FIG. 13C).

[0102] This solution is particularly advantageously applied to the treatment of target regions extending along non-linear segments T, for example to treat tumors along arteries or veins, along the digestive tract, along bones, along Wilson's duct of the pancreas, the urethra or the bile duct (Figure 13D).

[0103] From the above description, it can be seen that the object of the present invention is to form a focal region movement in depth (along the acoustic axis) and in a plane parallel to the transducer (perpendicular to the acoustic axis), effectively reducing the number of emitters. In contrast to the prior art, which proposes to form a focal spot and move it in space (electronic focusing), the object of the present invention is to directly form a volume (part of the crown) obtained by calculating a "virtual" generating surface or a "virtual" transducer, and to move this volume without going through a large number of emitters. Thus, the present invention not only reduces the cost of the control electronics, but also the cost of the transducer.

Claims

1. A treatment device for treating tissue by emitting focused ultrasound, comprising: The treatment device comprises a treatment probe having a transducer (2) including a number of ultrasound emitters (3) defining a radiation plane (4) of focused ultrasound waves having an axis of symmetry (S) corresponding to an acoustic axis or a plane of symmetry (A1) corresponding to an acoustic plane, the ultrasound emitters being driven by signals transmitted by a signal generator forming part of a control circuit (7) so as to define a generation plane (8) of a pressure field of the focused ultrasound waves; The generation plane (8) is the focal plane (Pf 1 , Pf 2 , ...) 1 , Zc 2 At least N sectors (8 , . . . ) are arranged so that the ultrasonic waves are focused on the 1 , 8 2 , ...) (N is from 2 to 32), and the sectors of this generating surface are divided into cross sections (P p ) having finite length concave curved portions (S1, S2, ...) that are asymmetric with respect to the symmetry plane (A1) or the symmetry axis (S), Its center of curvature (c 1 , c 2 , ...) are asymmetric with respect to the plane of symmetry (A1) or the axis of symmetry (S) such that the centers of curvature are located at different distances from the plane of symmetry (A1) or the axis of symmetry (S) and / or at different positions in the direction along the axis of symmetry, Each of the concave curved portions (S1, S2, ...) has a center of curvature (c 1 , c 2 , ...) and the center of the concave curved portion (S1, S2, ...) 1 , a 2 , ...) The individual axes (a 1 , a 2 , ...) are the beams originating from the sectors in the focal region (Zc 1 , Zc 2 , ...) and the generation surface (8), or between the focal region (Zc 1 , Zc 2 , ...) on the opposite side of the generation plane, and deviates from the symmetry plane (A1) or the symmetry axis (S) to the focal plane (Pf 1 , Pf 2 , ...) to form a focal range region (Zr) located at a distance from the focal region (Zc 1 , Zc 2 , ...) and the generation plane (8) or on the opposite side of the generation plane with respect to the focal region, The sector of this generating surface (8) is 1 , 8 2 by rotating the concave curved portion (S1, S2, ...) by 2π / N around the axis of symmetry (S) or by moving the concave curved portion along a direction (Y) perpendicular to the cross section (Pp) including the concave curved portion (S1, S2, ...) so that the concave curved portion (S1, S2, ...) can form an energy application region having a contour corresponding to the focal range region (Zr); The concave curved portions (S1, S2, ...) of the generation surface (8) extend within the cross section (Pp) on either side of the symmetry axis (S) or the symmetry plane (A1), and are spaced apart from each other so that the focal range region (Zr) is located at a position spaced apart from the generation surface. A treatment device characterized by:

2. 2. The treatment device according to claim 1, characterized in that the generation surface (8) is divided into two sectors.

3. In the generating surface (8), the inner end (8a 1 , 8a 2 2. The treatment device according to claim 1, characterized in that the aforesaid first and second electrodes (a) and (b) define a housing for mounting an ultrasound imaging probe.

4. 4. The treatment device according to claim 1, wherein the generating surface (8) originates from a surface (4) defined by transducer elements arranged in a circular geometric arrangement, the circular geometric arrangement being formed by rotating a concave curved section around the axis of symmetry (S) to describe arcs of mutually intersecting and non-coincident circles, the mutually intersecting and non-coincident circles intersecting such that the focal region has the shape of a portion of a circle.

5. 5. The treatment device according to claim 4, characterized in that the surface (4) has a shape that is symmetrically cut about the axis of symmetry (S).

6. The treatment device according to any one of claims 1 to 3, characterized in that the generation surface (8) is derived from a surface (4) defined by transducer elements arranged in a cylindrical geometric arrangement, the cylindrical geometric arrangement being formed by moving two of the concave curved portions by a finite length along a direction (Y) perpendicular to the cross section (Pp) including the concave curved portions so that the focal region has a linear shape.

7. The treatment device according to any one of claims 1 to 6, characterized in that the ultrasound emitter (3) of the transducer (2) defines a radiation surface (4) which corresponds to the generation surface (8) of the pressure field of focused ultrasound.

8. The treatment device according to any one of claims 1 to 6, characterized in that the signal generator forming part of the control circuit (7) is controlled to transmit signals for driving the ultrasound emitters (3) arranged in the part using a delay law or a phase law so that the generation surface (8) of the pressure field of focused ultrasound is formed.

9. In the exposure phase, the sector (8 1 , 8 2 9. The treatment device according to claim 1 , characterized in that the ultrasound emitters forming part of sectors symmetrically opposed to the axis of symmetry ( , ...) are driven by signals transmitted by the signal generator forming part of the control circuit (7) such that corresponding energy deposition areas are formed.

10. In the exposure phase, the sector (8 1 , 8 2 9. The therapeutic device according to claim 1, characterized in that the ultrasound emitters (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 109, 108, 109, 109, 108, 109, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 1

11. In the later exposure stage, the sector (8 1 , 8 2 11. The treatment device according to claim 10, characterized in that the ultrasound emitters (3) forming part of sectors symmetrically opposed to the plane of symmetry (A1) ( , ...) are driven by signals transmitted by the signal generator forming part of the control circuit (7) such that a corresponding energy deposition area is formed on a side opposite to the side on which the energy deposition area was formed in the previous exposure phase.

12. 12. The treatment device according to claim 10 or 11, characterized in that the ultrasound emitters (3) are arranged along a number of sectors perpendicular to the plane of symmetry (A1), and in successive exposure phases the ultrasound emitters of a sector are driven by signals transmitted by the signal generator forming part of the control circuit (7) such that energy deposition areas are formed on either side of the plane of symmetry (A1).

13. The center of curvature (c 1 , c 2 13. The treatment device according to claim 1, characterized in that in each successive exposure phase, in which the ultrasound emitters (1, 2, ...) are located at different distances from the plane of symmetry (A1) or the axis of symmetry (S) and / or at different positions in the direction along the axis of symmetry (S), the ultrasound emitters are driven by signals transmitted by the signal generator forming part of the control circuit (7) so as to obtain an energy deposition area outside the plane of symmetry (A1) or the axis of symmetry (S).

14. The center of curvature (c 1 , c 2 14. The treatment device according to claim 13, characterized in that in successive exposure phases, in which the ultrasound emitters (A1, ...) are located at different distances from the plane of symmetry (A1) or the axis of symmetry (S) and / or at different positions in the direction along the axis of symmetry (S), the ultrasound emitters are driven by signals transmitted by the signal generator forming part of the control circuit (7) in order to obtain, in these successive exposure phases, energy deposition areas at different positions, having the same or different sizes, outside the plane of symmetry (A1) or the axis of symmetry (S).

15. 15. The treatment device according to any one of claims 9 to 14, characterized in that in successive exposure stages, the energy application areas can be concentric and / or symmetric and / or asymmetric and / or overlapped along the axis of symmetry (S), by driving the ultrasound emitters by signals transmitted by a signal generator constituting part of the control circuit (7), such that the distance and / or the position of the centre of curvature is varied from one exposure stage to another.

16. 16. The treatment device according to claim 1, characterized in that, during at least one supplementary exposure phase, the ultrasound emitter (3) is driven by a signal transmitted by the signal generator (7), which constitutes part of the control circuit (7), in such a way that the ultrasound is focused in a focal region, resulting in a focal range region that is centered with respect to the plane of symmetry (A1) or the axis of symmetry (S) and located at a distance from the focal plane between the focal region and the generation plane (8) or on the opposite side of the generation plane with respect to the focal region.

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