Therapeutic ultrasound transducer for the emission of focused ultrasound waves

Abstract

The present disclosure relates to an ultrasound transducer for therapeutic ultrasound techniques, such as high intensity focused ultrasound (HIFU) techniques. The challenge is to design an ultrasound transducer that can apply the required pressure deep enough into biological tissue with sufficient precision to apply the required pressure within a target volume of tissue without destroying the surrounding tissue. It is therefore proposed to use a transducer with several ultrasound emission zones that can be activated independently. This allows the transducer to apply the required pressure to target locations that are not aligned with the emission axis.

Description

[Technical field]

[0001] The present disclosure relates to ultrasound transducers. [Background technology]

[0002] Therapeutic ultrasound techniques, such as high intensity focused ultrasound (HIFU) techniques, are increasingly being used in a wide range of applications as a non-invasive method for destroying targets, such as biological tissue or tumors in living organisms.

[0003] Typically, one or more ultrasound transducers are used to generate ultrasound beams that are directed at targets located within biological tissue or living organisms, generating mechanical pressure waves at specific locations within the biological tissue that cause localized temperature increases, resulting in the destruction of the target.

[0004] One challenge is to design an ultrasound transducer that can apply the required pressure deep enough into biological tissue with sufficient precision so that the required pressure can be applied within a target volume of tissue without destroying the surrounding tissue.

[0005] It has been proposed to use an ultrasonic probe that includes a concavely curved emission surface, the emission surface being toroidal and divided into two sectors with different focusing properties.

[0006] A drawback of this approach, although satisfactory for some applications, is that most of the pressure is still applied along the emission axis of the transducer. Thus, the transducer cannot apply maximum pressure to target locations that are not aligned with the emission axis (or acoustic axis). This sometimes means that the transducer must be physically moved. The ultrasound beam may then have to be refocused, which is time consuming and prone to error. In some cases, it may not be possible to position the transducer so that its emission axis is aligned with the target location.

[0007] In addition, the treatment of tissue areas with complex patterns that deviate from the acoustic axis presents a challenge. In fact, the treatment of complex structures with focused ultrasound in the broad sense requires many elements (and associated electronics) and long treatment times. In the case of treatment with focused ultrasound by a toroidal transducer, the pressure remains maximum along the acoustic axis, which means that it is difficult to extend the treatment area relative to the acoustic axis and treat complex structures that do not have rotational symmetry. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, there is a need for an ultrasonic transducer that can overcome at least some of the aforementioned drawbacks. [Means for solving the problem]

[0009] The object of the present invention is therefore to provide an ultrasonic transducer comprising a base part and a number of ultrasonic emitter elements located on a surface of the base part, the base part exhibiting rotational symmetry with respect to the emission axis of the transducer, said surface being divided into several ultrasonic emission zones, at least one of which, called a first central ultrasonic emission zone, has a rectilinear shape and is arranged in the center of said surface, the surface of the central ultrasonic emission zone constituting 25% to 50% of the total surface of the base part.

[0010] Such an approach makes it possible to obtain an optimal treatment of the target area by minimizing the pressure against the acoustic axis and maximizing the pressure away from the acoustic axis, thus minimizing the risk of secondary lesions along the acoustic axis, this optimization being related to the ratio between the rectilinear surface and the total surface of the transducer.

[0011] According to advantageous optional aspects, alternative embodiments of the invention may include one or more of the following features, taken alone or in all possible technical combinations: the second ultrasonic emission zone of the ultrasonic transducer has a rectilinear shape and is arranged in the center of said surface, the first and second central ultrasonic emission zones being arranged relative to each other to form a cross shape. - the second ultrasonic emission zone of the ultrasonic transducer has the shape of a straight line and is arranged in the center of said surface, the first and second central ultrasonic emission zones being arranged to intersect with each other at any angle between the first and second central ultrasonic zones. - Each of the two central ultrasound emission zones can be divided into two parts that can be activated independently. The ultrasonic transducer is configured such that the first and second central ultrasonic emission zones can be activated independently of each other. The ultrasonic transducer is configured such that other ultrasonic emission zones of the ultrasonic transducer can be activated independently from the central ultrasonic emission zone. The ultrasonic transducer is configured such that each ultrasonic emission zone of the ultrasonic transducer can be activated independently of the other ultrasonic emission zones. - the base part has a diameter comprised between 10 mm and 300 mm, preferably comprised between 90 mm and 130 mm. - The surface of the central ultrasonic emission zone constitutes 25% to 50% of the total surface of the base part, ideally equal to 33%. the base portion has a concave shape, preferentially a frustoconical or toroidal shape. - The ultrasound transducer is a high intensity focused ultrasound (HIFU) transducer. - the ultrasonic transducer comprises a layer of piezoelectric material and at least one conductive electrode layer arranged in contact with the layer of piezoelectric material, the electrode layer being divided into a number of conductor pads, each conductor pad being coupled with the piezoelectric layer to form an ultrasonic emitter element, each emission zone of the electronic transducer comprising one or more of said conductor pads.

[0012] According to another aspect, the present invention relates to a device comprising an ultrasonic transducer and a control unit connected to the ultrasonic transducer, the ultrasonic transducer being an ultrasonic transducer according to any one of the preceding claims, the control unit comprising at least one signal generator for driving the ultrasonic emitter elements, preferably with a matching circuit between the signal generator and the ultrasonic emitter elements.

[0013] According to another aspect, the control unit is configured to activate each ultrasound emission zone of the ultrasound transducer independently from the other ultrasound emission zones.

[0014] According to another aspect, the device is a therapeutic ultrasound device configured to generate at least one focused ultrasound beam.

[0015] According to another aspect, the invention relates to a method of treatment using the above-described device on a human patient.

[0016] The invention will be understood from a reading of the following detailed description, which proceeds with reference to the accompanying drawings, given by way of example only, in which: [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of an ultrasound system including an ultrasound transducer in accordance with an embodiment of the present invention. [Diagram 2] 2 illustrates several embodiments of the ultrasonic transducer of FIG. 1; [Diagram 3]1 shows a graph illustrating a comparison of the relative gain in pressure applied by several ultrasonic transducers as a function of the ratio between the surface of a linear emission zone and the total surface of the transducer. [Figure 4] 1 shows a comparison of the pressure fields and corresponding thermal doses applied by several exemplary ultrasound transducers. [Diagram 5] 2 is a schematic three-dimensional view of the ultrasonic transducer of FIG. 1. [Figure 6] 1 shows a graph illustrating a comparison of the relative gain in pressure applied by several ultrasonic transducers as a function of the ratio between the surface of a linear emission zone and the total surface of the transducer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS FIG. 1 shows an embodiment of an ultrasonic device 2 that includes an ultrasonic emitting device 4 that includes one ultrasonic transducer 6 .

[0019] In the illustrated example, the ultrasound device 2 also includes a control unit 8 and a user control interface 10 .

[0020] Control unit 8 includes suitable electronic circuitry for performing various operations in support of its functions. For example, control unit 8 may include a general purpose processor, such as a microprocessor or microcontroller, or a special purpose processor, such as a digital signal processor (DSP) or a graphic processing unit (GPU) or an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). In addition, analog circuitry may be used to perform many of the same functions.

[0021] In many embodiments, the control unit 8 includes at least one signal generator for driving the ultrasound emitter elements of the ultrasound transducer 6, as described below.

[0022] In practice, the control unit 8 is connected to the transducer 6 by one or more electrical connectors, such as cables.

[0023] The user control interface 10 may include a human machine interface, such as a display screen and / or data entry means, such as a keyboard or a touch-sensitive screen or a pointer or equivalent device, or a combination thereof.

[0024] The ultrasonic device 2 is configured to apply ultrasonic waves to destroy targets in a host material 20, such as, for example, biological tissue.

[0025] For example, the ultrasonic device 2 is configured to generate at least one focused ultrasonic beam that is directed toward a target area of ​​the host material 20 .

[0026] This generates mechanical vibrations in the host material 20 which in turn create controlled localized temperature increases within the host material 20 that can be used to destroy targets such as tumors, hereafter referred to as "thermal doses."

[0027] In some embodiments, the host material 20 need not necessarily be a biological tissue, but may be, for example, a soft material such as a food or a gel.

[0028] The ultrasound device 2 can be a medical device or a therapeutic device.

[0029] For example, the ultrasound transducer 6 is a high intensity focused ultrasound (HIFU) transducer.

[0030] In many embodiments, the ultrasound emitting device 4 includes a casing that surrounds the ultrasound transducer 6, and may also include a connector for connecting the transducer 6 to a cable that is connected to a control unit 8. Additionally, a matching circuit (such as an impedance matching circuit) may be used between the transducer 6 and the control unit 8 to transmit an electrical signal to the transducer 6 with minimal electrical losses.

[0031] In the illustrated embodiment, the control unit 8 is shown to be a separate device from the ultrasound device 4. However, in some embodiments, the control unit 8 may be located within the casing of the device 4.

[0032] In some embodiments, the control unit 8 may be combined with the interface 10 into a single device.

[0033] An embodiment of an ultrasonic transducer 6 is shown in FIG.

[0034] In most embodiments, the ultrasonic transducer includes a base portion and a number of ultrasonic emitter elements located on a surface (the so-called "emission surface") of the base portion. In this example, the base portion has a circular shape.

[0035] Preferably, the base portion has a concave shape centred on the emission axis of the transducer 6 .

[0036] For example, the base portion may have a frusto-conical (e.g., truncated cone), toroidal (e.g., truncated torus), conical or bell-like or curved disk shape. The base portion may be formed to exhibit rotational symmetry with respect to the emission axis. In other words, the base portion exhibits rotational symmetry with respect to the emission axis of the transducer.

[0037] An example of the concave shape of the base part can be found, for example, in EP 2035091 B1. In that case, the base part has a truncated toroidal shape (more precisely, the base part is constructed on a portion of the inscribed surface of a spindle torus). A torus can be mathematically constructed by rotating a circle about its axis of rotation, offset laterally from the axis of rotation (i.e. offset in a direction perpendicular to the axis of rotation). If the distance between the axis of rotation and the center of the circle is smaller than the radius of the circle, the torus is a spindle torus. The axis of rotation coincides with the emission axis of the transducer. An example of the construction rules for a truncated toroidal shape constructed on a portion of the inscribed surface of a spindle torus can be found in the academic paper Melodima et al., Applied Physics Letters 2009; 91(19):193901.

[0038] This example is not limiting and other shapes are possible.

[0039] For example, the diameter of the transducer 6 can be comprised between 1 cm and 30 cm, and is preferably equal to 12 cm. This example is not limiting.

[0040] According to a preferred embodiment, the surface is divided into several ultrasound emitting zones (or emitting regions).

[0041] For example, the ultrasound emission zone includes a portion of a piezoelectric material that is capable of emitting ultrasound waves independently from other areas of the transducer 6 .

[0042] At least one of the ultrasound emission zones, referred to as the first central ultrasound emission zone, has a rectilinear shape and is disposed in the center of the surface, which may be a rectangle or an elongated strip, for example the ultrasound emission zone may be a band.

[0043] Preferably, each linear ultrasound emission zone (e.g., band) straddles either side of the emission axis of the transducer, and the emission axis is disposed at a central position of the transducer (e.g., at the central position of the base portion, as in Figures 2 and 5).

[0044] In some embodiments, as shown in FIGS. 2 and 5, each band or linear feature that forms the central ultrasound emission zone is wider than the central opening 38 .

[0045] In some other embodiments, the bands or linear features that form the central ultrasound emission zone may be narrower than the central opening 38 .

[0046] This emission zone may conveniently be divided into two parts, preferably two equal parts.

[0047] FIG. 2 shows some possible embodiments of the ultrasonic transducer 6 .

[0048] In Figure 2, an exemplary transducer 6 is shown in a two-dimensional view corresponding to a top-down elevation view. Figure 5 shows two views (insets A and B) of an exemplary transducer 6 in an isometric perspective view (i.e., a three-dimensional view).

[0049] It will therefore be appreciated that the transducer 6 is a three-dimensional object, which is shown in two dimensions in FIG. 2 for convenience and illustrative purposes only.

[0050] In a first example, as can be seen in inset (a) of FIG. 2, an ultrasonic transducer 30 includes a central ultrasonic emission zone in the form of a strip 32, which is divided into two equal portions.

[0051] For example, the ultrasonic transducer 30 also includes other emission zones 34 , 36 separated from the central zone 32 by parallel straight cut lines 31 and 33 .

[0052] In many embodiments, the transducer includes a central opening 38 that can be used to insert an ultrasound imaging probe or camera or any measurement device.

[0053] In a second example, as can be seen in inset (b) of FIG. 2, an ultrasonic transducer 40 includes a central ultrasonic emission zone 32 that is rotated relative to the vertical but is otherwise identical or similar to the transducer 30 described above.

[0054] In a third example, as can be seen in the inset (c) of FIG. 2 and in FIG. 5, in the ultrasonic transducer 50, the second ultrasonic emission zone has a rectilinear shape and is disposed in the center of the surface.

[0055] For example, "centrally disposed" means that a straight line ultrasound emission zone spans either side of the emission axis of the transducer, and the emission axis is disposed at a central position of the transducer (e.g., at the central position of the base portion).

[0056] In addition, the first and second central ultrasound emission zones (52+54, 56+58) are disposed relative to one another to form a cross shape, in other words, the first and second zones are disposed perpendicular to one another. The transducer 50 is otherwise identical to or similar to the transducer 30 described above.

[0057] Preferably, the first and second zones extend across the entire diameter of the base portion, for example from one edge to the opposite edge of the base portion, and thus in many embodiments the first and second zones have the appearance of a cross inscribed within a circle or disk.

[0058] In other embodiments, the first and second central ultrasound emitting zones are disposed to intersect one another at an angle (ie, the first and second zones are not necessarily disposed perpendicular to one another).

[0059] Preferably, the first and second central ultrasound emission zones intersect each other at their respective geometric centres.

[0060] In the illustrated example, each of the first and second zones is divided into two sub-zones (52, 54 and 56, 58, respectively), but this need not be the case and in other embodiments each of the first and second zones can extend continuously, as in transducers 30 or 40 described above, or when central opening 38 is eliminated.

[0061] More precisely, in this example, the transducer 50 is divided into eight sectors, two of which form a first central zone, two of which form a second central zone, and each of the remaining sectors forms one of the remaining zones 60, 62, 64 and 66.

[0062] In practice, as shown by inset (d) of FIG. 2, which diagrammatically depicts a cutaway view of an exemplary transducer 6, the ultrasonic transducer 6 may include a layer 72 of piezoelectric material and at least one conductive electrode layer disposed in contact with the layer of piezoelectric material.

[0063] The electrode layer is divided into a plurality of conductive contact pads 74, for example by etching or by cutting the electrode layer with a mechanical saw or any suitable means.

[0064] Thus, the ultrasound emitter elements defined above are formed by the coupling of the conductor pads 74 and the piezoelectric layer 72. Corresponding regions of the piezoelectric layer 72 can be vibrated by applying appropriate electrical signals via the conductor pads 74. Each emission zone 32, 34, 36; 52, 54, 56, 58, 60, 62, 64, 66 of the electronic transducer includes one or more of said conductor pads 74.

[0065] In the illustrated example, only one side of the piezoelectric material layer 72 is shown covered with a conductive electrode layer, however, in practice, conductive electrode layers can be disposed on both the top and bottom surfaces of the piezoelectric layer 72, and conductive contact pads 74 can be formed on each of the conductive electrode layers.

[0066] Preferably, the ultrasonic transducer 6 is configured such that the first and second central ultrasonic emission zones 52+54 and 56+58 can be activated independently of each other.

[0067] In some further embodiments, the ultrasonic transducer 6 is configured such that the other ultrasonic emission zones 60, 62, 64, 66 of the ultrasonic transducer can be activated independently from the central ultrasonic emission zone.

[0068] In still further embodiments, the ultrasonic transducer 6 is configured such that each ultrasonic emission zone 32, 34, 36; 52, 54, 56, 58, 60, 62, 64, 66 can be activated independently from the other ultrasonic emission zones.

[0069] For example, zones 60, 62, 64 and 66 can be activated independently from each other and from central zones 52 / 54 and 56 / 58. In some embodiments, zones 60, 62, 64 and 66 may remain inactivated, i.e., they do not emit ultrasound waves.

[0070] In some embodiments, the zones can be controlled independently of each other by providing various control signals (excitation signals, i.e., electrical signals designed to vibrate the piezoelectric material at a given frequency with a particular amplitude and phase).

[0071] For example, each ultrasound emission zone 32 , 34 , 36 or 52 / 54 , 56 / 58 and optionally 60 , 62 , 64 , 66 is coupled to a control unit 8 to receive a control signal that is different from the control signal received from another emission zone 8 .

[0072] For example, a first excitation signal is provided to the central zone 32, 52 / 54 to simultaneously drive all emissive elements of the zone, e.g., the excitation signal is applied to all electrical conductor pads 74 located within said central zone.

[0073] If applicable, a second excitation signal is provided to the second central zone 56 / 58 in a similar manner.

[0074] One or more further excitation signals may be provided to one or more of the other zones 60 , 62 , 64 and 66 .

[0075] Thus, in a preferred embodiment, the transducer 50 can be operated in at least three different activation modes: a mode in which only the first central emission zone is activated, a mode in which both the first and second central emission zones are activated, and a mode in which all emission zones are activated.

[0076] As explained above, the control unit 8 comprises at least one signal generator, and preferably several signal generators, for driving the ultrasound emitter elements.

[0077] In some embodiments, a signal generator can be associated with each zone, while in some other embodiments, a signal generator can be used to drive several zones independently with the aid of appropriate signal processing circuitry.

[0078] For example, in some embodiments, the control unit 8 includes a multi-channel amplifier, such as a 32-channel amplifier, to generate a plurality of control signals. The control unit 8 may also include a switching device to address the plurality of control signals to corresponding XXX.

[0079] In a preferred embodiment, the surface of the central ultrasound emission zone 32 or 52 / 54 or 56 / 58, marked "T" in inset (c) of FIG. 2, comprises 15% to 70% of the surface of the transducer (i.e., the surface of the base portion), and preferably comprises 25% to 50% of the surface of the base portion.

[0080] In a preferred embodiment, the surface T of the central ultrasound emission zone is made up of 30% to 35% of the surface of the base portion, most preferably equal to 33% of the surface of the base portion.

[0081] Preferably, the surface T is equal to 1 / 3 of the surface of the base portion.

[0082] It has been found that the shape, dimensions and relative spatial arrangement of the central zones 32, 52 / 54, 56 / 58 allow for an increase in the thermal dose deposited transversely to the emission axis, especially when only the central zones (alternatively 32 or 52 / 54 or 52 / 54 and 56 / 58) are activated and the remainder of the transducer is not activated.

[0083] Preferably, the size and shape of the first and second central zones 52 / 54 and 56 / 58 are similar or identical, however, in some embodiments, the first central zones 32 or 52 and 54 or 56 and 58 can have different widths.

[0084] And, in some embodiments, the first central zones 32 or 52 and 54 or 56 and 58 can have different lengths. For example, each first central zone can be divided into multiple slices that can be activated independently of the other slices of the central zone. Thus, it is possible to increase or decrease the activation length of each first central zone.

[0085] 3, graph 80 displays the relative gain (expressed as a relative value) of pressure deposited along the emission axis (graph 82) compared to pressure deposited in areas of the target material 20 away from the emission axis (graph 84) as a function of relative surface S (ratio of surface T to total surface of the base portion). In this example, only one of the central zones 52 / 54 and 56 / 58 of transducer 50 was activated.

[0086] In this example, it can be seen that a surface T comprised of 15%-70% of the transducer's surface, preferably 25%-50% of the transducer's surface, maximizes the amount of off-axis pressure while minimizing the amount of pressure applied along the emission axis.

[0087] Data points 90, 92 and 94 show individual experimental measurements for two different transducer surfaces: 100% (ES mode) and 33% (normal mode). In all cases the focal point was shifted 9 mm from the acoustic axis. Experimental points 90, 92 and 94 show the absolute differences (which are between 2% and 15%) between the theoretical values ​​(graphs 80 and 82) and the corresponding measured values.

[0088] For example, when defining the transducer geometry, in ES mode the transducer is sliced ​​into two equal emission surfaces (surface T=100%) by applying one radial slicing while shifting the treatment zone. The pressure is maximum on the axis and not on the treatment zone, so that the ablated zone is longer rather than wider. In vertical mode, radial slicing is applied to obtain a band (vertical mode). As a result, the pressure reaches a maximum on the treatment zone and not on the emission axis while shifting the focus.

[0089] FIG. 4 shows a comparison of numerical simulation data showing four images of the magnitude and spatial distribution of the pressure field (left half of each image) and applied thermal dose (right half of each image) in a region of the host material 20 for four different configurations of transducer 50.

[0090] In the first configuration (top left), all emission zones of the transducer are activated simultaneously. As a result, most of the thermal dose is applied along or close to the emission axis. The surface T of the central zone is equal to 100% of the transducer surface.

[0091] In the second configuration (top right), one of the central zones 52 / 54 or 56 / 58 of the transducer 50 is activated. The other zones are not activated and do not emit ultrasound. The surface T of the central zone is equal to 83% of the surface of the transducer.

[0092] In the third configuration (bottom left), one of the central zones 52 / 54 or 56 / 58 of the transducer 50 is activated. The other zones are not activated and do not emit ultrasound. The surface T of the central zone is equal to 33% of the surface of the transducer.

[0093] In the fourth configuration (bottom right), the central zone 52 / 54 or 56 / 58 of the transducer 50 is activated. The other zones are not activated and do not emit ultrasound. The surface T of the central zone is equal to 10% of the surface of the transducer.

[0094] It can be seen that unless only the central zones 52 / 54 or 56 / 58 are activated, the majority of the thermal dose is applied along or near the emission axis.

[0095] Moreover, the effect becomes more pronounced when the surface T of the central zone is equal to 33% of the total surface of the transducer.

[0096] As the surface T decreases (e.g., below 10% of the total transducer surface), the applied pressure and heat dose decrease off-axis and become uniform along the path between the transducer and the focal zone. This may require increased pressure for treatment and thus potential side effects in non-target areas. As a corollary, as the surface T approaches the total transducer surface (e.g., 83%), the applied pressure, and therefore the heat dose, decrease off-axis and increase along the acoustic axis, limiting the desired effect.

[0097] An advantage of the present invention is that the transducer 6 can apply the necessary pressure to target locations in the host material 20 that are not aligned with the emission axis without moving or repositioning the transducer. Thus, by simply activating different emission zones, it is possible to target increased volumes within the host material 20 without moving or repositioning the transducer relative to the host material 20, and more importantly, without requiring a large number of components (and associated electronics) and long processing times.

[0098] In FIG. 6, a graph 100 shows a comparative example based on numerical simulations showing the evolution of the pressure gain (expressed as a ratio to the surface of the transducer) for different values ​​of the surface T for two different transducers 6 (curves 102 and 104).

[0099] In this example, both the first and second transducers correspond, albeit with different dimensions, to the transducer 50 shown in inset (c) of Figure 2 and in Figure 5. In both cases, the base of the transducer is a truncated cone, built on a portion of the inner envelope of the spindle torus.

[0100] The results obtained for the first transducer (curve 102) are the same as those presented in Figure 6 (curve 84). The dimensions and other characteristics of the transducer are summarized in the table below.

[0101] [Table 1]

[0102] The outer and inner diameters refer to the dimensions of the base portion. As can be seen in Figure 5, the inner diameter corresponds to the diameter at the bottom of the base portion and the outer diameter corresponds to the diameter at the top of the base portion, which tapers from the bottom to the top.

[0103] The radius of curvature refers to the curvature of the wall of the base portion.

[0104] The data show that improved pressure gain performance can be achieved using a surface T comprised of 25%-50% of the transducer surface, especially for a surface fraction T value of 33%.

[0105] Many other embodiments are possible.

[0106] In an optional embodiment, the device 2 may be used on a human patient as part of a treatment regimen.

[0107] Within the scope of the claims, the above embodiments and alternatives can be combined with each other to create new embodiments of the invention.

Claims

1. An ultrasonic transducer (6; 30; 40; 50) comprising a base portion and a plurality of ultrasonic emitter elements located on a surface of the base portion, the base portion exhibits rotational symmetry with respect to the emission axis of the transducer; said surface being divided into several ultrasound emission zones (32, 34, 36; 52 / 54, 56 / 58, 60, 62, 64, 66), At least one of the ultrasound emission zones, referred to as a first central ultrasound emission zone, has a rectilinear shape and is disposed in the center of the surface; An ultrasonic transducer, wherein the surface (T) of the central ultrasonic emission zone comprises 25% to 50% of the total surface of the base portion.

2. a second ultrasonic emission zone of the ultrasonic transducer (50) having a rectilinear shape and disposed centrally on said surface; 2. The ultrasonic transducer of claim 1, wherein the first and second central ultrasonic emission zones (52 / 54, 56 / 58) are disposed relative to one another to form a cross shape.

3. a second ultrasonic emission zone of the ultrasonic transducer (50) having a rectilinear shape and disposed centrally on said surface; 2. The ultrasonic transducer of claim 1, wherein the first and second central ultrasonic emission zones (52 / 54, 56 / 58) are disposed to intersect with one another at any angle between the first and second central ultrasonic zones.

4. The ultrasonic transducer of claim 2 , configured such that the first and second central ultrasonic emission zones (52 / 54, 56 / 58) can be activated independently of each other.

5. 3. The ultrasonic transducer of claim 2, wherein the first central ultrasonic emission zones (32, 52 / 54, 56 / 58) are configured to have different widths and / or different lengths.

6. An ultrasonic transducer according to any one of claims 2 to 5, wherein each of the two central ultrasonic emission zones can be divided into two parts which can be activated independently.

7. An ultrasonic transducer according to any one of claims 1 to 6, configured such that other ultrasonic emission zones of the ultrasonic transducer can be activated independently from the central ultrasonic emission zone.

8. An ultrasonic transducer according to any one of claims 1 to 7, configured such that each ultrasonic emission zone of the ultrasonic transducer can be activated independently of the other ultrasonic emission zones.

9. Ultrasonic transducer according to any one of the preceding claims, wherein the base portion has a diameter comprised between 10 mm and 300 mm, preferably comprised between 90 mm and 130 mm.

10. Ultrasonic transducer according to any one of the preceding claims, wherein the surface (T) of the central ultrasonic emission zone is equal to 33% of the total surface of the base part.

11. Ultrasonic transducer according to any one of claims 1 to 10, wherein the base portion has a concave shape, preferentially a frustoconical or toroidal shape.

12. The ultrasound transducer of any one of claims 1 to 11, which is a high intensity focused ultrasound (HIFU) transducer.

13. a layer of piezoelectric material (72) and at least one conductive electrode layer disposed in contact with the layer of piezoelectric material; The electrode layer is divided into a plurality of contact pads (74), each of which is coupled to the piezoelectric layer to form an ultrasound emitter element; An ultrasonic transducer according to any one of claims 1 to 12, wherein each emission zone of the electronic transducer comprises one or more of said conductor pads.

14. A device comprising an ultrasonic transducer (6) and a control unit (8) connected to the ultrasonic transducer, A device, wherein the ultrasonic transducer is an ultrasonic transducer according to any one of claims 1 to 13, and the control unit includes at least one signal generator for driving ultrasonic emitter elements, preferably with a matching circuit between the signal generator and the ultrasonic emitter elements.

15. 15. The device according to claim 14, wherein the control unit (8) is configured to activate each ultrasonic emission zone (32, 34, 36; 52, 54, 56, 58, 60, 62, 64, 66) of the ultrasonic transducer independently from the other ultrasonic emission zones.

16. 16. The device according to claim 14 or 15, which is a therapeutic ultrasound device configured to generate at least one focused ultrasound beam.

17. A method of treatment comprising administering to a human patient a device according to any one of claims 14 to 16.

Images