Self-positioning acoustic lens

Abstract

Today, there is a growing interest in using ultrasound in the medical field. Such ultrasound may be focused, for example, to treat zones within organs such as the brain. This focusing makes it possible to treat only the zones related to the disease and avoid treating healthy zones. Therefore, it is essential to use an image guidance system to monitor in real time the position where the ultrasound is focused. This guidance can be performed by magnetic resonance imaging (MRI), ultrasound imaging (echography), or optical imaging (neuronavigation). However, such systems increase the cost and the complexity of the overall process. The present disclosure overcomes the above drawbacks by proposing a self-positioning acoustic lens that enables reliable ultrasonic transmission in the zone to be treated without the need to use a navigation system.

Description

Technical Field

[0001] The present disclosure relates to a self-positioning acoustic lens configured to obtain a predetermined ultrasonic field in a substantially homogeneous medium masked by bone tissue, and a production method for implementing such a self-positioning acoustic lens for these purposes.

Background Art

[0002] Today, the interest in using ultrasound in the medical field no longer requires proof.

[0003] Generally, ultrasound can be generated from a probe comprising one or more transducers capable of generating ultrasound individually. Such ultrasound can be transmitted towards a medium and, in response thereto, generate a backscattered signal, which can be acquired and used, for example, to generate a 3D ultrasound image.

[0004] Another use of such ultrasonic waves may be, for example, for therapeutic purposes. In fact, such ultrasonic waves can be focused towards an organ (e.g., the brain or the heart, liver, etc.) to treat a specific zone of the organ. For example, in the case of the brain, this specific zone to be treated may be related to diseases such as essential tremor or glioblastoma or depression. The focusing can be carried out in different ways. For example, when using multiple transducers, the focusing can be carried out by adjusting the delay on each transmitted ultrasonic wave to obtain a focal spot in the target area. When using only one transducer or a small number of transducers (e.g., less than 128 transducers), the focal spot of the ultrasonic wave depends on the shape of the ultrasonic probe or the shape of the ultrasonic transducer (usually, the active surface is distributed on a spherical surface). The main advantage of using only one transducer or a small number of transducers (e.g., less than 128 transducers) is that the cost of the system used to perform the ultrasonic irradiation of the medium can be reduced and simplified compared to devices that use multiple transducers (more than 100). However, what is troublesome when using only one transducer or a small number of transducers to focus the ultrasonic wave is that the focal spot may be deformed in the area to be treated in the medium. Such deformation can occur when the ultrasonic wave has to cross a barrier such as bone before reaching the area to be treated in the medium. International Publication No. WO2017001781A1 describes a method for designing and machining an ultrasonic lens suitable for focusing ultrasonic waves into a medium such as the brain (i.e., located behind the skull barrier) while limiting the deformation of the focal spot.

[0005] In addition, when focusing ultrasound towards a specific zone of a medium, such as a specific zone of the brain, it is usually essential to use a navigation system that enables real-time knowledge of the position of the ultrasound probe with respect to the surface of the medium. Without such a navigation system, the focus may be placed in the wrong zone of the brain, risking damage to healthy tissue. For example, a magnetic resonance imaging (MRI) system can be used to place the transducer and induce treatment [Elias, W. Jeffrey et al., "A randomized trial of focused ultrasound thalamotomy for essential tremor," New England Journal of Medicine 375.8 (2016): 730-739]. Nevertheless, such systems are expensive, and the treatment has to be carried out within the MRI system. One way to reduce the cost of navigated treatment is to use a neuronavigation system that utilizes an optical or magnetic position tracking system. However, neuronavigation systems have several drawbacks. One of the main drawbacks is that such a system has to be preconfigured every time a patient needs to undergo treatment. In fact, before using the neuronavigation system on a patient, the system has to be configured by obtaining one or more images of the patient's head to obtain reference points in the brain (or ventricles) and even reference points on the surface of the skull. The images can be acquired, for example, by using magnetic resonance imaging, CT scanning, or ultrasound imaging. Then, anatomical landmarks (such as by pointing to the bridge of the nose or the tragus of the left and right ears, or by palpating the skin surface) are identified, and a reference tool is required to align the patient's head. This preconfiguration has to be done at the start of each treatment for all patients, which can be time-consuming for clinicians. Furthermore, neuronavigation systems are costly, and not all clinical departments own such systems.In addition, medical institutions and households would benefit from using focused ultrasound to avoid the use of a neuronavigation system.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, it is necessary to enable focusing of ultrasound on specific zones of the human brain without the need to use a neuronavigation system.

Means for Solving the Problems

[0009] For this purpose, the present disclosure proposes a self - positioning acoustic lens having a front surface and a back surface, the back surface facing the front surface, the self - positioning acoustic lens being adapted to transmit ultrasonic waves into a medium including at least one aberrating barrier and a substantially homogeneous internal portion masked by the aberrating barrier, the ultrasonic waves being generated by an ultrasonic probe disposed outside the medium, and the back surface facing the radiation surface of the ultrasonic probe. The self - positioning acoustic lens is configured to generate a predetermined target ultrasonic field in at least one predetermined region belonging to the internal portion when the self - positioning acoustic lens is sandwiched between an ultrasonic probe and an aberration barrier and when the ultrasonic probe transmits a predetermined ultrasonic wave, despite the presence of the aberration barrier. The front surface is constrained and can be adapted to match the outer surface of the medium, and the outer surface of the medium is not a perfect sphere. The back surface can be spaced from the front surface according to a specific acoustic lens thickness to generate the predetermined target ultrasonic field.

[0010] It is understood that by the self - positioning of the acoustic lens, the acoustic lens can be configured to be placed only at one correct possible position on the surface of the medium. The front surface is constrained and adapted to match the outer surface of the medium so that it can be self - positioned on the outer surface of the medium. The front surface of the self - positioning acoustic lens can be configured to complementarily match the outer surface of the medium only at one correct possible position on the surface of the medium, because only one position allows complete contact between the front surface of the lens and the outer surface of the medium.

[0011] Accordingly, advantageously, the self - positioning acoustic lens can serve to treat an area of interest (or a specific zone) that includes a focal spot (or focus) without using a neuronavigation system, as already described. The area of interest is located within the brain and can be, for example, a zone related to a disease such as depression or essential tremor. In fact, due to the fact that the front surface is shaped to fit only one specific area of the surface of the medium (or, for example, the surface of the skin surrounding the skull), the acoustic lens is placed at only one possible position on the skull and thus at a self - positioning position, and is configured to be able to treat the correct zone (for example, within the brain) without using a neuronavigation system. Further, the configuration of the self - positioning acoustic lens is such that the thickness of the acoustic lens corrects the distortion induced by the aberrating medium. Since the acoustic lens is designed to match a specific zone to be treated within the brain from only one possible position on the outer surface or on the head, the risk of error (for example, treating the wrong zone within the brain) is very small.

[0012] In one or some embodiments, the contact surface between the front surface of the self - positioning acoustic lens and the outer surface of the medium can be limited to a specific restricted area on the outer surface of the medium.

[0013] It can be understood that there is physical contact between the surface of the self - positioning acoustic lens (for example, the front surface) and the outer surface of the medium by the contact.

[0014] In one or some embodiments, the aberration barrier is the skull, the outer surface is the skin surrounding the skull, and the restricted specific area can correspond to a part of the outer surface that is in contact with the front surface of the self - positioning acoustic lens.

[0015] In one or some embodiments, the self - positioning acoustic lens may be made of polydimethylsiloxane, or polymethylpentene, or is a composite lens.

[0016] In one or several embodiments, the back surface of the self - positioning acoustic lens may be far from the radiation surface of the ultrasonic probe according to a value within the range of 0 to 5 centimeters.

[0017] In one or several embodiments, the thickness of the self - positioning acoustic lens from each point on the front surface of the self - positioning acoustic lens satisfies the formula

Number

[0018] In one or several embodiments, when the ultrasonic probe is a focused transducer, in spherical coordinates, each point on the back surface of the self - positioning acoustic lens

Number

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[0019] In one or some embodiments, the front surface may be constrained and adapted to complementarily coincide with the outer surface of the medium.

[0020] The present disclosure also relates to a production method for implementing a self-positioning acoustic lens comprising a front surface and a rear surface, said rear surface facing the front surface, said self-positioning acoustic lens being adapted to transmit ultrasonic waves into a medium comprising at least one aberration barrier and a substantially homogeneous internal portion masked by said aberration barrier, the ultrasonic waves being generated by an ultrasonic probe disposed outside the medium, said rear surface being adapted to face the radiation surface of the ultrasonic probe, This production method comprises at least - imaging the medium to generate a mapping of the acoustic properties of the medium, and - using a model for estimating the time delay at a given control surface included within the expected volume of the acoustic lens, said time delay enabling the generation of a given target ultrasonic field within at least one predetermined region belonging to said internal portion, using Calculating the geometric shape of a self-positioning acoustic lens, including determining the first shape of at least the front surface and the thickness between the front surface and the back surface, by using a model of a medium including mapping of acoustic characteristics, wherein the self-positioning acoustic lens is configured to generate a predetermined target ultrasonic field in at least one predetermined region belonging to the internal portion despite the presence of an aberration barrier when causing a time delay and when the self-positioning acoustic lens is sandwiched between an ultrasonic probe and the aberration barrier and the ultrasonic probe transmits a predetermined ultrasonic wave; Implementing the self-positioning acoustic lens by using the calculated self-positioning acoustic lens; may include; The first shape of the front surface of the self-positioning acoustic lens is determined to match the outer surface of the medium, and the outer surface of the medium is not a perfect sphere.

[0021] In one or some embodiments, the contact surface between the front surface of the self-positioning acoustic lens and the outer surface of the medium may be limited to a specific limited region on the outer surface of the medium.

[0022] It can be understood that there is physical contact between the surface (e.g., the front surface) of the self-positioning acoustic lens and the outer surface of the medium by contact.

[0023] In one or some embodiments, imaging of the medium may be performed by using computed tomography (CT) or magnetic resonance imaging (conventional imaging or ultra-short echo time imaging) or ultrasonic imaging.

[0024] In one or some embodiments, before calculating the geometric shape of the self-positioning acoustic lens, - (b1) simulating the backpropagation of the predetermined target ultrasonic field in the medium from a predetermined region to a selected position of the control surface; - (b2) The first arrival time t1(x,y,z) of the inverse propagation of the predetermined target ultrasonic field to the selected position of the control surface is determined; - (b3) The propagation in the coupling medium of the ultrasonic waves radiated by an ultrasonic probe disposed outside the medium to a selected position on the front surface of the self-positioning acoustic lens is calculated, and the second arrival time t0(x,y,z) of the ultrasonic waves to the selected position on the front surface of the self-positioning acoustic lens is determined; - (b4) A delay time law Δt(x,y,z) at the selected position of the control surface, which is equal to the sum of the first arrival time t1(x,y,z) and the second arrival time t0(x,y,z), is determined. A simulation including the above can be executed. The geometric shape of the self-positioning acoustic lens is calculated using the delay time law Δt(x,y,z), such that when the ultrasonic probe radiates ultrasonic waves through the self-positioning acoustic lens, the predetermined ultrasonic waves can regenerate a target ultrasonic field within the predetermined region after passing through the aberration barrier. The control points M(x,y,z) that are distributed on the front surface of the self-positioning acoustic lens and for which the second arrival time t0(x,y,z) and the first arrival time t1(x,y,z) are determined belong to a single control surface, and preferably, the control surface is disposed on the outer surface of the medium.

[0025] In one or some embodiments, when the ultrasonic probe is a focused transducer, in spherical coordinates, each point on the back surface of the self-positioning acoustic lens

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[0026] In one or several embodiments, when the ultrasonic wave is a single-frequency sound wave, in spherical coordinates, each point on the back surface of the self-aligning acoustic lens

Number

Number

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Number

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Number

[0027] In one or more embodiments, the thickness e(x, y, z) is given by the formula at each point M(x, y, z) on the front surface

Number

[0028] In one or more embodiments, when the ultrasound is a single-frequency sound wave, the thickness e(x, y, z) is given by the formula at each point M(x, y, z) on the front side

Number

Number

[0029] In one or some embodiments, implementing the self-positioning acoustic lens can be done by a method selected from three-dimensional printing of the self-positioning acoustic lens and / or digital control machining of at least one block of material for forming the self-positioning acoustic lens.

[0030] In one or some embodiments, implementing the self-positioning acoustic lens is at least (d1) mold implementation performed by a method selected from three-dimensional printing of at least one mold and / or numerical control machining of at least one block of material for forming the at least one mold, (d2) molding in which the self-positioning acoustic lens or at least one component of the self-positioning acoustic lens is molded within the at least one mold may include.

[0031] In one or some embodiments, the self-positioning acoustic lens can be made of a material having acoustic properties that can be modified by exposure to a predetermined radiation, When calculating the geometric shape of the self-positioning acoustic lens, the self-positioning acoustic lens is calculated in consideration of the local acoustic characteristics in the self-positioning acoustic lens. This method includes the implementation of the self-positioning acoustic lens in which the self-positioning acoustic lens is locally exposed to the predetermined radiation in order to obtain the local acoustic characteristics of the self-positioning acoustic lens necessary to generate the calculated time delay law Δt(x, y, z) necessary to reproduce a predetermined object despite the presence of an aberration medium.

[0032] In one or some embodiments, the first shape of the front surface of the self-positioning acoustic lens can be determined to complementarily match the outer surface of the medium.

[0033] In one or some embodiments, the calculation of the geometric shape of the self-positioning acoustic lens can be repeatedly performed using an analytical model or a numerical model to optimize the ultrasonic energy transmission yield within a predetermined zone.

[0034] In one or some embodiments, in sub-step (b3), the second arrival time t0(x, y, z) can be determined by simulating the propagation of the predetermined ultrasonic wave in a simplified model that enables analytical calculation.

[0035] In one or some embodiments, in the calculation of the geometric shape of the self-positioning acoustic lens, the travel time of the predetermined ultrasonic wave in the self-positioning acoustic lens, as well as the incident angle and the refraction angle of the predetermined ultrasonic wave on the surface of the self-positioning acoustic lens, may be considered.

[0036] In one or some embodiments, the calculation of the geometric shape of the self-positioning acoustic lens may consider the entire propagation of the predetermined ultrasonic wave, including refraction by each surface of the self-positioning acoustic lens, and / or echoes between the ultrasonic probe, the self-positioning acoustic lens, and the aberration barrier, and / or echoes within the self-positioning acoustic lens.

[0037] The present disclosure also relates to a method for ultrasonic irradiation of a medium including at least one aberration barrier and a substantially homogeneous internal portion masked by the aberration barrier, wherein the outer surface of the medium is not a perfect sphere, and the ultrasonic irradiation method may also include the manufacture of a self-positioning acoustic lens according to the present disclosure. The ultrasonic irradiation method - transmitting the predetermined ultrasonic waves through a self-positioning acoustic lens, wherein the ultrasonic waves are generated by the ultrasonic probe disposed outside the medium, and the back surface is adapted to face the radiation surface of the ultrasonic probe, and the transmitting may include. The self-positioning acoustic lens is disposed on the outer surface of the medium such that a first shape of a front surface of the self-positioning acoustic lens coincides with the outer surface of the medium.

[0038] In one or some embodiments, the contact surface between the front surface of the self-positioning acoustic lens and the outer surface of the medium may be limited to a specific limited region on the outer surface of the medium.

[0039] It can be understood that there is physical contact between the surface of the self-positioning acoustic lens (e.g., the front surface) and the outer surface of the medium by the contact.

[0040] In one or some embodiments, the medium through which the ultrasonic waves propagate may be a human or animal head, the aberration barrier may be a skull, and the internal portion may be a brain.

[0041] In one or some embodiments, the predetermined ultrasonic field may be focused within the internal portion within at least one predetermined zone.

[0042] The present disclosure also relates to a method for calculating the geometric shape of a self-positioning acoustic lens, the self-positioning acoustic lens being suitable for ultrasonic irradiation of a medium including at least one aberration barrier and a substantially homogeneous internal portion masked by the aberration barrier, wherein the outer surface of the medium is not a perfect sphere. This method calculates the geometric shape of a self-positioning acoustic lens by using a model of a medium that includes mapping of acoustic properties. The self-positioning acoustic lens is configured to generate a predetermined target ultrasonic field in at least one predetermined region belonging to the internal portion when the self-positioning acoustic lens is sandwiched between an ultrasonic probe and an aberration barrier and when the ultrasonic probe transmits a predetermined ultrasonic wave.

[0043] The present disclosure also relates to a device for calculating the geometric shape of a self-positioning acoustic lens. The self-positioning acoustic lens is suitable for ultrasonic irradiation of a medium that includes at least one aberration barrier and a substantially homogeneous internal portion masked by the aberration barrier. The outer surface of the medium is not a perfect spherical surface. The calculation device is configured to calculate the geometric shape of the self-positioning acoustic lens by using a model of a medium that includes mapping of acoustic properties. The self-positioning acoustic lens is configured to generate a predetermined target ultrasonic field in at least one predetermined region belonging to the internal portion when the self-positioning acoustic lens is sandwiched between an ultrasonic probe and an aberration barrier and when the ultrasonic probe transmits a predetermined ultrasonic wave.

[0044] The present disclosure also relates to a device for manufacturing a self-positioning acoustic lens, which includes a calculation device for the self-positioning acoustic lens according to the present disclosure and means for producing the self-positioning acoustic lens.

[0045] The present disclosure also relates to a computer program that includes instructions for causing a computer, when a program is executed by a computer including a processor and a storage device, to execute the method of the present disclosure.

[0046] The present disclosure also relates to a computer-readable medium on which the computer program of the present disclosure is stored.

[0047] The present disclosure also relates to a non-transitory computer-readable medium storing software instructions that, when executed by a processor, cause the processor to execute the method of the present disclosure.

[0048] Other features, details, and advantages are set forth in the detailed description and the figures shown below.

Brief Description of the Drawings

[0049]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5a

Figure 5b

Modes for Carrying Out the Invention

[0050] FIGS. 1 and 2 are schematic diagrams showing the overall ultrasonic generation mechanism according to the present disclosure, including a self-aligning acoustic lens.

[0051] In the various figures, the same reference numerals indicate the same or similar items.

[0052] The mechanism 100 for generating ultrasonic waves shown in FIG. 1 may be capable of generating a predetermined ultrasonic field (or ultrasonic waves) in a medium 103, for example, the head of a patient P. The medium 103 may include at least one aberration barrier 108 and at least one substantially homogeneous internal portion 107 masked by the aberration barrier 108.

[0053] According to one example, the aberration barrier may be the skull of patient P, and the internal part may be the brain of patient P.

[0054] Mechanism 100 may be intended to generate ultrasonic waves within the brain 107 of patient P (or more generally the internal part 107 of medium 103) from the outside of patient P, for example, at a frequency within the range of 0.1 to 10 MHz, particularly 0.2 to 3 MHz.

[0055] This generation of ultrasonic waves may be intended to treat zones of the brain that may be associated with certain pathologies such as, for example, Parkinson's disease, essential tremor, depression, anxiety neurosis, schizophrenia, Alzheimer's disease, or other mental or neurological disorders. The treatment may be, for example, ultrasonic thermal ablation, ultrasonic neuromodulation, ultrasonic histotripsy, or ultrasonic blood-brain barrier opening for drug delivery.

[0056] It should be noted that obtaining the target ultrasonic field itself is by no means a therapeutic treatment in these applications, but rather a simple technical means for focusing the sound waves. The possible therapeutic treatments selected by the physician include the selection of the target sound wave field, its intensity, its application duration, the number of applications of this target sound wave field, and its distribution over time.

[0057] The target sound wave field may be understood as a sound wave field that is focused (or focused on) a focal point within the brain 107, for example.

[0058] In all cases, it is necessary to be able to generate one or more predetermined target ultrasonic fields within the brain 107 of patient P as accurately as possible in order to focus the ultrasonic waves emitted, for example, by ultrasonic probe 102, on one or more points of the brain, or to generate a more complex sound wave field. As shown in FIG. 2 (or FIG. 4), the target sound wave field may be, for example, a focal spot F within the brain 107, or in some cases a plurality of focal spots, or a sound wave field focused on one or more more complex three-dimensional shapes.

[0059] The mechanism 100 may include an ultrasonic probe 102 and a control system 111. The ultrasonic probe 102 may be provided with a radiation surface and configured to transmit ultrasonic waves 210 into a homogeneous internal portion 107 (i.e., the brain of patient P) contained within the medium 103. The ultrasonic waves may be generated by one transducer 203 (or ultrasonic transducer) or a plurality of transducers (or a plurality of ultrasonic transducers) contained within the ultrasonic probe 102.

[0060] In one or some embodiments, the plurality of transducers may include a number of transducers within the range from 1 to 128.

[0061] According to one example, one or a plurality of transducers 203 may have a circular shape defined by a diameter within the range from 10 to 400 millimeters and may have a radius of curvature within the range from 5 to 200 millimeters. According to one example, the transducer may have a radius of curvature of 59 millimeters with respect to an aperture of 67 millimeters (at 500 kHz).

[0062] In one or a plurality of embodiments, the ultrasonic probe may be a single transducer, which may be a focused transducer or an unfocused transducer.

[0063] Furthermore, the control system can be programmed (or configured) such that ultrasonic waves can be transmitted at an ultrasonic frequency exceeding 100 per second, for example, an ultrasonic frequency of several hundreds to several thousands per second. The control system can include, for example, a control unit 111a and a computer 111b. In this example, the control unit 111a can be used to control the ultrasonic probe 102, and the computer 111b can be used to control, for example, the control unit 111a, determine the zone to be treated within the internal portion 107, and design the acoustic lens 109. In an alternative embodiment, it would also be possible for a single electronic device to perform all the functions of the control unit 111a and the computer 111b.

[0064] The mechanism 100 can be composed of an acoustic lens 109 (or self - positioning acoustic lens) that can be sandwiched between the ultrasonic probe 102 and the surface of the medium, for example, the skull 108 of the patient P. The acoustic lens can include a front surface 109a and a back surface 109b.

[0065] In one or some embodiments, the ultrasonic probe 102 can be mechanically constrained by 102a using the acoustic lens 109 (i.e., the self - positioning acoustic lens) such that the radiation surface of the ultrasonic probe faces the back surface 109b of the acoustic lens at a distance within the range of 0 to 150 millimeters. According to one example, the ultrasonic probe can be fixed by the edge of the acoustic lens by using a rod 102a (for example, made of metal or polymer), and this set (the acoustic lens with the ultrasonic probe) can be held against the head of the patient P by elastic means during the emission of ultrasonic waves. According to another example, this set can be held by the hand of the patient or the operator during the emission of ultrasonic waves, or can be held by using a robotic arm (for example, manually or automatically controlled by the operator).

[0066] According to another example, the ultrasonic probe 102 can be integrated, for example, into a helmet (not shown) positioned in a predetermined manner on the head 103 of the patient P, or else the ultrasonic probe 102 can be mounted on other known positioning systems.

[0067] In all cases, the ultrasonic probe 102 can be positioned at a predetermined position outside the patient's skull 108. Such a predetermined position of the ultrasonic probe may be a position near the zone to be treated at the focal spot 230 (or focus).

[0068] A gel or liquid, which can also be housed in a flexible pouch (not shown), is sandwiched between the acoustic lens 109 and the skull 108 and / or between the ultrasonic probe 102 and the acoustic lens 109, that is, between the front surface 109a and the skull 108, thereby ensuring good transmission of ultrasonic waves. Here, this gel or liquid is called an external medium and is considered to be part of the ultrasonic propagation medium 103.

[0069] The acoustic lens 109 (or self-positioning acoustic lens) is made of any material in which the speed of the compressive acoustic wave c l differs from the speed c of said wave in water (c is about 1480 m / s at 20 °C). The acoustic lens can be made, for example, of silicone, in particular polydimethylsiloxane, also known as PDMS (c l = 1030 m / s) or Elite Double products (Zhermack SpA, located in Italy), or of plastic, in particular polymethylpentene, known under the name of TPX® (c l = 2090 m / s).

[0070] Some parts of the acoustic lens are made of a damping material that reflects and / or absorbs ultrasonic waves, which can in particular locally damp the ultrasonic field formed within the brain 107 or the skull 108, for example enhance beam shaping and / or limit heating of the skull or limit the ultrasonic irradiation volume within the brain 107.

[0071] Referring to FIG. 2, the front surface 109a of the acoustic lens can physically contact the outer surface 108a of the medium 103. Generally, since the outer surface of the medium is not a perfect sphere, a plurality of specific regions appear on the surface of the medium.

[0072] For example, the surface of the medium 103 can be limited to a specific region (or a restricted specific region) of the surface of the medium with respect to a zone (e.g., the zone to be treated) within the inner portion 107, where it is desired to generate one or more focal spots or an object acoustic wave field having one or more more complex three-dimensional shapes. This surface of the medium (on FIG. 2) that is restricted to a specific region has a specific shape that exists only in this specific region, and thus can enable self-positioning of the acoustic lens on the surface of the medium. For example, this specific shape can be the specific shape (or a restricted specific region) of the skin at the top of the skull that exists only in this specific region on the surface of the medium. In fact, the aspherical shape of the head can exhibit different local configurations along the surface of the head.

[0073] As previously explained, when focusing ultrasonic waves using only one transducer or a small number of transducers (less than 128 transducers) within a homogeneous internal portion 107 such as the brain in the medium 103, the presence of a barrier such as the skull can disrupt the focusing of the ultrasonic waves and cause deformation of the focal spot 230 (or multiple focal spots or one or more more complex three-dimensional shapes). The deformation of the focal spot can be a problem when it is desired to treat a specific zone (or exact zone) within the internal portion 107 such as the brain. International Publication No. WO2017001781A1 describes a method for designing and fabricating an ultrasonic lens suitable for focusing ultrasonic waves into a medium such as the brain (i.e., located behind the bone barrier) and for partially or fully compensating for the deformation of the focal spot. For this purpose, the inventive method of the ultrasonic lens described in International Publication No. WO2017001781A1 is to determine the thickness "e(x,y)" from the back surface to the front surface of the ultrasonic lens in order to compensate for the phase delay induced by the barrier. In International Publication No. WO2017001781A1, no constraints are imposed on the front surface of the lens, only the thickness of the lens is constrained. According to International Publication No. WO2017001781A1, this is because when the ultrasonic wave 210 is generated by the ultrasonic probe 102 (including at least one transducer 203) and crosses the ultrasonic lens, the ultrasonic wave is shaped (by decreasing stepwise) to compensate for the delay caused by the barrier, thereby restoring the ultrasonic wave into the internal portion as if the barrier were not present or could be ignored, and thus potentially avoiding the deformation of the focal spot 230 (or the focus). However, such an acoustic lens described in International Publication No. WO2017001781A1 is not a self-positioning lens and still requires the use of a neuronavigation system or other navigation device for use in treating a specific zone of the brain.

[0074] Referring to FIG. 2, it may be possible to determine the geometric shape of an acoustic lens (or self - positioning acoustic lens) having a thickness “e(x,y,z)” from the front - side surface 109a to the back - side surface 109b of the acoustic lens, and for example, a specific shape of the front - side surface. The acoustic lens of FIG. 2 has a determined acoustic lens thickness, and the front - side surface fits only to a specific one region on the outer surface of the medium, enabling self - positioning on the surface of the medium, so that when transmitting a predetermined ultrasonic wave without using a neuronavigation system, it may be possible to obtain one or more focal spots, or one or more more complex three - dimensional shapes within a specific zone of an internal part 107 such as the brain.

[0075] FIG. 3 illustrates a method for obtaining a self - positioning acoustic lens such as the acoustic lens of the present disclosure.

[0076] A method for obtaining such an acoustic lens may be as follows.

[0077] (a) Determination of a three - dimensional model of the medium 103 In advance, a three - dimensional model of the medium 103 may be determined, which includes mapping the acoustic properties in the medium 103 including the homogeneous internal part 107 and the barrier 108. For example, the internal part 107 may be the brain of the patient P, and the barrier 108 may be the skull of the patient P.

[0078] This step generally may include an imaging operation by, for example, computed tomography (CT) or magnetic resonance imaging (MRI, using conventional imaging or ultrashort echo - time imaging) or ultrasonic imaging to determine the acoustic properties of the barrier 108. For example, the information obtained by imaging the medium 103 may be used to determine, in particular, the mass density ρ, the sound speed c, and / or the absorption coefficient τ of the ultrasonic wave at each point of the aberration barrier 108 and the medium 107.

[0079] The three-dimensional model can be loaded, for example, into computer 111b. The user may position a desired ultrasonic field, such as one or more focus spots (or foci) 230, on an image of the medium 107 (FIG. 2). This positioning can be done, for example, by displaying a target or other zone of interest to be treated on the image of the medium 107 and identifying the position of this zone on the image using the user interface of computer 111b (such as a mouse, touch screen, or other means).

[0080] Hereinafter, for simplicity, the "zone of interest" is referred to with respect to specifying one or more focus spots or one or more more complex three-dimensional shapes.

[0081] (b) Simulation: The propagation of ultrasonic waves through the aberration barrier 108 is simulated from the aforementioned three-dimensional model, and then the delay or phase shift that must be induced by the acoustic lens (or self-positioning acoustic lens) is determined, and then the geometric shape (or shape) to be given to the acoustic lens, such as the distance between the front and back surfaces of the acoustic lens (i.e., the thickness of the acoustic lens), can be inferred. This simulation step can be performed by the aforementioned computer 111b or another computer.

[0082] In one or some embodiments, this simulation step may include the following sub-steps.

[0083] (b1) Simulation (S2) of the backward propagation of the desired ultrasonic wave in the zone of interest within the three-dimensional model As shown in S2 of FIG. 3, in this sub-step b1, the backward propagation of a predetermined target ultrasonic field 320c in the medium 107 is simulated from the focus spot 230 (i.e., the zone of interest) in the medium 107 to a single control surface 330.

[0084] The predetermined control surface 330 may have a shape that can be shaped as the shape of the outer surface of the medium 107, i.e., the shape of the surface of the skin surrounding the skull (i.e., the shape of the surface of the barrier 108), in a specific region. This specific region may be a region of the surface of the medium that is close to the focal spot 230 and where an acoustic lens (or a self-positioning acoustic lens) is intended to be positioned.

[0085] The shape of the predetermined control surface 330 may be determined in advance by using the information obtained from the imaging operation in step (a) presented previously.

[0086] This simulation may be performed, for example, by the computer 111b using the wave equation such as Equation (1)

Number

Number

[0087] The propagation of ultrasonic waves in the aberration barrier 108 and the internal part 107 can be simulated in a computer by finite differences by discretizing the above Equation (1). The simulation can also be performed by the finite element method, the impulse diffraction method, or any other known method.

[0088] The simulation can be executed by the control unit of the control system or a computer, or by a single electronic device, or by other electronic devices including a processor, a storage device, and an instruction set configured to implement the simulation.

[0089] (b2) Determination of the first arrival time on the control surface 330 (S2’) As shown in S2’ of FIG. 3, the arrival times t1(x,y,z) of the ultrasonic waves 320c, 320b representing the backpropagation of a predetermined target sound wave field can preferably be determined at a control point M(x,y,z) belonging to a single control surface 330 arranged on the outer surface of the medium 103, for example, which may be confused with the surface 108a.

[0090] The arrival time t1(x,y,z) can be measured, for example, from the moment of emission of the ultrasonic wave 320c within the zone 230, where x, y, and z are the coordinates on the axes X, Y, and Z of each control point M under consideration, respectively. The arrival time t1(x,y,z) will hereinafter be referred to as the first arrival time.

[0091] (b3) Determination of the second arrival time on the control surface 330 (S1 - S1’) As shown in S1 and S1’ of FIG. 3, it may be possible to determine the arrival time t0(x,y,z) of a predetermined ultrasonic wave 320a emitted by an ultrasonic probe 102 including at least one transducer at different control points M(x,y,z) preferably belonging to a single control surface 330 arranged on the outer surface of the medium 103.

[0092] Regarding (b1), the predetermined control surface 330 can be shaped according to the shape of the surface of the medium, that is, the shape of the skin surface surrounding the skull in a specific region. This specific region is close to the focal spot 230 and may be the region of the surface of the medium where the acoustic lens (or self - positioning acoustic lens) is intended to be positioned.

[0093] The arrival time t0(x,y,z) can be determined by a computer 111b or other means (up to an arbitrary constant time T’0 common to the entire control surface 330) because the outer part of the medium (outside the aberration barrier) is considered to be homogeneous with respect to the propagation of ultrasonic waves.

[0094] In the simplest and most common case where the ultrasonic probe (or transducer) is spherical with a radius R, this determination can be made very simply by the mathematical formula

Number

[0095] More generally, the arrival time t0(x, y, z) can be determined by calculating the ultrasonic propagation between the ultrasonic probe and the control point, or by any other known wave propagation method that is simple in a homogeneous medium (the propagation can then be carried out in a simplified model that allows for analytical calculations).

[0096] The arrival time t0(x, y, z) will hereafter be referred to as the second arrival time.

[0097] (b4) Determination of the lens delay time law (S3) As shown in S3 of FIG. 3, the delay time law Δt(x, y, z) may be determined at various control points M(x, y, z), which is equal to the sum of the first arrival time t1(x, y, z) and the second arrival time t0(x, y, z).

[0098] (c) Calculation of the acoustic lens (S4) Computer 111b or other entity may start from the shape of the front surface (included in the geometric shape of the self-aligning acoustic lens) that must coincide with the aforementioned delay time law Δt(x,y,z) and the outer surface of the medium or a specific region of the outer surface of the medium, and then calculate the profile of the acoustic lens 109 that can add the delay time Δt(x,y,z) when sandwiched between the ultrasonic probe 102 and the aberration barrier 108 and positioned on the outer surface of the medium. Thereby, when the ultrasonic probe 102 emits a predetermined ultrasonic wave 320a, the predetermined sound wave after passing through the acoustic lens and then through the aberration barrier can generate a predetermined ultrasonic field within the region of interest corresponding to one or more focal spots or one or more more complex three-dimensional shapes 230 within the internal portion 107.

[0099] More precisely, the thickness e of the acoustic lens 109, i.e., the thickness between the front surface and the back surface of the acoustic lens, can be calculated at each point of the acoustic lens corresponding to the control point M(x,y,z) of the predetermined control surface 330. Thereby, the thickness e(x,y,z) of the acoustic lens can incorporate the ultrasonic propagation time correction corresponding to the delay time law with the ultrasonic period T = 1 / f (where f is the central frequency of the ultrasonic wave) as the law and / or up to any constant time T0 common to the entire control surface.

[0100] In one or some examples (such as when the ultrasonic probe is a focused transducer or a single focused transducer), the delay Δt(x,y,z) is such that the center of coordinates is arranged at the center of curvature of the transducer 102.

Number

Number

Number

Number

[0101] Here, c is the speed of ultrasound in the coupling medium 110 outside the aberration barrier 108, and c1 is the speed of ultrasound in the lens.

[0102] The constant e0 is a real value such that the thickness of the lens is positive at each point and greater than the minimum value required to ensure the robustness of the lens, and the minimum value depends on the material of the lens.

[0103] In the case of the emission of a single - frequency wave, in one or more embodiments, each point on the back surface of the acoustic lens

Number

Number

Number

Number

[0104] modulo

Number

Number

[0105] each point on the back surface of the acoustic lens [Number] These spherical coordinates of can be used to calculate the distance between the front surface and the back surface corresponding to the thickness of the acoustic lens (or self-aligning acoustic lens) with respect to the corresponding control point [Number] It can be used to calculate the distance between the front surface and the back surface corresponding to the thickness of the acoustic lens (or self-aligning acoustic lens) with respect to the corresponding control point.

[0106] Note that in lens calculation step (c), at least the travel time of a predetermined ultrasonic wave in the acoustic lens 109 and the incident angle and refraction angle of the predetermined ultrasonic wave with respect to the surface of the acoustic lens 109 can be considered. In lens calculation step (c), also, the refraction by each surface of the self-aligning acoustic lens, and / or the echo between the ultrasonic probe 102 including at least one transducer, the acoustic lens 109, and the aberration barrier 108, and / or the echo within the self-aligning lens, may be considered for the entire propagation of the predetermined ultrasonic wave. Lens calculation step (c) can be performed iteratively using an analytical model or a numerical model to optimize the ultrasonic energy in the region of interest.

[0107] This calculation step can be executed by a control unit or a computing device of the control system which can be a computer, or by a single electronic device, or by other electronic devices that may include a processor, a storage device, and an instruction set configured to implement the calculation step.

[0108] (d) Implementation of the acoustic lens Next, after the geometric shape of the self-aligning acoustic lens, including the shape of the front surface and the distance between the front and back surfaces (i.e., the thickness of the acoustic lens), is determined, the acoustic lens can be produced by any high-speed production method as follows. - 3D printing of the acoustic lens 109, - Numerical control machining of a block of material to form the acoustic lens 109, - A process having the following two sub-steps (d1) A sub-step of mold production (not shown) performed by a method selected from 3D printing of a mold and / or numerical control machining of a block of material to form a mold, (d2) A sub-step of molding in which the lens 109 is molded within the mold.

[0109] In all scenarios, the acoustic lens can be produced from a material having mechanical properties (especially hardness), and thus acoustic wave propagation properties, that can be altered by exposure to a predetermined radiation.

[0110] The predetermined radiation may be, for example, ultraviolet light.

[0111] The material in question may be, for example, silicone, especially polydimethylsiloxane (PDMS (c l = 1030 m / s), also called polydimethylsiloxane, or an Elite Double product (Zhermack SpA, Italy), or a plastic that cures under ultraviolet light, such as polyvinylmethylsiloxane (PVMS), for example.

[0112] In this case, in the lens calculation step (c), the acoustic lens 109 can be calculated by determining the local acoustic properties of the acoustic lens 109 that achieve the desired target acoustic wave field. These mechanical properties can be determined in addition to the shape of the acoustic lens 109, or as an alternative, it is possible that the target acoustic wave field can be obtained only by local variations in the local propagation properties of the acoustic lens 109.

[0113] In step (d) of the implementation of the acoustic lens 109, the lens is locally exposed to the predetermined radiation in order to obtain the local acoustic properties determined during the lens calculation step (c).

[0114] (e) Use After the acoustic lens 109 has been produced, it can be used to treat a specific zone within an internal part such as the brain. For this purpose, the acoustic lens 109 can be positioned on the skin of the patient P in such a way that the front surface of the acoustic lens is in physical contact with the surface of the skin and the shape of the front surface of the acoustic lens can fit complementarily to the shape of the surface of the medium. More precisely, the shape of the front surface of the acoustic lens may be such that it only matches one specific area of the surface of the skull so that the acoustic lens is self - positioning.

[0115] Since the acoustic lens is self - positioning, the patient P can position the acoustic lens, on which the ultrasonic probe is fixed, by himself / herself, but it is only possible in one position, corresponding to the position that enables the correct zone in the brain to be treated. For example, the patient may place the self - positioning acoustic lens on his / her head by hand before activating the ultrasonic probe and wait for instructions from the operator. In one or some alternative forms, the acoustic lens with the ultrasonic probe fixed (in a restricted form) can be placed manually, or automatically, using a robotic arm, or placed within a helmet, or held by the operator.

[0116] The operator can then send a predetermined sound wave 320a from the ultrasonic probe 102 through the self - positioning acoustic lens 109.

[0117] The ultrasonic irradiation method can be executed by the control unit or computer of the control system, or by a single electronic device. For example, the operator can activate the ultrasonic irradiation method by using the control system.

[0118] As shown in FIG. 4, the self - positioning acoustic lens 109, whose front - side surface is in physical contact with the surface of the skin in a specific region, can induce aberration correction to form a wavefront 320b upstream of the skull 108 such that after passing through the skull 108 (or another aberration barrier), the wavefront 320c is corrected from the aberration induced by the skull (or another aberration barrier). Thus, the target acoustic wave field can, as a result, cause, for example, a focal spot 230.

[0119] Thus, the acoustic waves sent to the brain or other internal part 107 can, as previously explained, serve to treat the region of interest (or a specific zone) 230 without using a neuronavigation system. In fact, thanks to the configuration of the acoustic lens as the thickness of the acoustic lens and the fact that the front - side surface is shaped only with respect to one specific region of the surface of the medium (e.g., the surface of the skin surrounding the skull), the acoustic lens is placed at only one possible position on the skin that enables it to generate a focal spot 230 (or multiple focal spots, or one or more more complex three - dimensional shapes) that includes the correct zone to be treated without using a neuronavigation system, and is thus configured to self - position. Since the acoustic lens is designed to match a specific zone to be treated in the brain from only one possible position on the skull, the risk of error (e.g., treating the wrong zone in the brain) is very small.

[0120] In addition, at least in the vicinity around the region of interest included in the focal spot 230, the brain or another internal part 107 can be imaged when the ultrasonic probe 102 is equipped with an ultrasonic transducer for imaging because the acoustic lens 109 can compensate for the aberration caused by the skull or another aberration barrier 108 in both transmission and reception.

[0121] The method according to the present disclosure may further include an optional step (f) of verifying the positioning of the device, wherein an ultrasonic echo that can be reflected on the aberration barrier is recorded on the ultrasonic probe, and the echo is compared with the same reflected signal simulated by using the aforementioned model of the medium 103.

[0122] The control unit and / or computer or / and single electronic device may include a processor, a storage device (such as a memory), and an instruction set configured to implement the method according to the present disclosure. The control unit and / or computer or / and single electronic device may be provided with an input interface and an output interface. In a variant, a computer may be used instead of the control unit, or the control unit may be used instead of the computer. In one variant, it would also be possible for a single electronic device to perform all the functions of the control unit and the computer.

[0123] Figures 5a and 5b illustrate the effect on a given ultrasonic field that occurs when a self-positioning acoustic lens is used. More precisely, Figure 5a illustrates a given ultrasonic field in an uncorrected region, and Figure 5b illustrates the same given ultrasonic field in the region corrected by the self-positioning acoustic lens.

[0124] In the experimental setup that enables obtaining the above-mentioned given ultrasonic field, the self-positioning acoustic lens was designed and manufactured for a human anatomical cadaver skull according to the method presented previously. The front surface of the self-positioning acoustic lens was constrained and shaped to match the surface of the outer surface of the skull. The back surface of the self-positioning acoustic lens was also shaped to compensate for skull abnormalities using structural and mechanical information derived from a CT scan. The experimental setup also includes a water tank, an ultrasonic transducer, and a hydrophone. The sound pressure field generated by the transducer is measured by the hydrophone.

[0125] Two sound pressure fields are recorded. One is after propagating through the human skull without a self-positioning acoustic lens (Figure 5a), and the other is after propagating through the self-positioning acoustic lens and the human skull (Figure 5b).

[0126] These data show that the self-positioning acoustic lens can correct the aberration induced by the skull so that it coincides with the outer surface of the aberration barrier, enabling lens positioning and accurate focusing of sound waves.

Explanation of symbols

[0127] P Patient 100 Mechanism for generating ultrasonic waves 102 Ultrasonic probe 102a Rod 103 Medium 107 Substantially homogeneous internal part 108 Aberration barrier 108a Outer surface of the medium 109 Acoustic lens 109a Front surface 109b Back surface 111 Control system 111a Control unit 111b Computer 203 Transducer 210 Ultrasonic wave 230 Focus spot 320a Ultrasonic wave 320b Ultrasonic wave, wavefront 320c Target ultrasonic field, ultrasonic wave, wavefront 330 Single control surface

Claims

1. A self - positioning acoustic lens having a front surface and a back surface, wherein the back surface faces the front surface, and the self - positioning acoustic lens is adapted to transmit ultrasonic waves into a medium including at least one aberration barrier (108) and a substantially homogeneous internal portion (107) masked by the aberration barrier (108), the ultrasonic waves being generated by an ultrasonic probe (102) disposed outside the medium, and the back surface facing the radiation surface of the ultrasonic probe, the self - positioning acoustic lens is configured to generate a predetermined target ultrasonic field in at least one predetermined region (230) belonging to the internal portion (107) when the self - positioning acoustic lens (109) is sandwiched between the ultrasonic probe (102) and the aberration barrier (108) and when the ultrasonic probe (102) transmits a predetermined ultrasonic wave (320a), despite the presence of the aberration barrier, the front surface is constrained and adapted to coincide with the outer surface (108a) of the medium, to self - position on the outer surface of the medium, the outer surface of the medium not being a perfect sphere, and the back surface is spaced from the front surface according to a specific self - positioning acoustic lens thickness to generate the predetermined target ultrasonic field. A self - positioning acoustic lens.

2. The contact surface between the front surface of the self - positioning acoustic lens and the outer surface of the medium is limited to a restricted specific region on the outer surface of the medium. The self - positioning acoustic lens according to claim 1.

3. The aberration barrier is the skull, the outer surface is the skin surrounding the skull, and the restricted specific region corresponds to a part of the outer surface in contact with the front surface of the self - positioning acoustic lens. The self - positioning acoustic lens according to claim 1 or 2.

4. The thickness of the self - positioning acoustic lens from each point on the front surface of the self - positioning acoustic lens is given by the formula 【Equation 1】 satisfies, where, - c is the speed of the ultrasonic wave in the coupling medium outside the aberration barrier, - c １ is the speed of the ultrasonic wave in the self - positioning acoustic lens, - e ０ is a real - valued number such that e(x, y, z) is greater than the minimum value required to ensure the robustness of the self - positioning acoustic lens, which is positive at each point of the self - positioning acoustic lens, and the minimum value depends on the material of the self - positioning acoustic lens, - Δt(x, y, z) is the delay time law calculated to reproduce the predetermined object despite the presence of the aberration medium. The self - positioning acoustic lens according to any one of claims 1 to 3.

5. When the ultrasonic probe is a focusing transducer, the thickness, in spherical coordinates, of each point on the back surface of the self - positioning acoustic lens 【Equation 2】 is defined to satisfy the 【Equation 3】 with respect to the corresponding point on the front surface, 【Equation 4】 is defined as holding, where, - c is the speed of the ultrasonic wave in the medium (103) outside the aberration barrier (108), - c １ is the speed of the ultrasonic wave in the self - positioning acoustic lens, - e ０ is a real - valued number such that the thickness of the self - positioning acoustic lens is positive at each point and greater than the minimum value required to ensure the robustness of the self - positioning acoustic lens, and the minimum value depends on the material of the self - positioning acoustic lens, - 【Equation 5】 is a delay time law calculated to reproduce the predetermined object despite the presence of an aberration medium, and the delay time law is defined in spherical coordinates in which the origin of the spherical reference system is located at the center of curvature of the focusing transducer on each point on the front surface [Equation 6] calculated at, the self-aligning acoustic lens according to any one of claims 1 to 3.

6. The front surface is constrained and adapted to complementarily match the outer surface (108a) of the medium, the self-aligning acoustic lens according to any one of claims 1 to 5.

7. A production method for implementing a self-aligning acoustic lens having a front surface and a back surface, the back surface facing the front surface, the self-aligning acoustic lens being adapted to transmit ultrasonic waves into a medium including at least one aberration barrier (108) and a substantially homogeneous internal portion (107) masked by the aberration barrier (108), the ultrasonic waves being generated by an ultrasonic probe disposed outside the medium, the back surface being adapted to face the radiation surface of the ultrasonic probe, The production method includes at least imaging the medium (103) to generate a mapping of the acoustic properties of the medium (103); using a model to estimate the time delay at a given control surface (330) included within the expected volume of the self-aligning acoustic lens, the time delay enabling generation of a predetermined target ultrasonic field within at least one predetermined region belonging to the internal portion (107); By using the model of the medium including the mapping of the acoustic characteristics, calculating the geometric shape of the self-positioning acoustic lens including at least determining a first shape of the front surface and determining a thickness between the front surface and the back surface, wherein the self-positioning acoustic lens causes the time delay such that when the self-positioning acoustic lens (109) is sandwiched between the ultrasonic probe (102) and the aberration barrier (108), and when the ultrasonic probe transmits a predetermined ultrasonic wave (320a), a predetermined target ultrasonic field is generated in at least one predetermined region belonging to the internal portion despite the presence of the aberration barrier, the step of Implementing the self-positioning acoustic lens by using the calculated self-positioning acoustic lens; and including The first shape of the front surface of the self-positioning acoustic lens is determined to coincide with the outer surface (108a) of the medium and to be self-positioned on the outer surface of the medium, and the outer surface of the medium is not a perfect sphere, a production method.

8. The imaging of the medium is performed by using computed tomography (CT) or magnetic resonance imaging (conventional imaging or ultra-short echo time imaging) or ultrasonic imaging, the production method according to claim 7.

9. Before the calculation of the geometric shape of the self-positioning acoustic lens, (b1) Simulating the backpropagation of the predetermined target ultrasonic field in the medium (103) from the predetermined region (230) to a selected position of the control surface (330); and (b2) Determining a first arrival time t １ (x, y, z) of the backpropagation of the predetermined target ultrasonic field to the selected position of the control surface (330); and (b3) calculating the propagation of the ultrasonic wave (320a) radiated by the ultrasonic probe (102) disposed outside the medium to the selected position on the front surface of the self-positioning acoustic lens (109a), and the second arrival time t of the ultrasonic wave to the selected position on the front surface of the self-positioning acoustic lens (109a) ０ (x, y, z) is determined, (b4) the first arrival time t １ (x, y, z) and the second arrival time t ０ determining the delay time law Δt(x, y, z) at the selected position of the control surface (330) equal to the sum of (x, y, z) and the second arrival time t A simulation including is executed, The geometric shape of the self-positioning acoustic lens is calculated using the delay time law Δt(x, y, z), so that when the ultrasonic probe (102) radiates the ultrasonic wave (320a) through the self-positioning acoustic lens, the predetermined ultrasonic wave, after passing through the aberration barrier (108), regenerates the target ultrasonic wave field within the predetermined region (230), Distributed on the front surface of the self-positioning acoustic lens, the control point M(x, y, z) at which the second arrival time t ０ (x, y, z) and the first arrival time t １ (x, y, z) is determined belongs to a single control surface (330), preferably, the control surface (330) is disposed on the outer surface (108a) of the medium (103), the production method according to claim 7 or 8.

10. When the ultrasonic probe is a focused transducer, in spherical coordinates, each point on the back surface of the self-positioning acoustic lens [Equation 7] is the corresponding point on the front surface [Equation 8] with respect to, the formula [Equation 9] The thickness is determined as calculated by Here, - c is the speed of the ultrasonic wave in the coupling medium (110) of the aberration barrier (108), - c １ is the speed of the ultrasonic wave in the self-aligning acoustic lens, - e ０ is a real value such that the thickness of the self-aligning acoustic lens is positive at each point and is greater than the minimum value required to ensure the robustness of the self-aligning acoustic lens, and the minimum value depends on the material of the self-aligning acoustic lens, - [Equation 10] is the delay time law calculated to reproduce the predetermined object despite the presence of the aberration medium, and the delay time law is defined in spherical coordinates where the origin of the spherical reference system is located at the center of curvature of the focusing transducer on each point [Equation 11] calculated at, the production method according to claim 9.

11. The thickness e(x, y, z) is given by the formula at each point M(x, y, z) of the front surface [Equation 12] calculated using, Here, - c is the speed of the ultrasonic wave in the medium (110) outside the aberration barrier (108), - c １ is the speed of the ultrasonic wave in the self-aligning acoustic lens, - e ０ is a real value such that the thickness e(x, y, z) of the self-aligning acoustic lens is positive at each point and is greater than the minimum value required to ensure the robustness of the self-aligning acoustic lens, and the minimum value depends on the material of the self-aligning acoustic lens, the production method according to claim 9.

12. The step of implementing the self-positioning acoustic lens is performed by a method selected from three-dimensional printing of the self-positioning acoustic lens (109) and / or digital control machining of at least one block of material for forming the self-positioning acoustic lens (109), the production method according to any one of claims 7 to 11.

13. In the calculation of the geometric shape of the self-positioning acoustic lens, the refraction by each surface of the self-positioning acoustic lens and / or the echoes between the ultrasonic probe, the self-positioning acoustic lens, and the aberration barrier, and / or the echoes within the self-positioning acoustic lens are considered for the entire propagation of the predetermined ultrasonic wave, the production method according to any one of claims 7 to 12.

14. The first shape of the front surface of the self-positioning acoustic lens is determined to complementarily match the outer surface (108a) of the medium, the production method according to any one of claims 7 to 13.

15. An ultrasonic irradiation method of a medium (103) including at least one aberration barrier (108) and a substantially homogeneous internal portion (107) masked by the aberration barrier (108), wherein the outer surface of the medium (103) is not a perfect spherical surface, and the ultrasonic irradiation method includes manufacturing the self-positioning acoustic lens (109) according to any one of claims 7 to 14, The ultrasonic irradiation method is, A step of transmitting the predetermined ultrasonic wave (320a) through the self-positioning acoustic lens (109), wherein the ultrasonic wave is generated by the ultrasonic probe disposed outside the medium, and the back surface is adapted to face the radiation surface of the ultrasonic probe, further including the step. The self-positioning acoustic lens is disposed on the outer surface of the medium such that the first shape of the front surface of the self-positioning acoustic lens matches the outer surface of the medium and the self-positioning acoustic lens is self-positioned on the outer surface of the medium.

16. The contact surface between the front surface of the self-positioning acoustic lens and the outer surface of the medium is limited to a specific limited area on the outer surface of the medium, the ultrasonic irradiation method according to claim 15.

17. The medium (103) through which the ultrasonic wave propagates is a human or animal head, the aberration barrier (108) is a skull, and the internal part (107) is a brain, the ultrasonic irradiation method according to claim 15 or 16.

18. A method for calculating the geometric shape of a self-positioning acoustic lens, the self-positioning acoustic lens being suitable for ultrasonic irradiation of a medium including at least one aberration barrier (108) and a substantially homogeneous internal part (107) masked by the aberration barrier (108), the outer surface of the medium not being a perfect sphere, The method calculates the geometric shape of the self-positioning acoustic lens by using a model of the medium including mapping of acoustic characteristics, the self-positioning acoustic lens being configured to generate a predetermined target ultrasonic field in at least one predetermined area (230) belonging to the internal part (107) when the self-positioning acoustic lens (109) is sandwiched between an ultrasonic probe (102) and the aberration barrier (108), and when the ultrasonic probe (102) transmits a predetermined ultrasonic wave (320a).

19. A device for calculating the geometric shape of a self-positioning acoustic lens, the self-positioning acoustic lens being suitable for ultrasonic irradiation of a medium including at least one aberration barrier (108) and a substantially homogeneous internal part (107) masked by the aberration barrier (108), the outer surface of the medium not being a perfect sphere, The computing device is configured to calculate the geometric shape of the self-positioning acoustic lens (109) using a model of the medium that includes a mapping of acoustic properties, the self-positioning acoustic lens being configured to generate a predetermined target ultrasonic field in at least one predetermined region (230) belonging to the inner portion (107) when the self-positioning acoustic lens (109) is sandwiched between the ultrasonic probe (102) and the aberration barrier (108) and when the ultrasonic probe (102) transmits a predetermined ultrasonic wave (320a). Computing device.

20. A device for manufacturing a self-positioning acoustic lens, comprising: a computing device for the self-positioning acoustic lens according to claim 18; and means for producing the self-positioning acoustic lens.

21. A computer program comprising instructions which, when the program is executed by a computer comprising a processor and a storage device, cause the computer to perform the method according to any one of claims 7 to 14 and / or the method according to any one of claims 15 to 17 and / or the method according to claim 18. Computer program.

22. A computer-readable medium storing the computer program according to claim 21.

Images