Process for testing ultrasonic transducer accuracy and performance

Abstract

The present invention relates to a method for testing the accuracy and performance of an ultrasonic transducer capable of generating cavitation bubbles by placing an elastomer block in a volume of an ultrasonic transmission medium at the expected cavitation region of the ultrasonic transducer, activating the ultrasonic transducer to generate cavitation bubbles in the elastomer block, detecting marks in the elastomer corresponding to the generated cavitation bubbles, and inferring three-dimensional characteristics of the actual cavitation region of the ultrasonic transducer from the marks. The present invention also relates to a system including a volume of an ultrasonic transmission medium, an elastomer block disposed in the volume of the ultrasonic transmission medium, and an ultrasonic transducer.

Description

[Technical Field]

[0001] The present invention relates to a process for testing the accuracy and performance of an ultrasonic transducer by inducing the generation of cavitation bubbles in an elastomer. The present invention also relates to a system including a volume of ultrasonic transmission medium, an ultrasonic transducer, and an elastomer block disposed within the volume of ultrasonic transmission medium. [Background technology]

[0002] Interest in ultrasound-based technologies has steadily grown as numerous potential applications have been discovered. Ultrasound can be used to induce cavitation bubbles by concentrating ultrasound pulses at a focal point, allowing mechanical energy to be emitted toward specific targets contained within, partially contained within, or near the focal point. Multiple cavitation bubbles may form in such an area near the focal point or at the focal point, which may therefore be identified as a cavitation region. The induced cavitation bubbles may be referred to as a cavitation cloud. Ultrasound-induced cavitation bubbles or clouds may be used for medical applications, such as histotripsy (mechanical destruction of tissue), thrombotripsy (mechanical destruction of blood clots), and lithotripsy (disintegration of stones), and such applications have the particular advantage of being non-invasive.

[0003] Such applications of focused ultrasound pulses, particularly in medical applications, require a high level of precision regarding the focal point and the cavitation region where the cavitation bubbles or clouds will form. Because the predicted cavitation region can vary depending on the target and the device's position, assessing and characterizing the location and / or size of the cavitation region remains challenging. It is particularly important to ensure that the predicted cavitation region corresponding to the location where the cavitation bubbles are expected to form is closest to the actual cavitation region corresponding to the location where the cavitation bubbles will form, with minimal uncertainty.

[0004] A simple solution is to place a target in the predicted cavitation region that can be damaged by the generated cavitation bubbles and test the ultrasound transducer in vitro before using it for a treatment procedure. However, while this ensures that cavitation at least occurs in the predicted cavitation region if the target is damaged, such a method does not allow for reliable evaluation of the three-dimensional characteristics of the actual cavitation region. Therefore, such a method is not rigorous enough to ensure the reliability of the method for a treatment procedure.

[0005] U.S. Patent No. 8,539,813 discloses a cavitational damage indicator platform including a container, a gel disposed in the container, and an indicator disposed in the container, the indicator configured to undergo a visible change during application of cavitational ultrasonic energy to the indicator. The disclosed indicator includes microspheres or polystyrene beads, microencapsulated beads, or carbon particles. The visible change corresponds to the particles becoming darker, their size decreasing, or the bleeding of a dye. However, these visible changes do not provide sufficient information to evaluate the three-dimensional characteristics of the actual cavitation region because the indicator exists in a single layer and therefore provides only limited three-dimensional information. When an ultrasonic transducer is used at an increased pulse repetition frequency at a critical center frequency for an extended period of time, the indicator structure may become insufficiently durable and may fracture. Therefore, the visible change corresponds to tears in the indicator, which provide no information or false information about the actual cavitation region. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 8,539,813 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there is a need for a process and system that allows for more accurate identification of actual cavitation regions where cavitation bubbles arise. Furthermore, because procedures using ultrasound transducers can include ultrasound emission sequences, with predicted cavitation regions being displaced during the emission sequence and / or transducer parameters being changed during the emission sequence, it is particularly important to reliably determine the location and / or three-dimensional characteristics of the actual cavitation region. The present invention aims to overcome the aforementioned shortcomings of the prior art by providing a process for testing ultrasound transducers based on more reliable information regarding the correspondence between predicted and actual cavitation regions to ensure the accuracy and performance of the ultrasound transducer. [Means for solving the problem]

[0008] To this effect, the present invention discloses a method for testing the accuracy and performance of an ultrasonic transducer capable of causing the generation of cavitation bubbles, the method comprising placing an elastomer block in the expected cavitation region of the ultrasonic transducer within a volume of an ultrasonic transmission medium, activating the ultrasonic transducer to generate cavitation bubbles in the elastomer block, detecting marks in the elastomer block corresponding to the generated cavitation bubbles, and estimating the actual cavitation region of the ultrasonic transducer from the marks.

[0009] Advantageously, the elastomeric block has a total light transmittance of at least 20%. Such a percentage of total light transmittance allows the naked eye to observe visible changes in the elastomer when cavitation bubbles are generated. Preferably, the total light transmittance is at least 50%, or even more preferably at least 95%.

[0010] Advantageously, the elastomeric block comprises a material selected from silicone, urethane, polyurethane or combinations thereof.

[0011] Advantageously, the method includes the step of verifying correct alignment of the one or more imaging systems with the ultrasound transducer.

[0012] Advantageously, the elastomeric block has a hardness comprised between Shore 10A and Shore 80D, preferably between Shore 30A and Shore 80D, and even more preferably between Shore 30A and Shore 95A. The preferred hardness of the elastomeric block is comprised between Shore 30A and Shore 35A.

[0013] Advantageously, the method further includes embedding a plurality of graduation elements in the elastomeric block, said graduation elements being resistant to distortion or mechanical damage from the generated cavitation bubbles.

[0014] Advantageously, the graduation elements are wires or markers that are visible to the naked eye and / or with an imaging modality, preferably a medical imaging modality. By imaging modality, imaging methods using X-ray, computed tomography, ultrasound imaging or magnetic resonance imaging are understood. These imaging modalities may include one or more imaging systems, which may include an imaging probe. For example, the wires or markers may emit sound waves to allow their observation by ultrasound and / or may be opaque to X-rays to allow their observation by radiology. By "graduation elements" is meant any type of element that allows a comparison of these elements with marks formed on the elastomeric block to determine the three-dimensional characteristics of the actual cavitation area. In particular, the graduation elements may correspond to elements spaced at regular intervals on the elastomeric block.

[0015] Advantageously, the ultrasound transmission medium is liquid or semi-liquid and is contained within a vessel.

[0016] Alternatively, the volume of ultrasound transmission medium forms a solid block containing an access port, the access port adapted to expose a portion of the surface of the elastomeric block to ultrasound waves emitted by the ultrasound transducer.

[0017] Advantageously, the solid block further comprises at least one opening, the at least one opening being adapted for viewing and / or replacing the elastomeric block.

[0018] Advantageously, the ultrasound transducer is a therapeutic ultrasound transducer.

[0019] The present invention also discloses a system including a volume of ultrasound transmission medium including an acoustic coupling medium, an elastomeric block disposed in the volume of ultrasound transmission medium, and an ultrasound transducer mounted to a support structure such that the ultrasound transducer is within the acoustic coupling medium or acoustically coupled with the volume of ultrasound transmission medium.

[0020] Advantageously, the system further comprises one or more imaging systems.

[0021] Advantageously, the ultrasound transmission medium of the system is liquid or semi-liquid and is contained within a vessel.

[0022] Alternatively, the volume of ultrasound transmission medium forms a solid block containing an access port, the access port adapted to expose a portion of the surface of the elastomeric block to ultrasound waves emitted by the ultrasound transducer.

[0023] Advantageously, the solid block further comprises at least one opening, the at least one opening being adapted for viewing and / or replacing the elastomeric block.

[0024] Advantageously, at a temperature of 25° C. and a pressure of 1 atm, the velocity of sound in the volume of the ultrasonic transmission medium and in the elastomer block is less than 500 m.s. -1~2500m.s -1 and differing by no more than 10%, and even more preferably by 1200 m.s -1 ~1800m.s -1 and differ by no more than 5%, and / or the volume of the ultrasound transmission medium and the acoustic impedance of the elastomer block are comprised between 0.5 MRayl and 2.5 MRayl and differ by no more than 10%, and even more preferably between 0.8 MRayl and 2.1 MRayl and differ by no more than 5%.

[0025] Additionally and preferably, the acoustic attenuation in the volume of the ultrasound transmission medium and in the elastomer block is less than 20 dB.cm -1 .MHz -1 less than and differing by no more than 20%, and even more preferably 1 dB.cm -1 .MHz -1 less than and differ by no more than 20%.

[0026] Advantageously, the ultrasound transducer of the system is a therapeutic ultrasound transducer.

[0027] Advantageously, the system further includes a plurality of graduation elements embedded in the elastomeric block, said graduation elements being resistant to distortion or mechanical damage caused by generated cavitation bubbles.

[0028] Advantageously, the material of the solid block is chosen from urethane, hydrogel polymers, or a combination of at least two of these materials.

[0029] The invention will be better understood and its various features and advantages will become apparent from the following description of a number of exemplary embodiments and the accompanying drawings, in which: FIG. [Brief explanation of the drawings]

[0030] [Figure 1] 1 shows a system including a volume of ultrasound transmission medium that is liquid or semi-liquid and contained within a vessel, an elastomer block disposed in the volume of ultrasound transmission medium, and a transducer. [Figure 2] 1 shows a system including a volume of ultrasound transmission medium that is a solid block and an elastomeric block disposed in the solid block. [Figure 3] 1 shows an elastomer block where cavitation bubbles occur and form cavitation marks. [Figure 4a] 1 shows an elastomer block containing wires as embedded scale elements forming squares. [Figure 4b] 1 shows an elastomer block containing wires as embedded scale elements forming a cross shape. [Figure 4c] 1 shows an elastomeric block including protrusions forming a cross shape on the face of the elastomeric block. DETAILED DESCRIPTION OF THE INVENTION

[0031] In this specification, the present invention is described by way of examples, but the present invention is not limited to these examples.

[0032] FIG. 1 shows a system 10 including a volume 12 of ultrasound transmission medium contained within a vessel 11 that is liquid or semi-liquid and contains an acoustic coupling medium, an elastomer block 13 positioned in an anticipated cavitation region 15 in the volume of ultrasound transmission medium, and an ultrasound transducer 14 with an imaging probe 19 of an imaging system.

[0033] As shown in Figure 1, the vessel 11 has a parallelepiped shape, although other shapes are possible, such as a prism of revolution, a pyramid, or a trapezoid. Typically, the vessel is made of clear glass to allow visibility into the vessel's surface, although other materials are possible. Typically, the top of the vessel is open and allows for placement or removal of an elastomeric block into or from the vessel's interior, however, other shapes are possible.

[0034] The vessel 11 contains a volume 12 of ultrasound transmission medium, including an acoustic coupling medium. Typically, the volume of ultrasound transmission medium fills the entire volume of the vessel, although the vessel may be only partially filled. The liquid or semi-liquid ultrasound transmission medium may be water, but may also be other ultrasound transmission media, such as degassed or degassed water or ultrasound gel. The choice of ultrasound transmission medium used depends on the environment in which the ultrasound transducer needs to be used after testing. If the ultrasound transducer will also be used for treatment in a patient, the volume of ultrasound transmission medium will most likely be selected to have the same acoustic characteristics as the human body. The acoustic coupling medium enables coupling between the ultrasound transducer and the volume of ultrasound transmission medium and is typically water, although other acoustic coupling media may be used. For example, the acoustic coupling medium may be degassed or degassed water or ultrasound gel.

[0035] As shown in FIG. 1, the elastomeric block 13 has a parallelepiped shape and is disposed within the volume 12 of ultrasound transmission medium, although other shapes are possible, such as a prism of revolution, a pyramid, or a trapezoid.

[0036] Preferably, the elastomeric block has a total light transmittance of at least 20%, and even more preferably at least 50%.

[0037] The size of the elastomer block is larger than the wavelength of the ultrasound emitted by the transducer, preferably much larger, for example, the elastomer block is at least 1 cm*1 cm*1 cm. The dimensions of the elastomer block can be adapted to entirely encompass the path of the predicted cavitation region as it is moved during use of the ultrasound transducer.

[0038] The elastomer block has a hardness comprised between Shore 10A and Shore 80D, preferably between Shore 30A and Shore 80D, and even more preferably between Shore 30A and Shore 95A. A preferred hardness of the elastomer block is comprised between Shore 30A and Shore 35A.

[0039] As shown in FIG. 1 , an elastomer block 13 is placed in a predicted cavitation region 15 of an ultrasonic transducer 14. For example, the surface of the elastomer block is exposed to ultrasonic waves emitted by the ultrasonic transducer so that the predicted cavitation region is located within the volume of the elastomer block. The predicted cavitation region corresponds to the region where multiple cavitation bubbles are expected to occur with a particular configuration of the ultrasonic transducer, and therefore typically corresponds to the targeted portion of the elastomer block. The actual cavitation region corresponds to the location where multiple cavitation bubbles occur in the elastomer block with a particular configuration of the ultrasonic transducer. Therefore, if the ultrasonic transducer is already properly calibrated while performing the method of the present invention, the predicted cavitation region location will be identical to the actual cavitation region location. If the ultrasonic transducer is not properly calibrated while performing the method of the present invention, the actual cavitation region location may correspond to a portion of the elastomer block that is different from the targeted portion of the elastomer block. For example, the actual cavitation region may be adjacent to the predicted cavitation region location.

[0040] In some embodiments, the ultrasonic transducer may have a moving focal point. The focal point may be moved, for example electronically or mechanically, in volume by, for example, changing the configuration of the ultrasonic transducer. In such cases, an elastomer block is placed in the expected cavitation region for a particular configuration of the ultrasonic transducer. The operation of the ultrasonic transducer may be repeated multiple times with multiple different configurations and therefore multiple different focal points. Thus, it is possible to test the ultrasonic transducer in multiple configurations while the focal point moves between each configuration.

[0041] As shown in FIG. 1 , the system includes an imaging probe 19 of an imaging system. The imaging system makes it possible to image the zone surrounding the expected cavitation region, i.e., the elastomer block and the area surrounding the elastomer block. The imaging system makes it possible to detect marks formed in the elastomer block by cavitation clouds or bubbles generated by the ultrasound transducer, although the step of detecting the marks can also be performed with the naked eye. Typically, the imaging system is an ultrasound imaging system, but other imaging modalities, such as imaging methods using X-rays, computed tomography, or magnetic resonance imaging, may also be used. Using the imaging system to test the ultrasound transducer makes it possible to verify the correct alignment of the imaging system with the ultrasound transducer and with the actual cavitation region. Typically, the step of verifying the correct alignment of the imaging system with the ultrasound transducer is performed after the step of detecting marks in the elastomer block or after the step of estimating the location of the actual cavitation region of the ultrasound transducer from the marks.

[0042] 2 shows a system 20 including a volume of ultrasound transmission medium forming a solid block 21, an elastomer block 23 disposed in the solid block, an ultrasound transducer 24, and an imaging probe 29 of an imaging system. The elastomer block is disposed in an anticipated cavitation region 25. The solid block 21 has a parallelepiped shape, although other shapes, such as a prism of revolution, a cone, or a trapezoid, may also be used. The solid block may also have an irregular shape with recesses or protrusions. In some embodiments, the solid block has a shape that mimics a part of the human body.

[0043] As shown in Figure 2, the solid block 21 includes an access port 27 on a first surface of the solid block. The access port is adapted to expose a portion of the surface of the elastomeric block 23 to ultrasound waves emitted by the ultrasound transducer. The access port may have a rectangular shape, although other shapes are possible, such as a circle. Advantageously, the shape of the access port corresponds to the shape of the ultrasound transducer so as to provide a plug-in interface with the ultrasound transducer.

[0044] 2, the solid block 21 is hollow, and the hollow of the solid block contains the acoustic coupling medium 22. The solid block may also include a protrusion extending from the inner surface of the solid block toward the interior of the solid block, the protrusion being positioned to retain the elastomeric block 23 within the solid block.

[0045] Typically, the solid block 21 is silicone, polyurethane, urethane, hydrogel polymer, compatible ultrasonic fluid, or a combination thereof, although other materials may be used. In an embodiment, at least one side of the solid block is transparent. In an embodiment, the solid block is made of one or more materials that mimic parts of the human body.

[0046] As shown in Figure 2, on a second face of solid block 21, perpendicular to the first face, solid block includes an opening 26. The opening has a square or rectangular shape and corresponds to the size and shape of elastomeric block 23, allowing for replacement of the elastomeric block in the solid block. Opening 26 also allows the elastomeric block to be viewed from the outside of the solid block when the elastomeric block is placed inside the solid block. As also shown in Figure 2, solid block includes a second opening 28 on a third face of the solid block, which is filled with a second elastomeric block or a compatible acoustic coupling medium.

[0047] In some embodiments, the access port 22 and the opening 26 are on the same side of the solid block 21. In other embodiments, the access port and the opening are on opposite sides, although other configurations are possible.

[0048] In some embodiments, the solid block 21 may further include additional openings for viewing or replacing the elastomeric block 23, and these additional openings may be on the same side of the solid block as the access port 27 and opening 26 or on a different side.

[0049] In some embodiments, the solid block may be hollow and filled with an acoustic coupling medium. If the acoustic coupling medium is a liquid, the liquid can exit the solid block through the openings. In such embodiments, an elastomeric block is placed through the openings and fills the openings to prevent the liquid from exiting through the openings. In other embodiments, the shape of the solid block is such that at least one opening leads to a cavity within the solid block that is not in communication with the hollow of the solid block containing the acoustic coupling medium. In such embodiments, the elastomeric block is thus almost completely surrounded by the solid block, and the acoustic coupling medium cannot exit the solid block through the openings because they are not in communication with each other.

[0050] In yet a further embodiment, the solid block has the shape of a part of the human body that mimics one or more tissues, such as bone and epidermal tissue, is filled with an acoustic coupling medium that mimics one or more other tissues, and has openings for replacing the elastomeric block in the predicted cavitation region.

[0051] FIG. 3 shows an elastomer block in which cavitation bubbles form and create marks. The elastomer block in FIG. 3 has a parallelepiped shape and a total light transmittance of 95%, allowing the marks of cavitation bubbles created within its body by focused ultrasound to be visible to the naked eye. The cavitation bubble marks 30 created in the elastomer block form a cavitation cloud having an elliptical shape and are entirely contained within the volume of the elastomer block. In some embodiments, the cavitation bubble or cloud marks may have different shapes depending on the configuration of the ultrasound transducer, the materials of the elastomer block and the ultrasound transmission medium volume, and the acoustic coupling medium. The marks created by the created cavitation bubbles do not allow the entire cavitation region to be observed, but only the central portion of the cavitation region, where the ultrasound intensity is highest. This central portion of the cavitation region corresponds to the area where marks may appear in the elastomer block and therefore corresponds to what is referred to as the actual cavitation region in this description.

[0052] In particular, it should be noted that the marks on the elastomer block can be easily evaluated with the naked eye and in three dimensions without the use of specific indicators or compounds whose effusion brings to the fore a zone in which multiple cavitation bubbles have been generated.

[0053] According to the present invention, the elastomeric block may include graduation elements embedded in the elastomeric block, said graduation elements being resistant to distortion or mechanical damage caused by generated cavitation bubbles. By "gradation elements" is meant any type of elements that allow comparison of these elements with marks formed in the elastomeric block to determine the three-dimensional characteristics of the actual cavitation area. In particular, the graduation elements may correspond to regularly spaced elements in the elastomeric block.

[0054] In some embodiments, the graduation elements are equally spaced and arranged sequentially in the measurement direction to form a measurement scale that allows for determining the size of the actual cavitation region in the elastomeric block. The graduation elements may be located in the bulk of the elastomeric block or on one or more faces of the elastomeric block. In some embodiments, the graduation elements are arranged across the cross section of the elastomeric block. In some embodiments, the graduation elements are arranged to measure the length of the actual cavitation region along the axial direction of the ultrasound transducer and / or perpendicular to the axial direction of the ultrasound transducer.

[0055] In some embodiments, the graduation elements are disposed on a surface of the elastomeric block that is visible from the exterior of the solid block through an opening in the solid block.

[0056] In some embodiments, the scale elements correspond to wires. The wires may be made of any material that is resistant to distortion or mechanical damage caused by the generated cavitation bubbles. The wires may be arranged to form a grid.

[0057] Figure 4a shows an elastomer block including wires 41 that are visible to the naked eye and form a rectangle. As can be seen from Figure 4a, the wires are embedded in the elastomer block essentially in a single plane to form a rectangle at the center of the elastomer block. Such a rectangle may correspond to a target. Thus, the elastomer block may be placed in a volume of an ultrasound transmission medium such that the expected cavitation region falls within the rectangle formed by the wires.

[0058] In certain embodiments, the scale elements correspond to wires or markers visible in the imaging modality, e.g., the wires are wires that generate sound waves. An imaging probe of an imaging system that may be embedded in the ultrasound transducer can therefore identify targets formed by the wires or markers in ultrasound imaging. Imaging modalities other than ultrasound imaging, such as computed tomography and magnetic resonance imaging, may also be used. In addition to testing the ultrasound transducer, such a system with wires or markers visible in the elastomer block in such imaging modalities allows for verification of whether the imaging modality is properly aligned with the ultrasound transducer and the actual cavitation region.

[0059] Additionally, the ultrasonic transducer may be connected to an electromechanical or robotic arm that can move the ultrasonic transducer. The system of the present invention makes it possible to verify that the movement of the ultrasonic transducer due to the movement of the electromechanical or robotic arm corresponds to the movement of the actual cavitation area by estimating whether the cavitation area predicted from the marks formed in the elastomer block corresponds to the actual cavitation area.

[0060] Figure 4b shows an elastomer block including a wire 42 that is visible to the naked eye and forms a cross shape. As can be seen from Figure 4b, the wire is embedded in the elastomer block essentially in a single plane to form a cross shape at the center of the elastomer block. Such a cross shape may correspond to a target. Therefore, the elastomer block may be positioned in the volume of the ultrasound transmission medium such that the anticipated cavitation region is at the center of the cross shape formed by the wire.

[0061] 4c shows an elastomer block including protrusions 43 on the face of the elastomer block, which are visible to the naked eye and form a cross shape, through which the three-dimensional shape and location of the actual cavitation region can be assessed with the naked eye, which can assist in determining whether the ultrasound transducer is properly calibrated.

[0062] The elastomer block protrusions and scale elements, which may be wires or markers, may be used together to aid in testing of the ultrasonic transducer.

[0063] As shown in Figures 3, 4a, 4b, and 4c, the elastomeric block is homogenous and does not contain elements that change color or liquefy due to temperature, light radiation, and pH fluctuations during use of the ultrasound transducer. In particular, the elastomeric block does not contain leuco dyes or other encapsulated dyes whose release may not accurately reflect the shape of the resulting cavitation cloud and therefore the actual cavitation region when a cavitation bubble is generated.

[0064] Typically, the ultrasonic transducer is configured to operate at a frequency between 100 kHz and 10 MHz, even more preferably between 500 kHz and 2.5 MHz, with high intensity pulsed ultrasonic radiation of duration between 0.1 and 50 μs, even more preferably between 1 and 20 μs, delivered at a pulse repetition frequency between 1 Hz and 1000 Hz, even more preferably between 50 and 500 Hz, for a total test time between 10 and 180 seconds.

[0065] In the systems of the present invention, the ultrasonic transducer is attached to a support structure such that the ultrasonic transducer is within the acoustic coupling medium or is acoustically coupled with the volume of the ultrasonic transmission medium. Typically, when the volume of the ultrasonic transmission medium is liquid or semi-liquid, the support structure extends from the outside of the vessel to the inside of the vessel, particularly in the acoustic coupling medium, to support at least the ultrasonic transducer in the acoustic coupling medium. However, the support structure may have a different shape and may be partially or entirely included in the vessel and / or the acoustic coupling medium. In other embodiments, the support structure is not included in the volume of the ultrasonic transmission medium but supports the ultrasonic transducer such that the ultrasonic transducer is acoustically coupled with the volume of the ultrasonic transmission medium. In another specific embodiment, the support structure is a robotic arm that allows the ultrasonic transducer to be positioned in the acoustic coupling medium or to be acoustically coupled with the volume of the ultrasonic transmission medium.

[0066] The method of the present invention includes placing an elastomeric block in a predicted cavitation region of an ultrasonic transducer. The elastomeric block is typically positioned so that the predicted cavitation region corresponds to a central portion of the bulk of the elastomeric block; however, the elastomeric block may also be positioned so that the predicted cavitation region corresponds to a peripheral portion of the bulk of the elastomeric block.

[0067] The method of the present invention includes activating an ultrasonic transducer to generate cavitation bubbles in the elastomer block. Activation of the ultrasonic transducer typically corresponds to emission of repeated pulses at a single frequency and for a specific duration, however, activation may also correspond to emission of one or more sequences of pulses at the same or different frequencies, the sequences having the same or different durations.

[0068] The method of the present invention includes detecting marks in the elastomeric block corresponding to the generated cavitation bubbles. The detection typically corresponds to observing with the naked eye whether marks corresponding to the generated cavitation bubbles are present in the elastomeric block. In certain embodiments where the elastomeric block may be removed from the volume of ultrasound transmission medium, for example, when the elastomeric block is placed in a solid block with an opening for replacing the elastomeric block, the elastomeric block is removed from the volume of ultrasound transmission medium after activating the ultrasound transducer and before detection of the marks in the elastomeric block.

[0069] Alternatively, the step of detecting corresponds to a step of seeing, by medical imaging, for example ultrasound imaging, computed tomography or magnetic resonance imaging, whether marks are present in the elastomer block corresponding to cavitation bubbles generated in the elastomer block.

[0070] The method of the present invention includes estimating the actual cavitation region location of the ultrasonic transducer from the marks in the elastomeric block. The step of estimating the actual cavitation region from the marks may include the use of a scale element, for example, by determining the centroid of the mark formed by the generated cavitation bubble.

[0071] The method may further include identifying a difference between the localization of the predicted cavitation region and the actual cavitation region. If a difference between the localizations is identified, the method may further include modifying the configuration of the ultrasound transducer so that the predicted cavitation region and the actual cavitation region have the same localization. Also, if a difference between the localizations is identified, the method may further modify the predicted cavitation region to correspond with the actual cavitation region.

[0072] The method of the present invention allows for testing an ultrasonic transducer capable of generating cavitation bubbles, ensuring that the cavitation bubbles occur in the cavitation region expected for use of the ultrasonic transducer, e.g., that the expected cavitation region corresponds to the actual cavitation region of the ultrasonic transducer. [Example]

[0073] Specific examples Example 1 The elastomer block corresponds to a 1:1 mixture by volume of 4,4'-methylenedisilohexyl diisocyanate (A) and a modified aliphatic diisocyanate (B), with a cure time of 16 hours at 23°C. The resulting elastomer block has a Shore hardness of A30, a tensile strength of 5 MPa, and a clear, opaque color. The elastomer block is placed within a solid block of urethane through an opening in the first face of the solid block, which is then coupled to a transducer via a second face of the solid block that is mechanically adapted to receive the transducer. The second face has a shape that complements the transducer, e.g., a concave face if the transducer has a convex face. The second face includes an access port that allows ultrasound to pass through. The elastomer block is 2 cm thick.

[0074] The transducer is operated at a center frequency of 1 MHz, a pulse repetition frequency (PRF) of 100 Hz, and 10 oscillations in 120 seconds. After transducer operation, the elastomer block is optionally removed and the marks are evaluated. A cone-shaped permanent mark is visible so that the shape of the cavitation cloud can be evaluated. From the cavitation mark, the actual cavitation area of ​​the transducer can be estimated and compared to the predicted cavitation area to determine if the transducer needs to be calibrated.

[0075] Example 2 The elastomer block corresponds to a mixture of 4,4'-methylenedisilohexyl diisocyanate (A) and phenylmercuric neodecanoate (B) in a 1:1.5 ratio by weight (A:B) with a 16-hour cure time at 23°C. The resulting elastomer block has a Shore hardness of A95, a tensile strength of 17 MPa, and a clear, opaque color. The elastomer block has a thickness of 1.9 cm. The transducer is operated at a center frequency of 1 MHz, a PRF of 100 Hz, and 10 oscillations for 180 seconds. After transducer operation, the elastomer block is optionally removed and the cavitation cloud is evaluated. Permanent rice-grain-shaped cavitation marks are visible, so the shape of the actual cavitation area can be evaluated. From the cavitation marks, the actual cavitation area of ​​the transducer can be estimated and compared to the predicted cavitation area to determine whether the transducer needs to be calibrated.

[0076] Example 3 The elastomer block corresponds to a clear, opaque silicone with a Shore hardness of A33. The elastomer thickness is 1.8 cm. The transducer is operated at a center frequency of 700 kHz, a PRF of 70 Hz, and 10 oscillations for 60 seconds. After transducer operation, the elastomer block is optionally removed and the actual cavitation area is evaluated. Permanent rice-grain-shaped marks are visible, so the shape of the cavitation marks can be evaluated. From the cavitation marks, the actual cavitation area of ​​the transducer can be estimated and compared to the predicted cavitation area to determine if the transducer needs to be calibrated.

[0077] Example 4 In another specific embodiment, the elastomer block corresponds to a clear silicone with a Shore hardness of A30 and a clear amber color. The thickness of the elastomer block is 1.5 cm. The transducer is operated at a center frequency of 700 kHz, a PRF of 70 Hz, and 10 oscillations in 60 seconds. After the transducer is activated, the elastomer block is optionally removed and evaluated for cavitation marks. Permanent rice-grain-shaped marks are visible, allowing the shape of the cavitation cloud to be evaluated. From the cavitation marks, the actual cavitation area of ​​the transducer can be estimated and compared to the predicted cavitation area to determine whether the transducer needs to be calibrated.

[0078] Example 5 In another specific embodiment, the elastomer block corresponds to a polyurethane matrix with a Shore hardness of D80 and is solid yellow in color. The thickness of the elastomer block is 2 cm. The transducer is operated at a center frequency of 700 kHz, a PRF of 100 Hz, and 10 oscillations in 95 seconds. After transducer operation, the elastomer block is optionally removed and evaluated for cavitation marks. A permanent oval mark is visible, allowing the shape of the cavitation cloud to be evaluated. From the cavitation marks, the actual cavitation area of ​​the transducer can be estimated and compared to the predicted cavitation area to determine whether the transducer needs to be calibrated.

[0079] The above examples are provided as illustrations of embodiments of the present invention. They in no way limit the scope of the invention, which is defined by the following claims.

Claims

1. 1. A method for testing the accuracy and performance of an ultrasonic transducer capable of generating cavitation bubbles, comprising: placing an elastomer block in the volume of the ultrasound transmission medium in the anticipated cavitation area of ​​said ultrasound transducer; - activating the ultrasonic transducer to generate cavitation bubbles in the elastomer block; - detecting marks on the elastomer block corresponding to the generated cavitation bubbles; - estimating from said marks the three-dimensional characteristics of the actual cavitation area of ​​said ultrasonic transducer; A method comprising:

2. The method of claim 1 , wherein the elastomeric block has a total light transmittance of at least 20%.

3. The method of claim 1 or 2, wherein the method includes verifying proper alignment of one or more imaging systems with the ultrasound transducer.

4. The method of any one of claims 1 to 3, wherein the elastomeric block comprises a material selected from silicone, urethane, polyurethane, or combinations thereof.

5. The method according to any one of claims 1 to 4, wherein the elastomeric block has a hardness comprised between Shore 10A and Shore 80D, between Shore 30A and Shore 80D, or between Shore 30A and Shore 95A.

6. 6. The method of claim 1, further comprising a plurality of graduation elements embedded in the elastomeric block, the graduation elements being resistant to distortion or mechanical damage from the generated cavitation bubbles.

7. The method of claim 6 , wherein the graduation elements are wires or markers visible to the naked eye and / or to imaging modalities.

8. The method of any one of claims 1 to 7, wherein the ultrasound transmission medium is liquid or semi-liquid and is contained within a vessel.

9. 8. The method of claim 1, wherein the volume of ultrasound transmission medium forms a solid block including an access port, the access port adapted to expose a portion of a surface of the elastomeric block to ultrasound emitted by the ultrasound transducer.

10. The method of claim 9 , wherein the solid block further comprises at least one opening, the at least one opening adapted for viewing and / or replacing the elastomeric block.

11. 1. A system comprising: - a volume of ultrasound transmission medium including an acoustic coupling medium; an elastomer block arranged in said volume of ultrasound transmission medium; an ultrasonic transducer mounted on a support structure such that the ultrasonic transducer is within the acoustic coupling medium or is acoustically coupled to the volume of ultrasonic transmission medium; Including, the ultrasonic transducer is configured to generate cavitation bubbles in the elastomer block; The system, wherein the elastomeric block is capable of forming a mark corresponding to the generated cavitation bubbles.

12. The system of claim 11 further comprising one or more imaging systems.

13. 13. The system of claim 11 or 12, wherein the ultrasound transmission medium is liquid or semi-liquid and is contained within a vessel.

14. 13. The system of claim 11 or 12, wherein the volume of ultrasound transmission medium forms a solid block including an access port, the access port adapted to expose a portion of a surface of the elastomeric block to ultrasound emitted by the ultrasound transducer.

15. The system of claim 14 , wherein the solid block further comprises at least one opening, the at least one opening adapted for viewing and / or replacing the elastomeric block.

16. At a temperature of 25° C. and a pressure of 1 atm, the speed of sound in said volume of ultrasonic transmission medium and in said elastomer block is 500 m.s. －１ ~2500 m.s －１ and differing by no more than 10%, and / or 16. The system of claim 14 or 15, wherein the acoustic impedances of the material of the solid block and the elastomeric block are comprised between 0.5 MRayl and 2.5 MRayl and differ by no more than 10%.

17. 17. The system of claim 11, further comprising a plurality of graduation elements embedded in the elastomeric block, the graduation elements being resistant to distortion or mechanical damage caused by the generated cavitation bubbles.

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