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EP-4301235-B1 - QUALITY ASSURANCE DEVICES AND METHODS TO ENSURE PROPER ULTRASOUND EXPOSURE

EP4301235B1EP 4301235 B1EP4301235 B1EP 4301235B1EP-4301235-B1

Inventors

  • SCHAFER, MARK, E.
  • SCHAFER, Samantha, F.
  • GESSERT, JAMES, M.

Dates

Publication Date
20260506
Application Date
20220304

Claims (15)

  1. An apparatus for calibrating an ultrasound transducer (200), the apparatus comprising: a hydrophone assembly (400) including a first layer (440) comprising a first solid material and a hydrophone element (450) embedded in the first solid material of the first layer (440), characterized in that the hydrophone assembly (400) includes a matching element (415) configured to receive the ultrasound transducer (200) and to substantially align a central axis of an ultrasound beam emitted from the ultrasound transducer (200) with a center of a face of the hydrophone element (450).
  2. The apparatus of claim 1 wherein the hydrophone element (450) comprises a piezoelectric material.
  3. The apparatus of claim 1 wherein the first solid material comprises a low-durometer urethane or a low-durometer polyurethane.
  4. The apparatus of claim 1 wherein the hydrophone assembly (400) includes a second layer (430, 470) comprising a second solid material different from the first solid material, and the first layer (440) is positioned at least in part between the second layer (430, 470) and the hydrophone element (450).
  5. The apparatus of claim 4 wherein the second layer (430, 470) is positioned between the matching element (415) and the hydrophone element (450).
  6. The apparatus of claim 4 wherein the first solid material comprises a low-durometer urethane or a low-durometer polyurethane, and wherein the second solid material comprises an acrylic or a high-durometer urethane, a high-durometer polyurethane, or a high-durometer silicone.
  7. The apparatus of claim 4 wherein the first layer (440) and the hydrophone element (450) are positioned between the matching element (415) and the second layer (430, 470).
  8. The apparatus of claim 7 wherein the first layer (440) and the second layer (430, 470) adjoin along an interface, and the interface is angled with respect to a propagation direction of an ultrasound beam from the ultrasound transducer (200) and, optionally, wherein the second solid material has a higher acoustic attenuation than the first solid material and/or wherein the second solid material has a higher sound speed than the first solid material.
  9. The apparatus of claim 1 wherein the hydrophone assembly (400) includes a second layer (430) comprising a second solid material different from the first solid material, and a third layer (470) comprising a third solid material different from the first solid material and the second solid material, and the first layer (440) and the hydrophone element (450) are positioned between the second layer (430) and the third layer (470) and, optionally, wherein the first solid material comprises a low-durometer urethane or a low-durometer polyurethane, the second solid material comprises an acrylic, and the third solid material comprises a high-durometer urethane, a high-durometer polyurethane, or a high-durometer silicone.
  10. The apparatus of claim 1 wherein the hydrophone assembly (400) includes a housing (410), and the housing (410) includes a trough region (405) that extends about the matching element (415).
  11. The apparatus of claim 1 wherein the hydrophone assembly (400) further includes a temperature sensing element (455) positioned in the first layer adjacent to the hydrophone element (450).
  12. A method of calibrating a therapeutic ultrasound system including an ultrasound transducer (200) and system electronics, the method comprising: connecting the ultrasound transducer (200) to an electronics module (300); separately connecting the system electronics to the electronics module (300); connecting the system electronics to the ultrasound transducer (200) within the electronics module (300); driving the ultrasound transducer (200) at a first frequency to emit a first ultrasound beam; sensing the ultrasound beam with a hydrophone element (450) of a hydrophone assembly (400), the hydrophone assembly (400) including a matching element (415) configured to receive the ultrasound transducer (200) and to substantially align a central axis of the ultrasound beam emitted from the ultrasound transducer (200) with a center of a face of the hydrophone element (450); and measuring a first signal that is output from the hydrophone element (450).
  13. The method of claim 12 further comprising: disconnecting the system electronics from the ultrasound transducer (200) within the electronics module (300); driving the ultrasound transducer (200) from the electronics module (300) at a second frequency to emit a second ultrasound beam; sensing the second ultrasound beam with the hydrophone element (450); and measuring a second signal that is output from the hydrophone element (450).
  14. The method of claim 12 further comprising: disconnecting the system electronics from the ultrasound transducer (200) within the electronics module (300); receiving an electrical drive signal from the system electronics at the electronics module (300); and analyzing the electrical drive signal for voltage amplitude, frequency, bandwidth, pulse duration, pulse repetition frequency, or average power.
  15. The method of claim 12 further comprising: disconnecting the system electronics from the ultrasound transducer (200) within the electronics module (300); and determining an electrical impedance of the ultrasound transducer (200).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63/157,248, filed March 5, 2021. TECHNICAL FIELD The technical field relates to ultrasonics and focused ultrasound treatment of tissue using energy levels that do not cause damage such as heating or cavitation, and in particular to calibration or quality assurance devices and methods that ensure proper ultrasound exposure. BACKGROUND When treating tissue with ultrasound, the treatment should be conducted with the intended level of ultrasound energy. If the energy level is too low, the treatment may be ineffective. If the energy level is too high, the treatment may cause unintended negative biological effects. Consistency ensures that neither overtreatment nor undertreatment occur. The ultrasound treatment system includes a system that can produce the necessary electrical drive signals; a transducer which converts those electrical signals into an ultrasound (mechanical) wave that is then transmitted into tissue; and a connection, typically a cable, that interconnects the drive system and the transducer. The transducer may have one or more electro-acoustic conversion devices within it, typically but not exclusively piezoelectric ceramic, composite, or single crystal elements. There are other portions of the overall treatment system, such as positioning, guidance, etc. When the ultrasound treatment system is first delivered, installed, or set up at the treatment facility (e.g., hospital, clinic, physician's office), it is presumed to be in complete working order. This is usually confirmed by personnel familiar with the equipment, typically the installation service personnel of the company that manufactured the system. At that point, the acoustical output characteristics of the system are known. The goal then is to ensure that the output remains at that known level so that proper treatments are provided. The acoustic output relative to that initial condition is an indicator of a change in the condition of the system, and potentially a source of incorrect treatment. There are potential causes of incorrect or improper treatment, principally a change in the efficiency, internal connectivity, focusing, or geometry of the transmitting ultrasound transducer; a change in the electronic system which electrically drives the transducer; or a change in the connection between the electronic system and the transmitting transducer. The transmitting transducer is subject to aging after repeated use, especially with high drive levels which may be used for such treatment. More commonly, the transducer is subject to being accidentally dropped or mishandled in a way that affects the output of the transducer but does not cause any damage that might be assessed through visual inspection. For instance, a delamination of the internal structures would affect the acoustic output but would not be detectable by visual inspection. Similarly, a broken connection internal to the transducer can occur that would be undetectable. The electronic system that drives the transducer may be subject to degradation of components, such as drive circuit transistors or feedback resistors, that could cause a change in the transmit voltage, either increasing or decreasing it. In either case, the treatment of tissue would not be as expected. The cable or other type of connection between the electronic system and the transducer is also subject to hidden damage, for instance, if it were to be run over by the wheels of an equipment cart. This type of damage is not readily visible but can negatively affect the output performance of the entire system. These issues may arise at the location, i.e. physician's office, hospital, clinic, or other health care facility, at which the treatment is to occur. The personnel who may be administering the treatment often are not technically qualified in the requisite engineering skills to perform a proper evaluation of the output of the ultrasound system. The treatment should be checked just prior to the actual administration of the ultrasound to ensure that the system is performing repeatably and within the expected or necessary clinical limits, both higher and lower than the intended level. Further, for clinical research studies, the treatment should be consistent over the duration of the entire study, which can involve months or years. If the ultrasound system degrades with time, it may be that subjects who are treated at the end of the clinical trial do not receive the same treatment as those at the start of the trial, which may invalidate the entire trial. Conventional systems exist to provide a simple, quantitative means to provide repeatability information with regard to the ultrasound delivered to the tissue. Such conventional systems are either very qualitative and inconsistent, are difficult for non-technical personnel to operate, or are specifically designed for a single system and not universally applicab