US-12623095-B2 - System and method for volume insonation

Abstract

In an embodiment, a method for providing insonation volume in ultrasound therapy treating tissues, e.g., brain tissues, at a target region includes: using a catheter to introduce a linear transducer array into a body lumen to be near the brain tissues to be treated; causing to determine an operating frequency and a length of the linear transducer array to be excited, based at least in part on the attenuation coefficient of the brain tissues and the distance of the target region from the catheter; and causing to excite the length of the linear transducer with a signal at the operating frequency to produce ultrasound intensity in a volume between a self-focusing point and the linear transducer array, wherein the ultrasound intensity in the volume is between a maximum intensity and half of the maximum intensity. The linear transducer array may include a plurality of ring transducer segments.

Inventors

• David Vilkomerson

Assignees

• DVX LLC

Dates

Publication Date

20260512

Application Date

20250404

Claims (20)

1. 1 . A method for providing insonation volume in ultrasound therapy treating tissues at a target region, wherein the tissues have an attenuation constant, the method comprising: using a catheter to introduce a linear transducer array into a body lumen to treat the tissues, the linear transducer array comprising a plurality of equally spaced transducer segments; causing to determine an operating frequency for exciting the linear transducer array and a length of the linear transducer array to be excited by: determining a self focus distance from an axial center of the linear transducer array based on a size of the target region; determining an initial transducer length as a function of an initial wavelength and the self focus distance, wherein the initial transducer length is proportional to a square root of the self focus distance multiplied by the initial wavelength; determining the length of the linear transducer array to be excited as the initial transducer length; determining the operating frequency as corresponding to the initial wavelength; and calculating ultrasound intensity in the target region by adjusting the length of the linear transducer array and the operating frequency such that the ultrasound intensity in the target region is within a desirable intensity pattern, wherein the ultrasound intensity in the target region is calculated based at least in part on the attenuation constant of the tissues, the operating frequency, and the length of the linear transducer array; and causing to excite the length of the linear transducer with a signal at the operating frequency to produce ultrasound intensity in the target region.
2. 2 . The method of claim 1 , further comprising: determining whether the ultrasound intensity in a volume at the target region would have at least one area not within a range between a maximum intensity and a half of the maximum intensity; and in response to determining that the ultrasound intensity in the volume at the target region would have at least one area not within the range between the maximum intensity and the half of the maximum intensity: spatially moving the catheter axially by an offset after exciting the linear transducer array; and exciting the linear transducer array a second time after spatially moving the catheter.
3. 3 . The method of claim 2 , further comprising: determining the offset based on a size of the at least one area in which the ultrasound intensity is not within the range between the maximum intensity and the half of the maximum intensity.
4. 4 . The method of claim 1 , further comprising: determining whether the ultrasound intensity in the target region would have at least one area not within a range between a maximum intensity and half of the maximum intensity; and in response to determining that the ultrasound intensity in the target region would have at least one area not within the range between the maximum intensity and half of the maximum intensity, exciting the length of the linear transducer with the signal at the operating frequency by applying, via a cable coupled to the plurality of transducer segments, selective excitation pulses of the signal to the plurality of transducer segments.
5. 5 . The method of claim 4 , wherein applying the selective excitation pulses of the signal comprises: applying a first excitation pulse of the signal to a first group of consecutive transducer segments in the linear transducer array; and alternately applying a second excitation pulse of the signal to a second group of consecutive transducer segments in the linear transducer array; wherein the first group of consecutive transducer segments and the second group of consecutive transducer segments are overlapping and spatially shifted at an offset from each other along an axial direction of the catheter.
6. 6 . The method of claim 5 , further comprising: determining the offset based on a size of the area in which the ultrasound intensity is not within the range between the maximum intensity and half of the maximum intensity.
7. 7 . The method of claim 5 , wherein: applying the first excitation pulse of the signal comprises causing at least one switch coupling an excitation source to the linear transducer array to operate at a first state to provide the signal from the excitation source to the first group of consecutive transducer segments in the linear transducer array; and applying the second excitation pulse of the signal comprises causing the at least one switch to operate at a second state to provide the signal from the excitation source to the second group of consecutive transducer segments in the linear transducer array.
8. 8 . The method of claim 7 , wherein: the first group of consecutive transducer segments comprise a first portion of consecutive transducer segments and a second portion of consecutive transducer segments; the second group of consecutive transducer segments comprise the second portion of consecutive transducer segments and a third portion of consecutive transducer segments; and the at least one switch is configured to operate at the first state to couple the excitation source to the first portion of consecutive transducer segments while disconnecting the third portion of consecutive transducer segments from the excitation source, and at the second state to couple the excitation source to the third portion of consecutive transducer segments while disconnecting the first portion of consecutive transducer segments from the excitation source; wherein the second portion of consecutive transducer segments are constantly coupled to the excitation source.
9. 9 . The method of claim 4 , wherein applying the selective excitation pulses of the signal comprises: applying a first excitation pulse of the signal to a first group of consecutive transducer segments in the linear transducer array; and alternately applying a second excitation pulse of the signal to a second group of consecutive transducer segments in the linear transducer array; wherein the first group of consecutive transducer segments encompass the second group of consecutive transducer segments along an axial direction of the catheter.
10. 10 . The method of claim 9 , wherein the first group of consecutive transducer segments comprise a first portion of consecutive transducer segments, a second portion of consecutive transducer segments, and the second group of consecutive transducer segments sandwiched between the first portion of consecutive transducer segments and the second portion of consecutive transducer segments, wherein a length of the first portion of consecutive transducer segments and a length of the second portion of consecutive transducer segments are each determined based on a size of the at least one area in which the ultrasound intensity is not within the range between the maximum intensity and the half of the maximum intensity.
11. 11 . The method of claim 10 , wherein: applying the first excitation pulse of the signal comprises causing at least one switch coupling an excitation source to the linear transducer array to operate at an on state to provide the signal from the excitation source to the first portion of consecutive transducer segments and the second portion of consecutive transducer segments; and applying the second excitation pulse of the signal comprises causing the at least one switch to operate at an off state to disconnect the first portion of consecutive transducer segments and the second portion of consecutive transducer segments from the excitation source; wherein the second group of consecutive transducer segments are constantly coupled to the excitation source.
12. 12 . The method of claim 1 , wherein the desirable intensity pattern comprises an intensity range between a maximum intensity and half of the maximum intensity.
13. 13 . The method of claim 1 , wherein calculating the ultrasound intensity in the target region comprises: for each of a plurality of observation points on an observation plane in the target region, determining a respective intensity based on a square of a sum of amplitudes each contributed by a respective transducer segment of the a plurality of transducer segments in the length of the linear transducer array, wherein the amplitude contributed by the respective transducer segment is: proportional to a transmitter amplitude of the respective transducer segment; inversely proportional to the attenuation constant of the tissues multiplied by the operating frequency and a distance from the respective transducer segment to the observation point on the observation plane; and proportional to a distance from the axial center of the linear transducer array to the observation plane divided by a square of the distance from the respective transducer segment to the observation point on the observation plane.
14. 14 . An apparatus for providing insonation volume in ultrasound therapy treating tissues at a target region, wherein the tissues have an attenuation constant, the apparatus comprising: a catheter having a linear transducer array disposed thereon, the catheter is configured to be introduced into a body lumen to treat the tissues, wherein the linear transducer array comprises a plurality of equally spaced transducer segments configured in a manner in which a length of the linear transducer array is excited by a signal at an operating frequency, wherein the length of the linear transducer array to be excited and the operating frequency of the signal are determined by: determining a self focus distance from an axial center of the linear transducer array based on a size of the target region; determining an initial transducer length as a function of an initial wavelength and the self focus distance, wherein the initial transducer length is proportional to a square root of the self focus distance multiplied by the initial wavelength; determining the length of the linear transducer array to be excited as the initial transducer length; determining the operating frequency as corresponding to the initial wavelength; and calculating ultrasound intensity in the target region by adjusting the length of the linear transducer array and the operating frequency such that the ultrasound intensity in the target region is within a desirable intensity pattern, wherein the ultrasound intensity in the target region is calculated based at least in part on the attenuation constant of the tissues, the operating frequency, and the length of the linear transducer array.
15. 15 . The apparatus of claim 14 further comprising a single cable coupled to the linear transducer array to provide the signal from an excitation source to excite the equally spaced transducer segments in the length of the linear transducer array simultaneously.
16. 16 . The apparatus of claim 14 further comprising a single cable configured to be coupled to an excitation source and at least one switch coupled to the single cable and the linear transducer array to provide selective excitation pulses of the signal from the excitation source to the linear transducer array.
17. 17 . The apparatus of claim 16 , wherein: the linear transducer array comprises a first portion of consecutive transducer segments coupled to the at least one switch, a second portion of consecutive transducer segments configured to be coupled to the excitation source, and a third portion of consecutive transducer segments coupled to the at least one switch; and the at least one switch is configured to operate at a first state to provide a first excitation pulse of the signal from the excitation source to the first portion of consecutive transducer segments while the third portion of consecutive transducer segments are disconnected from the excitation source, and at a second state to provide a second excitation pulse of the signal from the excitation source to the third portion of consecutive transducer segments while the first portion of consecutive transducer segments are disconnected from the excitation source.
18. 18 . The apparatus of claim 17 , wherein a length of the first portion of consecutive transducer segments and a length of the third portion of consecutive transducer segments are each based at least in part on the operating frequency of the signal and the attenuation of the tissue.
19. 19 . The apparatus of claim 16 , wherein: the linear transducer array comprises a first portion of consecutive transducer segments coupled to the at least one switch, a second portion of consecutive transducer segments configured to be coupled to the excitation source, and a third portion of consecutive transducer segments coupled to the at least one switch; and the at least one switch is configured to operate at an on state to provide a first excitation pulse of the signal from the excitation source to the first portion of consecutive transducer segments and the third portion of consecutive transducer segments, and at an off state to disconnect the first portion of consecutive transducer segments and the third portion of consecutive transducer segments from the excitation source.
20. 20 . The apparatus of claim 19 , wherein a length of the first portion of consecutive transducer segments and a length of the third portion of consecutive transducer segments are each based at least in part on the operating frequency of the signal and the attenuation constant of brain tissues.

Description

RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. § 119 (e) of U.S. Provisional Application No. 63/575,806, filed Apr. 7, 2024 and U.S. Provisional Application No. 63/661,407, filed Jun. 18, 2024. The entire contents of these applications are incorporated herein by reference. FIELD This technology relates to using ultrasound energy for therapeutic purposes, and more particularly to techniques for volume insonation of ultrasound. BACKGROUND There is increasing interest in using ultrasound energy for advanced therapeutic purposes. Ultrasound diathermy has been used for decades to heat joint and muscle tissues for pain and soreness relief. More recently, techniques of focused ultrasound (FUS) that allow for precise ablation of certain brain areas with high-intensity sound waves, in combination with MRI imaging, have shown to be effective for treatment in the brain to, for example, reduce or eliminate essential tremor. Other ultrasound techniques exist that use low-intensity ultrasound in conjunction with microbubbles to open the blood-brain-barrier. The blood-brain-barrier (“BBB”) prevents drugs whose molecular size exceed about 400 Daltons from passing from the blood into the brain, preventing most drugs from being effective therapy for neurodegenerative conditions, e.g. Alzheimer disease, amyotrophic lateral sclerosis (ALS), Parkinson disease and brain tumors. Opening the blood-brain-barrier has been achieved by ultrasound applied through the skull (with correction for the skull's distorting of the beam) to a desired area where it interacts with infused microbubbles to open the BBB. In these techniques that utilize microbubbles, the intensity of the insonation is controlled to avoid “inertial cavitation,” which is when the oscillating acoustic pressure is so high that it causes the microbubbles to overexpand and then collapse, releasing so much energy that it injures nearby tissue. “Stable cavitation” uses lower pressures where the bubbles expand and contract continuously with the acoustic field and affect the vessel walls to open the BBB, allowing drugs to enter brain tissue. The range of acoustic intensity between undesired inertial cavitation and the desired stable cavitation is understood to be approximately two-to-one. This range of acoustic pressure is referred herein as the therapeutic range. BRIEF DESCRIPTION OF DRAWINGS Additional embodiments of the disclosure, as well as features and advantages thereof, will become more apparent by reference to the description herein taken in conjunction with the accompanying drawings. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views. FIG. 1 is a schematic diagram of an example device used for producing large volume insonation, according to some embodiments. The ring transducers in a linear array of ring transducers as shown emit wavefronts equivalent to a point source at their center. FIG. 2A illustrates an observation plane and observation point relative to a point source in the transducer array of the device in FIG. 1, according to some embodiments. FIG. 2B illustrates a longitudinal slice through the field produced by a device shown in FIG. 1 in a vein, showing the shape of the therapeutic intensity that falls in the therapeutic range (between the maximum and the half-maximum in the field), according to some embodiments. FIG. 2C illustrates an axial slice of the cylindrical, rotationally symmetric field produced by the linear array of rotationally symmetric transducers of FIG. 1, according to some embodiments. FIG. 3 is a contour plot illustrating the intensity in a longitudinal slice of the cylindrical volume surrounding the array of FIG. 1 when all the transducers are driven in parallel with unit intensity and in a certain attenuating medium, according to some embodiments. FIG. 4 illustrates a binarized intensity plot of FIG. 3, in which the gray areas indicate where the intensities in FIG. 3 fall in the therapeutic range (between the maximum and the half-maximum in the field), and the “holes” indicate where the intensities fall below the therapeutic range. FIG. 5 illustrates movement of the catheter of a transducer device to provide a shift of 2.8 mm to eliminate “holes” in intensity in the “near field” shown in FIG. 4, according to some embodiments. FIG. 6 illustrates a binarized intensity plot in which “holes” have been eliminated as a result of two excitations of a linear array when the array is moved axially 2.8 mm between the two excitations in a manner according to FIG. 5. FIG. 7 illustrates an example of applying selective excitation pulses in which two groups of transducers are excited alternately, according to some embodiments. FIG. 8 illustrates another example of applying selective excitation pulses in which two groups of transducers are excited alternately, according to some embodiments. FIGS. 9A-9C ill