Ultrasound phased arrays

• US 20050240127A1
• Filed: 03/02/2005
• Published: 10/27/2005
• Est. Priority Date: 03/02/2004
• Status: Active Grant

• Current Assignee: Focus Surgery, Inc. (Sonacare Medical, LLC)
• Original Assignee: Focus Surgery, Inc. (Sonacare Medical, LLC)
• Inventors: Sanghvi, Narendra T., Seip, Ralf, Chen, Wo-Hsing
• Granted Patent: US 7,662,114 B2
• Time in Patent Office: Days
• US Class Current: 601/2
• CPC Class Codes: A61N 2007/0052 using the same transducer for therapy and imaging
• CPC Class Codes: A61N 2007/0065 Concave transducers
• CPC Class Codes: A61N 2007/0078 with multiple treatment transducers
• CPC Class Codes: A61N 2007/0095 by modifying an excitation signal
• CPC Class Codes: A61N 2007/027 with multiple foci created simultaneously
• CPC Class Codes: A61N 7/02 Localised ultrasound hyperthermia hyperthermia in general A61F7/00

Abstract

Ultrasound transducers are disclosed which focus acoustic energy at various focal locations while minimizing focal spot degradation and the generation of unwanted on-axis or off-axis energy concentrations through using a generally constant f-number at the various focal locations.

Claims

1. A method of treating tissue with a HIFU System including a transducer, the method comprising the steps of:

providing HIFU Therapy to a first portion of the tissue, the first portion being located at a first distance from the transducer;

providing HIFU Therapy to a second portion of the tissue, the second portion being located at a second distance from the transducer;

maintaining a generally constant f-number with the transducer when providing HIFU Therapy to both the first portion of the tissue and the second portion of the tissue.

2. The method of claim 1, wherein the transducer includes an active surface having a plurality of transducer elements and wherein the step of maintaining the generally constant f-number comprises the steps of:

selecting a first aperture of the active surface including a first number of the plurality of transducer elements for the provision of HIFU Therapy to the first portion of the tissue, the first number of transducer elements being configured to emit acoustic energy which will focus at the first distance from the transducer; and

selecting a second aperture of the first active surface including a second number of the plurality of transducer elements for the provision of HIFU Therapy to the second portion of the tissue, the second number of transducer elements being configured to emit acoustic energy which will focus at the second distance from the transducer, wherein a ratio of the second distance to an active extent of the second aperture is generally equal to a ratio of the first distance to an active extent of the first aperture.

3. The method of claim 2, wherein the first portion of tissue and the second portion of tissue are located generally along an axis generally normal to a plane defined by a face of the transducer and further comprising the step of maintaining the transducer at a fixed location relative to the tissue for the provision of HIFU Therapy to each of the first portion of the tissue and the second portion of the tissue.

4. The method of claim 3, wherein the first number of transducer elements and the second number of transducer elements include at least one common transducer element of the plurality of transducer elements.

5. The method of claim 2, wherein the first portion of tissue is located along a first axis generally normal to a plane defined by a face of the transducer and the second portion of tissue is located along a second axis generally normal to the plane defined by the face of the transducer, the second axis being spaced apart from the first axis, and further comprising the step of maintaining the transducer at a fixed location relative to the tissue for the provision of HIFU Therapy to each of the first portion of the tissue and the second portion of the tissue.

6. The method of claim 5, wherein the first number of transducer elements are distinct from the second number of transducer elements.

7. The method of claim 2, wherein the first number of elements are centered relative to the first portion of the tissue and the second number of elements are centered relative to the second portion of the tissue.

8. A method of conducting a HIFU treatment to a target tissue, the method comprising the steps of:

positioning a transducer proximate to target tissue, the transducer having a variable aperture;

imaging the target tissue;

selecting a plurality of treatment sites within the target tissue to be treated with HIFU Therapy, a first treatment site being located a first distance from the transducer and a second treatment site being located a second distance from the transducer; and

providing HIFU Therapy to the plurality of treatment sites with the transducer, the transducer having a first aperture when providing therapy to the first treatment site and having a second aperture when providing therapy to the second treatment site, at least one of an active extent of the first aperture and an active extent of the second aperture being chosen so that a ratio of the second distance to the active extent of the second aperture is generally equal to a ratio of the first distance to the active extent of the first aperture.

9. The method of claim 8, wherein the first treatment site and the second treatment site are located generally along an axis generally normal to a plane defined by a face of the transducer and further comprising the step of maintaining the transducer a fixed location relative to the tissue for the provision of HIFU Therapy to each of the first treatment site and the second treatment site.

10. The method of claim 8, wherein the first treatment site is located along a first axis generally normal to a plane defined by a face of the transducer and the second treatment site is located along a second axis generally normal to the plane defined by the face of the transducer, the second axis being spaced apart from the first axis, and further comprising the step of maintaining the transducer at a fixed location relative to the tissue for the provision of HIFU Therapy to each of the first treatment site and the second treatment site.

11. A transducer for use with a HIFU System, the transducer, comprising:

an active surface having a plurality of transducer elements; and

a controller operably coupled to the transducer, the controller being configured to select which transducer elements emit acoustic energy and to control such emissions to focus the acoustic energy at various focal depths so that the active surface has a generally constant f-number at the various focal depths.

12. The transducer of claim 11, wherein a first subset of the plurality of transducer elements are selected to define a first aperture of the active surface, the acoustic energy emitted from the first subset of the transducer elements being configured to focus at a first distance from the active surface and wherein a second subset of the transducer elements of the plurality of transducer elements are selected to define a second aperture of the active surface, the acoustic energy emitted from the second subset being configured to focus at a second distance from the active surface, the ratio of the first distance to an active extent of the first aperture being generally equal to the ratio of the second distance to an active extent of the second aperture.

13. The transducer of claim 12, wherein the controller configures each transducer element in the first subset of transducer elements to emit a respective continuous acoustic wave, a phase of each respective acoustic wave being chosen to produce a constructive interference of the acoustic waves at the first distance.

14. The transducer of claim 12, the ratio of the second distance to an active extent of the second aperture is about 1.0.

15. The transducer of claim 13, wherein the continuous acoustic waves have a frequency of about 4 MHz and a duration of about 3 seconds.

16. A method for controlling the emission of acoustic energy from a plurality of transducer elements of a multi-element transducer such that the acoustic energy is focused at a desired location, the method comprising the steps of:

determining a phase and an amplitude required for each transducer element;

providing a reference continuous wave signal to each transducer element;

digitally generating from the reference signal a delayed and pulse-width modulated signal for each transducer element;

generating an amplitude modulated analog signal for each transducer element based on the delayed and pulse-width modulated signal for the respective transducer element; and

driving the transducer element with the amplitude modulated analog signal.

17. The method of claim 16, wherein the amplitude modulated analog signal is generated by filtering of the delayed and pulse-width modulated signal.

18. The method of claim 16, wherein the digital electronics are provided a programmed phase input and a programmed amplitude input based on the determined required phase and amplitude.

19. A method of imaging a targeted tissue and treating portions of the tissue with HIFU Therapy, the method comprising the steps of:

providing a transducer having a longitudinal extent at least equal to a longitudinal extent of the targeted tissue, the transducer including a plurality of individually controlled transducer elements;

electronically scanning a first sub-aperture of the transducer to generate at least one image of the targeted tissue while the transducer is held in place longitudinally;

identifying portions of the targeted tissue for treatment with HIFU Therapy;

treating each of the identified portions of the targeted tissue with HIFU Therapy.

20. The method of claim 19, wherein the step of electronically scanning the first sub-aperture, includes the steps of:

activating a first subset of transducer elements proximate to a first side of the transducer;

generating an acoustic pulse with the first subset of transducer elements;

receiving a echo signal reflected back from the targeted tissue with the first subset of transducer elements;

activating a second subset of transducer elements, the second subset being further from the first side than the first subset, the second subset and the first subset being generally the same size;

generating an acoustic pulse with the second subset of transducer elements; and

receiving a echo signal reflected back from the targeted tissue with the second subset of transducer elements.