Ultrasound therapy

• US 6,612,988 B2
• Filed: 12/15/2000
• Issued: 09/02/2003
• Est. Priority Date: 08/29/2000
• Status: Expired due to Term

• Current Assignee: Brigham and Women's Hospital Incorporated, InSightec Ltd.
• Original Assignee: Brigham and Women's Hospital Incorporated, Insightec-Image-Guided Treatment Limited (InSightec Ltd.)
• Inventors: Grinfeld, Javier, Maor, Dov, Hynynen, Kullervo
• Primary Examiner(s): Jaworski, Francis J.
• Assistant Examiner(s): PATEL, MAULIN M
• Application Number:
  US09/738,514
• Publication Number:
  US 20020111552A1
• Time in Patent Office: 991 Days
• Field of Search: 600/443, 600/447, 600/437, 600/439, 600/445, 600/448, 600/459, 600/456, 600/458, 600/432
• US Class Current: 600/439
• CPC Class Codes: A61B 2090/374 NMR or MRI
• CPC Class Codes: A61B 2090/376 using X-rays, e.g. fluoroscopy
• CPC Class Codes: A61B 8/0816 using echo-encephalography
• CPC Class Codes: A61N 2007/0095 by modifying an excitation signal
• CPC Class Codes: A61N 7/02 Localised ultrasound hyperthermia hyperthermia in general A61F7/00

Abstract

The invention provides a method of delivering ultrasound signals. The method includes providing an image of at least a portion of a subject intended to receive ultrasound signals between sources of the ultrasound signals and a desired region of the subject for receiving focused ultrasound signals, identifying, from the image, physical characteristics of different layers of material between the sources and the desired region, and determining at least one of phase corrections and amplitude corrections for the sources depending on respective thicknesses of portions of each of the layers disposed between each source and the desired region.

Claims

1. A method of delivering ultrasound signals, the method comprising:

providing an image of at least a portion of a subject intended to receive ultrasound signals between sources of the ultrasound signals and a desired region of the subject for receiving focused ultrasound signals;

identifying, from the image, physical characteristics of different layers of material between the sources and the desired region; and

determining at least one of phase corrections and amplitude corrections for the sources depending on respective thicknesses of portions of each of the layers disposed between each source and the desired region.

2. The method of claim 1 wherein the physical characteristics are associated with material type and at least one of material density and material structure, the identifying further comprising identifying thicknesses of the layers.

3. The method of claim 2 wherein the phase corrections are determined in accordance with propagation characteristics of each of the layers.

4. The method of claim 3 wherein the propagation characteristics are determined based upon the material type and at least one of the material density and the material structure of each of the respective layers.

5. The method of claim 3 wherein the layers are identified using values associated with portions of the image.

6. The method of claim 5 wherein the values are intensities of the portions of the image.

7. The method of claim 6 wherein the phase corrections are determined using a three-layer model of a skull of the subject.

8. The method of claim 7 wherein two of the three layers are assumed to have approximately identical speeds of sound, c_i, therein, with the other layer having a speed of sound c_ii therein, wherein the phase corrections are determined using a phase shift determined according to:

$\mathrm{\phi <br><br>}=360<br><br>f<br><br>\underset{n=1}{\overset{3}{\sum <br><br>}}<br><br>D_n<br><br>\left(\frac{1}{c_0}-\frac{1}{c_n}\right)$

where c_n is a speed of sound in the n^th layer, and D_n is a thickness of the n^th layer, and

wherein the speeds of sound in the layers are determined according to;

$c_i<br><br>\left(\mathrm{\rho <br><br>}\right)={\left(d_1+d_3\right)<br><br>\left[\frac{d_1+d_2+d_3}{c_0}-\frac{d_2}{c_{\mathrm{ii}}}-\frac{\mathrm{\phi <br><br>}<br><br>\left(\mathrm{\rho <br><br>}\right)}{360<br><br>\mathrm{fD}}\right]}^{-1}$

 

where d₁, d₂, d₃, are thicknesses of the three layers, φ

(ρ

) is a measured phase shift as a function of density, and ρ

is density.

9. The method of claim 1 wherein the physical characteristics are associated with x-ray attenuation coefficients, μ

.

10. The method of claim 9 wherein the material between the sources and the desired region is bone.

11. The method of claim 9 wherein the phase corrections are related to the attenuation coefficient by a phase function including parameters derived at least partially experimentally.

12. The method of claim 11 wherein each phase correction equals M+BΣ

(1/μ

(x))+CΣ

(1/μ

(x))², where μ

(x) is the attenuation coefficient as a function of distance x along a line of propagation between each source and the desired region, and where M, B, and C are derived at least partially experimentally.

13. The method of claim 9 wherein the amplitude corrections are related to the attenuation coefficient by an amplitude function including parameters derived at least partially experimentally.

14. The method of claim 13 wherein each amplitude correction is related to N+FΣ

μ

(x)+GΣ

(μ

(x))², where μ

(x) is the attenuation coefficient as a function of distance x along a line of propagation between each source and the desired region, and where N, F, and G are derived at least partially experimentally.

15. The method of claim 1 wherein the layers are identified according to both material density and material structure.

16. The method of claim 1 wherein providing the image includes producing the image using magnetic resonance imaging.

17. The method of claim 1 wherein providing the image includes producing the image using computer tomography.

18. The method of claim 1 wherein the sources are piezoelectric transducer elements.

19. The method of claim 1 wherein both phase and amplitude corrections are determined.

20. A system for delivering ultrasound signals, the system comprising:

an apparatus configured to analyze an image of at least a portion of a subject intended to receive ultrasound signals between sources of the ultrasound signals and a desired region of the subject for receiving focused ultrasound signals, the apparatus configured to determine, from the image, information about different layers of the at least a portion of the subject; and

an array of sources of ultrasound signals having at least one of their relative phases and their amplitudes set in accordance with the information about each layer of the at least a portion of the subject provided by the apparatus.

21. The system of claim 20 wherein the phases are set in accordance with propagation characteristics of each layer of the at least a portion of the subject.

22. The system of claim 21 wherein the propagation characteristics are dependent upon the material type and at least one of the material density and the material structure of each layer of the at least a portion of the subject.

23. The system of claim 21 wherein the apparatus is configured to identify the layers using values associated with portions of the image.

24. The system of claim 23 wherein the values are intensities of the portions of the image.

25. The system of claim 24 wherein the apparatus is configured to determine the information about different layers of bone.

26. The system of claim 24 wherein the apparatus is configured to determine the phase corrections using a three-layer model of a skull of the subject.

27. The system of claim 23 wherein the information is associated with an x-ray attenuation coefficient, μ

.

28. The system of claim 27 wherein the phase corrections are related to the attenuation coefficient by a phase function including parameters derived at least partially experimentally.

29. The system of claim 27 wherein the amplitude corrections are related to the attenuation coefficient by an amplitude function including parameters derived at least partially experimentally.

30. The system of claim 20 further comprising a magnetic resonance imager coupled to the apparatus and configured to produce the image.

31. The system of claim 20 further comprising a computer tomography imager coupled to the apparatus and configured to produce the image.

32. The system of claim 20 wherein the sources are piezoelectric transducer elements.

33. A computer program product residing on a computer readable medium and comprising instructions for causing a computer to:

analyze an image of at least a portion of a subject to receive ultrasound signals between sources of the ultrasound signals and a desired region of the subject for receiving focused ultrasound signals to identify, from the image, physical characteristics of layers of material between the sources and the desired region; and

determine at least one of phase corrections and amplitude corrections for the sources depending on respective thicknesses of portions of each of the layers disposed between each source and the desired region.

34. The computer program product of claim 33 wherein the phase corrections are determined in accordance with propagation characteristics of each of the layers.

35. The computer program product of claim 34 wherein the propagation characteristics are dependent upon the material type and at least one of the material density and the material structure of each of the respective layers.

36. The computer program product of claim 33 wherein the layers are identified according to both material density and material structure.

37. The computer program product of claim 33 further comprising instructions for causing a computer to produce the image using magnetic resonance imaging.

38. The computer program product of claim 33 further comprising instructions for causing a computer to produce the image using computer tomography.

39. The computer program product of claim 33 wherein the instructions for causing a computer to identify layers of materials are for causing the computer to identify the layers of materials based upon intensities of portions of the image.

40. The computer program product of claim 33 wherein the layers are identified using values associated with portions of the image.

41. The computer program product of claim 40 wherein the values are intensities of the portions of the image.

42. The computer program product of claim 41 wherein the layers analyzed are layers of bone.

43. The computer program product of claim 41 wherein the phase corrections are determined using a three-layer model of a skull of the subject.

44. The computer program product of claim 43 wherein two of the three layers are assumed to have approximately the same speed of sound, c_i, therein, with the other layer having a speed of sound c_ii therein, wherein the phase corrections are determined using a phase shift determined according to:

$\mathrm{\phi <br><br>}=360<br><br>f<br><br>\underset{n=1}{\overset{3}{\sum <br><br>}}<br><br>D_n<br><br>\left(\frac{1}{c_0}-\frac{1}{c_n}\right)$

where c_n is a speed of sound in the n^th layer, and D_n is a thickness of the n^th layer, and

wherein the speeds of sound in the layers are determined according to;

$c_i<br><br>\left(\mathrm{\rho <br><br>}\right)={\left(d_1+d_3\right)<br><br>\left[\frac{d_1+d_2+d_3}{c_0}-\frac{d_2}{c_{\mathrm{ii}}}-\frac{\mathrm{\phi <br><br>}<br><br>\left(\mathrm{\rho <br><br>}\right)}{360<br><br>\mathrm{fD}}\right]}^{-1}$

 

where d₁, d₂, d₃, are thicknesses of the three layers, φ

(ρ

) is a measured phase shift as a function of density, and ρ

is density.

45. The computer program product of claim 33 wherein the physical characteristics are associated with x-ray attenuation coefficients, μ

.

46. The computer program product of claim 45 wherein the phase corrections are related to the attenuation coefficient by a phase function including parameters derived at least partially experimentally.

47. The computer program product of claim 46 wherein each phase correction equals M+BΣ

(1/μ

(x))+CΣ

(1/μ

(x))², where μ

(x) is the attenuation coefficient as a function of distance x along a line of propagation between each source and the desired region, and where M, B, and C are derived at least partially experimentally.

48. The computer program product of claim 45 wherein the amplitude corrections are related to the attenuation coefficient by an amplitude function including parameters derived at least partially experimentally.

49. The computer program product of claim 48 wherein each amplitude correction is related to N+FΣ

μ

(x)+GΣ

(μ

(x))², where μ

(x) is the attenuation coefficient as a function of distance x along a line of propagation between each source and the desired region, and where N, F, and G are derived at least partially experimentally.

50. A method of providing ultrasound signals into a subject from at least one source of an array of sources of ultrasound signals, the method comprising:

(a) transmitting ultrasound energy of a selected frequency from a selected source into the subject;

(b) receiving superimposed reflections of the transmitted energy, the reflections being from an outer surface of the subject and at least one interface inside the subject;

(c) repeating (a) and (b) using ultrasound energy of frequencies other than the selected frequency;

(d) determining a frequency difference between frequencies associated with relative extrema of the received reflections; and

(e) using the determined frequency difference and a thickness, of at least a portion of material between the selected source and a desired region in the subject for receiving focused ultrasound energy signals, to determine a phase correction for the selected source.

51. The method of claim 50 further comprising:

(f) providing an image of at least a portion of a subject intended to receive ultrasound energy signals between sources of the energy signals and the desired region; and

(g) identifying, from the image, the thickness of at least a portion of material between the selected source and the desired region.

52. The method of claim 50 further comprising repeating (a)-(e) for each of the sources other than the selected source.

53. The method of claim 50 wherein the phase correction is determined according to:

54. Logic for use in a system for providing ultrasound energy into a living subject from an array of sources of ultrasound energy signals, the logic being configured to control apparatus to:

(a) transmit ultrasound energy of a selected frequency from a selected source into the subject;

(b) receive superimposed reflections of the transmitted energy, the reflections being from an outer surface of the subject and at least one interface inside the subject;

(c) repeat (a) and (b) using ultrasound energy of frequencies other than the selected frequency;

(d) determine a frequency difference between frequencies associated with relative extrema of the received reflections; and

(e) use the determined frequency difference and a thickness, of at least a portion of material between the selected source and a desired region in the subject for receiving focused ultrasound energy signals, to determine a phase correction for the selected source.

55. The logic of claim 54 further configured to cause the apparatus to:

(f) provide an image of at least a portion of a subject intended to receive ultrasound energy signals between sources of the energy signals and the desired region; and

(g) identify, from the image, the thickness of at least a portion of material between the selected source and the desired region.

56. The logic of claim 54 further configured to cause the apparatus to repeat (a)-(e) for each of the sources other than the selected source.

57. The logic of claim 54 wherein the logic is configured to cause the apparatus to determine the phase correction according to: