THERMOACOUSTIC IMAGING WITH QUANTITATIVE EXTRACTION OF ABSORPTION MAP

• US 20120123256A1
• Filed: 06/29/2009
• Published: 05/17/2012
• Est. Priority Date: 06/29/2009
• Status: Active Grant

• Current Assignee: Helmholtz Zentrum München Deutsches Forschungszentrum für. Gesundheit und Umwelt (GmbH)
• Original Assignee: Helmholtz Zentrum München Deutsches Forschungszentrum für. Gesundheit und Umwelt (GmbH)
• Inventors: Razansky, Daniel, Ntziachristos, Vasilis, Rosenthal, Amir
• Granted Patent: US 9,271,654 B2
• Time in Patent Office: Days
• US Class Current: 600/431
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0093 Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: G01N 21/17 Systems in which incident light is modified in accordance with the properties of the material investigated where the material investigated is optically excited causing a change in wavelength of the incident light G01N21/63
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids

Abstract

A method of thermoacoustic imaging of an object includes providing thermoacoustic signals representing a mechanical wave response to a delivery of electromagnetic energy into the imaged object, reconstructing an energy deposition image representing a local energy absorption within the object based on the thermoacoustic signals, and decomposing the energy deposition image into a quantitative absorption image representing a distribution of a local absorption coefficient in the object and at least one further image component.

Claims

1-36. -36. (canceled)

37. A method of thermoacoustic imaging of an object comprising:

providing thermoacoustic signals representing a mechanical wave response to a delivery of electromagnetic energy into the imaged object;

reconstructing an energy deposition image representing a local energy absorption within the object based on the thermoacoustic signals; and

decomposing the energy deposition image into a quantitative absorption image representing a distribution of a local absorption coefficient in the object and at least one further image component.

38. The imaging method according to claim 37, wherein the thermoacoustic signals represent a mechanical wave response to a delivery of light pulses.

39. The imaging method according to claim 38, wherein the thermoacoustic signals represent a mechanical wave response to delivery of light pulses which have at least one illumination wavelength and at least one polarization state.

40. The imaging method according to claim 39, wherein:

the energy deposition image is reconstructed based on the thermoacoustic signals acquired with at least one of the at least one illumination wavelength and the at least one light polarization;

multiple energy deposition images are separately reconstructed based on the thermoacoustic signals acquired with at least one of different illumination wavelengths and different light polarizations;

or

the energy deposition image is reconstructed based on a combination of the thermoacoustic signals acquired with at least one of different illumination wavelengths and different light polarizations, wherein the combination comprises linear or nonlinear combinations of signals.

41. The imaging method according to claim 37, further comprising pre-processing the thermoacoustic signals by analog or digital signal processing operations.

42. The imaging method according to claim 37, wherein the energy deposition image reconstructing comprises:

providing a forward model matrix of thermoacoustic signal propagation; and

matrix-based acoustic inversion of the thermoacoustic signals utilizing an inverted model matrix approach.

43. The imaging method according to claim 42, wherein the inverted model matrix approach includes at least one of a pseudo inverse or singular value decomposition, a least-squares-based (LSQR) method and an algebraic reconstruction technique (ART).

44. The imaging method according to claim 43, including at least one of:

the model matrix depends on geometry of a detector device collecting the thermoacoustic signals; and

the model matrix is adjusted depending on at least one of acoustic heterogeneity of the object, a geometric profile of the delivered electromagnetic energy in the imaged object, a frequency response of a detector device utilized for collecting the thermoacoustic signals and a result of the decomposing step.

45. The imaging method according to claim 37, wherein the energy deposition image reconstructing comprises an iterative propagation model based simulation.

46. The imaging method according to claim 37, wherein the energy deposition image decomposing comprises:

providing a logarithmic representation of the energy deposition image; and

calculating the quantitative absorption image and the at least one further image component as summands of the logarithmic representation.

47. The imaging method according to claim 37, wherein the energy deposition image decomposing comprises providing the quantitative absorption image and the at least one further image component as expansions in complementary libraries.

48. The imaging method according to claim 47, wherein the expansion coefficients in the complementary libraries are obtained with a minimization algorithm.

49. The imaging method according to claim 37, wherein the at least one further image component comprises at least one of an excitation light fluence distribution image, a distribution of the optical scattering coefficient, a distribution of speed of sound, an image representing local polarization state, an electric or magnetic field distribution, a dielectric constant distribution, a thermoelastic expansion coefficient distribution, and a heat capacity distribution.

50. The imaging, method according to claim 37, wherein the at least one further image component comprises an image representing a local state of the object.

51. The imaging method according to claim 50, wherein the local state comprises a physiological condition of the object.

52. The imaging method according to claim 37, wherein the at least one further image component comprises an image representing a spatial distribution of a tissue bio-marker in the object.

53. The imaging method according to claim 52, wherein the biomarker comprises one or more of an extrinsically administered molecular agent, a fluorescent protein, and a chromogenic assay.

54. The imaging method according to claim 37, further comprising:

irradiating the imaged object by electromagnetic energy; and

recording the thermoacoustic signals produced in response to the irradiation.

75. A computer program on a computer-readable medium, with a program code that carries out the method according to claim 37.

76. An apparatus comprising a computer-readable storage medium containing program instructions that carries out the method according to claim 37.

55. A method of thermoacoustic imaging comprising:

providing thermoacoustic signals representing a mechanical wave response to a delivery of electromagnetic energy to an imaged object; and

reconstructing an energy deposition image representing a local energy deposition within the object based on the thermoacoustic signals, said reconstructing step including a matrix-based acoustic inversion of the thermoacoustic signals utilizing an inverted model matrix.

56. The imaging method according to claim 55, including at least one of:

the model matrix depends on a geometry of collecting the thermoacoustic signals; and

the model matrix is adjusted in dependency on at least one of acoustic heterogeneity of the object, a geometric profile of the illumination of the imaged object by the light pulses, a frequency response of a detector device utilized for collecting the thermoacoustic signals and a result of the decomposing step.

57. The imaging method according to claim 55, further comprising:

irradiating the imaged object by electromagnetic energy; and

recording the thermoacoustic signals produced in response to the irradiation.

58. An imaging device for thermoacoustic imaging of an object comprising:

a signal collecting device that collects thermoacoustic signals representing a mechanical wave response to a delivery of electromagnetic energy into the imaged object;

an energy deposition image reconstruction device that reconstructs an energy deposition image representing a local energy deposition within the object based on collected thermoacoustic signals; and

an absorption image decomposition device that decomposes the energy deposition image into a quantitative absorption image representing a distribution of a local absorption coefficient in the object and at least one further image component.

59. The imaging device according to claim 58, wherein the signal collecting device comprises:

an electromagnetic energy source; and

an acoustic signal recording device including at least one acoustic detection element.

60. The imaging device according to claim 58, wherein the signal collecting device comprises a membrane separating the imaged object from a liquid medium where the at least one acoustic detection element is located.

61. The imaging device according to claim 60, wherein the membrane is made of a optically transparent material acoustically matched to the liquid medium.

62. The imaging device according to claim 58, wherein the energy deposition image reconstruction device comprises an inversion circuit that subjects the thermoacoustic signals to a matrix-based acoustic inversion utilizing an inverted model matrix.

63. The imaging device according to claim 62, wherein the inversion circuit includes at least one of:

a matrix storage storing at least one of the model matrix and its inverse; and

an adjustment device that adjusts the model matrix in dependency on at least one of an acoustic heterogeneity of the object, a geometric profile of the illumination of the imaged object by the light pulses, a frequency response of a detector device utilized for collecting the thermoacoustic signals and an output of the decomposition device.

64. The imaging device according to claim 63, wherein the inversion circuit comprises an iteration circuit that implements an iterative propagation model based simulation.

65. The imaging device according to claim 58, wherein the absorption image decomposition device:

provides a logarithmic representation of the energy deposition image; and

calculates the quantitative absorption image and the at least one further image component as summands of the logarithmic representation.

66. The imaging device according to claim 58, wherein the absorption image decomposition device provides the quantitative absorption image and the at least one further image component as expansions in complementary libraries.

67. The imaging device according to claim 58, wherein the electromagnetic energy source comprises an illumination device that illuminates the imaged object by electromagnetic pulses.

68. The imaging device according to claim 58, wherein the acoustic signal recording device comprises at least one of a detector array and a single detector.

69. The imaging device according to claim 58, wherein the acoustic signal recording device and the object are movable relative to each other.

70. An imaging device for optoacoustic imaging of an object, comprising:

an energy-deposition image reconstruction device that reconstructs an energy deposition image representing a local energy deposition within the object based on the thermoacoustic signals, wherein

the energy deposition image reconstruction device comprises an inversion circuit that subjects the thermoacoustic signals to a matrix-based acoustic inversion utilizing an inverted model matrix.

71. The imaging device according to claim 70, wherein the inversion circuit includes at least one of:

a matrix storage storing the inverted model matrix; and

an adjustment device that adjusts the model matrix in dependency on at least one of acoustic heterogeneity of the object, a geometric profile of the illumination of the imaged object by the light pulses, a frequency response of a detector device utilized for collecting the thermoacoustic signals and an output of the decomposition device.

72. The imaging device according to claim 70, wherein the electromagnetic energy source comprises an illumination device that illuminates the imaged object by electromagnetic pulses.

73. The imaging device according to claim 70, wherein the acoustic signal recording device comprises at least one of a detector array and a single detector.

74. The imaging device according to claim 70, wherein the acoustic signal recording device and the object are movable relative to each other.