Non-invasive stationary system for three-dimensional imaging of density fields using periodic flux modulation of compton-scattered gammas

• US 20030161526A1
• Filed: 02/26/2003
• Published: 08/28/2003
• Est. Priority Date: 02/28/2002
• Status: Active Grant

• Current Assignee: Clyde P. Jupiter, Nenad N. Kondic
• Original Assignee: Clyde P. Jupiter, Nenad N. Kondic
• Inventors: Kondic, Nenad N., Jupiter, Clyde P.
• Granted Patent: US 7,412,022 B2
• Time in Patent Office: Days
• US Class Current: 382/154
• CPC Class Codes: A61B 6/4258 for detecting non x-ray radiation, e.g. gamma radiation A61B6/037 takes precedence
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]

Abstract

A three-dimensional image-generating device includes a radiation source, a modulating unit and a radiation detector. All these components may either be stationary or movable. The radiation source is configured to irradiate an object with mono-energetic gamma rays. The modulating unit is configured to encode the single-scattered gamma fluxes scattered from the object as the gamma fluxes travels to the detector. The modulating unit, in conjunction with the Compton scattering process, is configured to enable the identification of the spatial origin of the single-scattered gamma fluxes as they pass through the modulating unit enroute to the detector. The radiation detector and the computer-processor of the detected data are configured to identify local gamma fluxes scattered from various locations within the object. The three-dimensional distribution of local single-scattered gamma fluxes is converted to a three-dimensional mass distribution within the inspected object.

Claims

1. A three-dimensional image-generating device comprising:

a radiation source configured to irradiate an object with gamma rays to generate a three-dimensional representation of said object;

a modulating unit configured to encode gamma flux scattered from the inspected object as said gamma rays interact wherein said object generates scattered gamma rays,

said modulating unit configured to identify spatial origins of said scattered gamma rays as said scattered gamma rays pass through said modulating unit; and

a radiation detector configured to detect gamma rays scattered from said object, and passing through said modulating unit.

2. The device as recited in claim 1, wherein said three-dimensional representation is generated by reconstructing a volumetric density distribution within said object.

3. The device as recited in claim 1, wherein said radiation source, said modulating unit, and said radiation detector are stationary having a fixed orientation.

4. The device as recited in claim 1, wherein said radiation source, said modulating unit, and said radiation detector are positioned based on a pre-selected region surrounding said object.

5. The device as recited in claim 4, wherein said modulating unit is positioned between said object and said radiation detector.

6. The device as recited in claim 4, wherein said modulating unit is positioned between said object and said radiation source.

7. The device as recited in claim 5, wherein said modulating unit encodes a selected cross-sectional area of the scattered gamma flux with a time-dependent oscillatory attenuation.

8. The device as recited in claim 7, wherein said modulating unit comprises a rectangular-shaped unit.

9. The device as recited in claim 7, wherein said modulating unit comprises a circular-shaped unit.

10. The device as recited in claim 1, wherein said radiation detector comprises a gamma spectrometer;

and

wherein said gamma spectrometer is configured to register a plurality of single detection events of said scattered gamma rays, wherein said plurality of single detection events are detected individually; and

wherein said gamma spectrometer is configured to concurrently measure energies of scattered gammas photons associated with said detection events.

11. The device as recited in claim 10, further comprising:

a multi-channel pulse height analyzer coupled to said gamma spectrometer and configured to analyze voltage pulse heights representing the energies of the scattered gamma photons and sort the voltage pulse heights based upon the energies of the scattered gamma photons.

12. The device as recited in claim 11, wherein said gamma spectrometer and the multi-channel pulse-height analyzer are configured to determine an average value of energy for said scattered gamma rays having a predetermined energy bin width.

13. The device as recited in claim 10, wherein said gamma spectrometer is configured to determine values of the gamma count rate for said gamma rays arriving at the detector, wherein predetermined energy bin widths are established for said counted gamma rays.

14. The device as recited in claim 1, wherein said modulating unit comprises a planar array of nodal windows.

15. The device as recited in claim 14, wherein each nodal window of said planar array of nodal windows is configured to impart a time-varying attenuation on each segment of the said gamma flux as said each segment of said gamma flux passes through said each nodal window.

16. The device as recited in claim 15, wherein each said nodal window comprises an attenuating element for performing a time-dependent gamma attenuation;

wherein said attenuating element is configured to impose a time-dependent oscillatory attenuation of said each segment of said gamma flux as said scattered gamma flux passes through said attenuating element of said modulating unit; and

wherein said attenuating element is mounted on a vertical shaft within a frame of said modulating unit and wherein said attenuating element is capable of oscillatory movement in a vertical direction.

17. The device as recited in claim 16, wherein a variation of intensity of said gamma flux passing through said nodal windows and wherein said variation of intensity is accomplished by a rotational movement of said each attenuating element.

18. The device as recited in claim 1, wherein said modulating unit encodes said scattered gamma rays to enable identification of a location of a point of scattering from individual voxels contained within said object.

19. The device as recited in claim 18, wherein said modulating unit includes a plurality of nodal windows containing a plurality of periodically-oscillating gamma attenuators arranged to form a matrix configuration, and wherein said each gamma attenuator oscillates with a different time-varying attenuation function.

20. The device as recited in claim 19, wherein said different time-varying attenuation function is unique.

21. The device as recited in claim 1, wherein said radiation source comprises a mono-energetic gamma source.

22. The device as recited in claim 21, wherein said radiation source is selected from at least one of cesium-137, sodium-22, or another mono-energetic isotopic gamma source.

23. The device as recited in claim 1, further comprising:

a radiation shield configured to house said radiation source, wherein said radiation shield includes an opening to allow said radiation source to project said gamma rays outwardly in a direction capable of irradiating said inspected object.

24. The device as recited in claim 1, wherein said radiation source comprises a selected source strength based upon gamma signal strength required to reach the radiation detector, following scattering in the inspected object.

25. The device as recited in claim 24, wherein said image-generating device includes a modulator comprising a plurality of nodal windows.

26. The device as recited in claim 24, wherein said image-generating device comprises a plurality of voxels.

27. A measurement system comprising:

a modulating unit configured to receive gamma rays scattered from an object irradiated by mono-energetic gamma rays and to modulate gamma fluxes of said scattered gamma rays with a periodic function;

said modulation unit configured to implement an encoding process, wherein said encoding process tags a plurality of solid angle segments of said scattered gamma flux individually with different tags; and

said modulation unit configured to encode said gamma fluxes, wherein said encoded gamma fluxes are used in combination with a scattering process defined by a Compton energy-angle relationship to determine a three-dimensional distribution of local scattered gamma flux within said object.

28. The measurement system as recited in claim 27, wherein said periodic function comprises a time-variant function for varying attenuation of said gamma fluxes.

29. The measurement system as recited in claim 27, wherein said encoding process aids in determining a two-dimensional mass distribution within said object.

30. A measurement system comprising:

a measuring device configured to apply a Compton scattering process to an analysis of gamma rays scattered from an inspected object;

wherein scattering points of said scattered gamma rays having identical energies form an isogonic surface; and

a modulating unit for encoding a two-dimensional cross-section of scattered gamma fluxes.

31. The measurement system as recited in claim 30, wherein said isogonic surface within the inspected object is represented by a thin layer isogonic shell having a thickness related to a spatial resolution of the measurement system.

32. The measurement system as recited in claim 31, wherein an isogonic slice comprises only a portion of said isogonic shell within the inspected object.

33. The measurement system as recited in claim 32, further comprising:

a multi-channel analyzer configured to sort voltage pulse heights associated with detected gamma rays according to a plurality of energies to determine the scattered gamma fluxes associated with scattering from a plurality of voxels contained within said isogonic slice.

34. A three-dimensional density image generating system comprising:

a measuring device configured to identify and separate single-scattered gamma fluxes originating from a plurality of isogonic slices within an object;

wherein said measuring device is configured to determine a spatial distribution of single-scattered gamma fluxs; and

wherein said single-scattered gamma flux determination includes a magnitude of gamma fluxes of said gamma rays arriving from isogonic slices internal to said object, wherein the isogonic slices comprises portions of isogonic shells within said object.

35. A non-invasive three-dimensional density distribution measuring device comprising:

an isotopic source configured to irradiate an object with gamma rays to generate single-scattered gamma photons, wherein said single-scattered gamma photons obey a Compton energy law;

a modulator configured to encode a periodic time-dependent oscillation distributed over a two-dimensional area of single-scattered gamma flux comprising a plurality of said single-scattered gamma photons;

a spectrometer configured to detect energies and intensities of said single-scattered gamma photons; and

a multi-channel pulse-height analyzer configured to sort detected gamma signals according to the energies of the detected gamma photons.

36. The device as recited in claim 35, wherein said single-scattered gamma photons originate from scattering points located in a virtual isogonic shell, associated with a virtual isogonic surface of said virtual isogonic shell;

and

wherein said single-scattered gamma photons originating from identical isogonic surfaces have identical energies.

37. The device as recited in claim 36, wherein said isogonic surface is generated by rotating an isogonic curve about a source-detector segment.

38. The device as recited in claim 37, wherein said virtual isogonic surfaces comprise a plurality of types of oblong rotary surfaces having pointed poles, a sphere, and a dual curvature rotary surface having indented poles.

39. An inspection device comprising:

mono-energetic gamma radiation source configured to irradiate an inspected object with gamma photons;

a gamma photon detection unit configured to detect scattered gamma photons emanating from said inspected object;

a modulation unit configured to encode scattered gammas emanating from the inspected object, enroute toward the gamma photon detection unit;

a time-varying attenuation unit configured to modulate said scattered gammas with a time variation character;

a gamma signal sorting unit configured to sort counts of said detected scattered gamma photons into various energy bins;

a signal splitting unit configured to split output signals from each of said energy bins into multiple equal components;

an electronic function generator unit configured to generate digital signals having time-dependent functions;

a multiplication unit configured to multiply said digital signals with said output signals to form a combined product-function signal;

an integration unit configured to integrate said combined product-function signal to yield a plurality of linear algebraic equations;

an equation-solving unit configured to solve said plurality of linear algebraic equations and produce a determination of local gamma fluxes at at least one point of interest inside the inspected object; and

a data processing unit configured to analyze said determination of said local gamma fluxes and reconstruct an image of density distribution within said inspected object.

40. The device as recited in claim 39, wherein single-scattered gamma fluxes are generated by said inspected object and wherein single-scattered gamma flux generation is a result of a Compton scattering process.

41. The device as recited in claim 39, wherein said modulation unit comprises a plurality of nodal windows.

42. The device as recited in claim 41, wherein attenuators within said plurality of nodal windows are configured to oscillate individually in a different manner to encode said single-scattered gamma fluxes.

43. The device as recited in claim 42, wherein said modulation unit generates a plurality of time-dependencies of the attenuators within said plurality of nodal windows, wherein said plurality of time-dependencies exhibit a different time-dependence function for each of said plurality of nodal windows.

47. The method as recited in claim 41, further comprising the step of positioning the modulating unit between said object and a radiation detector.

48. The method as recited in claim 41, further comprising the step of positioning the modulating unit between said object and a radiation source.

49. The method as recited in claim 41, further comprising the step of encoding cross-sectional segments of the single-scattered gamma flux.

50. The method as recited in claim 41, further comprising the step of providing a rectangular-shaped modulating unit to modulate said single-scattered gamma flux.

51. The method as recited in claim 41, further comprising the step of providing a polar modulating unit to modulate said single-scattered gamma flux.

52. The method as recited in claim 41, further comprising the steps of:

registering of a plurality of single detection events of said single-scattered gamma flux;

measuring energies of scattered gammas in said detection events; and

sorting said detection events based upon said energies of said scattered gammas.

53. The method as recited in claim 52, further comprising the steps of:

analyzing heights of voltage pulses associated with said detection events to identify energies of the detected gamma photons;

applying the Compton energy-angle relationship to the identified energies of the detected gamma photons to determine a spatial origin of scattered gammas; and

measuring an intensity of components of the single-scattered gamma fluxes by registering count rates of the detection events, wherein the components of the single-scattered gamma fluxes represent gamma fluxes arriving at the detector from at least one of different directions and different portions of the inspected object.

54. The method as recited in claim 52, further comprising the step of:

determining a bin-average value of energy for said components of the single-scattered gamma flux based upon a calibration of the energy bins.

55. The method as recited in claim 49, further comprising a step of:

imparting a time-varying attenuation on said single-scattered gamma fluxes to generate a variation of intensity of said single-scattered gamma fluxes as said segments of said single-scattered gamma fluxes pass through each corresponding said nodal window.

56. The method as recited in claim 55, further comprising a step of:

imposing a time-dependent oscillatory attenuation on said segments of said single-scattered gamma fluxes as said scattered gamma fluxes pass through an attenuating element within said nodal window; and

wherein said attenuating element is mounted on a shaft connected to a frame of said rectangular modulating unit and wherein said attenuating element is capable of translatory movement.

57. The method as recited in claim 55, further comprising the steps of:

rotating said attenuating element to vary the intensity of said gamma flux in said polar modulating units.

58. The method as recited in claim 55, further comprising the step of:

encoding said segments of said single-scattered gamma fluxes to help identify a point of scattering from a voxel contained within said object.

59. The method as recited in claim 55, further comprising the step of:

modulating each of said cross-sectional segments of said single-scattered gamma fluxes passing through the modulating unit and directed towards the radiation detector.

60. The method as recited in claim 59, further comprising the step of:

encoding a cross-sectional distribution of said single-scattered gamma fluxes to help locate scattering points within said object.

61. The method as recited in claim 60, wherein said step of encoding generates two-dimensional coordinates indicating origins of the plurality of cross-sectional components of said single-scattered gamma fluxes.

62. The method as recited in claim 59, wherein said step of encoding further comprises modulating said single-scattered gamma fluxes with a periodic trigonometric function such as a sine or cosine function

77. The device as recited in claim 39, wherein the inspection device employs at least one of a multiple number of source energies, a multiple number of source locations and a multiple number of detector locations.

78. The device as recited in claim 77 wherein a relocation of at least one of said mono-energetic gamma radiation source, said gamma photon detection unit, and a change in the at least one of a multiple number of source energies produces a different configuration for said inspection device;

and

wherein said different configuration results in a different set of solvable plurality of linear algebraic equations.

44. A method of generating a three-dimensional density image, comprising:

irradiating an object with gamma photons;

observing segments of single-scattered gamma fluxes of said gamma photons passing through and encoded by a modulating unit; and

modulating each segment of said single-scattered gamma fluxes with a different time-varying attenuation function.

45. The method as recited in claim 44, further comprising the steps of:

detecting individual scattered gamma photons within said single-scattered gamma fluxes;

generating output signals associated with each of said detected individual scattered gamma photons;

counting gamma photon signals generated from detection of said individual scattered gamma photons; and

sorting the counted gamma photon signals into separate bins according to the energy of the counted photons.

46. The method as recited in claim 45, further comprising the steps of determining a volumetric distribution of the single-scattered gamma fluxes within the inspected object and imaging a volumetric density distribution within said object.

63. A method for imaging comprising the steps of:

applying a Compton scattering process to a gamma ray scattered from an inspected object;

defining isogonic surfaces and isogonic shells as loci of scattering points associated with gammas scattered through identical scattering angles; and

using an entire portion of the said isogonic shell within the inspected object to form a locus of said scattering points within the inspected object, from which fluxes of said single-scattered gamma photons having the same energy originate, wherein the entire portion of the isogonic shell within the inspected object defines an isogonic slice.

64. The method as recited in claim 63, further comprising the steps of:

detecting said gamma photons;

sorting the signals from the detected photons according to a plurality of energies; and

analyzing said signals to determine gamma fluxes associated with voxels contained within said isogonic shells.

67. The method as recited in claim 64, further comprising the step of:

calculating the loci of said scattering points, wherein said loci comprises an isogonic surface.

65. A method for generating a three-dimensional image, the method comprising the steps of:

identifying and separating gamma fluxes originating from a plurality of scattering locations from an inspected object; and

formulating a gamma flux calculation procedure, wherein said gamma flux calculation yields magnitudes of single-scattered gamma fluxes arriving from a plurality of known scattering points within identified isogonic slices and eliminates multiple-scattered gamma fluxes arriving from said object and most background fluxes.

66. A method of generating a flux distribution image, comprising the steps of:

irradiating an object with gamma rays to generate single-scattered gamma rays, wherein said single-scattered gamma rays obey the Compton scattering law;

encoding single-scattered gamma flux;

determining energies and intensity levels of said flux of single-scattered gamma rays; and

sorting said energies and measuring flux intensities of segments of the gamma flux to produce a three-dimensional representation of the local single-scattered gamma flux distribution.

68. A method of inspecting comprising the steps of:

irradiating an object with gamma rays;

encoding scattered gamma fluxes by modulating said scattered gamma fluxes with a time variation character;

detecting the single-scattered gamma fluxes of scattered gamma photons transmitted from said object;

generating output voltage pulse height signals from a detector, based upon individual energies of said detected scattered gamma photons;

sorting of registered counts of the detected single-scattered gamma photons into energy bins of a multi-channel analyzer, according to energies of individual single-scattered gamma photons;

splitting the output voltage pulse height signals from the multi-channel analyzer into a plurality of equal sets;

generating electronic digital signal functions;

multiplying components of said output voltage pulse height signals with said digital signal functions to form combined product-function signals;

integrating said combined product-function signals to yield a plurality of linear algebraic equations;

solving said linear algebraic equations; and

reconstructing a mass density field of said object by converting numerical local single-scattered gamma fluxes into local mass densities.

79. The method as recited in claim 68, further comprising the step of determining a three-dimensional density distribution within the inspected object.

69. A modulating unit comprising:

an encoder configured to encode gamma flux scattered from an inspected object as gamma rays irradiated from a source interact with said inspected object, wherein said object generates scattered gamma rays;

a spatial origin identifier configured to identify spatial origins of said gamma rays as said scattered gamma rays pass through said modulating unit; and

at least one nodal window.

70. The modulating unit as recited in claim 69, wherein said at least one nodal window is configured to impart a time-varying attenuation on segments of the gamma flux as said segments of said gamma flux pass through said at least one nodal window.

71. The modulating unit as recited in claim 70, wherein said at least one nodal window is associated with an attenuating element for performing a time-dependent gamma attenuation;

wherein said attenuating element is configured to impose a periodic, time-dependent oscillatory attenuation on said segments of said gamma flux as said scattered gamma flux pass through said attenuating element of said modulating unit; and

wherein said attenuating element is mounted on a vertical shaft within a frame of said modulating unit and wherein said attenuating element is capable of movement in a vertical direction.

72. The modulating unit as recited in claim 71, wherein said time-varying attenuation generates variation of intensity of said gamma flux passing through said at least one nodal window and wherein said variation varies with a rotational movement of said attenuating element.

73. The modulating unit as recited in claim 72, wherein said modulating unit encodes said scattered gamma rays for enabling identification of a point of scattering from at least one voxel contained within said object.

74. The modulating unit as recited in claim 73, wherein said modulating unit includes a plurality of nodal windows containing a plurality of periodically-oscillating gamma attenuators arranged to form a matrix configuration, and wherein said gamma attenuators oscillate with different time-dependent attenuator functions.

75. The modulating unit as recited in claim 74, wherein a first gamma attenuator of said plurality of gamma attenuators within at least one of said plurality of nodal windows is configured to periodically oscillate independently of a second gamma attenuator of said plurality of gamma attenuators.

76. The modulating unit as recited in claim 75, wherein periodic oscillation of said gamma attenuators in the at least one of said plurality of said nodal windows influence at least one of said scattered gamma fluxes passing through the at least one of said nodal windows of said modulating unit enroute towards said radiation detector.

82. The modulating unit as recited in claim 69, wherein the modulating unit is configured to be inserted into a path of a gamma flux, between said inspected object and a detector, for encoding a cross-section of the gamma flux with a unique periodic oscillatory attenuation in each of the at least one nodal windows;

and

wherein said modulating unit is configured to be integrated into a different measuring device to enable a two-dimensional determination of density within said inspected object.

83. The modulating unit as recited in claim 82, further comprising:

a tag configured to indicate an origin of each gamma photon within a two-dimensional cross section of said inspected object.

80. A method of determining an image, the method comprising the steps of:

locating at least two sources having different energies at a same location so that a number of source locations is less than or equal to a number of source energies;

combining the number of source locations and the number of source energies to generate a total number of source configurations; and

multiplying the total number of source configurations by a number of detector locations to indicate a number of solvable equations and to indicate a maximum number of unknown density distributions having solvable solutions.

81. The method as recited in claim 80, further comprising the steps of:

determining multiple density fields in an inspected object comprising multiple substances; and

using the total number of source configurations to determine different density distributions of said total number of source location, wherein said different density distributions represents different substances located within an inspected object.