Method and apparatus for radiation detection

• US 20030006376A1
• Filed: 06/20/2002
• Published: 01/09/2003
• Est. Priority Date: 02/02/1996
• Status: Abandoned Application

• Current Assignee: Tumay O. Tumer
• Original Assignee: Tumay O. Tumer
• Inventors: Tumer, Tumay O.
• Application Number:
  US10/175,084
• Publication Number:
  US 20030006376A1
• Time in Patent Office: Days
• US Class Current: 250/370.09
• CPC Class Codes: A61B 6/037 Emission tomography
• CPC Class Codes: G01T 1/006 Total absorption calorimeters; Shower detectors
• CPC Class Codes: G01T 1/2928 using solid state detectors
• CPC Class Codes: G01T 1/2985 In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); using external radiation sources A61B6/02
• CPC Class Codes: H01L 27/14659 Direct radiation imagers structures
• CPC Class Codes: H01L 31/115 Devices sensitive to very short wavelength, e.g. X-rays, gamma-rays or corpuscular radiation

Abstract

A detection system is provided. In one embodiment a silicon Compton recoil electron detector uses the Compton double scatter technique with recoil electron tracking to detect medium energy gamma rays from 0.05 to 10 MeV. Two detector layers are required, a silicon microstrip hodoscope and a calorimeter. The incoming photon Compton scatters in the hodoscope. The second scatter layer is the calorimeter where the scattered gamma ray is totally absorbed. The recoil electron in the hodoscope is tracked through several detector planes until it stops. The x and y position signals from the first two planes of the electron track determine the direction of the recoil electron while the energy loss from all planes determines the energy of the recoil electron. In another embodiment of the invention, the Compton double scatter technique with recoil electron tracking is used to detect x-rays from 300 to 5,000 keV. This embodiment is useful for nondestructive, real time imaging, for example for use in medical imaging and the inspection of munition items. In another embodiment, a high sensitivity, high spatial resolution and electronically collimated single photon emission computed tomography system which is sensitive from 81 keV to 511 keV gamma ray photons is provided. In another embodiment, a Compton scatter positron emission tomography system is provided.

Claims

1. A imaging system for imaging an object, comprising:

an x-ray source emitting x-rays;

a detection system comprised of a hodoscope, wherein said object is located between said x-ray source and said hodoscope, said hodoscope comprised of a plurality of position sensitive detector planes, wherein a portion of said x-rays passing through said object pass into said hodoscope and are scattered within said hodoscope;

a multi-channel readout system coupled to said plurality of position sensitive detector planes;

a shielding member, said shielding member substantially preventing exposure of said multi-channel readout system to said emitted x-rays;

a processor coupled to said multi-channel readout system; and

a monitor coupled to said processor, said monitor displaying an image of said object.

2. The imaging system of claim 1, wherein said shield collimates said emitted x-rays.

3. The imaging system of claim 1, wherein said plurality of position sensitive detector planes is comprised of a plurality of silicon detection planes.

4. The imaging system of claim 3, wherein each of said plurality of silicon detection planes has an area between 4 square centimeters and 1,000 square centimeters.

5. The imaging system of claim 3, wherein each of said plurality of silicon detection planes has an area between 16 square centimeters and 144 square centimeters.

6. The imaging system of claim 3, wherein each of said plurality of silicon detection planes has a thickness between about 0.1 and about 10 millimeter.

7. The imaging system of claim 3, wherein each of said plurality of silicon detection planes has a thickness between about 0.5 and about 1 millimeter.

8. The imaging system of claim 3, wherein a portion of said emitted x-rays undergo at least one Compton scatter within said plurality of silicon detection planes to yield a track direction corresponding to each of said portion of emitted x-rays, wherein a total energy corresponding to each of said portion of said emitted x-rays is absorbed within said plurality of silicon detection planes, and wherein said track direction and said total energy corresponding to each of said portion of emitted x-rays is combined by said processor to generate said image.

9. The imaging system of claim 3, wherein a recoil electron is formed by a portion of said emitted x-rays undergoing Compton scatter within said plurality of silicon detection planes, said recoil electron passing through a portion of said plurality of silicon detection planes, wherein a position of said recoil electron is recorded for each of said portion of said plurality of silicon detection planes.

10. The imaging system of claim 3, wherein said plurality of silicon detection planes have a predetermined orientation with respect to said emitted x-rays, said predetermined orientation selected from the group consisting of parallel, perpendicular, or an angle.

11. The imaging system of claim 3, wherein said plurality of silicon detection planes is selected from the group consisting of silicon microstrip detectors, silicon strip detectors, silicon pad detectors, silicon pixel detectors, double-sided silicon microstrip detectors, and double-sided silicon strip detectors.

12. The imaging system of claim 1, wherein said plurality of position sensitive detector planes is selected from the group consisting of CdTe microstrip detectors, CdTe strip detectors, CdTe pad detectors, CdTe pixel detectors, double-sided CdTe microstrip detectors, double-sided CdTe strip detectors, CdZnTe microstrip detectors, CdZnTe strip detectors, CdZnTe pad detectors, CdZnTe pixel detectors, double-sided CdZnTe microstrip detectors, and double-sided CdZnTe strip detectors

13. The imaging system of claim 1, wherein said emitted x-rays have an energy in the range of 50 to 600 keV.

14. The imaging system of claim 1, wherein said emitted x-rays have an energy in the range of 600 to 5000 keV.

15. The imaging system of claim 1, wherein said emitted x-rays are monoenergetic.

16. The imaging system of claim 1, wherein said emitted x-rays are from a radioactive source with multiple emission lines.

17. The imaging system of claim 1, wherein said x-ray source is a continuous energy x-ray source.

18. The imaging system of claim 1, said detection system further comprising a calorimeter at least partially enclosing said hodoscope.

19. The imaging system of claim 18, wherein said calorimeter is shielded from said emitted x-rays not passing through said object.

20. The imaging system of claim 18, wherein said calorimeter is comprised of CsI(Tl) crystals.

21. The imaging system of claim 20, wherein said CsI(Tl) crystals are coupled to PIN photodiodes.

22. The imaging system of claim 18, wherein said calorimeter is selected from the group of calorimeter detector materials consisting of HPGe, BGO, LSO, GSO, CdWO₄, CsF, NaI(Tl), CsI(Na), CsI(Tl), CdTe, CdZnTe, HgI₂, GaAs, and PbI₂.

23. The imaging system of claim 1, further comprising a rotation stage coupled to said object, wherein said rotation stage rotates said object relative to said detection system, wherein said image is a three-dimensional tomographic image.

24. The imaging system of claim 17, wherein said image includes energy spectrum information.

25. The imaging system of claim 24, wherein different energy spectra of said energy spectrum information are represented in said image by different colors.

26. The imaging system of claim 25, wherein an intensity corresponding to each of said different energy spectra is represented by a color intensity corresponding to said different colors.

27. The imaging system of claim 1, wherein said image is a two-dimensional image.

28. The imaging system of claim 1, wherein said image is a three-dimensional image.

29. The imaging system of claim 18, wherein said calorimeter is coupled to said multi-channel readout system.

30. The imaging system of claim 18, wherein said scattered x-rays passing through said hodoscope form recoil electrons during passage through said plurality of position sensitive detector planes, wherein said hodoscope determines a track direction by a first scatter vertex and an energy associated with said recoil electrons, wherein said scattered x-rays are totally absorbed within said calorimeter, and wherein an energy of said absorbed x-rays is determined by said calorimeter.

31. The imaging system of claim 1, comprising a second shielding member proximate to an entrance aperture of said hodoscope.

32. The imaging system of claim 3, wherein said multi-channel readout system is comprised of ASIC chips, wherein said plurality of silicon detection planes is comprised of silicon strip detectors, and wherein said strips are fanned in to match a chip bonding pitch corresponding to said ASIC chips.

33. A positron emission tomography system for imaging a portion of a living organism, said portion treated with a radionuclides, said radionuclide emitting positrons, said emitted positrons creating photon pairs within said portion of said living organism, said system comprising:

a first and a second detection system, said portion of said living organism interposed between said first and second detection systems, wherein said first and second detection systems are diametrically opposed, wherein said first and second detection systems are comprised of a plurality of position sensitive strip detectors, wherein a portion of said photons undergo multiple Compton scatters within said detection systems;

means for rotating the relative positions of said first and second detection systems to said portion of said living organism;

a multi-channel readout system coupled to said plurality of position sensitive strip detectors;

a processor coupled to said multi-channel readout system, said processor determining track directions and total energies for said portion of said photons; and

a monitor coupled to said processor, said monitor displaying an image of said portion of said living organism.

34. The positron emission tomography system of claim 33, said rotation means comprising a rotation stage coupled to said first and second detection systems for rotating said detection systems relative to said portion of said living organism.

35. The positron emission tomography system of claim 33, said rotation means comprising a rotation stage coupled to said living organism for rotating said portion of said living organism relative to said first and second detection systems.

36. A positron emission tomography system for imaging a portion of a living organism, said portion treated with a radionuclide, said radionuclide emitting positrons, said emitted positrons creating photon pairs within said portion of said living organism, said system comprising:

a plurality of detection systems at least partially surrounding said portion of said living organism, wherein said plurality of detection systems are comprised of diametrically opposed detection system pairs, wherein each of said plurality of detection systems is comprised of a hodoscope, each of said hodoscopes comprised of a plurality of position sensitive detectors, wherein a portion of said photons undergo Compton scatters within said detection systems;

a multi-channel readout system coupled to said plurality of position sensitive strip detectors;

a processor coupled to said multi-channel readout system, said processor determining track directions and total energies for said portion of said photons; and

a monitor coupled to said processor, said monitor displaying an image of said portion of said living organism.

37. The positron emission tomography system of claim 36, said radionuclide selected from the group consisting of carbon-11, nitrogen-13, oxygen-15, fluorine-18, gallium-68, bromine-75, and strontium-82.

38. The positron emission tomography system of claim 36, wherein said position sensitive detectors are CdZnTe strip detectors.

39. The positron emission tomography system of claim 36, said plurality of detection systems further comprising a plurality of calorimeters, said calorimeters positioned proximate an end portion of each of said hodoscopes.

40. The positron emission tomography system of claim 39, wherein said plurality of calorimeters are CdZnTe calorimeters.

41. The positron emission tomography system of claim 36, further comprising passive septa interposed between said detection systems.

42. The positron emission tomography system of claim 36, further comprising active septa interposed between said detection systems, wherein said active septa are calorimeters.

43. The positron emission tomography system of claim 36, wherein said position sensitive detectors are selected from the group consisting of pad detectors and strip detectors.

44. A radiation detector for detecting gamma rays, comprising:

a detector aperture, said aperture limiting said detector to a predetermined field-of-view;

a detection system comprised of a hodoscope, said hodoscope comprised of a plurality of position sensitive detector planes, wherein a portion of said gamma rays pass through said aperture into said hodoscope and are scattered within said hodoscope;

a multi-channel readout system coupled to said detection system;

a processor coupled to said multi-channel readout system; and

an output device coupled to said multi-channel readout system, said output device outputting information corresponding to said detected gamma rays.

45. The radiation detector of claim 44, wherein said plurality of position sensitive detector planes is comprised of a plurality of silicon detection planes.

46. The radiation detector of claim 44, wherein said gamma rays have an energy between about 0.05 and 10 MeV.

47. The radiation detector of claim 44, wherein said output device is a monitor, said monitor displaying an image corresponding to said detected gamma rays.

48. The radiation detector of claim 45, wherein a portion of said gamma rays undergo at least one Compton scatter within said plurality of silicon detection planes to yield a track direction corresponding to each of said portion of gamma rays, wherein a total energy corresponding to each of said portion of said gamma rays is absorbed within said plurality of silicon detection planes, and wherein said track direction and said total energy corresponding to each of said portion of gamma rays is combined by said processor to generate said outputted information.

49. The radiation detector of claim 45, wherein a recoil electron is formed by a portion of said gamma rays undergoing Compton scatter within said plurality of silicon detection planes, said recoil electron passing through a portion of said plurality of silicon detection planes, wherein a position of said recoil electron is recorded for each of said portion of said plurality of silicon detection planes.

50. The radiation detector of claim 45, wherein said plurality of silicon detection planes have a predetermined orientation with respect to said gamma rays, said predetermined orientation selected from the group consisting of parallel, perpendicular, or an angle.

51. The radiation detector of claim 45, wherein said plurality of silicon detection planes is selected from the group consisting of silicon microstrip detectors, silicon strip detectors, silicon pad detectors, silicon pixel detectors, double-sided silicon microstrip detectors, and double-sided silicon strip detectors.

52. The radiation detector of claim 44, wherein said plurality of position sensitive detector planes is selected from the group consisting of CdTe microstrip detectors, CdTe strip detectors, CdTe pad detectors, CdTe pixel detectors, double-sided CdTe microstrip detectors, double-sided CdTe strip detectors, CdZnTe microstrip detectors, CdZnTe strip detectors, CdZnTe pad detectors, CdZnTe pixel detectors, double-sided CdZnTe microstrip detectors, and double-sided CdZnTe strip detectors.

53. The radiation detector of claim 44, said detection system further comprising a calorimeter at least partially enclosing said hodoscope.

54. The radiation detector of claim 53, wherein said calorimeter is coupled to said multi-channel readout system.

55. The radiation detector of claim 53, wherein said calorimeter is selected from the group of calorimeter detector materials consisting of HPGe, BGO, LSO, GSO, CdWO₄, CsF, NaI(Tl), CsI(Na), CsI(Tl), CdTe, CdZnTe, HgI₂, GaAs, and PbI₂.

56. The radiation detector of claim 53, wherein said scattered gamma rays passing through said hodoscope form recoil electrons during passage through said plurality of position sensitive detector planes, wherein said hodoscope determines a track direction by a first scatter vertex and an energy associated with said recoil electrons, wherein said scattered gamma rays are totally absorbed within said calorimeter, and wherein an energy of said absorbed gamma rays is determined by said calorimeter.

57. The radiation detector of claim 45, wherein said multi-channel readout system is comprised of ASIC chips, wherein said plurality of silicon detection planes is comprised of silicon strip detectors, and wherein said strips are fanned in to match a chip bonding pitch corresponding to said ASIC chips.

58. The radiation detector of claim 53, further comprising an anti-coincidence shield substantially surrounding said hodoscope, said anti-coincidence shield not covering said detector aperture.

59. The radiation detector of claim 53, further comprising an anti-coincidence shield substantially surrounding said calorimeter.

60. The radiation detector of claim 53, said detection system further comprising a position sensitive detection layer interposed between said hodoscope and said calorimeter.

61. The radiation detector of claim 53, said position sensitive detection layer having a thickness between about 0.1 millimeter and 1 centimeter.

62. The radiation detector of claim 44, further comprising a scout interceptor missile, wherein said detection system is located within said scout interceptor missile.

63. The radiation detector of claim 62, wherein a portion of said gamma rays is emitted by warheads.

64. The radiation detector of claim 63, wherein said warheads are launched from an ICBM bus.

65. The radiation detector of claim 63, wherein said warheads are irradiated by an external source.

66. The radiation detector of claim 65, wherein said external source is selected from the group consisting of directed energy sources, particle beams, and neutron bombs.

67. The radiation detector of claim 62, wherein a portion of said gamma rays is emitted by a nuclear powered satellite.