Method and apparatus for gamma ray detection

• US 6,448,560 B1
• Filed: 07/20/1998
• Issued: 09/10/2002
• Est. Priority Date: 02/02/1996
• Status: Expired due to Term

• Current Assignee: Nova R&D Incorporated (Kromek Group PLC)
• Original Assignee: Tumay O. Tumer
• Inventors: Tümer, Tümay O.
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US09/119,144
• Publication Number:
  US 20020036270A1
• Time in Patent Office: 1,513 Days
• Field of Search: 250/370.09
• US Class Current: 250/370.09
• CPC Class Codes: A61B 6/4258 for detecting non x-ray radiation, e.g. gamma radiation A61B6/037 takes precedence
• CPC Class Codes: G01T 1/006 Total absorption calorimeters; Shower detectors
• CPC Class Codes: G01T 1/1647 Processing of scintigraphic data not related to a particular imaging system G01T1/2992
• CPC Class Codes: G01T 1/2928 using solid state detectors

Abstract

A high sensitivity, three-dimensional gamma ray detection and imaging system is provided. The system uses the Compton double scatter technique with recoil electron tracking. The system preferably includes two detector subassemblies; a silicon microstrip hodoscope and a calorimeter. In this system 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.

Claims

1. A method of imaging a portion of a human body, the method comprising the steps of:

providing a radiopharmaceutical to said portion of said human body, said radiopharmaceutical producing gamma ray photons;

positioning a detection system proximate to said portion of said human body, wherein said detection system is comprised of a hodoscope and a calorimeter, wherein said hodoscope is comprised of a plurality of detector planes;

determining a direction and an energy for a portion of said gamma ray photons entering said detection system from a plurality of hodoscope output signals and from a plurality of calorimeter output signals;

processing said direction and energy data for said portion of gamma ray photons; and

displaying an image of said portion of said human body, wherein said image is based on said processed direction and energy data.

2. The method of claim 1, wherein said portion of said human body is an organ.

3. The method of claim 1, wherein said portion of said human body is a breast.

4. The method of claim 1, further comprising the step of positioning a shielding member around an entrance of said detection system, wherein said shielding member limits background gamma ray photons.

5. The method of claim 1, further comprising the steps of:

positioning a second detection system proximate to said portion of said human body, wherein said second detection system is comprised of a second hodoscope and a second calorimeter, wherein said second hodoscope is comprised of a second plurality of detector planes;

determining a second direction and a second energy for said portion of gamma ray photons entering said second detection system from a plurality of second hodoscope output signals and from a plurality of second calorimeter output signals;

processing said second direction and second energy data for said portion of gamma ray photons; and

displaying a three-dimensional image of said portion of said human body, wherein said image is based on said processed first and second direction data and said first and second energy data.

6. The method of claim 1, further comprising the steps of:

repositioning said detection system proximate to said portion of said human body;

determining a second direction and a second energy for said portion of gamma ray photons entering said detection system;

processing said second direction and second energy data for said portion of gamma ray photons; and

displaying a three-dimensional image of said portion of said human body, wherein said image is based on said processed first and second direction data and said first and second energy data.

7. The method of claim 1, wherein said processing step comprises applying a data analysis technique selected from the group consisting of a Radon transform and back projection technique, a Maximum Likelihood and Maximum Entropy technique, a Direct Linear Algebraic Deconvolution technique, and a Constrained Linear Algebraic Deconvolution technique.

8. The method of claim 1, wherein full energy of a gamma ray photon is determined by adding all of the energy deposited at said hodoscope and said calorimeter.

9. A medical imaging system for imaging a portion of a living organism, said portion treated with a radiopharmaceutical, said radiopharmaceutical emitting gamma ray photons, comprising:

a hodoscope comprised of a plurality of silicon detection planes, wherein an entrance aperture of said hodoscope is external to said living organism and proximate to said portion of said living organism, wherein emitted gamma ray photons pass into said hodoscope and are scattered within said hodoscope;

a multi-channel readout system coupled to said plurality of silicon detection planes;

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

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

10. The medical imaging system of claim 9, wherein a portion of said emitted gamma ray photons 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 gamma ray photons, wherein a total energy corresponding to each of said portion of said emitted gamma ray photons 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 gamma ray photons is combined by said processor to generate said image.

11. The medical imaging system of claim 9, wherein a recoil electron is formed by a portion of said emitted gamma ray photons 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.

12. The medical imaging system of claim 9, further comprising a calorimeter enclosing a portion of said hodoscope, wherein said calorimeter is coupled to said multi-channel readout system.

13. The medical imaging system of claim 12, wherein said scattered gamma ray photons passing through said hodoscope form recoil electrons during passage through said plurality of silicon detection 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 ray photons are totally absorbed within said calorimeter, and wherein an energy of said absorbed gamma ray photons is determined by said calorimeter.

14. The medical imaging system of claim 12, further comprising a shielding member proximate to said hodoscope entrance aperture positioned to limit background gamma ray photons.

15. The medical imaging system of claim 12, wherein said calorimeter is selected from the group of calorimeter detector materials consisting of HPGe, BGO, CdWO₄, CsF, NaI(Tl), CsI(Na), CsI(Tl), CdTe, CdZnTe, HgI₂, GaAs, and PbI₂.

16. The medical imaging system of claim 12, wherein said calorimeter is comprised of CdZnTe detectors selected from the group consisting of CdZnTe strip detectors, CdZnTe pad detectors, and CdZnTe pixel detectors.

17. The medical imaging system of claim 12, wherein said calorimeter is comprised of CsI(Tl) crystals coupled to PIN photodiodes.

18. The medical imaging system of claim 12, wherein said calorimeter is comprised of multiple calorimetry layers.

19. The medical imaging system of claim 12, wherein said portion of said hodoscope enclosed by said calorimeter is a side portion.

20. The medical imaging system of claim 12, wherein said portion of said hodoscope enclosed by said calorimeter is a back portion, wherein said back portion is opposed to said hodoscope entrance aperture.

21. The medical imaging system of claim 12, further comprising a slot collimator proximate to said hodoscope entrance aperture.

22. The medical imaging system of claim 9, wherein said radiopharmaceutical is selected from the group consisting of thallium-201, technetium-99m, iodine-123, iodine-131, and fluorine-18.

23. The medical imaging system of claim 9, 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.

24. The medical imaging system of claim 9, wherein said plurality of silicon detection planes have a predetermined orientation with respect to said entrance aperture, said predetermined orientation selected from the group consisting of parallel, perpendicular, or an angle.

25. The medical imaging system of claim 9, wherein each of said plurality of silicon detection planes is comprised of at least two bridged silicon detectors, wherein said silicon detectors are selected from the group consisting of strip and microstrip detectors.

26. The medical imaging system of claim 9, wherein each of said plurality of silicon detection planes has a corresponding thickness within a range of about 100 micrometers to about 5 millimeters.

27. The medical imaging system of claim 9, wherein said plurality of silicon detection planes are separated by a distance of between about 0.2 and 2 centimeters.

28. The medical imaging system of claim 9, wherein said plurality of silicon detection planes is between 10 and 25 silicon detection planes.

29. The medical imaging system of claim 9, said processor applying a data analysis technique selected from the group consisting of a Radon transform and back projection technique, a Maximum Likelihood and Maximum Entropy technique, a Direct Linear Algebraic Deconvolution technique, and a Constrained Linear Algebraic Deconvolution technique.

30. The medical imaging system of claim 9, wherein said emitted gamma ray photons have an energy within a range of about 40 keV to about 2,000 keV.

31. The medical imaging system of claim 9, 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.

32. The method of claim 9, wherein full energy of a gamma ray photon is determined by adding all of the energy deposited at the hodoscope and a calorimeter.