Nuclear imaging system using scintillation bar detectors and method for event position calculation using the same

• US 20050006589A1
• Filed: 06/27/2003
• Published: 01/13/2005
• Est. Priority Date: 06/27/2003
• Status: Active Grant

• Current Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Original Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Inventors: Joung, Jinhun, Chowdhury, Samir, Engdahl, John C.
• Granted Patent: US 7,238,946 B2
• Time in Patent Office: Days
• US Class Current: 250/370.90
• CPC Class Codes: G01T 1/20182 Modular detectors, e.g. tiled scintillators or tiled photodiodes stacked detectors G01T1/20181
• CPC Class Codes: G01T 1/20187 Position of the scintillator with respect to the photodiode, e.g. photodiode surrounding the crystal, the crystal surrounding the photodiode, shape or size of the scintillator
• CPC Class Codes: G01T 1/202 the detector being a crystal

Abstract

A gamma camera having a scintillation detector formed of multiple bar detector modules. The bar detector modules in turn are formed of multiple scintillation crystal bars, each being designed to have physical characteristics, such as light yield, to achieve a sufficient spatial resolution for nuclear medical imaging applications. According to another aspect of the invention, the bar detector modules are arranged in a three-dimensional array, where each module is made up of a two-dimensional array of bar detectors with at least one photosensor optically coupled to each end of the module. Such a camera can be used for both PET (coincidence) and single photon imaging applications. According to another aspect of the invention, a bar detector gamma camera is provided, which utilizes an improved positioning algorithm that greatly enhances spatial resolution in the z-axis direction (i.e., the direction along the length of the scintillation crystal bar).

Claims

1. A gamma camera, comprising:

a plurality of bar detector modules, each comprising

a plurality of elongated scintillation crystal bars, each bar having two end surfaces, said plurality of bars being arranged in a two-dimensional array with respect to said end surfaces, and

at least two photosensors, each optically coupled to a respective end of said module, for detecting

a scintillation interaction of a gamma photon with one of said bars; and

a position calculator for determining the spatial location of a detected scintillation interaction in the elongated dimension of a scintillation crystal bar, according to the formula;

$\hat{z}=\underset{\forall <br><br>z}{\arg }<br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{z=\hat{z}}{\min }<br><br>\left(\frac{{\left(R-{\mathrm{\mu <br><br>}}_R<br><br>\left(z\right)\right)}^2}{{\mathrm{\sigma <br><br>}}_R^2<br><br>\left(z\right)}\right)$

where z is the elongated dimension of said bar,

$R=\frac{E_1-E_2}{E_1+E_2},$

E₁=the total energy detected at a first end of said bar,

E₂=the total energy detected at a second end of said bar,

μ

R=the mean of ratio R at a given location z, and

σ

R=the variance of the ratio R at a given location z.

2. The gamma camera of claim 1, wherein said at least two photosensors comprise photomultiplier tubes.

3. The gamma camera of claim 1, wherein said at least two photosensors comprise position-sensitive photomultiplier tubes.

4. The gamma camera of claim 1, wherein said at least two photosensors comprise photodiode arrays.

5. The gamma camera of claim 1, wherein said scintillation crystal bars are formed of CsI.

6. The gamma camera of claim 1, wherein said scintillation crystal bars are formed of LaBr3.

7. The gamma camera of claim 1, wherein said scintillation crystal bars are formed of LaCl3.

8. The gamma camera of claim 1, wherein said scintillation crystal bars have grounded elongated surfaces.

9. The gamma camera of claim 8, wherein said grounded elongated surfaces are sealed with a high reflectivity material for increasing optical isolation and maximizing light collection.

10. The gamma camera of claim 1, wherein said camera is used for SPECT imaging applications.

11. A gamma camera, comprising:

a plurality of bar detector modules arranged in a three-dimensional array, each of said modules comprising

a plurality of elongated scintillation crystal bars, each bar having two end surfaces, said plurality of bars being arranged in a two-dimensional array with respect to said end surfaces, and

at least two photosensors, each optically coupled to a respective end of said module.

12. The gamma camera of claim 11, wherein said at least two photosensors comprise photomultiplier tubes.

13. The gamma camera of claim 11, wherein said at least two photosensors comprise position-sensitive photomultiplier tubes.

14. The gamma camera of claim 11, wherein said at least two photosensors comprise photodiode arrays.

15. The gamma camera of claim 11, wherein said scintillation crystal bars are formed of CsI.

16. The gamma camera of claim 11, wherein said scintillation crystal bars are formed of LaBr3.

17. The gamma camera of claim 11, wherein said scintillation crystal bars are formed of LaCl3.

18. The gamma camera of claim 11, wherein said scintillation crystal bars have grounded elongated surfaces.

19. The gamma camera of claim 18, wherein said grounded elongated surfaces are sealed with a high reflectivity material for increasing optical isolation and maximizing light collection.

20. The gamma camera of claim 11, wherein said camera is used for SPECT imaging applications.

21. A gamma camera, comprising:

a plurality of bar detector modules, each comprising

a plurality of elongated scintillation crystal bars, each bar having two end surfaces and at least one elongated surface, said plurality of bars being arranged in a two-dimensional array with respect to said end surfaces, and

at least two photosensors, each optically coupled to a respective end of said module, for detecting

a scintillation interaction of a gamma photon with one of said bars;

wherein

said elongated surfaces of said bars are sealed with a high reflectivity material for increasing optical isolation and maximizing light collection.

22. The gamma camera of claim 21, wherein said at least two photosensors comprise photomultiplier tubes.

23. The gamma camera of claim 21, wherein said at least two photosensors comprise position-sensitive photomultiplier tubes.

24. The gamma camera of claim 21, wherein said at least two photosensors comprise photodiode arrays.

25. The gamma camera of claim 21, wherein said scintillation crystal bars are formed of CsI.

26. The gamma camera of claim 21, wherein said scintillation crystal bars are formed of LaBr3.

27. The gamma camera of claim 21, wherein said scintillation crystal bars are formed of LaCl3.

28. The gamma camera of claim 21, wherein said elongated surfaces of said scintillation crystal bars are grounded.

29. The gamma camera of claim 21, wherein said camera is used for SPECT imaging applications.