CT detector having an optical mask layer

• US 7,233,640 B2
• Filed: 12/11/2003
• Issued: 06/19/2007
• Est. Priority Date: 11/26/2003
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Ikhlef, Abdelaziz, Possin, George E., Wen, Li, Zeman, Gregory S.
• Primary Examiner(s): Glick; Edward J.
• Assistant Examiner(s): KAO, CHIH CHENG G
• Application Number:
  US10/707,407
• Publication Number:
  US 20050111612A1
• Time in Patent Office: 1,286 Days
• Field of Search: 378/19, 378/154, 378/98.8, 250/370.11, 250/366, 250/367, 250/368
• US Class Current: 378/19
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: A61B 6/5205 involving processing of raw data to produce diagnostic data
• CPC Class Codes: A61B 6/5282 due to scatter
• CPC Class Codes: G01T 1/20182 Modular detectors, e.g. tiled scintillators or tiled photodiodes stacked detectors G01T1/20181
• CPC Class Codes: G01T 1/20183 Arrangements for preventing or correcting crosstalk, e.g. optical or electrical arrangements for correcting crosstalk

Abstract

An optical mask layer for a CT detector is disclosed and is disposed between the photodiode array and scintillator array of a CT detector. The optical mask layer, which may extend along the x-axis, z-axis, or both, is designed to absorb and/or reflect light emitted the scintillators of the scintillator array. Through this absorption and/or reflection, transference of light photons from a scintillator to the photodiode corresponding to a neighboring scintillator is reduced. This reduction in cross-talk reduces artifacts in a reconstructed image and therefore improves the diagnostic value of the image.

Claims

1. A CT detector comprising:

a scintillator array having a plurality of scintillators arranged along a first plane;

a photodiode array having a plurality of photodiodes arranged along a second plane different from the first plane and parallel to the first plane, and configured to detect illumination of the scintillator array;

the first plane and the second plane orthogonal to a direction of x-ray incidence on the scintillator array; and

an optical mask formed of optical absorbing material and arranged and extended in major part along a third plane parallel to the first and the second planes, and disposed between the scintillator array and the photodiode array without encroachment upon any of the first plane or the second plane, the optical mask configured to reduce optical transference between a scintillator and a neighboring photodiode, the optical mask located closer to the scintillator array than the plurality of photodiodes.

2. The CT detector of claim 1 wherein the optical mask includes a grid of intersecting optical inhibitor elements.

3. The CT detector of claim 2 wherein the grid is dimensionally equivalent to the scintillator array and the photodiode array.

4. The CT detector of claim 1 wherein the optical mask is defined by a plurality of parallel optical inhibitor elements extending transversely along a width of the photodiode array.

5. The CT detector of claim 1 wherein each scintillator/photodiode combination defines a detector cell and wherein the optical mask is configured to reduce cross-talk between adjacent cells.

6. The CT detector of claim 1 wherein at least a majority of the optical mask is disposed adjacent to the scintillator array.

7. A CT system comprising:

a rotatable gantry having a bore centrally disposed therein;

a table movable fore and aft through the bore and configured to position a subject for CT data acquisition;

a high frequency electromagnetic energy projection source positioned within the rotatable gantry and configured to project a high frequency electromagnetic energy fan beam toward the subject; and

a detector array disposed within the rotatable gantry and configured to detect high frequency electromagnetic energy projected by the projection source and impinged by the subject, the detector array including;

an array of scintillators located in a layer;

an array of photodiodes located in a layer; and

an array of optical cross-talk inhibitors formed of optically absorbent material and interstitially layered between, without encroachment upon, the layer of the array of scintillators and the layer of the array of photodiodes, the array of optical cross-talk inhibitors located closer to the layer of the array of scintillators than the array of photodiodes, the array of optical cross-talk inhibitors located in a layer that comprises a substantially same major orientation as the layer of the array of scintillators and the layer of the array of photodiodes.

8. The CT system of claim 7 wherein the array of optical cross-talk inhibitors is fabricated from light absorbent silicon.

9. The CT system of claim 7 wherein the array of optical cross-talk inhibitors is fabricated from opaque materials.

10. The CT system of claim 7 wherein at least a majority of the array of optical cross-talk inhibitors is disposed adjacent to the array of scintillators.

11. A method of CT detector manufacture comprising the steps of:

providing a cellular arrangement of scintillators;

providing a cellular arrangement of photodiodes, each photodiode configured to detect illumination of a corresponding scintillator;

providing an optical cross-talk mask, wherein providing an optical cross-talk mask includes the step of forming a grid of light-absorbing elements; and

arranging the cellular arrangement of scintillators, the cellular arrangement of photodiodes, and the optical cross-talk mask in a multi-planar stack wherein each of the cellular arrangements and the optical cross-talk mask are arranged orthogonal to a central axis of x-ray incidence on the cellular arrangement of scintillators such that the optical cross-talk mask is sandwiched between the cellular arrangement of scintillators and the cellular arrangement of photodiodes, such that the optical cross-talk mask is located closer to the cellular arrangement of scintillators than the cellular arrangement of photodiodes, and such that in the multi-planar stack a plane of the cellular arrangement of scintillators, a plane of the cellular arrangement of photodiodes, and a plane of the optical cross-talk mask comprise a substantially same major orientation.

12. The method of claim 11 wherein the optical cross-talk mask includes a cellular arrangement of mask elements.

13. The method of claim 11 wherein the optical cross-talk mask is formed of one of:

black polyamide;

metal;

doped silicon; and

opaque material(s).

14. The method of claim 11 wherein the optical cross-talk mask is constructed to reduce cross-talk between a scintillator and a neighboring photodiode.

15. The method of claim 11 wherein the step of arranging includes the step of arranging the cellular arrangement of scintillators, the cellular arrangement of photodiodes, and the optical cross-talk mask in the multi-planar stack such that each of the cellular arrangements and the optical cross-talk mask are arranged orthogonal to the central axis of x-ray incidence on the cellular arrangement of scintillators such that at least a majority of the optical cross-talk mask is disposed adjacent to the cellular arrangement of scintillators.

16. A CT detector comprising:

a first scintillator and a second scintillator positioned adjacently to one another and distanced from one another by a given width;

a first photodiode operationally aligned to detect illumination of the first scintillator and a second photodiode operationally aligned to detect illumination of the second scintillator;

at least one mask element of optically absorbing material arranged and extended in major part along a plane disposed between the first and the second scintillators and the first and the second photodiodes to reduce optical transference between the first scintillator and the second photodiode and the second scintillator and the first photodiode, the at least one mask element having a width that exceeds the given width separating the first and the second scintillators from one another, wherein the plane avoids intersection with any of the first scintillator, the second scintillator, the first photodiode, or the second photodiode, the at least one mask element located closer to the first and the second scintillators than the first and the second photodiodes;

wherein the plane comprises a third plane, wherein the first and the second scintillators are arranged along a first plane, wherein the first and the second photodiodes are arranged along a second plane different from the first plane and parallel to the first plane, wherein the first plane and the second plane are orthogonal to a direction of x-ray incidence on the first and the second scintillators, wherein the third plane is parallel to the first and the second planes; and

wherein the at least one mask element of optically absorbing material is arranged and extended in major part along the third plane parallel to the first and the second planes to reduce optical transference between the first scintillator and the second photodiode and the second scintillator and the first photodiode, and disposed between the first and the second scintillators and the first and the second photodiodes without encroachment upon any of the first plane or the second plane.

17. The CT detector of claim 16 wherein the first and the second scintillators are spaced from one another by a lateral gap.

18. The CT detector of claim 16 wherein each scintillator is spaced from its corresponding photodiode by a vertical gap.

19. The CT detector of claim 16 wherein each mask element has a thickness at least equal to a height of the vertical gap.

20. The CT detector of claim 16 wherein the at least one mask element is fabricated of at least black polyamide.

21. The CT detector of claim 16 wherein a portion of the mask element is disposed adjacent to the first and second scintillators.