CT detector having a segmented optical coupler and method of manufacturing same

• US 7,173,998 B2
• Filed: 06/09/2006
• Issued: 02/06/2007
• Est. Priority Date: 03/12/2003
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Hoffman, David M., Hoge, Michael F.
• Primary Examiner(s): Thomas; Courtney
• Application Number:
  US11/423,277
• Publication Number:
  US 20060233299A1
• Time in Patent Office: 242 Days
• Field of Search: 378/4, 378/19, 378/98.8, 378/154, 378/147, 378/149, 250/370.09, 250/370.11, 250/368, 250/370.08
• US Class Current: 378/19
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 2223/612 biological material
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: G01T 1/2002 Optical details, e.g. reflecting or diffusing layers
• CPC Class Codes: G01T 1/20183 Arrangements for preventing or correcting crosstalk, e.g. optical or electrical arrangements for correcting crosstalk
• CPC Class Codes: G01T 1/20185 Coupling means between the photodiode and the scintillator, e.g. optical couplings using adhesives with wavelength-shifting fibres
• CPC Class Codes: G01T 1/202 the detector being a crystal
• 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

Abstract

The present invention is a directed to a CT detector for a CT imaging system that incorporates a segmented optical coupler between a photodiode array and a scintillator array. The segmented optical coupler also operates as a light collimator which improves the light collection efficiency of the photodiode array. The segmented optical coupler is defined by a series of reflector elements that collectively form a plurality of open cells. The open cells form light transmission cavities and facilitate the collimation of light from a scintillator to a photodiode. The cavities may be filled with optical epoxy for sealing to the photodiode array.

Claims

1. 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 high frequency electromagnetic energy 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, wherein the detector array comprises;

a plurality of scintillators arranged in a scintillator array;

a plurality of photodiodes arranged in a photodiode array that comprises a light reception substantially planar surface; and

a 2D gridded light collimator plate array having a plurality of collimator plates that collectively define a plurality of light transmission cavities disposed between the plurality of scintillators and the plurality of photodiodes, the plurality of collimator plates formed of light reflective material and arranged such that each light transmission cavity is disposed entirely between the light reception substantially planar surface of the photodiode array and a light emission surface of a scintillator;

wherein the 2D gridded light collimator plate array extends to the light reception substantially planar surface of the photodiode array substantially without encroachment past the light reception substantially planar surface of the photodiode array.

2. The CT system of claim 1, wherein the detector array includes a thin film optical coupler that secures the 2D gridded light collimator plate array to the light reception substantially planar surface of the photodiode array.

3. The CT system of claim 2, wherein the thin film optical coupler comprises an optical coupling film or resin that coats the plurality of collimator plates and secures the plurality of collimator plates to the plurality of photodiodes at the light reception substantially planar surface.

4. The CT system of claim 1, wherein the plurality of collimator plates is bonded to the light reception substantially planar surface of the photodiode array.

5. The CT system of claim 1, wherein the plurality of light transmission cavities is filled with an optical epoxy that permits transmission of light between the scintillator array and the photodiode array and operates as adhesive to secure the scintillator array to the photodiode array.

6. The CT system of claim 1, wherein the plurality of light transmission cavities is filled with a thermoplastic that operates as adhesive to secure the photodiode array to the scintillator array.

7. The CT system of claim 1, wherein the detector array comprises a plurality of reflector elements that extend as a reflector wall between adjacent instances of the plurality of scintillators, wherein the plurality of collimator plates and the plurality of reflector elements comprise a substantially same material.

8. The CT system of claim 7, wherein the scintillator array is integrated with the plurality of reflector elements, wherein the plurality of collimator plates and the plurality of reflector elements are unitary and extend to the light reception substantially planar surface of the photodiode array substantially without encroachment past the light reception substantially planar surface of the photodiode array.

9. The CT system of claim 7, wherein the detector array comprises a reflector layer that coats a high frequency electromagnetic energy reception surface of the plurality of scintillators, wherein the plurality of reflector elements is integrated with the reflector layer;

wherein the plurality of collimator plates, the plurality of reflector elements, and the reflector layer comprise the substantially same material, wherein the substantially same material allows the high frequency electromagnetic energy projected from the high frequency electromagnetic energy projection source to pass therethrough and reflects light generated by the plurality of scintillators toward the plurality of photodiodes.

10. The CT system of claim 1, wherein the plurality of light transmission cavities comprises a series of cells defined by semiconductor material and vertically aligned with light emission surfaces of the scintillator array and/or light reception surfaces of the light reception substantially planar surface the photodiode array.

11. The CT system of claim 10, wherein the series of cells defined by the semiconductor material are filled with an optical epoxy that permits transmission of light between the scintillator array and the photodiode array and operates as adhesive to secure the scintillator array to the photodiode array.

12. The CT system of claim 1, wherein the 2D gridded light collimator plate array comprises a grid that defines a plurality of cells dimensionally equivalent to the plurality of scintillators and the plurality of photodiodes.

13. The CT system of claim 1 wherein each light transmission cavity collimates light between a single scintillator and a single photodiode.

14. The CT system of claim 1, wherein the plurality of collimator plates comprises a plurality of substantially uniform cross-section collimator plates arranged such that each light transmission cavity is disposed entirely between the light reception substantially planar surface of the photodiode array and a light emission surface of a scintillator and that extends to the light reception substantially planar surface of the photodiode array substantially without encroachment past the light reception substantially planar surface of the photodiode array.

15. The CT system of claim 1, wherein the 2D gridded light collimator plate array comprises a grid that defines a plurality of cells dimensionally equivalent to a respective immediately adjacent plurality of emission surfaces of the scintillator array and a respective immediately adjacent plurality of light reception surfaces, of the light reception substantially planar surface, of the photodiode array.

16. The CT system of claim 9, wherein the high frequency electromagnetic energy reception surface of the plurality of scintillators comprises a high frequency electromagnetic energy reception substantially planar surface of the scintillator array that is substantially parallel with the light reception substantially planar surface of the photodiode array.

17. A CT scanner having a detector array designed to convert received x-rays to electrical signals that can be processed to reconstruct a CT image, the detector array comprising:

a scintillator array;

a photodiode array that comprises a light reception substantially planar surface; and

a light collimator array formed between the scintillator array and the photodiode array, the light collimator array arranged to sit atop the light reception substantially planar surface of the photodiode array, substantially without encroachment past the light reception substantially planar surface of the photodiode array, and define a single optical transmission window between an aligned scintillator and an aligned photodiode, wherein the light collimator array is defined by a 2D grid of collimator plates, each collimator plate including light reflective material.

18. The CT scanner of claim 17, wherein the light collimator array is bonded to at least one of the scintillator array and the light reception substantially planar surface of the photodiode array.

19. The CT scanner of claim 17, wherein each collimator plate further includes x-ray absorbent material.

20. The CT scanner of claim 17, wherein voids defined between adjacent collimator plates are epoxy-filled.

21. The CT scanner of claim 17, wherein the light collimator array comprises a plurality of substantially uniform cross-section collimator plates arranged to sit atop the light reception substantially planar surface of the photodiode array, substantially without encroachment past the light reception substantially planar surface of the photodiode array, and define a single optical transmission window between an aligned scintillator and an aligned photodiode.

22. The CT scanner of claim 17, wherein the detector array comprises a plurality of reflector elements that extend as a reflector wall between adjacent instances of a plurality of scintillators of the scintillator array;

wherein the detector array comprises a reflector layer that coats a high frequency electromagnetic energy reception substantially planar surface of the scintillator array that is substantially parallel with the light reception substantially planar surface of the photodiode array, wherein the plurality of reflector elements is integrated with the reflector layer;

wherein the 2D grid of collimator plates, the plurality of reflector elements, and the reflector layer comprise a substantially same material that allows the received x-rays to pass therethrough and reflects light generated by the plurality of scintillators toward a plurality of photodiodes of the photodiode array.

23. The CT scanner of claim 17, wherein the 2D grid of collimator plates comprises a grid that defines a plurality of cells dimensionally equivalent to a respective immediately adjacent plurality of emission surfaces of the scintillator array and a respective immediately adjacent plurality of light reception surfaces, of the light reception substantially planar surface, of the photodiode array.

24. A CT detector, comprising:

a plurality of scintillators arranged in an array to receive x-rays and output light in response to the reception of x-rays;

a plurality of reflector elements with a single reflector element disposed between adjacent scintillators;

a plurality of light detection elements arranged in an array to output electrical signals in response to light detected from the plurality of scintillators wherein the array of the plurality of light detection elements comprises a light reception substantially planar surface; and

a 2D gridded light collimator plate optical coupler that permits transmission of light between the plurality of scintillators and the plurality of light detection elements and secures the plurality of scintillators to the plurality of light detection elements, wherein the 2D gridded light collimator plate optical coupler comprises a plurality of light transmission cavities defined by light collimator plates disposed between the plurality of scintillators and the light reception substantially planar surface of the array of the plurality of light detection elements;

wherein the 2D gridded light collimator plate optical coupler extends to the light reception substantially planar surface of the array of the plurality of light detection elements substantially without encroachment past the light reception substantially planar surface of the array of the plurality of light detection elements.

25. The CT detector of claim 24, wherein the 2D gridded light collimator plate optical coupler comprises a non-contiguous optical coupler that defines the plurality of light transmission cavities between the plurality of scintillators and the light reception substantially planar surface of the array of the plurality of light detection elements;

wherein the non-contiguous optical coupler extends to the light reception substantially planar surface of the array of the plurality of light detection elements substantially without encroachment past the light reception substantially planar surface of the array of the plurality of light detection elements.

26. The CT detector of claim 24, wherein the light collimator plates are arranged in an array that sits atop the light reception substantially planar surface of the array of the plurality of light detection elements and defines a single optical transmission window between an aligned scintillator and an aligned light detection element.

27. The CT detector of claim 24, wherein the light collimator plates of the 2D gridded light collimator plate optical coupler comprise a plurality of substantially uniform cross-section collimator plates that define the plurality of light transmission cavities disposed between the plurality of scintillators and the light reception substantially planar surface of the array of the plurality of light detection elements;

wherein the plurality of substantially uniform cross-section collimator plates extends to the light reception substantially planar surface of the array of the plurality of light detection elements substantially without encroachment past the light reception substantially planar surface of the array of the plurality of light detection elements.

28. The CT detector of claim 24, wherein the plurality of reflector elements extend as a reflector wall between adjacent instances of the plurality of scintillators;

the CT detector further comprising;

a reflector layer that coats a high frequency electromagnetic energy reception substantially planar surface of the array of the plurality of scintillators that is substantially parallel with the light reception substantially planar surface of the array of the plurality of light detection elements, wherein the plurality of reflector elements is integrated with the reflector layer;

wherein the 2D gridded light collimator plate optical coupler, the plurality of reflector elements, and the reflector layer comprise a substantially same material that allows received x-rays to pass therethrough and reflects light generated by the plurality of scintillators toward the plurality of light detection elements.

29. The CT detector of claim 24, wherein the 2D gridded light collimator plate optical coupler comprises a grid that defines a plurality of cells dimensionally equivalent to a respective immediately adjacent plurality of emission surfaces of the array of the plurality of scintillators and a respective immediately adjacent plurality of light reception surfaces, of the light reception substantially planar surface, of the array of the plurality of light detection elements.