CT detector having a segmented optical coupler and method of manufacturing same
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.
1. A method of manufacturing a CT detector comprising the steps of:
forming a scintillator array having a plurality of scintillators;
forming a photodiode array having a plurality of photodiodes;
depositing an open-celled collimator between the scintillator array and the photodiode array, the open-celled collimator having collimator plates extending in a direction generally parallel to x-ray transmission and having a width perpendicular to the direction generally parallel to x-ray transmission that substantially matches a width separating adjacent scintillators; and
securing the scintillator, the open-celled collimator, and the photodiode array to one another.
2. The method of claim 1 wherein the steps of forming the scintillator array and depositing an open-celled collimator include the steps of:
mounting a block of scintillator material onto a dissolvable substrate;
dicing through the block and the dissolvable substrate to form a plurality of voids;
casting reflector material into the plurality of voids; and
dissolving the dissolvable substrate to form the open-celled collimator.
3. The method of claim 2 further comprising the step of filling each cell of the open-celled collimator with an optical coupling substance.
4. The method of claim 2 wherein the step of securing the scintillator, the open-celled collimator, and the photodiode array includes the step of coupling a thin layer of adhesive to the open-celled collimator.
5. The method of claim 1 wherein the steps of forming the scintillator array and depositing the open-celled collimator include the steps of:
mounting a block of scintillator material onto a thermoplastic substrate;
dicing through the block of scintillator material and at least partially through the thermoplastic material to form a plurality of voids; and
casting reflector material into the plurality of voids.
6. The method of claim 1 wherein the step of depositing an open-celled collimator includes the step of depositing a thermoplastic material with an embedded mesh between the scintillator array and the photodiode array, the mesh defining a plurality of light transmission cavities.
7. The method of claim 6 further comprising the step of filling the plurality of light transmission cavities with an optical epoxy.
8. The method of claim 1 wherein the step of depositing an open-celled collimator further includes the steps of:
coating the plurality of photodiodes with a semiconductor material; and
etching the semiconductor material to form a plurality of light transmission cavities.
9. The method of claim 8 further comprising the step of filling the plurality of light transmission cavities with optical epoxy.
10. The method of claim 1 wherein the open-celled collimator includes a metallic grid having a plurality of light transmission cavities.
11. The method of claim 10 further comprising the step of etching the metallic grid from a substrate.
12. The method of claim 10 wherein the step of securing includes the step of bonding the metallic grid to the plurality of scintillators and the plurality of photodiodes.
13. The method of claim 10 further comprising the step of filling the plurality of light transmission cavities with optical epoxy.
14. A method of constructing a CT detector comprising the steps of:
forming a scintillator array;
forming a photodiode array; and
securing the scintillator array to the photodiode array with an open-celled collimator, the open-celled collimator arranged to reduce optical cross-talk between adjacent scintillator-photodiode pairs.
15. The method of claim 14 wherein the steps of forming the scintillator array and securing the open-celled collimator include the steps of:
mounting a block of scintillator material onto a thermoplastic substrate;
dicing through the block of scintillator material and at least partially through the thermoplastic material to form a plurality of voids; and
casting reflector material into the plurality of voids.
16. The method of claim 14 wherein the open-celled collimator is formed by:
coating the photodiode array with a semiconductor material;
etching the semiconductor material to form a plurality of light transmission cavities; and
filling the plurality of light transmission cavities with optical epoxy.