The objective of this proposal is to demonstrate the feasibility of a novel pixel structure to realize low-cost avalanche gain and ultrafast radiation sensing for time-of- ight (TOF) PET. The proposed detector, which we call selenium solid-state photomultiplier (Se-SSPM) employs three major components: a substrate which houses the readout electronic circuit (CMOS readout with coincidence timing) identical to existing products; an integrated multi- well structure with fully encapsulated grids built on top of each pixel; and deposition of a thin indirect conversion a-Se photoconductive layer with thickness ranging from 10 to 35 m, also identical to existing products. The key innovations are the following: 1) unipolar time-di erential (UTD) charge sensing inside avalanche a-Se detector: UTD charge sensing within the a-Se bulk using a high-density multi-well structure over the pixel electrode of the readout circuit; 2) picosecond time-resolution of the proposed Se-SSPM to enable optimal TOF-PET. Our objective will be achieved through two speci c aims: 1) Design and fabricate prototype Se-SSPM pixel detectors; 2) Characterize the performance of prototype Se-SSPM and demonstrate UTD charge sensing and picosecond time resolution. Successful accom- plishment of these speci c aims will prove the feasibility of a low-cost indirect conversion a-Se detector structure for TOF applications, and pave the way for future development of prototype detectors. These detectors will be investigated for TOF-PET and TOF-PET/MR to achieve optimal clinical and cost e ectiveness. In addition, these detectors will be studied for the construction of a whole-body TOF-PET to maximize geometric detection eciency and reach the fundamental sensitivity limits of PET. 1
s/Relevance In the proposed work we will investigate the feasibility of a new detector structure for time-of- ight (TOF) PET imaging using indirect conversion amorphous selenium. It will permit high photon detection eciency and fast coincidence timing resolution. Also, given that the photosensor material is amorphous, the detector structure is inherently inexpensive, and thus, it enables reaching the fundamental sensitivity limits of PET by the construction of a whole-body clinical TOF-PET imager and extending the axial eld-of-view to maximize geometric detection eciency. In addition, this technology will have a high impact on the development of high resolution simultaneous TOF-PET/MR imagers with optimal clinical and cost e ectiveness.