PET Detector Configuration with Thick Light Guide and GAPD Array Having Large-Area Microcells

초록

Light sharing PET detector configuration coupled with thick light guide and Geiger-mode avalanche photodiode (GAPD) with large-area microcells was proposed to overcome the energy non-linearity problem and to obtain high light collection efficiency (LCE). Theoretical evaluations were performed for 90 types of PET detector modules. A Monte Carlo simulation was conducted for the three types of LSO block, 4x4 array of 3x3x20 mm(3), 6x6 array of 2x2x20 mm(3), and 12x12 array of 1x1x20 mm(3) discrete crystals, to investigate the scintillation light distribution after conversion of the gamma-rays in LSO. The incident photons were read out by three types of 4x4 array photo-sensors, which were PSPMT of 25% quantum efficiency (QE), GAPD1 with 50x50 mu m(2) microcells of 30% photon detection efficiency (PDE) and GAPD2 with 100x100 mu m(2) of 45% PDE. The number of counted photons in each photo-sensor was analytically calculated. The LCE, linearity and flood histogram were examined for each PET detector module as a function of light guide thickness ranging from 1 to 10 mm. The performance of PET detector modules based on GAPDs was significantly improved by using the thick light guide. The LCE was increased from 24 to 30% and from 14 to 41%, and the linearity was also improved from 0.96 to 0.99, from 0.78 to 0.99, for GAPD1 and GAPD2, respectively. In the contrary, the performance was not changed for PSPMT based detector. The flood histogram of 12x12 array PET detector modules using 3 mm light guide coupled with GAPDs was obtained by simulation, and all crystals of 1x1x20 mm(3) size was clearly identified. PET detector module coupled with thick light guide and GAPD array with large-area microcells was proposed to obtain high QE and high spatial resolution, and its feasibility was verified. It demonstrates GAPDs could be a competitive and cost-effective photo-sensor respect to the high QE (similar to 40%) PMT.

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