Dual-ended readout PET detector module based on GAPD having large-area microcells

A dual-ended readout PET detector module based on Geiger-mode avalanche photodiode (GAPD) with large-area microcells was proposed to obtain high photon detection efficiency (PDE) and to overcome the energy non-linearity problem. Theoretical analysis and experimental measurement were performed for the single- and dual-ended PET detector modules which were consisted of the two types of GAPDs with 50×50 μm² and 100×100 μm² microcell sizes. A Monte Carlo simulation was conducted to predict the number of incident photons impinging on the GAPD entrance surface to estimate the light collection efficiency (LCE) and linearity performance. Also, the depth of interaction (DOI) ratio histogram was obtained. Experimental study was performed to acquire the energy spectra of different γ-rays, and the linearity was evaluated by analyzing the photo-peak channels. The simulation results showed the LCE of dual-ended PET detector modules were improved 9% and 55% comparing to the single-ended one, with 50×50 μm² and 100×100 μm² microcells GAPDs, respectively. Also, it was estimated that the proposed method can provide excellent (3-4 mm) and uniform DOI resolution. In the experimental measurement, the 511 keV photo-peak channels of dual-ended PET detector modules was increased 26% and 71% comparing to the single-ended one, with 50×50 μm² and 100×100 μm² microcells GAPDs, respectively. The coefficient of determination (R²) was improved from 0.86 to 0.93 with 100×100 μm² microcells GAPD. The similar improvement in photo-peak channel and linearity was observed in the simulation results. It demonstrated that the dual-ended PET detector configuration could considerably improve the non-linearity properties of GAPD without modification of microcell size and, hence, such configuration could - - provide high LCE, as well as DOI capabilities, for high PET detector performance.