SiPM based PET detector modules with air-gapped pixelated LYSO

Stticon Photomultiplier (SiPM) is a promising sensor for PET with a number of advantages. A traditional design for PET detector module is using a pixelated scintillator array coupled to a SiPM array, and it is critical to design reflectors between crystals to decode photon event location. Unlike PMT based detectors, the pixelated scintillator array may not necessarily require complex reflector schemes for optimal light sharing. An intuitive design method is to fill the gaps between adjacent crystals with reflective materials such as ESR or BaSO4. However, the manufacture of the array with reflectors is still time-consuming and costly. In this paper, we evaluate the performances of pixelated LYSO arrays separated by only air-gap. A mathematical calculation shows that there is not much difference between reflector based and air-gap based detector module design. Three groups of experiments were conducted based on a home-made 8×8 SiPM array, including a single LYSO crystal with three types of reflector process, three 8×8 LYSO arrays and two 15×15 LYSO arrays with different crystal surface treatments and with air or reflective-material gaps. The results show that the air-gap design for polished LYSO has similar event decoding capability and energy resolution compared with the reflector-filled design. In conclusion, the scintillator arrays with air-gap are simple and feasible for SiPM based detector, which would greatly reduce the cost and manufacture time of detector modules without performance deterioration.