Depth encoding PET detectors using single layer crystal array with different reflector arrangements along depths

摘要

Depth encoding detectors are preferred for PET scanners with a small ring diameter and a long axial field of view. In this work, novel depth encoding detectors using different inter-crystal reflector arrangements along the depth of single layer crystal arrays are proposed and their performance is evaluated. As compared to the previous four-layer detector with different reflector arrangements, the detectors proposed in this work are expected to improve the energy and timing resolution of the detectors. 4x4 LYSO arrays with a crystal size of 3x3x20 mm(3) and 6x6 LYSO arrays with a crystal size of 2x2x20 mm(3) are fabricated using two and four reflector arrangements along the crystal's depth. The LYSO arrays are single-ended read out by 4x4 SiPM arrays with a pixel size of 3x3 mm(2). The first and second half of the crystals are clearly resolved from the flood histograms for the two detectors with two reflector arrangements. 80% of the events can be correctly assigned to each half. The detectors provide a two layer depth encoding capability. The photopeak value and average energy resolution of the first and second half of the crystal are almost the same. The average crystal energy resolutions of the 4x4 and 6x6 LYSO arrays with two reflector arrangements are 10.4% and 11.6%, respectively. The timing resolutions of the two detectors are 284 ps and 442 ps for an energy window of 400 similar to 600 keV. However, each quarter of the crystals cannot be clearly resolved for the two detectors with four reflector arrangements and further optimization is still required. The detectors developed in this work simultaneously provide a two layer depth encoding capability, good energy and timing resolution, and show great promise for developing high performance dedicated brain, whole body and total body PET scanners in the future.