A dual-layer TOF-DOI detector block for whole-body PET

We developed a dual-layer high-resolution detector block for whole-body positron-emission tomography systems. The top layer is a 13×13 array of lutetium yttrium orthosilicate (LYSO) crystals (2.85×2.85×10mm³) and the bottom layer a 13×13 array of lutetium gadolinium oxyorthosilicate (LGSO) crystals (2.85×2.85×10mm³). The LGSO layer was coupled to four Hamamatsu R11194HA photomultiplier tubes (PMTs) by a photomultiplier quadrant×sharing configuration. This block has both time-of-flight and depth-of-interaction functions. Using a Na-22 position source, the performance of this block was evaluated by coinciding with a reference detector which consisted of a 4×4×10mm³ LYSO crystal coupled to a Hamamatsu R9779 PMT. A total of 4.7% of the counts were mixed among the two layers. The LYSO layer had 11.4% energy resolution and 329ps coincidence time resolution.