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 x 13 array of lutetium yttrium orthosilicate (LYSO) crystals (2.85 x 2.85 x 10 mm(3)) and the bottom layer a 13 x 13 array of lutetium gadolinium oxyorthosilicate (LGSO) crystals (2.85 x 2.85 x 10 mm(3)). 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 point source, the performance of this block was evaluated by coinciding with a reference detector which consisted of a 4 x 4 x 10 mm(3) 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 329 ps coincidence time resolution against the reference detector. The LGSO layer had 14.8% energy resolution and 356 ps coincidence time resolution against the reference detector.