Development of a depth of interaction detector using a multi-pixel photon counter module for positron emission tomography

A novel depth-of-interaction (DOI) detector with a single-ended readout was proposed previously. Each crystal unit of the detector consisted of a U-shaped transform of a dual-ended readout detector constructed using scintillator pillars segmented by sub-surface laser engraving (SSLE), and two multi-pixel photon counters (MPPCs) were coupled at the bottom of the crystal unit. In this work, we applied a single-ended readout DOI to an MPPC module for positron emission tomography (PET) manufactured by HAMAMATSU Photonics K.K., which resulted in a more compact DOI detector than that proposed previously. Using the block detector, practical six-layer DOI information was obtained. The average energy resolution of the crystal unit was 10.9%, and the timing resolution of the six-layer DOI was 224-389 ps FWHM.