Development of a novel DOI detector using laser manufacturing

A novel single-ended-readout depth-of-interaction (DOI) detector is proposed for application in positron emission tomography (PET). The crystal unit of this detector is formed by a transform of the crystal unit of a dual-ended readout detector, which is constructed from a LYSO scintillator pillar segmented using sub-surface laser engraving (SSLE). Specifically, two scintillator pillars are coupled with optical glue at the first (top) segment, and an enhanced specular reflector (ESR) film is inserted between the second segment and the bottom segment. By placing these crystal units in a two-dimensional array and coupling them to an multi-pixel photon counter (MPPC) array, a six-layer block detector can be constructed. We developed a new MPPC array with 64 (8 × 8) channels; each pixel had an active area of 2.0 × 2.0 mm and the pitch was 2.2 mm in both directions. Single-ended-readout DOI detectors were fabricated using these block detectors, which produced clearly resolved position maps with an average energy resolution of 12%. For both the individual crystal units and the block detector, the first layer exhibited the best timing resolution, 715 ps FWHM and 726 ps FWHM, respectively.