A Crosshair Light Sharing PET Detector With DOI and TOF Capabilities Using Four-to-One Coupling and Single-Ended Readout

Abstract

To improve positron emission tomography (PET) image quality, depth-of-interaction (DOI) information and time-of-flight (TOF) information are key technologies. In this work, we developed the DOI-TOF detector based on our original single-ended readout scheme with the continuous layered gadolinium fine aluminum garnet (GFAG) array. The size of each GFAG crystal is <inline-formula> <tex-math notation= LaTeX >$1.45\\times 1.45\\times 20$ </tex-math></inline-formula> mm³. The multipixel photon counter (MPPC) used as a photo sensor has a surface area of <inline-formula> <tex-math notation= LaTeX >$3.0\\times 3.0$ </tex-math></inline-formula> mm². One pair of crystals coupled with a partial optical window is arranged across two MPPCs. Boundaries without the partial optical window are covered with optical reflectors. Each pair is coupled with paired MPPCs of different patterns. Crystal identification is obtained from paired MPPCs of different patterns and output rates. By limiting the spread of scintillation light, the proposed DOI detector based on the local centroid calculation was expected to improve crystal response, including the edge. For performance comparison, we prepared three discrete layers of the GFAG array with the same total thickness. For the continuous layer, the DOI resolution, the energy resolution and the timing resolution of the pair of detectors are 4.7 mm, 14%, and 402 ps, respectively. Their respective values are 29%, 20%, and 33% better than those with the three discrete layers.