title: Potential for reducing the numbers of SiPM readout surfaces of laser-processed X'tal cube PET detectors.
abstract: We are developing a three-dimensional (3D) position-sensitive detector with isotropic spatial resolution, the X'tal cube. Originally, our design consisted of a crystal block for which all six surfaces were covered with arrays of multi-pixel photon counters (MPPCs). In this paper, we examined the feasibility of reducing the number of surfaces on which a MPPC array must be connected with the aim of reducing the complexity of the system. We evaluated two kinds of laser-processed X'tal cubes of 3 mm and 2 mm pitch segments while varying the numbers of the 4 × 4 MPPC arrays down to two surfaces. The sub-surface laser engraving technique was used to fabricate 3D grids into a monolithic crystal block. The 3D flood histograms were obtained by the Anger-type calculation. Two figures of merit, peak-to-valley ratios and distance-to-width ratios, were used to evaluate crystal identification performance. Clear separation was obtained even in the 2-surface configuration for the 3 mm X'tal cube, and the average peak-to-valley ratios and the distance-to-width ratios were 6.7 and 2.6, respectively. Meanwhile, in the 2 mm X'tal cube, the 6-surface configuration could separate all crystals and even the 2-surface case could also, but the flood histograms were relatively shrunk in the 2-surface case, especially on planes parallel to the sensitive surfaces. However, the minimum peak-to-valley ratio did not fall below 3.9. We concluded that reducing the numbers of MPPC readout surfaces was feasible for both the 3 mm and the 2 mm X'tal cubes.
authors: Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan. yhirano@nirs.go.jp
authors: Yoshiyuki
authors: Y
authors: Hirano
authors: Naoko
authors: N
authors: Inadama
authors: Eiji
authors: E
authors: Yoshida
authors: Fumihiko
authors: F
authors: Nishikido
authors: Hideo
authors: H
authors: Murayama
authors: Mitsuo
authors: M
authors: Watanabe
authors: Taiga
authors: T
authors: Yamaya
mesh_terms: D005240:Feasibility Studies; D021621:Imaging, Three-Dimensional; D007834:Lasers; D049268:Positron-Emission Tomography / Q000295:instrumentation*; D012588:Scintillation Counting / Q000295:instrumentation; D013499:Surface Properties