@article{oai:repo.qst.go.jp:00046665,
 author = {Hirano, Yoshiyuki and Inadama, Naoko and Yoshida, Eiji and Nishikido, Fumihiko and Murayama, Hideo and Watanabe, Mitsuo and Yamaya, Taiga and 平野 祥之 and 稲玉 直子 and 吉田 英治 and 錦戸 文彦 and 村山 秀雄 and 山谷 泰賀},
 issue = {5},
 journal = {Physics in Medicine and Biology},
 month = {Feb},
 note = {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.},
 pages = {1361--1374},
 title = {Potential for reducing the numbers of SiPM readout surfaces of laser-processed X'tal cube PET detectors},
 volume = {58},
 year = {2013}
}