@article{oai:repo.qst.go.jp:00046555,
 author = {Yoshida, Eiji and Hirano, Yoshiyuki and Tashima, Hideaki and Inadama, Naoko and Nishikido, Fumihiko and Moriya, Takahiro and Omura, Tomohide and Watanabe, Mitsuo and Murayama, Hideo and Yamaya, Taiga and 吉田 英治 and 平野 祥之 and 田島 英朗 and 稲玉 直子 and 錦戸 文彦 and 大村 知秀 and 村山 秀雄 and 山谷 泰賀},
 journal = {Nuclear Instruments & Methods in Physics Research Section A},
 month = {May},
 note = {The X'tal cube is a depth-of-interaction (DOI)-PET detector which is aimed at obtaining isotropic resolution by effective readout of scintillation photons from six sides of the crystal block. The X'tal cube is composed of a 3D crystal block with isotropic segments. Each face of the 3D crystal block is covered with a 4*4 array of multi-pixel photon counters (MPPCs). Previously, in order to fabricate the 3D crystal block efficiently and precisely, we applied a sub-surface laser engraving technique to a monolithic crystal block instead of gluing segmented small crystals. A dense arrangement of multiple micro-cracks carved by the laser beam works efficiently as a scattering wall for the scintillation photons. The X'tal cube with the laser-processed block showed excellent performance with respect to crystal identification and energy resolution. In this work, for characteristics comparison between the laser-processed block and the conventional segmented array block, we made the laser-processed block and two types of segmented array blocks, one with air gaps and the other with glued segmented small crystals. All crystal blocks had 3D grids of 2 mm pitch. The 4*4 MPPC arrays were optically coupled to each surface of the crystal block. When performance was evaluated using a uniform irradiation of 511 keV, we found that the X'tal cubes with the laser-processed block could easily achieve 2 mm3 uniform crystal identification. Also, the average energy resolution of each 3D grid was 11.1+-0.7%. On the other hand, the glued segmented array block had a pinched distribution and crystals could not be separated clearly. The segmented array block with air gaps had satisfactory crystal identification performance; however, the laser-processed block had higher crystal identification performance. Also, the energy resolution of the laser-processed block was better than for the segmented array blocks. In summary, we found the laser-processed X'tal cube had excellent crystal identification performance and high energy performance due to its effective dense arrangement of micro-cracks.},
 pages = {83--88},
 title = {The X'tal cube PET detector with a monolithic crystal processed by the 3D sub-surface laser engraving technique: Performance comparison with glued crystal elements},
 volume = {723},
 year = {2013}
}