@misc{oai:repo.qst.go.jp:00068667,
 author = {Takahashi, Hisashi and Yamaya, Taiga and Kobayashi, Tetsuya and Kitamura, Keishi and Hasegawa, Tomoyuki and Murayama, Hideo and Suga, Mikio and 高橋 悠 and 山谷 泰賀 and 小林 哲哉 and 北村 圭司 and 長谷川 智之 and 村山 秀雄 and 菅 幹生},
 month = {Sep},
 note = {Depth-of-interaction (DOI) detectors, which can improve resolution uniformity in the field-of-view (FOV), enable high sensitivity PET scanners with small bore detector rings. We are developing a small bore PET scanner dedicated for small animals or mammography. We have proposed a DOI detector which consists of a four-layer array of 32x32 LYSO crystals (1.44mmx1.44mmx4.5mm). In this work, we simulated following three geometries based on this detector blocks using GATE, and compared imaging performance: (A) six detector blocks arranged in a hexagonal shape (85.2mm diameter FOV), (B) four detector blocks arranged in a tetragonal shape (49.2mm diameter FOV), and (C) in overlapped tetragonal shape (38.1mm diameter FOV). In order to deal with irregular detector sampling, list-mode maximum likelihood expectation maximization image reconstruction with accurate system modeling was applied. At this stage, effects of positron range, attenuation and Compton scattering were not included, and implementation was restricted to 2D in this simulation. The spatial resolution of geometry (B) and geometry (C) were approximately 1.35mm and that of geometry (A) was 1.25mm. The resolution non-uniformity of geometry (A) and geometry (C) improved 17% comparing to geometry (B). These results show that the hexagonal geometry has better resolution performance than the tetragonal geometry, and the uniformity of spatial resolution can be improved by overlapping detector blocks and filling gap. We should note that the resolution performance of overlapped tetragonal geometry almost equals hexagonal geometry in spite of fewer total number of crystals (hexagon geometry has 49152 crystals, while overlapped tetragonal geometry has 32768 crystals)., World Congress on Medical Physics and Biomedical Engineering 2006},
 title = {Resolution Performance of Simulated Small Bore DOI-PET Scanners Using},
 year = {2006}
}