@misc{oai:repo.qst.go.jp:00067008,
 author = {Nishikido, Fumihiko and Uenomachi, M. and Zhihong, Z. and Shimazoe, Kenji and Okumura, Yusuke and Yoshida, Eiji and Tashima, Hideaki and Parodi, Katia and Takahashi, H. and Yamaya, Taiga and 錦戸 文彦 and 島添 健次 and 奥村 勇介 and 吉田 英治 and 田島 英朗 and パロディ カティア and 山谷 泰賀},
 month = {Nov},
 note = {Whole-gamma imaging (WGI) is our concept to combine PET and Compton imaging so as to utilize all measured gamma rays for imaging. During the last year, we developed the first WGI prototype, in which an additional scatterer detector ring was inserted in the bore of a PET ring. The prototype WGI system used GSO scintillation detectors for the absorber and GAGG scintillation detectors for the scatterer. However, the energy resolution of the scatterer was much worse than the best energy resolution which have been reported for GAGG, and the limited energy resolution resulted in degraded performance of the Compton imaging. An alternative approach we investigated was the use of a silicon (Si) detector for the scatterer. In this paper, we report Geant4 simulation results as well as our initial development of the Si detector.
\nThe total chip size of the developed Si detector is 45.5 mm × 45.5 mm. The thickness of the Si is 600 μm. Strip pitch is 900 μm and the number of the strips is 48 channels for each side. The Si chip is connected to the readout circuit board with two ASICs which contain 48 channel pre-amplifiers and time-over-threshold circuits.
\nIn the simulation, we compared performances between the first WGI prototype (GAGG +GSO WGI) and the WGI with Si scatterer (Si +GSO WGI) by Geant4. Crystal and array size of the GAGG scatterer were 1 mm × 1 mm × 6 mm and 24 × 24, respectively. The respective numbers of layers of the GAGG and Si scatterers were 1 and 10. Total volume of the scatter for both WGI devices was almost the same. The Si +GSO WGI achieved better angular resolutions than that of the GAGG +GSO WGI for various energy gamma-rays. Although the sensitivity of the Si +GSO WGI was lower than that of the GAGG +GSO WGI for high energy gamma-rays, higher sensitivity was achieved for low energy gamma-rays due to the high scattering fraction of Si. We concluded that the WGI with the Si scatterer can improve spatial resolution of Compton imaging., IEEE NSS-MIC2018},
 title = {Development of silicon detectors of whole gamma imager for low energy gamma ray measurement},
 year = {2018}
}