@misc{oai:repo.qst.go.jp:00082749,
 author = {Hideaki, Tashima and Eiji, Yoshida and Takumi, Nishina and Mikio, Suga and Hidekatsu, Wakizaka and Miwako, Takahashi and Kotaro, Nagatsu and Atsushi, Tsuji and Kamada, Kei and Yoshikawa, Akira and Parodi, Katia and Taiga, Yamaya and Hideaki, Tashima and Eiji, Yoshida and Takumi, Nishina and Mikio, Suga and Hidekatsu, Wakizaka and Miwako, Takahashi and Kotaro, Nagatsu and Atsushi, Tsuji and Parodi, Katia and Taiga, Yamaya},
 month = {Apr},
 note = {[Purpose] Compton imaging has been expected to be realized as collimator-less SPECT, but it has not yet been put to practical use in the field of nuclear medicine. Last year, in contrast, we had succeeded in obtaining 909-keV Compton images with a quality approaching that of PET in a mouse experiment using the whole gamma imaging (WGI) prototype. In this study, therefore, we aimed at experimentally identify the factors behind this success.
[Method] The WGI prototype was composed of an absorber ring with 4-layer DOI detectors of 2.8&times;2.8&times;7.5 mm<SUP>3</SUP> GSO crystals and a scatterer ring with non-DOI detectors of 0.9&times;0.9&times;6.0 mm<SUP>3</SUP> GAGG crystals. We measured a cylindrical phantom with a 38 mm diameter filled with a <SUP>89</SUP>Zr solution of 10.2 MBq by the WGI prototype for 60 min. We also measured a mouse placed at a close position to the upper side of the scatterer ring for 60 min, 22 hours after injection of 9.8 MBq <SUP>89</SUP>Zr oxalate. To compare with the full-ring geometry, we simulated partial scatterer ring geometries with various angular coverage by limiting the number of the scatterer detectors used in the ring direction. Image artifacts in reconstructed images were visually evaluated.
[Results] Strong streaking artifacts appeared in the direction from the scatterer detector toward the subjects when only one detector was used in the scatterer ring. The more the scatterer detectors covered, the better the streaking artifacts mitigated. We found that, when the cylindrical phantom was covered by more than 180&deg; with the scatterer detectors, the streaking artifact was suppressed, and the shape of the cylinder was reproduced equivalently to the full-ring geometry. In the mouse imaging case, we also found that the streaking artifacts were suppressed when the subjects were covered more than 180&deg; by the scatterer detectors.
[Conclusion] We experimentally showed that it is necessary to cover the field-of-view with more than 180&deg; with the scatterer detector to achieve accurate 3D Compton images., 第121回日本医学物理学会学術大会},
 title = {Experimental Verification of the Effect of the Full-ring Geometry in WGI Compton Imaging},
 year = {2021}
}