@misc{oai:repo.qst.go.jp:00064642,
 author = {Yamaya, Taiga and Yoshida, Eiji and Kinouchi, Shoko and Wakizaka, Hidekatsu and Tsuji, Atsushi and Tashima, Hideaki and Nishikido, Fumihiko and Nakajima, Yasunori and Satou, Shinji and Inaniwa, Taku and 山谷 泰賀 and 吉田 英治 and 木内 尚子 and 脇坂 秀克 and 辻 厚至 and 田島 英朗 and 錦戸 文彦 and 中島 靖紀 and 佐藤 眞二 and 稲庭 拓},
 month = {Jun},
 note = {Objectives:
The OpenPET geometry is our original idea to visualize a physically opened space between two detector rings. One of our targets is in-beam PET, which is a method for <i>in situ</i> monitoring of particle therapy. We expect the OpenPET will be the first practical 3D geometry to be realized, as conventional systems using positron cameras are basically limited to 2D imaging. For the usual carbon beam irradiation, the activity of produced positron emitters is generally low, in addition to there being a theoretical difference between the dose distribution and positron emitter distribution. Therefore direct irradiation of radioactive beams is ideal for in-beam PET. We have previously developed a small prototype to show a proof-of-concept of in-beam imaging in the Heavy Ion Medical Accelerator in Chiba (HIMAC). In this paper, we carried out the first animal imaging tests in the HIMAC, and we evaluated the biological washout effect.
\nMethods:
The OpenPET prototype (two detector rings of 110 mm diameter separated by a gap of 42 mm) was positioned so that the beam passed through the gap. In order to increase signals, we used a <sup>10</sup>C beam, whose half-life is about 19 s. Washout of <sup>10</sup>C in brain and thigh muscle of F344 rats was observed. Reconstructed images were obtained from 97 s PET measurement after 2 s irradiation (~0.7 Gy). Two cases, live and dead, were compared.
\nResults:
Distribution of primary particles in the rat was clearly visualized. Comparing the live case and the dead case, it was shown that the washout effect largely depends on the irradiation field; activity ratios remained in the brain and the thigh muscle were 48% and 81%, respectively.
\nConclusion:
Feasibility of in-beam OpenPET imaging for a living body was shown. It was also indicated that PET measurement during irradiation is desired to escape the space-variant washout effect., SNM2012},
 title = {Washout effect in rats during in-beam imaging by the small OpenPET prototype},
 year = {2012}
}