@misc{oai:repo.qst.go.jp:00070118, author = {Nishikido, Fumihiko and Yazaki, Yujiro and Osada, Hiroto and Mitsuhashi, Takayuki and Inadama, Naoko and Yoshida, Eiji and Inaniwa, Taku and Satou, Shinji and Murayama, Hideo and Yamaya, Taiga and 錦戸 文彦 and 矢崎 祐次郎 and 長田 拓人 and 三橋 隆之 and 稲玉 直子 and 吉田 英治 and 稲庭 拓 and 佐藤 眞二 and 村山 秀雄 and 山谷 泰賀}, month = {May}, note = {1. Propose We have proposed the "OpenPET" geometry which consists of two detector rings separated axially. The OpenPET is suitable for use as in-beam PET in carbon ion therapy due to the open space between the separated detector rings. Although the primary carbon ions do not enter into the PET detector in the OpenPET, light fragment ions from a target can enter into the detectors. Therefore the detector components, especially scintillators, are strongly activated and our usual measurement system could not be work normally due to high background from activated nuclei. In previous experiments, we applied some improvements to the measurement system and succeeded the off-beam measurement under high count rate environments after heavy ion irradiation. Then, we performed in-beam experiments using two OpenPET detector. We will report results about the in-beam experiment in this presentation. \n2. Methods The experiments were performed using 12C beam in the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences. The energy and intensity of the carbon beam were 290MeV/u and 10E8-10E9 pps. Carbon ions entered into a water phantom through an ionization chamber used as a beam intensity monitor. All of the primary carbon ions were stopped in the water phantom. The OpenPET detector consists of a 14x14x4 LGSO (Hitachi Chemical Co., Ltd., Japan) crystal array with the optimized reflector arrangement and a 64ch PS-PMT (H8500, Hamamatsu Photonics K.K., Japan). The OpenPET detector were positioned 30cm apart from the backside of the water phantom at an angle of 30 degree. A coincidence detector which consisted of a 14x14x4 LGSO crystal array and a PS-PMT was positioned at the opposite side of the water phantom. \n3. Results The sufficient crystal identification performance as a PET detector can be achieved in the center part of the crystal array. Because pile up events and baseline variance during intervals of beam spills were not corrected, crystal identification performances of a part of the crystals were degraded. These problems can be resolved by using a pulse sampling method and we will apply the method to the OpenPET detector in future experiments. \n4. Conclusion We are developing the OpenPET detector for heavy ion therapy. The in-beam experiment using the pair of the OpenPET detectors were performed in HIMAC. We conclude that the OpenPET detector worked sufficiently as a PET detector under the in-beam environment., PTCOG49}, title = {In-beam experiment using two OpenPET detectors for carbon beam therapy}, year = {2010} }