@misc{oai:repo.qst.go.jp:00073044,
 author = {田島, 英朗 and 赤松, 剛 and 岩男, 悠真 and 脇坂, 秀克 and 吉田, 英治 and 山下, 大地 and 山谷, 泰賀 and Tashima, Hideaki and Akamatsu, Go and Iwao, Yuma and Wakizaka, Hidekatsu and Yoshida, Eiji and Yamashita, Taichi and Yamaya, Taiga},
 month = {Nov},
 note = {We are developing a brain-dedicated PET system, which has a spherically arranged detector unit and an add-on detector unit at the back side of the neck for improving sensitivity. To achieve quantitative images without imaging artifacts, normalization of detector sensitivity is essential for PET imaging. For normalization, every line of response having a cross section within the field of view (FOV) or imaging region should also have a cross section within the radioactivity distribution of a normalization phantom. Because our PET prototype has the spherical detector arrangement, rotating line sources typically used for cylindrical PET cannot be used. In our previous work, we used a double-cylinder shaped pool phantom fit into the hemispherical detector arrangement. However, the pool phantom filled with solution attenuates emitted gamma-rays significantly, and the measured data contains a lot of scattered events. In this study, therefore, we propose a new normalization phantom, a hollow-dome phantom, having radioactivity and attenuation distributions only at the surrounding region of the FOV. We measured the hollow-dome and the double-cylinder pool phantoms each filled with 18F solution of 15 MBq for 9 hours by the first helmet-neck PET prototype. Also, we conducted a Monte Carlo simulation to estimate scatter fraction. As a result, he hollow-dome phantom provided 3 times higher count rate with the random fraction of 23%. The scatter fraction was 5% for the hollow-dome phantom and 31% for the double-cylinder phantom. Therefore, the true count rate for the hollow-dome phantom was estimated 5 times higher. In addition, imaging test showed that the hollow-dome phantom could reduce noise for the same radioactivity and measurement time., IEEE NSS MIC RTSD},
 title = {Normalization for brain-dedicated PET with the hemispherical detector arrangement},
 year = {2018}
}