@misc{oai:repo.qst.go.jp:00075717,
 author = {田島, 英朗 and 吉田, 英治 and 赤松, 剛 and 岩男, 悠真 and 高橋, 美和子 and 山下, 大地 and 山谷, 泰賀 and Tashima, Hideaki and Yoshida, Eiji and Akamatsu, Go and Iwao, Yuma and Takahashi, Miwako and Yamashita, Taichi and Yamaya, Taiga},
 month = {Apr},
 note = {[Purpose] A strong potential demand for high sensitivity, high spatial resolution, and low-cost brain PET is expected for early diagnosis of dementia. Therefore, we have proposed helmet-type PET having a novel hemispherical detector arrangement to significantly increase the sensitivity with a small number of detectors. On the other hand, recent improvement of the time-of-flight (TOF) PET detector technology is significant. Although the effectiveness of TOF is better for large objects, we can expect certain improvement for brain imaging. In this study, therefore, we developed a TOF helmet-type PET prototype using state-of-the-art TOF detector technology. Also, we developed a reconstruction method incorporating TOF information for the helmet-type
PET geometry.
[Method] The TOF helmet-type PET prototype was developed using 54 TOF-PET detectors made based on the Hamamatsu TOF-PET module (C13500-4075LC-12). The module is composed of a 4.2 mm-pitch 12x12 array of Lutetium Fine Silicate (LFS) crystals coupled to an array of 12x12 multi-pixel photon counters (MPPCs) in a one-by-one manner. The thickness of the LFS crystals were reduced to 10 mm from original 20 mm to reduce parallax error and further improve the timing resolution. We used 45 modules to form a hemisphere unit with the inner diameter of 279 mm and 9 modules to form the add-on detector placed at the back of the neck position. We developed an image reconstruction method for the TOF helmet-type PET geometry based on the list-mode TOF ordered subset expectation maximization (OSEM) incorporating sensitivity, attenuation, scatter, and random corrections. We conducted imaging test of the 3D Hoffman brain phantom processed to fit into the hemispherical gantry.
[Results] The timing resolution of 245 ps coincidence resolving time (CRT) was finally obtained after fine timing correction. Also, we could obtain the 3D Hoffman image with high contract and clear structure by using the developed list-mode TOF OSEM method.
[Conclusion] We showed promising imaging performance of the TOF helmet-type PET having CRT of better than 250 ps., 第117回日本医学物理学会学術大会},
 title = {Development of a TOF helmet-type PET prototype having a timing resolution of 250 ps and its image reconstruction method},
 year = {2019}
}