@article{oai:repo.qst.go.jp:00045521,
 author = {Lam, ChihFung and Yamaya, Taiga and Obi, Takashi and Yoshida, Eiji and Inadama, Naoko and Shibuya, Kengo and Nishikido, Fumihiko and Murayama, Hideo and Ｌａｍ ＣｈｉｈＦｕｎｇ and 山谷 泰賀 and 小尾 高史 and 吉田 英治 and 稲玉 直子 and 澁谷 憲悟 and 錦戸 文彦 and 村山 秀雄},
 issue = {1},
 journal = {IEEE Transactions on Nuclear Science},
 month = {Feb},
 note = {One way to speed-up iterative image reconstruction is by parallel computing with a computer cluster. However, as the number of computing threads increases, parallel efficiency decreases due to network transfer delay. In this paper, we proposed a method to reduce data transfer between computing threads by introducing an intra-thread update. The update factor is collected from each slave thread and a global image is updated as usual in the first K sub-iteration. In the rest of the sub-iterations, the global image is only updated at an interval which is controlled by a parameter L. In between that interval, the intra-thread update is carried out whereby an image update is performed in each slave thread locally. We investigated combinations of K and L parameters based on parallel implementation of RAMLA for the jPET-D4 scanner. Our evaluation used four workstations with a total of 16 slave threads. Each slave thread calculated a different set of LORs which are divided according to ring difference numbers. We assessed image quality of the proposed method with a hotspot simulation phantom. The figure of merit was the full-width-half-maximum of hotspots and the background normalized standard deviation. At an optimum K and L setting, we did not find significant change in the output images. We also applied the proposed method to a Hoffman phantom experiment and found the difference due to intra-thread update was negligible. With the intra-thread update, computation time could be reduced by about 23%.},
 pages = {129--135},
 title = {Parallel Implementation of 3-D Iterative Reconstruction With Intra-Thread Update for the jPET-D4},
 volume = {56},
 year = {2009}
}