@inproceedings{oai:repo.qst.go.jp:00053312,
 author = {遠藤, 真広 and 森, 慎一郎 and 角尾, 卓紀 and 西澤, かな枝 and 青山, 隆彦 and 遠藤 真広 and 森 慎一郎 and 角尾 卓紀 and 西澤 かな枝},
 book = {Proceedings of SPIE},
 month = {},
 note = {[Purpose] We have developed a four-dimensional CT (4D-CT) using continuous rotation of cone-beam x-ray. The maximum field of view for 4D-CT is 128mm at the center of rotation in the longitudinal direction. In order to obtain appropriate estimations of exposure dose, we have measured dose profiles perpendicular to the rotation axis in a lucite cylinder of 320mm diameter.
[Methods] We have used cylindrical lucite phantom of 320mm diameter and 750mm length. Dose profiles were measured at the center and a peripheral point of 10mm depth. A pin silicon photodiode sensor with 3x3x3mm sensitive region was used as an x-ray detector, which was scanned along longitudinal direction in the phantom for collimator widths of 10, 32, 64, 96 and 128mm.
[Results] The dose profiles had long tails caused by scattered radiation. For 128 mm collimator width 90% of integral dose was distributed along 350mm length at the center and 220mm at the periphery. Even for 10 mm collimator width 90% of integral dose was distributed along 250mm length at the center and 160mm length at the periphery. [New or breakthrough work to be presented] Before the advent of multi-detector CT CTDI100 was a good estimation of exposure dose, because it expressed approximate integral dose for clinical scan conditions. For 4D-CT employing a variable collimator, the standard CTDI was not a good estimation. In the present work we measured dose profiles for 4D-CT, and showed long tails distributed more than 100mm out of the collimator edge.
[Conclusion] In order to estimate exposure dose for cone-beam CT such as 4D-CT, it should be recommended to measure integral dose over collimator width plus at least 200mm length.},
 title = {4DCTにおける線量プロファイル測定},
 year = {2004}
}