本研究利用Philips Brilliance 之256-MSCT 進行病人全腹部掃瞄檢查時，改變iCT 的操作參數，包括tube voltage (kV) 和effective mAs 等。在不影響診斷要求的解析度條件下，評估受檢者的有效劑量(effective doses)。輻射劑量之度量係利用兩種熱發光劑量計(thermoluminescent dosimeters, TLDs) GR-200F 與GR-200 (LiF: Mg, Cu, P)分別置於侖道外表與內部度量皮膚與器官劑量輻射加權因數(radiation weighting factors, WR)與組織加權因數(tissue weighting factor , WT)，參照國際放射防護委員會第60 號報告。探討在臨床CT 的例行條件(routine protocol)檢查之外，是否有其他可行的作業條件又能降低病人的有效劑量。結果顯示臨床例行條件檢查全腹部有效劑量，iCT 掃描為25.2 mSv，Mode C 的體內組織或器官吸收劑量最高，而Mode B 最低。總結來說，減少偵檢器排數時會使得輻射劑量值增加，但若使用的是單次切面數較少亦可以有效的減低輻射劑量。管電壓值與管電流的增加，都會使輻射劑量值明顯的增加。利用ACR phantom 分析影像空間解析度(spatial resolution)，符合診斷的需求。

This study aims to compare the effect of Philips Brilliance’s 256-MSCT on effective doses when changing the operating parameters in the scan examination of patients’ whole body or whole abdomen, including the changes in detector rows, pitch, tube voltage (kV) effective tube current (mAs) and other parameters. This is to assess the effective doses when the resolution requirement in the diagnosis will not be affected. The radiation doses are determined by placing two kinds of thermoluminescent dosimeters (TLDs), GR-200F and GR-200 (LiF: Mg, Cu, P), on the surface and inside the Rando phantom. The purpose of the study is aims to investigate the possibility of using other probable operating conditions to reduce patients’ effective doses, in addition to the routine protocol examination of clinical CT. The results show that the regard to effective doses of the whole abdomen examined by clinical routine protocol, iCT scanners are 25.2 mSv respectively, and the effective dose of iCT is higher when we change the pitch, effective mAs and tube voltage (kV). Finally, the image spatial resolution is evaluated by the ACR CT accreditation phantom. The resolution meets the diagnostic requirement.