- 學位論文
頭部血流灌注電腦斷層檢查之輻射劑量評估
Radiation dose assessment for brain CT perfusion
摘要
目的:本研究目的是評估當病人進行急性缺血性腦中風檢查時的器官劑量及 有效劑量,包含評估二種最新型多切片電腦斷層掃描儀所使用不同掃描模式下的 結果。 材料方法:本研究使用熱發光劑量計(GR200A)及類人型假體(RAN100) 評估器官吸收劑量,依據國際輻射防護委員會(ICRP)103 號報告計算全身有效 劑量。使用 nonenhanced、perfusion 與 neck enhanced(或 CTA)三種臨床掃描參 數之 protocol,評估缺血性中風檢查時的器官劑量與有效劑量。使用兩台最新型 多切片電腦斷層掃描儀,機型分別為;Aquilion ONE Aquilion ONE(Toshiba Medical Systems, Otawara, Japan)與 Definition Flash(Siemens Medical Solutions, Forchheim, Germany)。利用鉍屏蔽與器官導向管電流調控技術,降低體表輻射敏 感器官之吸收劑量。 結果:Aquilion ONE 掃描儀針對在掃描範圍內的眼球水晶體劑量,在三種檢 查 protocols 時分別為 46.7 mGy(nonenhanced)、151.5 mGy(perfusion)、12.4 mGy (neck enhanced 或 CTA)。掃描範圍內皮膚劑量分別為 36.11 mGy、114.37 mGy、 2.16 mGy。全身有效劑量分別為 2.02 mSv、5.18 mSv、6.43 mSv。Definition Flash 掃描儀針對眼球水晶體器官劑量,在三種檢查 protocols 時分別為 38.48 mGy (nonenhanced)、287.71 mGy (perfusion)、9.91 mGy (neck enhanced 或 CTA)。 掃描範圍內的皮膚劑量分別為 37.28 mGy、218.45 mGy、11.27 mGy。全身有效劑 量分別為;2.39 mSv、8.64 mSv、4.0 mSv。兩台 CT 使用鉍屏蔽降低水晶體劑量 分別為;19.7%至 46.9%,器官導向管電流調控技術可降低 32.2%劑量。 結論:Aquilion ONE 與 Definition Flash 兩台掃描儀以臨床使用於缺血性中風 檢查時,在常用掃描參數下量測 nonenhanced、perfusion 與 neck enhanced(或 CTA)三種 protocols 的總和有效劑量分別為 13.6 mSv 與 15.0 mSv。使用鉍屏蔽 及器官導向管電流調控技術,可有效保護體表輻射敏感器官,降低其輻射吸收劑 量。因此,本研究建議,使鉍屏蔽及器官導向管電流調控功能,以降低體表輻射 敏感器官之吸收劑量。
並列摘要
Purpose The goal of this study was to assess the organ doses and effective doses to patients of two latest multi-slice computed tomography scanners for acute stroke examination. Materials and methods The radiation doses were measured at Aquilion ONE (Toshiba Medical Systems, Otawara, Japan) and Definition Flash (Siemens Medical Solutions, Forchheim, Germany) CT scanners. The organ doses were measured using GR200A thermoluminscent dosimeters (TLD) chips inserted into RAN100 anthropomorphic phantom at the ischemia stoke CT scan protocol. The protocol included nonenhanced, perfusion, and neck enhanced (or neck CT angiogrpahy procedures) scans. The measured organ doses were used to calculae the effective doses according to ICRP tissue weighting factors. The bismuth shield and organ-based tube current modulation (OB-TCM) technique was used to reduce absorbed doses to radiosensitive surface oragns. Results The absorbed doses to eye lens within scan range during nonenhanced, perfusion , and neck enhanced (or neck CTA) were 46.7, 151.5, 12.4 mGy for Aquilion ONE CT scanner and 38.48, 287.71, 9.91 mGy for Definition Flash CT scanner. The skin dose within scan range within three scans were 36.11, 114.37, 216 mGy for Aquilion ONE CT scanner and 37.28, 218.45, 11.27 mGy for Definition Flash scanner. The effective doses according to ICRP 103 report were 2.02, 5.18, 6.43 mSv for Aquilion ONE scanner and 2.39, 8.64, 4.0 mSv for Definition Flash scanner. The radiation dose reduction using the bismuth shield were 19.7% to 46.9%. The radiation dose reduction using OB-TCM was 32.2%. Conclusion The effective doses of ischemia stoke CT protocol include nonenhanced, perfusion, and neck enhanced (or neck CTA) scans were 13.6 mSv for Aquilion ONE CT scanner and 15.0 mSv for Definition Flash CT scanner. The bismuth shield and OB-TCM technique can effectively reduce the absorbed doses to radiosensitive surface organs. We proposed these two methods for radiation dose reduction to superficial organs expecially in acute stoke CT examination.