Translated Titles

Radiation Dosimetry in Multi-slice versus Single-slice CT



Key Words

電腦斷層劑量指標 ; 多切片電腦斷層 ; 單切片電腦斷層 ; 診斷參考水平 ; 劑量長度乘積 ; 有效劑量 ; diagnostic reference level ; computed tomography dose index ; dose length product ; effective dose ; SSCT ; MSCT



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Chinese Abstract

本研究目的為了解醫療院所CT檢查設備的使用情形,已採取大規模的問卷調查方式,探究台灣電腦斷層的輻射劑量,建立參考劑量水平,並比較多切片與單切片電腦斷層輻射劑量。 本次調查表得到臨床上的成人頭部與軀幹常規檢查的照射條件,回收比例為56 %,SSCT與MSCT約各佔一半,其掃描機類型在上一次調查時主要為SSCT,而目前MSCT已超過全台機器數量一半以上,顯示CT之整體型態已大幅度汰舊換新,而2003年至2007年五年內受檢人次已增加約70 %。探究機器設備數無明顯成長,但檢查人次卻明顯增加,可能是MSCT擁有大掃描範圍、X光管球旋轉速度變快及強大影像後處理運算能力,縮短掃描時間,致使受檢人次明顯增加。分析調查表中六項成人的常規檢查:頭部檢查、胸腔檢查、高解析度胸腔檢查、腹腔檢查、腹腔與骨盆腔檢查、全身檢查,CT檢查中的各醫療院所的CT對於有效管電流時間乘積的變化最大,會受到不同CT臨床放射師經驗與醫生的要求而改變,也直接影響受檢者接受的輻射劑量。根據英國國家電腦斷層評鑑中心的CT輻射劑量計算軟體與英國國家放射防護委員會SR250號報告的器官劑量資料庫,計算各醫療院所每項檢查的輻射劑量,包含:電腦斷層劑量指標、劑量長度乘積與有效劑量。研究結果顯示,MSCT與SSCT檢查之輻射劑量有差異,MSCT的有效劑量高於SSCT約16 % ~ 60 %,其中以頭部檢查的劑量差異最顯著(p<0.05)。以四分之三水平法推導參考劑量水平,與歐盟建議值相比,頭部與軀幹檢查的CTDIw與DLP皆低於歐盟建議值,僅在MSCT的DLP略高於歐盟建議值。本研究也比歐盟多提供了三種檢查的參考劑量水平:高解析度胸部、腹腔與骨盆腔、全身檢查。比較各檢查項目的劑量轉換因子,頭部檢查與歐盟建議值相似,胸腔與腹腔檢查則顯示其軀幹檢查的有效劑量較過去有所增加,轉換因子已略高於歐盟建議值。 台灣CT劑量研究業已完成,研究成果對暸解台灣使用CT之現況是極具價值,所訂定的參考劑量水平可提供主管機關制訂合乎國情之劑量品質保證方法與合理的決策判斷資訊。

English Abstract

The purpose of this study is to understand the CT growth and radiation dose level, to determine the diagnostic reference level, and to compare the radiation doses between MSCT and SSCT. The received rate of questionnaires was 56 %, and the percentiles for MSCT and SSCT were almost equal. The majority of the first survey in 2003 is SSCT, however, MSCT increased rapidly during 2003 to 2008. The CT using frequency raised about 70 % from 2003 to 2007 while the total number of CT scanners didn’t change. The wider scan range, shorter tube rotation time, and excellent image processing software reduce the scanning time and then make more people undergo CT examinations. The technical factors, such as kVp, mAs, pitch, for brain, thoracic, high resolution chest, abdomen, abdomen-pelvis, and whole body scans were analyzed. The CTDIs, DLP, and effective doses were calculated by ImPACT CT dosimetry calculator with UK SR-250 Monte Carlo simulation data set. The variation for effective tube current time product was the largest. The effective mAs was dramatically different between SSCT and MSCT. The effective doses for MSCT were larger than those for SSCT about 16 % to 60 %, especially in brain scan (p< 0.05). The diagnostic reference level set in this study was lower than EC recommended values. All of the results of this study were very valuable to understand the computed tomography radiation dose in Taiwan.

Topic Category 醫藥衛生 > 醫藥總論
健康科學院 > 放射科學研究所
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