以空間矩陣法探討透視攝影空間輻射劑量分佈

原能會於2018年進行透視品保的工作，在透視下醫師無可避免的將接受到輻射劑量，但其劑量多寡，可因其所站立位置、使用不同儀器操作及輻射劑量條件組合而有所不同。如果能知道在透視檢查室內，哪一個矩陣空間在進行透視攝影時，其所遭受到的輻射劑量最高並提供一個友善的等劑量曲線，可使包括醫師在內的醫事人員安心的保障，將是一個重要的課題。本實驗以醫院angio-room X光機來進行，選用TLD-100(Harshaw，美國)的熱發光劑量計(Thermoluminescent dosimeter，TLD)置入已編號的夾鏈袋中並懸吊於細繩上，此細繩兩端連接並用旗桿來當作支撐點固定，而TLD位置的佈點將以X光中心射束為中心軸，設定長300公分、寬180公分的平面空間，以每30公分為一個間隔來放置TLD，再分別以85、95、125、155以及180公分高作量測，如此將可形成一個立體空間的劑量分布曲線。為了增加在臨床上醫療技術人員有可能會帶來的散射劑量，在本實驗設置三個假人並穿上鉛衣以模擬散射情形。讀取熱發光劑量手動參數劑量，觀察5分鐘透視攝影的平均劑量，由下往上分五層分別測得的劑量結果為1.46±0.45mGy、1.54±0.69 mGy、2.12±0.82 mGy、1.42±0.56 mGy、1.36±0.38 mGy。從結果發現，在五層數據中 125 公分處測量到最高平均劑量，但即使是最高劑量也低於法規的限值，甚至低於背景劑量，因此可以判定在透視攝影室作業都在安全範圍內。此外主要探討攝影室內劑量分佈情形以及操作人員之間的距離是否也會增加輻射劑量，再加上操作人員在臨床上都會穿著鉛衣，會有散射輻射的影響，增加搭檔之間的輻射劑量，而測量結果顯示操作人員之間距離至少30公分以上，人員劑量可達到降低的效果，測量數據中劑量都達到輻射防護中合理抑低之原則。

關鍵字

透視劑量；散射輻射；空間矩陣；熱發光劑量計

並列摘要

The Atomic Enengy Council (AEC) conducted a programme to maitain the quality image under fluoroscopy since 2018. The medical staffs including radiologist, radiographer, assisted nurse are invesitable exposed to the radiation. The dose distribution depends on the location in the room, different kind of modalities, and the dose protocols. 　　78 TLD-100H (Harshaw, USA) were allocated in the matrix of space of 300×180 cm². Seven cotton threads were fixed on a pole with both ends, 11 TLDs were set at a distance of 30cm equally. Thus, 77 TLDS were allocated at one level. Five levels were set at 85cm, 95cm, 125cm, 155cm, and 180cm from floor to measure the radiation in a room undergoing fluoroscopy. Three models wore apron and simulated the standard position in a room to simulate regular examinations. Each level were exposed three time for justifications. Fluoroscopic time were set respectively at 10sec, 20sec, 30sec, 60sec, 90sec, 120sec, and 150sec. 　　The average dose from first level to the fifth one respectively of 1.46±0.45mGy、1.54±0.69 mGy、2.12±0.82 mGy、1.42±0.56 mGy、1.36±0.38 mGy。According to the result, the average dose at 125cm reaches highest dose but still lower than the allowance of the regulation in Taiwan. Aside from this findings, one result was suggested that medical staffs would also be a source of scatter radiation during fluoroscopy, a 30 cm between two staffs was suggested accordingly.