移動式X光機周遭之空間劑量評估

本研究使用熱發光劑量計評估移動式X光機附近的曝露，包括實際現場的照射及實驗室的模擬。在移動X光機儀器周遭做TLD佈點，經實際巡迴病房現場累積一個月的曝露；實驗室的模擬則以移動式X光機、假人、病床、熱發光計的空間懸吊，曝射100次以模擬現場照射及空間劑量評估。X光管管套表面附近，曝露最大值位於X光管下方之X光射出窗附近，曝露值為75.02 mR；而X光管上方因有球外殼屏所以其值偏低，僅為下方射出窗周遭的二十五分之一。X光管左右二端相差大，右端曝露值為15.49 mR約為左端的五倍，主要可能為陰陽極與跟效應所致。本研究評估某醫院之移動式X光機在無鉛屏蔽條件下，所站位置至X光管之水平距離1.5公尺，一個月累積的劑量約為0.046 mSv，相當於年劑量0.55 mSv，此值低於職業平均年限度值20 mSv。而在有屏蔽的情況下，鉛屏蔽後方之放射師等醫護人員曝露為1.1 mR，換算成年累積劑量約為0.125 mSv。於X光室內空間曝露之模擬，屏蔽離X光管球1.6公尺，鉛屏蔽前端曝露平均值為2.42 mR；而後端平均值為1.28 mR，屏蔽約阻擋減少47%的輻射曝露。屏蔽後方平均值1.28 mR應可作為100次移動式X光照射曝露參考之保守值。高度於1.0 m到1.5 m空間之曝露量較其他高度大。而距離X光管0.5公尺、1.0公尺、1.5公尺的曝露量分別為12.27 mR、4.41 mR、2.82 mR，距離越遠曝露越低。

關鍵字

移動式X光機；曝露；劑量；熱發光劑量計

並列摘要

The thermoluminescent dosimeters (TLD) were adopted to assess radiation dose that were resulted from exposure of portable X-ray machine. The study includes two parts, a field study and a laboratory experiment. Some TLDs were attached on the surface of an X-ray machine that was actually performed in the hospital and exposed to X-ray in one month. Besides, that a portable X-ray machine, a body phantom, and a table were assembled to setup on a clinical room and exposed 100 times to simulate the field study and investigate exposure strength. The maximum accumulated dose around the surface of X-ray tube was 75.02 mR that was found beneath the X-ray tube, near the window. But the dose that located upper the tube was low, a twenty-fifths of the maximum dose. Doses on the sides of the tube were rather different as a result of heel effect. The dose, 15.49 mR, on the right side is five times of that on the left side. The dose with a distance of 1.5 m from X-ray tube without any lead shield was 0.046 mSv for a month. It is equivalent to 0.55 mSv for a year that is lower than annual occupational dose limit, 20 mSv. The exposure behind the lead shield was 1.1 mR for a month. It is equivalent to 0.125 mSv for a year. The laboratory experiment was performed to simulate and assess space exposure around an X-ray machine. After one hundred exposures, doses before and behind of lead shield were 2.42 mR and 1.28 mR, respectively. Lead shield prevents 47% X-ray exposure. The space exposures at the altitude of 1.0 m and 1.5 m were higher that at the altitude of 0.5 m. The exposures with a distance of 0.5 m, 1.0 m, and 1.5 m from the place to X-ray tube were 12.27 mR, 4.41 mR, and 2.82 mR, respectively. The data showed longer distance lower exposure.

並列關鍵字

portable x-ray unit ； exposure ； dose ； TLD

國際替代計量

移動式X光機周遭之空間劑量評估

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