熱發光劑量計於臨床劑量量測之應用

The Study of Thermoluminescence Dosimeter for Clinical Surface Dose Measurement

薛德輝(Te-Hui Hsueh) ； 劉衣祺(Yi-Chi Liu) ； 林招膨(Jao-Perng Lin)

《台灣應用輻射與同位素雜誌》 6卷3期 (2010/09) Pp. 921-925

https://doi.org/10.29832/TJARI.201009.0004

摘要

熱發光劑量計具有化學性質穩定、對外在因素高抵抗性、對輻射反應具有良好再現性等特性，且與生物組織等效，有效原子序大約爲8.2至7.4，一直是輻射量測的最佳材料，熱發光是物質在吸收輻射能後，藉由外加熱的過程中，將其吸收的輻射能激發所發射的光，熱發光劑量計對光子輻射敏度反應，隨著光子輻射能量變化而改變。輻射光子穿越高低原子序材料，會對材料界面劑量分布造成劑量干擾，臨床對於這種界面效應的探討是劑量學重視的現象。本文使用熱發光劑量計敷蓋不同厚度高原子序數材料例如金，照射6MV光子，以探討界面劑量的差異是否與理論預期相符。由於高原子序物質所產生二次電子的增建影響，通常會造成在界面前端與回散射端的劑量增加。由實驗結果顯示，當金厚度小於二次電子射程，界面劑量下降，但在厚度達增建區厚度，界面劑量增加，此結果與理論相輔，可應用於皮膚劑量之探討。

關鍵字

熱發光劑量計 ； 界面劑量

並列摘要

Dose enhancement was found in an environment of tissue-equivalent material close to the surface of a metallic gold thin film. Validity of estimation of dose perturbations is critical in the evaluation of radiation effect associated with high-Z interface. Thermoluminescence dosimeters covered with different thickness of gold foil were used as interface dose measurement device. The irradiation source used in this work is photons generated by a 6MV LINAC. The results simulated show dose reduction for the thickness of gold foil within sub-micrometer region. The dose enhancement can only be found when gold foil thicker than several micrometers. If gold foil is thick enough, the flux of secondary electron increases and enhances the interface dose. In this work, we found that the interface dose enhancement is related to the thickness of gold film. The ultra-thin film with high-Z material could reduce interface dose is confirmed by Monte Carlo simulation and measurement. With proper design this ultra-thin film might be applied for skin dose reduction.

並列關鍵字

thermoluminescence dosimeter ； interface dosimetry