探討CVD-鑽石薄膜劑量計對醫療用高能量光子與電子射束的敏度反應

The Sensitivity Study of Chemical Vapor Deposition Diamond Film for Clinical High Energy Photon and Electron

張東浩(Tung-Hao Chang) ； 郭瓊文(Chiung-Wen Kuo) ； 賴源淳(Yuan-Chun Lai) ； 王銘志(Ming-Chih Wang) ； 陳苑蓉(Yuan-Jung Chen) ； 楊英傑(Ying-Chieh Yang) ； 謝忠志(Chung-Chih Hsieh)

《中華放射線技術學雜誌》 34卷4期 (2010/12) Pp. 252-257

https://doi.org/10.30045/CJRT.201012.0006

摘要

本研究主要探討不同厚度CVD-鑽石薄膜劑量計於醫療用高能量光子與電子射束量測之敏度反應、消光效應及入射輻射角度對其敏度之影響。研究中量測厚度0.2mm及0.5mm-CVD劑量計對直線加速器之能量6MV、10MV光子及能量6MeV、9MeV、12MeV、15MeV電子射束的敏度反應，並探討兩種不同厚度CVD劑量計受環境光因素影響所造成之消光反應，及其對劑量之曲線回應。研究中亦探討CVD劑量計對不同能量射束之能量依恃反應及不同入射角度的敏度反應。結果顯示CVD鑽石薄膜容易受光線影響造成消光反應，照射後60分鐘內消光反應不明顯；但於亮室中放置46小時後，0.5mm-CVD發光亮減少49.24%，0.2mm-CVD發光亮減少71.11%。當劑量給到500cGy時，0.5mm-CVD及0.2mm-CVD之劑量回應曲線R-square值分別為0.993及0.991；當劑量給到4000cGy時，對其作二次多項式曲線擬合，其R-square值則可達至0.995及0.991。CVD對於光子射束的能量依恃反應因子變化不大，但12MeV及15MeV電子射束反應較為明顯，其能量依恃反應因子大於1.04。此外，CVD之入射角度敏度反應因子也會隨著入射角增加而增加。CVD鑽石薄膜適用於放射治療之高劑量量測，惟使用須注意環境光線對其造成之消光反應，最好能於照射後1小時內計讀或存於暗室之中。

關鍵字

CVD ； 放射治療 ； 消光 ； 劑量回應

並列摘要

The purpose of this study is to make a study of clinical characteristics and fading effect of CVD diamond detectors with different thickness as applying for radiotherapy. Measurements were performed for 6MV, 10MV photon and 6MeV, 9MeV, 12MeV, 15MeV electron with 0.2mm-CVD and 0.5mm-CVD. The CVD fading effect caused by indoor light in blight room and darkroom, and the linearity of dose response for 0cGy to 4000cGy were measured. We also measured the oblique factor caused by difference incident angle and the energy dependence factor of CVD for Co-60 and linear accelerator beams. Our results show that the indoor light will make CVD fading acutely. The fading effect is not obvious when reading is performed no more than 60 minutes after irradiating. The TL response decrease 49.24% for 0.5mm-CVD and 71.11% for 0.2mm-CVD as they were placed in bright room for 46 hours. The linearity of TL response of CVD is good for dose get up to 500cGy, the R-square values are 0.993 and 0.991 for 0.5mm-CVD and 0.2mm-CVD, respectively. As the CVD are irradiated up to 4000cGy, the R-square values are 0.995 and 0.991 respectively. The energy dependence factors of CVD for photon beam don’t vary greatly but vary greatly for 12MeV and 15MeV electron that energy dependence factors are greater than 1.04. Furthermore, the oblique factors also increase with increased incident angle.

並列關鍵字

CVD ； radiotherapy ； fading ； dose response