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氟化鋰熱發光劑量計的劑量校正

Dose Calibration of Lithium Fluoride Thermoluminescent Dosimeters

摘要


由於不同的6Li、7Li含量與含有Mg、Ti、Cu、P雜質的氟化鋰(LIF),其對劑量回應的靈敏度不同,所以為了得到準確的劑量測量結果,在實際劑量測量前的熱發光劑量計(thermoluminescent dosimeters, TLDs)之劑量校正是非常重要的。本實驗使用一部Varian 2100 CD醫用直線加速器,其輸出劑量校正是依據AAPM TG-21,選擇使用6MV及10MV之X光射束。將片狀TLD-100置於固態水假體中,並利用一片5mm的組織填充物(bolus)。TLDs的計讀儀為Harshaw 3500。照射的設置方法為SAD=100 cm、照野10×10平方公分、6 MV X光射束最大劑量深度dmax=1.5 cm、10 MV X光射束最大劑量深度dmax=2.5 cm。所測量的劑量範圍10-300 cGy,分成10-100 cGy的低劑量區、100-200 cGy的中劑量區與200-300 cGy的高劑量等三個區域,利用最小平方線性回歸(least squares linear regression)分別得到3條劑量校正曲線。實驗數據採用信賴區間(confidence interval),並且利用盲測法(blind test)來驗證劑量校正曲線的準確性。由低劑量到高劑量的校正曲線其斜率不會是固定的,當劑量值越大其斜率會有小幅度地增加。由於TLD-100在整個劑量範圍內並非有相同的斜率,所以在進行TLDs之校正時必須把劑量校正範圍涵蓋可能被測到的劑量範圍內,以確保其準確性,以符合臨床劑量學±2%的誤差容許值。本實驗且證實TLD-100對6 MV X光射束與10 MV X光射束是沒有能量依存性。

並列摘要


The LiF thermoluminescent dosimeters (TLDs) with different proportion 6Li and 7Li, along with different intentional dopants (Mg, Ti, Cu, P) have varied dose response sensitivity. In order to implement a more accurate measurement, therefore the dose calibration of the TLDs is very important. A Varian 2100 CD LINAC which has calibrated following AAPM TG-21 is used in this study. TLDs were irradiated by 6 and 10 MV x-ray beams in solid water phantom, respectively. TLD-l00 chips were in d(subscript max)=1.5 cm for 6 MV x-ray, and d(subscript max)=2.5 cm for 10 MV x-ray by field size 10×10 cm^2 at SAD=100 cm. The dose range was 10-300 cGy, which 10-100 cGy was defined as low dose range, 100-200 cGy as medium dose range, and 200-300 cGy for high dose range. Least squares linear regression, and blind test were applied in this study. The slightly increase of the calibration curves shows its nonlinearity. Dose dependence and non-energy dependence are assured in this study as well.

被引用紀錄


賴威豪(2015)。以侖道假體與自研數學假體評估鼻咽癌病人在動態弧形調控放射治療下的輻射劑量分布〔碩士論文,中山醫學大學〕。華藝線上圖書館。https://doi.org/10.6834%2fCSMU.2015.00059
呂憶鑫(2012)。利用熱發光劑量劑評量桃園研究用反應器停爐後之軸向衰變加馬線分佈〔碩士論文,中臺科技大學〕。華藝線上圖書館。https://doi.org/10.6822%2fCTUST.2012.00047

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