目的：根據美國醫學物理學會第 142 號報告建議，利用 EBT3 自顯底片執行 Varian Millennium 120-Leaf 多葉準直儀的例行品質保證作業。 材料與方法：採用第三代 EBT 自顯底片收集 Varian Millennium 120-Leaf 多葉準直儀的例行品質 保證作業的影像，使用 PIPS pro 軟體分析量化其誤差值並建立其多葉準直儀品保基準值。品質 保證施作項目包括每月品質保證，項目有光照野與輻射照野吻合度、備用準直儀設定、葉片遷移 速度、葉片位置準確度。每年品質保證，項目有光照野與輻射照野吻合度、葉片輻射中心點測 試、葉片位置再現性及葉片穿透率。本研究依照多葉準直儀品保的要求，對於照射 EBT3 自顯底 片的步驟、曝光條件與設計的品保照射模組提供可行的建議。 結果：各項多葉準直儀品保結果都符合美國醫學物理學會第 142 號報告的要求，這結果只限於該 部直線加速器配置 Varian Millennium 120-Leaf 多葉準直儀。數項多葉準直儀品保測量值都能與直 線加速器驗收時的基準值相吻合。只要有適當的軟體與方法，EBT3 自顯底片能夠滿足多葉準直 儀的例行品質保證作業。 結論：項目中的葉片輻射中心點測試會與直線加速器品質保證中的準直儀輻射中心點測試一致. ， 由於 Varian Millennium 120-Leaf 的多葉準直儀與準直儀位於相同機頭但只是上下層位置不同。葉 片位置準確度會因重力的影響隨著機頭角度的變化呈現不同結果。

Purpose : Follow recommendation of AAPM report no.142; applying EBT3 film to process routine quality assurance for Varian Millennium 120-Leaf multileaf collimator. Materials and Methods : The study was designed the specific pattern for MLC quality assurance and acquired the images by EBT3 film. The commercial software can be analyzing the images scanned from EBT3 film and creating reference values. The monthly QA items was included setting versus radiation field for two patterns、travel speed and leaf position accuracy. The items for annual QA was consisted of MLC transmission for all energies, leaf position repeatability, MLC spoke shot, coincidence of light field and x-ray field and IMRT testing for segment and sliding window. The paper was described particularly for the QA procedure, method of exposed film and specific testing pattern. Results : The results of quality assurance for Varian Millennium 120-Leaf were satisfied with criteria which were recorded on AAPM report no.142. The QA reference values were only available for this specific MLC on this linear accelerator. The paper is presenting the QA procedure of Varian Millennium 120-Leaf MLC using EBT3 film and appropriate software. Discussions : Several MLC QA reference values could be consist with record on customer acceptance procedure document. Due to MLC was installed lower level than collimator but on same gantry head. The result of MLC spoke shot could be same with collimator spoke shot. The accuracy of leaf position must be varying with gantry angle causing gravity.