現今各大醫療院所之放射腫瘤單位，皆多引進強度調控放射治療技術，以作為另一種放射治療技術選擇；醫用直線加速器機頭內之多葉式準直儀，即為達成此治療技術之必需工具，多葉式準直儀之葉片可直接形成治療照野。然而當射束經過葉片時所形成之射束半影，將影響放射治療計畫之製定與處方劑量給予之準確性及可靠度。為降低強度調控放射治療之處方劑量差異，由放射治療計畫系統之射束模式與實際測量之射束模式，探討多葉式準直儀射束半影特性造成之影響，並進一步了解兩者差異來源。
本研究採用Gafchromic EBT膠片劑量計，進行多葉式準直儀射束半影特性之實驗測量；在規則照野部份，將幾何條件變化如照野大小、偏移射束中軸距離列入評估；在不規則照野部份，將葉片逐漸移動、葉片形成空隙時之類似實際治療照野情形列入評估，分析在上述情況時，葉片四周形狀所造成之射束半影特性與相對變化關係，再與放射治療計畫系統之相同射束模式比較，以研究葉片之射束半影特性對放射治療劑量分布造成之擾動情形，並了解放射治療計畫系統與實際測量結果之差異。本研究並嘗試建立Gafchromic EBT膠片劑量計之最佳化校正方法，透過校正參數之改變與膠片影像之處理，了解此類膠片之特性並提供較準確之劑量─響應關係。
放射治療計畫系統未良好考慮葉片射束半影之影響，且治療照野邊緣之劑量差異，為葉片射束半影與輻射照野差異所共同貢獻，因此計算所得劑量分布在照野邊緣範圍，與實驗測量之結果略具差異；而在葉片移動時所造成之劑量擾動區與葉片產生之散射光子，在照野邊緣範圍處，計算所得劑量分布與實驗測量之結果亦存有差異；本研究將透過多葉式準直儀葉片之設計概念及放射治療計畫系統之運算模式特性，試圖解釋此差異產生之由來；惟研究結果顯示，放射治療計畫系統在劑量計算時，除須考慮因照野邊緣劑量梯度變化，所形成葉片射束半影之影響外，更需準確考慮多葉式準直儀葉片之幾何形狀特性與移動細節，並改善因射束發散性而產生之輻射照野差異，如此方可實際提升放射治療計畫運算結果之可靠度；另經不同校正參數之測試，已建立Gafchromic EBT膠片劑量計之使用程序，在實驗上有良好之穩定性。

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