本研究的目的是量測光子射束在小照野下之劑量分佈，所使用的工具是MAGAT抗氧化聚合物膠體劑量計、EDR2膠片劑量計以及蒙地卡羅電腦模擬程式等三種方法進行測量與模擬。進行小照野照射前，本研究先進行在大照野下MAGAT劑量膠相關特性之測試，測試項目包含評估圈選不同感興趣區域半徑大小對R2值分佈之影響、不同時間對劑量膠進行磁振造影掃描以及觀察在不同批次的劑量膠中， R2劑量反應曲線的差異。在小照野的照射方面，我們利用由BrainLab公司為光子刀放射手術所製作三種不同尺寸的圓錐型準直儀(14 mm, 4 mm及3.1 mm)進行照射，並比較蒙地卡羅模擬程式與MAGAT劑量膠在絕對劑量下之劑量剖面分佈。本研究也利用由柯達公司所生產的EDR2膠片劑量計進行劑量驗證，並與蒙地卡羅模擬程式比較相對劑量與絕對劑量下之差異。除了利用上述工具測量光子在小照野之劑量分佈外，本研究亦探討蒙地卡羅模擬程式以切割不同大小的體素，模擬光子射束在小照野中絕對劑量分佈之影響。

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