建立以直線加速器為基礎可廣泛使用之小動物照射系統是臨床動物實驗的一個重要的過程，本文為電子照射系統發展之初步研究，主要探討6 MeV與18 MeV電子射束於小照野下之劑量分佈與特性。本研究提出以電子射束來取代先前研究者使用的光子射束來發展此一系統。在Varian 2100 C/D直線加速器上建立小動物照射系統，並以6×6 cm2電子照射筒下方放置不同大小的鉛合金擋塊限制出小照野（直徑30 mm、14 mm、6 mm、4 mm圓形照野），之後以蒙地卡羅BEAMnrc06模擬程式模擬6 MeV與18 MeV電子射束於小照野下之劑量分佈，使用diamond detector與XV film分別測量直徑30 mm與4 mm小照野下之劑量分佈與輸出因子，以驗證模擬系統的準確性。研究結果顯示，diamond detector測量直徑30 mm圓形照野之百分深度劑量曲線與模擬結果差異為±2.2%，劑量剖面之FWHM差異小於0.5 mm，然而因偵檢器解析度限制，使直徑4 mm照野下百分深度劑量曲線與模擬不盡相符，劑量剖面差異有1.2 mm；此外，模擬6 MeV與18 MeV電子射束在直徑4 mm圓形照野下，R90深度之半高全寬分別為8.1 mm與4.7 mm，輸出因子分別為0.13與0.61，說明了使用電子射束照射小動物的可行性。

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