目的：以電子驗證影像快速估測光與輻射照野一致性、光子平坦性與對稱性。材料與方法：本研究所使用之電子驗證影像，其來源為 Elekta Precise Sli 直線加速器，配置型號為 Perkin Elmer XRD 1640 之電子影像驗證裝置所拍攝。以所附 iViewGT 軟體將影像轉存為 16 位元的標記影像檔案格式後，在工程計算軟體 Matlab 版本 2008b 中，撰寫程式對輸出影像進行分析。我們首先測量在不同的照射條件下所測得之輻射照野與光照野是否吻合。接著再分別計算不同條件下的光子平坦性與對稱性。結果：根據我們的實驗結果，測量10張影像水平軸與垂直軸的光與輻射照野的一致性、光子平坦性與對稱性僅需花費0.414秒。其內容顯示，光與輻射照野一致性與光子對稱性之測量全數符合標準。但是在平坦度的測量則發現，以6 MV照射時，水平軸照野為5 cm、10 cm、15 cm與10 MV照射時，水平軸照野為5 cm共四組資料，因MLC較大的半影區導致測量結果超出規定限值。結論：相較於其他測量儀器，電子驗證影像裝置之解析度為1024×1024，經換算後約0.25 mm，可以偵測出小照野細微的變化。快速的測量計算搭配檢測頻率的提高可以提早發現問題，再使用更精密的儀器如水假體等儀器進行更進一步的測量。

Purpose : Fast evaluation of light/radiation field coincidence, beam f latness and symmetry measurement by electronic portal image device.
Material and Methods : In this study, EPIs was taken by Elekta precise SLi linear accerator equipped with Perkin Elmer XRD 1640 EPID. Images were exported by iView GT software as 16 bits Tagged Image File Format. All images were analyzed by Matlab 2008b. Light/radiation fields coincidence was calculated under different exposure condition. Finally, beam flatness and symmetry of different photon energy and collimator setting were analyzed.Results : According to the experiment results, it takes 0.414 seconds to analyze 10 EPIs with light/radiation field coincidence, beam flatness and symmetry. Each has vertical and horizontal data respectively. All of the results of light/radiation field coincidence and symmetry measurement could meet the standard of tolerance. But the horizontal flatness of 6 MV with 5 cm, 10 cm and 15 cm
collimator settings and 10 MV with 5 cm collimator setting exceeded the tolerance level due to larger penumbra of MLC.Conclusion : Compare with other instruments, the resolution of EPID is 1024×1024. It means that
each pixel represents 0.25 mm that is suitable for small field analysis. The calculation is fast enough to increase analysis frequency and any abnormality could be uncovered as early as possible.