本研究利用田口方法探討治療參數對劑量的影響，在放射治療的領域內，新的技術複雜度與新的機器設備日 趨先進及功能變化多，使得從處方劑量到實際劑量給予的治療過程中，會產生許多不可預知的不確定錯誤及誤 差，本實驗使用三個不同大小的自製圓柱型劑量假體，分別為直徑16cm、24cm 和32cm，高皆為15cm，配合直 線加速器可調控的輸出的八個參數，依序為射束能量、弧形治療角度、照野大小、準直儀旋轉角度、治療床旋轉 角度、等中心點偏移量、假體偏移量和劑量率。將所選取之八個參數與設定每個參數的改變量範圍，配合田口的 L18 (21x73) 直交表，依序套入各參數的變化量，並使用法默型游離腔(Farmer ion chamber)測電量及記錄結果，重 複量測4 次，並使用變異數分析ANOVA(Analysis of Variance) 驗證研究所得結果，亦顯示98%以上信心水準， 具有統計上顯著的意義。實驗結果得知照野大小的影響對機器輸出之劑量影響程度最大，其影響順序分別為照野 大小、射束能量、弧形治療角度、等中心點偏移量、準直儀旋轉角度、劑量率、治療床旋轉角度和假體偏移量。 研究結果顯示機器參數的改變對劑量輸出上有影響程度的高低，以提供臨床人員參考。

New technology and machine are more and more complicated in the radiation field. The treatment process from the prescribed dose to the actual dose will generate a lot of uncertainty error and setup error. In this study, three different size of homemade phantom with all 15 cm height and 16 cm, 24 cm and 32 cm diameter, respectively, were used. Eight parameters in machine for dose were chosen for analyses. By setting the range of change of each parameter with Taguchi L18 (21x37) orthogonal array, Farmer ion chamber were used to measure the electric charge. All measurements were repeated 4 times and the results were analyzed by analysis of variance (ANOVA). The most important factor is field size, followed by beam energy, the angle of arc treatment, isocenter offset, the angle of collimator rotation, dose rate, the angle of couch rotation, and the offset of the phantom, respectively. Each parameter has different impact on radiation dose. These results can be helpful for clinical staff.