目的:藉著比較模擬定位片與治療前驗證片照野中心點的位移量評估從模擬定位到實際進行放射治療之間其治療部位再現性的程度。材料與方法:由本科自87年度l10位患有子宮頸癌的案例中，抽取35名病患資枓，以恥骨聯合處和病人左右側髖臼頂的位置為解剖參考點，以這些部位此較其模擬定位片與治療前驗證片的照野中心點位移量進行統計分析。結果:35個患有子宮頸癌病患的病例中，在X軸方向誤差小於2 mm的有91.42%;Y軸方向誤差小於4 mm佔有85.72%，顯示出在Y軸方向上誤差比X軸方向上大。結論:在模擬定位片AP位置和治療前驗證片AP位置所得數據中，可發現照野中心點的位移誤差大多皆在可接受的程度內，且其誤差範圍多在0~1 mm之間，表示出從模擬定位室到治療室,治療部位的AP位置準確性很高，這對於整個放射治療的品質保證而言是極重要的一環。

　　　　　Purpose: The objective of this study is to evaluate and compare patient setup errors usingsimulation film and port film in radiation therapy for cervical cancer.Materials and Methods: Simulation films and port films of 35 patients with cervical cancer areanalyzed. Two anatomical landmarks, roof of the acetabulum and symphysis pubis, are used toevaluate the difference between simulation film and port film.Results: Errors in X axis of 31 cases are less than 2 mm. Errors in Y axis of 30 cases are less than 4mm. In other words, the error in Y axis is larger than that in X axis.Conclusion: Based on the analysis of the data of AP simulation films and AP port films, most of theradiation field deviations are within the range of 0 to 1 mm. Therefore, setup errors in ourdepartment are acceptable.