鼻咽癌三维适形放疗中的摆位技术的体会

目的计算和分析鼻咽癌三维适形放疗（Three Dimensional Conformal Radiation Therapy, 3D-CRT）摆位误差大小，为鼻咽癌适形放疗提供参考数据。方法以鼻咽癌三维适性放疗患者78例为对象，于每次摆位后、治疗前拍摄一次正、侧位验证片，计算摆位误差。结果78例患者个体随机误差和系统误差呈正态分布，X／Y／Z方向群体随机误差分别为：1．24mm，1．71mm，1．03mm；系统误差分别为：0．13mm，0．66mm，-0．39mm；按照公式计算的外扩边界分别为2．104mm，2．847mm，-0．245mm。结论随机误差对实施3D—CRT过程中的外扩边界影响较大。放疗过程中减小患者躯体纵轴摆位误差，有助于提高鼻咽癌3D—CRT的精确摆位。

Experience of Setup in Three Dimensional Conformal Radiation Therapy of Nasopharyngeal Carcinoma

Objective： To calculate and analyze the setup errors in three-dimensional conformal radiotherapy （3D-CRT） of Nasopharyngeal Carcinoma and provide reference date for 3D-CRT. Method： The seventy-eight patients of Nasopharyngeal Carcinoma were treated with 3D-CRT. The verification films were taken for each patient and matched with digitally reconstructed radiograph （DRR）. Setup errors, in X-axis, Y-axis and Z-axis could be measured. Result： The global random translational errors of X-axis, Y-axis and Z-axis were 1.24 mm, 1.71 mm and 1.03 m, and the systematic errors were 0.13 mm, 0.66 mm and -0.39 ram, margins for planning target volume were 2.104 mm, 2.847 mm, -0.245 mm respectively. Conclusion： Analysis of setup errors in 3D-CRT by using verification films matched with DRR and reduction of Y-axis error could help to improve setup accuracy in 3D-CRT of Nasopharyngeal Carcinoma.