三维适形及调强放疗摆位误差分析

Analyzing of Set-up Errors in Three-dimensional Conformal and Intensity Modulated Radiotherapy

目的:测定和分析三维适形及调强放疗的摆位误差,并依此计算CTV外扩PTV边界的大小。方法:对2007年5月-6月的162例患者的摆位误差进行测定。体位固定头颈部采用头模或头颈肩模,胸、腹部采用负压袋。每例患者第一次治疗前及以后的每周都在加速器上拍摄正、侧位等中心验证片各一张,与治疗计划系统中的DRR片比较,计算出摆位误差。CTV到PTV外扩边界的大小由公式2.5Σ+0.7σ计算得出,其中Σ为系统误差,σ为随机误差。结果:由公式得出我科外扩PTV的理论边界分别为:头颈部X、Y、Z方向各为1.01mm,0.59mm,2.29mm,胸部各方向分别为2.77mm,2.16mm,3.41mm,腹部各方向分别为2.50mm,4.11mm,3.55mm。结论:通过对摆位误差的分析为我科外扩CTV边界提供了理论依据,确定了CTV到PTV外扩边界的大小,使得我科治疗计划的设计更为科学合理。

Objective： To examine and analyze the set-up errors for patients with three dimensional conformal and Intensity Modulated Radiotherapy to calculate CTV referential safety margins of PTV. Methods： The set-up errors of 162 patients during May-June in 2006 were examined in this study. Thermoplastic mask was used for head and neck and vacuum cushion was used for chest and abdomen immobilization. The verification films were taken for each patient prior the first treatment and the latter per week were compared with the digitally reconstructed radiographs （DRR） on treatment planning system, in order to make sure set-up errors. CTV margin should be calculated with the formula 2.5∑＋0.7σ, ∑means Systematic Error, σ means Random Error. Result： The margin of PTV of head and neck in three directions （X,Y,Z） was 1.01 mm, 0.59 mm and 2.29 mm respectively, the margin of PTV of chest in three directions （X,Y,Z） was 2.77 mm ,2.16 mm and 3.41 mrn respectively and the margin of PTV of abdomen in three directions （X,Y,Z） was 2.50 mm, 4.11 mm and 3.55 mm respectively. Conclusion： It has laid a theoretic foundation for our CTV margins by analyzing the set-up errors and made our design of radiotherapy system more scientific and normal.