【摘要】 目的 分析在肺癌立体定向放射治疗（SBRT）中基于锥形束CT（CBCT）影像的摆位误差及对靶区剂量的影响。方法 28例行SBRT的肺癌患者，每次放疗前行CBCT扫描，将得到的CBCT图像与定位CT图像配准，获得左右（X轴）、上下（Y轴）、前后（Z轴）方向的摆位误差值。并计算临床靶区（CTV）外扩至计划靶区（PTV）的边界。在Eclipes计划系统中将治疗中心移至扫描中心，模拟未移床的参数进行计划优化，与治疗前的计划进行对比，分析摆位误差对靶区及危及器官剂量的影响。结果 28例患者共获得222次CBCT扫描，考虑误差数值时左右（X轴）、上下（Y轴）和前后（Z轴）方向的摆位误差分别为（2.00±0.90）、（2.05±1.00）、（1.70±0.70）mm。根据摆位误差得到CTV外扩至PTV的边界在X、Y、Z轴三个方向外扩边界分别为7.60、9.14、5.41 mm。模拟未移床时靶区计划D_98%、D_2%为原计划的（84.6±77.0）%、（100.9±100.0）%,差异具有统计学意义（P<0.05）;原计划靶区的剂量均匀性指数（HI）及适形性指数（CI）显著优于未移床的计划，差异具有统计学意义（P<0.05）。危及器官为模拟未移床计划的肺受量与原计划比较，差异无统计学意义（P>0.05）。模拟未移床计划的心脏D_mean和脊髓D_Max分别为原计划的（99.0±95.0）%、（122.4±98.0）%,差异有统计学意义（P<0.05）。结论 CBCT可有效降低肺癌SBRT的摆位误差，避免危及器官受量和防止靶区受量不足。更多还原

【Abstract】 Objective To analyze the effect of cone beam CT on setup error and radiation dose distribution in stereotactic body radiotherapy（SBRT） of lung cancer.Methods Twenty-eight patients with SBRT pulmonary malignant tumor underwent CBCT scanning before each radiotherapy. The CBCT images were matched with the planning CT images to obtain the setup errors in the left-right（X axis）, superior-inferior（Y axis）, and anterior-posterior（Z axis）. The margins of clinical target volume（CTV） expanded to planning target volume（PTV） was calculated. The actual dosimetric distribution in the target areas and in the organs at risk（OARs） were estimated by inputting the errors into Eclipes treatment planning system for simulating the actual radiation if the isocenter was replaced by the actual location which obtained from the CBCT scan. The effects of the errors in radiation dose distribution were assessed by comparing with the errors in the simulation and original plan.Results A total of 222 CBCT scans were obtained in 28 patients. The setup errors of the left-right（X axis）, superior-inferior（Y axis）, and anterior-posterior（Z axis） were（2.00±0.90）,（2.05±1.00） and（1.70±0.70） mm, respectively. The margin of CTV of lung cancer in three directions（X, Y, Z） were 7.60 mm, 9.14 mm, 5.41 mm, respectively. In the simulation test without shifting the couch, D_98% and D_2% of the target area plan were（84.6±77.0） % and（100.9±100.0） %, and the difference was statistically significant（P<0.05）. The dose Homogeneity index（HI） and Conformal index（CI） of the original plan were signifi cantly better than the plans without couch moving（P<0.05）. There was no significant difference between the simulated unmoved couch plan and the original plan（P>0.05）. In the simulation plan without shifting the couch, the cardiac D_mean and spinal D_Max were（99.0±95.0） % and（122.4±98.0） % respectively, and the differences were statistically significant（P<0.05）.Conclusion CBCT can effectively reduce the setup errors of SBRT in lung cancer to avoid exposure to organs at risk and prevent insufficient exposure to target area.更多还原