独立准直器调强放疗系统的验收测试  

Commissioning of intensity - modulated radiation therapy system with independent collimator

作　　者：张可[1] 戴建荣[1] 陈利 李宇恒 李亮[3] 

机构地区：[1]中国医学科学院北京协和医学院肿瘤医院肿瘤研究所放疗科,北京100021 [2]第四医院放疗科,鞍山市114034 [3]徐州医学院附属医院放疗科,221002

出　　处：《中华放射肿瘤学杂志》2011年第2期164-167,共4页Chinese Journal of Radiation Oncology

摘　　要：目的建立IC。IMRT系统的验收测试方法并完成该系统的验收测试。方法采用NE2571电离室和2570剂量仪测量加速器的启动特性和下咽、肺及宫颈癌3个病例的等中心和其他剂量特征点的绝对剂量。采用Mapcheck2二维半导体矩阵验证基本测试例和3个病例的二维平面剂量分布。基本测试例由矩形或方形射野组成，分别为2cm×2cm、5cm×5cm、10cm×10cm、20cm×20cm、2cm×10cm、10cm×2cm、5cm×20cm和20cm×5cm的对称射野，2cm×2cm（x1=4cm、Y1=10cm，x2=-2cm、y2=-8cm）和5cm×5cm（xl=-2em、Y1=-5cm，x2=7em、y2=10cm）的非对称射野及由5个20cm×4cm的射野合成的20cm×20cm的条状叠加野。采用1分析法比较测量和计算的剂量分布，通过率标准为3mm／3％I〉90％。结果当加速器输出跳数达到4即可保证2％的剂量精确性；对所有测试例等中心及特征点的绝对剂量误差最大为-3．67％；在全部11个基本测试野和3个病例的24个照射野中只有条状叠加野和下咽癌病例2个野的通过率稍低于90％，分别是83．6％、88．3％和89．7％。3个计划的实施时问依次是15、14、27min。结论测试结果总体满足临床要求，系统可用于患者治疗。Objective To perform an acceptance test for the IMRT system with independent collimator. Methods An ion chamber dosimeter were used to measure the startup characteristics of the accelerator and the absolute dose at isocenter and given characteristic points for three clinical cases （a lower nasopharyngeal carcinoma, a lung cancer and a cervical cancer）. The characteristic points represented the organs at risk or the target. A Mapcheck2 was used to measure dose maps of basic test fields and the treatment fields for the clinical cases. The basic test fields were as follows ： 1 ）. Symmetric fields in size of 2 cm×2 cm, 5cm×5 cm, 10 cm×10 era, 20 cm×20 cm, 2 cm×10 cm, 10 cm×2 cm, 5 cm ×20 cm and 20 cm×5 cm;2）. Asymmetric fields in size of 2 cm ×2cm （x1 =4 era, yl = 10 cm;x2 = -2 cm, Y2 = -8 cm） and 5cm×5 cm （x1 = -2 cm, y1 = -5 era;x2 =7 era, y2 = 10 era） ;3） A 20cm ×20 cm composite field composed of five 20 em~ 4 cm narrow bar fields side by side. Gamma Index was used to compare calculated and corresponding measured dose distributions. When the criterion was 3% dose difference or 3 mm distance-to-agreement, the pass rate was required to be more than 90%. Results The accuracy of machine output was better than 2% when machine monitor units increased to 4. Among all basic test fields and all the treatment fields of three clinical cases, the maximal absolute dose error was - 3.67%, and only the composite test field and two treatment fields of the lower nasopharyngeal carcinoma case had a pass rate slightly less than 90%, which were 83.6%, 88.3% and 89.7% ,respectively. For the three clinical cases the treatment delivery times were 15, 14, and 27 minutes, respectively. Conclusions The overall commissioning results are acceptable, and the system can be used in clinic.

关 键 词：调强放疗系统 独立准直器 验收 

分 类 号：R730.55[医药卫生—肿瘤]