应用Detector729的两种IMRT剂量验证方法比较

目的：比较、分析Detector729用于IMRT质量控制的两种剂量验证方法。方法用Pinnacle 8.0 m计划系统对13例肿瘤患者做IMRT治疗计划，根据Detector729的CT扫描图像，分别做出实际机架角和0＆#176;机架角的验证计划，并在Varian 23EX加速器上实施剂量验证；依据剂量偏差（距离偏差）分别为3%（3 mm）、3%（4 mm）和4%（4 mm）的判定标准，得到两种验证方法的γ验证通过率，采用SAS统计学软件对验证结果进行分析。结果 Detector729两次测量的重复性均＜0.3%；应用Detector729对IMRT实际机架角验证3%（3 mm）、3%（4 mm）和4%（4 mm）的平均通过率分别为91.2%、92.4%和95.6%，较0＆#176;机架角计划验证通过率分别低了2.2%（t=-2.04，P=0.053）、2.2%（t=-2.02，P=0.055）和1.4%（t=-1.97，P=0.060），两种剂量验证方法的通过率差异无统计学意义。结论 Detector729测量结果可信、准确；实际照射剂量验证和0＆#176;机架角剂量验证均与验证计划剂量分布基本一致；建议医疗机构采取符合实际治疗情况的剂量验证方法。

Comparison of two dosimetric verification methods of IMRT using Detector729

Objective To compare and analyze the dose distribution of IMRT between fixed-gantry and unfixed-gantry dosimetric verification. Methods Thirteen patients treated by IMRT were cho-sen randomly for this study. For each case, 2 different plans （fixed-gantry plan and unfixed-gantry plan） were worked out with Pinnacle 8.0 m planning system. The dose verification for each plan was carried out with Varian 23EX by using Detector729 with the octagonal phantom OCTAVIUS. The verification results of the dose distribution between the treatment planning system calculation and the measurement were done by the gamma analysis quantization with dose difference and distance to agreement of 3%（3 mm）, 3%（4 mm） and 4%（4 mm） respectively, and the data were analyzed by Statistical Analysis System. Results The repeatability of Detector729 was within 0.3%. According to the gamma analysis , the overall average passing rate of unfixed-gantry verification for the dosimetric deviation of 3%（3 mm）, 3%（4 mm）and 4%（4 mm） were 91.2%, 92.4%and 95.6%, which were slightly lower compared with the passing rate of fixed-gantry verification of 2.2%（t=-2.04, P=0.053）, 2.2%（t=-2.02, P=0.055） and 1.4%（t=-1.97, P=0.060） respectively, and the difference between the two verification methods was not statistically sig-nificant. Conclusions The Detector729 is a reliable and accurate dosimeter. The two dosimetric verifi-cation methods of IMRT by using Detector729 are efficient and valuable. The radiotherapy department should select suitable and available dosimetric verification method for radiotherapy.