摘要目的 研究测量数据插值、计划系统剂量计算网格及剂量评估阈值等因素对立体定向调强放射治疗患者计划的剂量验证结果的影响.方法 回顾性分析了50例立体定向放射治疗的患者放疗计划的剂量验证结果 .剂量验证设备采用MatriXX及配套MultiCube固体水模.测量数据分别选择线性插值(1.00 mm)和不插值(7.62 mm)两种分辨率;计划系统剂量计算网格分别选择1.0、2.5和4.0 mm;剂量评估阈值分别选择10％、20％和30％,γ评估标准分别选择2％/2 mm、3％/2 mm和3％/3 mm,分析不同因素选择对平面剂量验证结果的影响.结果测量数据插值选择线性插值和不插值,2％/2 mm标准下,γ 平均通过率分别为(86.3±7.3)％和(93.7±5.5)％;3％/2 mm标准下,γ平均通过率分别为(94.1±4.4)％和(97.7±3.9)％;3％/3 mm标准下,γ平均通过率分别为(97.7±2.2)％和(99.1±1.7)％.相比1.0 mm的剂量计算网格,使用2.5 mm计算网格,3种标准下γ平均通过率分别降低3.8％、1.9％和0.8％(t=8.41、9.06、5.30,P<0.05),4.0 mm分别降低6.5％、6.0％和3.5％(t=-13.76、-13.15、-9.80,P<0.05),差异有统计学意义.相比剂量评估阈值为10％,当阈值设置为20％时,2％/2 mm、3％/2 mm和3％/3 mm标准下,γ平均通过率分别降低2.4％、1.0％和0.6％(t=-8.60、-5.86、-4.68,P<0.05);当阈值设置为30％,3种标准下γ平均通过率分别降低4.0％、1.7％和0.9％(t=-9.45、-6.66、-5.06,P<0.05),差异有统计学意义.结论 测量数据插值、剂量计算网格大小及剂量评估阈值对立体定向放射治疗患者计划剂量验证结果均有明显影响,因此在进行立体定向放射治疗患者计划剂量验证时需要考虑这些因素.

abstractsObjective To analyze the patient-specific dosimetric verification result of stereotactic body radiotherapy ( SBRT ) plans, and to investigate the sensitivity of the result to three factors:interpolation of measured data, size of dose calculation grid and assessment threshold. Methods The dosimetric verification results of SBRT plans of 50 patients were retrospectively analyzed to evaluate the impact of the following factors. The linear interpolation ( 1. 00 mm) and non-interpolation ( 7. 62 mm) were applied to measured data respectively. Three dose calculation grid sizes of Eclipse planning system, i.e., 1. 0 mm, 2. 5 mm and 4. 0 mm were compared respectively. The threshold of dose assessment was selected as 10％, 20％ and 30％, respectively. Three criteria of γ analysis were selected: 2％/2 mm, 3％/2 mm and 3％/3 mm. Results Under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, the average γ passing rates were (86. 3±7. 3)％ and (93. 7±5. 6)％, (94. 1±4. 4)％ and(97. 7±3. 9)％, (97. 7 ±2. 2)％ and (99. 1±1. 7)％, respectively, with and without linear interpolation. Relative to the 1. 0 mm reference grid, the grids of 2. 5 mm and 4. 0 mm significantly decreased γ passing rates by 3. 8％, 1. 9％, 0. 8％ ( t=8. 41, 9. 06, 5. 30, P<0. 05) and by 6. 5％, 6. 0％, 3. 5％ ( t=-13. 76, -13. 15, -9. 80, P<0. 05) under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, respectively. Relative to the 10％ reference threshold, the shresholds of 20％ and 30％ significantly decreasedγpassing rates by 2. 4％, 1. 0％, 0. 6％(t=-8. 60, -5. 86, -4. 68, P<0. 05) and by 4. 0％, 1. 7％, 0. 9％ (t=-9. 45, -6. 66, -5. 06, P<0. 05) under criteria of 2％/2 mm, 3％/2 mm and 3％/3 mm, respectively. Conclusions Interpolation, dose calculation grid size and dose assessment threshold are influential factors of dose verification result, and need to be considered during dosimetric verification of stereotactic radiotherapy patients.