治疗床旋转误差对立体定向放射治疗计划剂量验证的影响

Influence of the rotational error of treatment couch on dose verification of the SRT plan

目的:分析治疗床旋转误差对立体定向放射治疗(SRT)计划剂量验证的影响。方法:选取医院收治的22例已行SRT患者的临床计划,通过旋转治疗床模拟患者±0.5°、±1°、±1.5°和±2°的摆位误差,利用ArcCheck剂量的验证设备在Axesse直线加速器上进行剂量验证,分析不同治疗床旋转误差在γ通过率3%/3 mm、2%/2 mm不同评价标准下对剂量验证通过率的影响。再根据患者肿瘤体积(PTV)大小将计划分为PTV≤25 cm^(3)组、PTV25~50 cm^(3)组、PTV50~75 cm^(3)组和PTV>75 cm^(3)组,对4组不同肿瘤体积大小分组的计划剂量验证通过率行双因素方差分析,分析不同治疗床旋转角度对不同体积肿瘤的计划剂量验证通过率的影响。结果:在γ通过率3%/3 mm标准下,除0.5°和-0.5°外,模拟治疗床旋转误差角度为1°、1.5°、2°、-1°、-1.5°和-2°剂量验证γ通过率的γ通过率与临床计划相比分别降低了1.4%、1.2%、5.8%、6.1%、12.4%和9.1%,差异均有统计学意义(t=5.241,t=9.733,t=16.641,t=5.387,t=10.792,t=11.292;P<0.05)。在γ通过率2%/2 mm标准下旋转误差角度为0.5°、-0.5°、1°、-1°、1.5°、-1.5°、2°和-2°剂量验证γ通过率与临床计划相比分别降低了2.3%、2.8%、9%、7.4%、19.1%、19.3%、29.5%、24.5%,差异均有统计学意义(t=5.365,t=11.533,t=16.640,t=21.992,t=6.575,t=11.884,t=18.264,t=19.603;P<0.05)。当评估标准设为3%/3 mm时,在相同治疗床旋转误差角度-2°、-1.5°、-1°、-0.5°、0°、0.5°、1°、1.5°和2°下,不同体积的4组γ通过率比较,差异均有统计学意义(F=10.129,F=4.887,F=3.280,F=3.379,F=3.396,F=4.087,F=3.335,F=4.625,F=11.687,P<0.05)。当评估标准设为2%/2 mm时,在相同治疗床旋转误差角度-2°、-1.5°、-1°、-0.5°、0.5°、1°、1.5°和2°下,不同体积的4组γ通过率比较,差异均有统计学意义(F=7.716,F=6.886,F=3.338,F=3.666,F=3.411,F=4.968,F=6.035,F=5.439,P<0.05)。结论:治疗床旋转误差对SRT计划的剂量验证有较大的影响。

Objective:To investigate the influence of the rotational error of treatment couch on dose verification of the plan of stereotactic radiotherapy(SRT).Methods:The clinical plans of 22 patients who had undergone SRT were selected,and the position errors of±0.5°,±1°,±1.5°and±2°of patients were simulated through rational treatment couch.The dose verification was implemented on Axesse linear accelerator by using ArcCheck dose verification equipment.The influence of the different rotational error of treatment couch on the passing rate of dose verification were analyzed under different criteria of 3%/3mm and 2%/2mm ofγpassing rate.Then,the plans were divided into group of PTV≤25 cm^(3),group of PTV25-50 cm^(3),group of PTV50-75 cm^(3) and group of PTV>75 cm^(3) according to the size of planning target volume(PTV).The passing rate of the verification for planning dose of 4 groups with different sizes of tumor volume were analyzed by two-way ANOVA in order to explore the influences of the different rotational angles of treatment couch on the passing rate of dose verification for tumor with different volumes.Results:The error angles of rotational errors of simulated treatment couch were respectively 1°,1.5°,2°,-1°,-1.5°and-2°except 0.5°and-0.5°under 3%/3mm standard ofγpassing rate,and compared with clinical plan,theγpassing rates of dose verification decreased respectively by 1.4%,1.2%,5.8%,6.1%,12.4%and 9.1%,and the differences of them between two clinical plan andγpassing rates of dose verification were statistically significant(t=5.241,t=9.733,t=16.641,t=5.387,t=10.792,t=11.292,P<0.05),respectively.The angles of rotational errors were respectively 0.5°,-0.5°,1°,-1°,1.5°,-1.5°,2°and-2°under 2%/2mm standard ofγpassing rate,and compared with clinical plan,theγpassing rates of dose verification decreased respectively by 2.3%,2.8%,9.0%,7.4%,19.1%,19.3%,29.5%and 24.5%,and the differences of them between two clinical plan andγpassing rates of dose verification were statistically significant(t=5.365,t=11.533,t=16.640,t=21.992,t=6.575,t=11.884,t=18.264,t=19.603,P<0.05),respectively.The differences ofγpassing rates among 4 groups with different volumes under same angle of rotational error of treatment couch were significant when the assessment standard was set as 3%/3(F=10.129,F=4.887,F=3.280,F=3.379,F=3.396,F=4.087,F=3.335,F=4.625,F=11.687,P<0.05),respectively.The differences ofγpassing rates among 4 groups with different volumes under same angle of rotational error of treatment couch were significant when the assessment standard was set as 2%/2(F=7.716,F=6.886,F=3.338,F=3.666,F=3.411,F=4.968,F=6.035,F=5.439,P<0.05),respectively.Conclusion:The rotational error of treatment couch has greater influence on the dose verification of SRT plan.