G4射波刀两年质量保证检测结果的回顾与评价

Review and Evaluation on The Results of Quality Assurance Test for The 4th Generation CyberKnife in Two Years

目的:对G4射波刀两年的重要QA检测结果进行回顾和统计,评价射波刀的各项性能。方法:2011年1月-2013年1月,射波刀正常运行443天,设备保养24天,故障57天。对两年内射波刀的剂量率、剂量输出一致性、自动质量保证、TPR20/10、平坦度、对称性、半影、剂量输出精确性、端到端(E2E)测试、影像中心检查等检测结果进行回顾。结果:剂量率725 MU/min～810 MU/min;剂量输出一致性检查有31次(7.0%)超过2%,需要校准;TPR20/10值:0.663～0.678;AQA检测有13次(9.2%)总偏差大于0.8 mm,其中1次(0.7%)检测出设备存在故障;平坦度:6.24%～8.78%;对称性:0.22%～0.38%;射野半影:3.20 mm～3.51 mm;剂量输出验证:2.34%～4.55%;15次E2E检测中有1次超过规定值;影像中心偏差均在1 mm以内。结论:G4射波刀的剂量率、TPR20/10、平坦度、对称性、半影、剂量输出精确性、影像中心一致性均很稳定,测量结果均在规定范围之内。剂量输出一致性发生偏差的概率为7.0%。AQA和E2E检测结果都超过规定值,需要查找造成射波刀精度下降的原因。

Abjective：Review the important quality assurance testing results of the 4th generation CyberKnife in these two years, gather related statistics and evaluate the various function of CyerKnife. Methods; Between January 2011 and January 2013, the CyberKnife operated normally for 443 days, stayed out of service 24 days for corrective maintenance and 57 days for breakdown. We reviewed the testing results of CyberKnife during these two years, including the items of dose rate, consistency of dose delivery, automatic quality assurance, TPR20/10, flatness, symmetry, penumbra, accuracy of dose delivery, E2E test, and the test of image center. Results： The dose rate was 725 MU/min-810 MU/min; the test on consistency of dose delivery had re- suits surpassing 2% for 31 times （7.0%）, which requires calibration; the value of TPR20/10 were between 0.663-0.678; the results of AQA test had overall deviation larger than 0.8 mm for 13 times （9.2%）; the value of penumbra of field size were among 3.20 mm-3.51 mm; the testing result of dose delivery： 2.34%--4.55%; one of the 15 times of E2E test had the result surpassing rated value; the deviation of image center was kept within 1 mm. Conclusions; The dose rate, TPR20/10, flatness, symmetry, penum- bra, accuracy of dose delivery, consistency of image center were stable, and all the testing results were within rated range. The deviation probability of dose delivery was 7%. The results of AQA and E2E test all surpassed rated value, so we need to find out the reasons causing the decline of CyberKnife＇s accuracy.