螺旋断层治疗装置剂量输出稳定性检测及三年质量控制分析

明确螺旋断层治疗装置(tomotherapy,TOMO)剂量输出检测的理论及方法,并建立完善的质量控制操作规范。依据国家卫生标准WS 531—2017及美国医学物理学家协会AAPM TG-148号报告,首先对相关理论部分进行解释,再利用8通道计量仪(Tomo Electrometer)、电离室A1SL(standing imaging,USA)、圆柱形模体(cheese phantom)、等效矩形固体水,对TOMO剂量输出相关的静态剂量、旋转剂量和射线质(百分深度剂量,PDD)的稳定性进行检测,最后分析整理近三年的检测数据。首先建立了完整的剂量统计、计算表格;并通过SPSS22分析数据得出静态输出剂量偏差平均值为(-0. 36±0. 47)%,664 d中仅有1 d偏差超过±2%,数据较为稳定;旋转输出剂量偏差平均值为(-0. 82±1. 6)%,有70%的结果在±2%的范围内,91%的结果在±3%,99%的结果在±4%的评价值范围内;射线质PDD10和PDD20的偏差平均值分别为(-0. 02±1. 15)%和(-0. 45±1. 06)%,100%的结果在±3%的评价值范围内,95%的结果在±2%范围内,56%和58%的结果在±1%的范围内;三个检测项目的稳定性都比较好,并对于超出评价值范围的检测项目进行原因分析。通过近三年的质量控制,整理出了完整的TOMO剂量输出质量控制操作规范,建议在标准WS 531—2017的基础上将评价值标准提升,旋转输出剂量评价值设定为±3%,射线质输出评价值设定为±2%,并在日检中适当增加射线质输出检测项目,为TOMO的精准放疗提供技术支持。

Testing of Dose Output Stability and Analysis of Tree-year Quality Control in Helical Tomotherapy Unit

Objective:In order to clarify the theory and method of dose output testing of helical tomotherapy unit(TOMO), and establish a perfect quality control operation specification. Methods: According to the national health standard WS531-2017 and AAPM TG-148 report.Firstly,the related theory was explained,secondly,the static output,rotary output dose and beam quality(percentage depth dose,PDD) were tested by 8 channel measurement instrument (TomoElectrometer), ionization chamber A1SL (Standing Imaging, USA), the Cheese Phantom, and the equivalent rectangular solid water,finally, the testing data of nearly three years was analyzed.Results: a complete dose statistics and calculation table were established. According to SPSS22 software, the mean value of static output dose deviation was (-0.36±0.47)%, and only 1 day deviation exceeded ±2% in 664 days, which made the data stable.The mean value of the deviation of the rotary output dose was (-0.82±1.6)%, 70% of the results were within the range of ±2%, 91% were within the range of ±3%, and 99% were within the range of ±4%.The mean value of beam quality PDD10 and PDD20 deviation was (-0.02±1.15)% and(-0.45±1.06)%, 100% results are within the range of ±3%, 95% results were within the range of ±2%, 56% and 58% results were within the range of ±1%.The stability of the three items were good, and the reasons of the test items beyond the evaluation value range were analyzed.Conclusion: with the quality control of nearly three years, the complete TOMO dose output quality control specification was collated, and suggested the evaluation criteria should be improved, the rotary output dose value should set to ±3%, the beam quality value should set to ±2%, and the test of beam quality should be added in the daily quality control appropriately , the technical support for the TOMO precise radiotherapy was provided.