气压和温度对G3射波刀立体定向放疗系统剂量及相关参数影响研究

Effects of Air Pressure and Temperature on Dose and Related Parameters of G3 Cyberknife Stereotactic Radiotherapy System

目的分析G3射波刀立体定向放疗系统温度气压校准因子(Temperature Pressure Calibration Factor,K_(ctp))、经过K_(ctp)校正后的吸收剂量D_(kctp)和剂量校准因子Nk随每日温度、气压和吸收剂量的变化规律,为立体定向精确放疗的剂量校准和质量保证提供参考依据。方法测量2019年1月1日至12月31日,251个工作日射波刀立体定向放疗系统的吸收剂量D,得到随温度和气压变化的校准因子K_(ctp)和经过K_(ctp)校正后的吸收剂量D_(kctp),最终得到当日的剂量校准因子Nk,分析之间相关性和变化规律。结果K_(ctp)变化范围0.98~1.05,达7.1%;Dkctp变化范围32.5~34 nC,达4.6%,呈现“两头低,中间高”的变化趋势。吸收剂量D变化范围32.4~33.2 nC,达2.4%;Nk变化范围0.97~1.02,达5.2%,呈现“两头低,中间高”的变化趋势。结论气压、温度变化影响G3射波刀立体定向放疗系统的输出剂量,每日治疗前应对G3射波刀立体定向放疗系统进行剂量校准。使用K_(ctp)及剂量校准因子Nk对射波刀立体定向放疗系统进行长期稳定性监测与准确性校准,符合质量保证QA和质量控制QC要求,是实施精确立体定向放疗的必要条件。

Objective Analysis of Temperature Pressure Calibration Factor(K_(ctp))of G3 Cyberknife Stereotactic Radiotherapy System,the absorbed dose D_(kctp) corrected by K_(ctp) and dose calibration factor Nk of G3 CyberKnife stereotactic radiotherapy system,it provided reference for dose calibration and quality assurance of stereotactic precise radiotherapy.Methods From January 1,2019 to December 31,2019,Absorbed dose D of cyberknife radiosurgery stereotactic radiotherapy system was measured.Temperature pressure calibration factor K_(ctp) and absorbed dose D_(kctp) corrected by K_(ctp) were obtained.Finally,dose calibration factor Nk was obtained in 251 working days.The correlation and change rule were analyzed.Results The change range of Kctp was 0.98~1.05,reaching 7.1%;range of Dkctp was 32.5~34 nc,reaching 4.6%,showing a trend of“low at both ends and high in the middle”.The absorbed dose D ranged from 32.4 nC to 33.2 nC,up to 2.4%,Nk ranged from 0.97 to 1.02,reaching 5.2%,showing a trend of“high at both ends and low in the middle”.Conclusion The changes of air pressure and temperature affect output dose of G3 cyberknife stereotactic radiotherapy system.Dose calibration with the G3 cyberknife stereotactic radiotherapy system should be carried out before daily treatment.Long-term stability monitoring and accuracy calibration of cyberknife stereotactic radiotherapy system were carried out by using temperature and pressure calibration factor K_(ctp) and dose calibration factor Nk,which met requirements of quality assurance QA and quality control QC.It is a necessary condition for precise stereotactic radiotherapy.