基于胶片测量方法研究金属植入物对放疗剂量分布的影响

摘要

Objective:To investigate the impact of metal implants with different material on radiation dose distribution based on film measurement method.Methods:Titanium plate and Stainless steel plate were set into VENUS-SPD phantom and irradiated separately by 6 MV ray from siemens ARTISTE linear accelerator.Dose distributions derived from different material metal implants are measured and analyzed by GAFCHROMIC EBT2 film,and the results were compared and evaluated with treatment planning system by Film QA Pro3.0 Film analysis software.Results:The maximal dose deviation from X direction Off-axis dose curve of stainless steel plate and titanium plate between treatment planning system calculation and EBT2 film measurement was 9.6％and 6.6％.With the same defined value of DTA and △ D,the Gamma test pass rate of Flux dose distribution between treatment planning system calculation and EBT2 film measurement was 78.11％ and 81.07％ for stainless steel plate and titanium plate,respectively.Conclusions:Metal implants with different material has obvious impact on radiation dose distribution.With the increase of the metal atomic number and energy of radiation,the degree of elevated dose also increased.Treatment planning system can't calculate and evaluate the dose distribution of metallic implants accurately.These results suggested that corrected of dose distribution is required for radiotherapy of patients with metal implants.%目的:采用胶片剂量仪测量方法研究不同材质金属植入物对放疗剂量分布的影响.方法:应用西门子ARTISTE直线加速器6MV X线在VENUS-SPD模体中分别对钛合金内固定板及不锈钢钢板进行照射,采用美国ISP公司GAFCHROMIC EBT2胶片进行测量并采用Film QA Pro3.0胶片分析软件将测量结果与治疗计划系统计算结果进行比较和评估.结果:不锈钢板和钛合金板X方向离轴曲线胶片测量值与TPS计算值的最大剂量偏差分别为9.6％和6.6％,相同DTA和△D条件下,不锈钢板和钛合金板治疗计划计算与胶片剂量测量通量分布比较Gamma检验通过率分别为78.11％和81.07％.结论:不同材质金属植入物对放疗剂量分布存在明显影响,治疗计划系统不能精确计算和评估金属植入物的剂量分布,建议实际放射治疗中对金属植入物患者进行剂量分布修正.