碳离子束混合LET辐照的EBT3辐射变色胶片剂量修正方法

针对EBT3辐射变色胶片对碳离子束混合LET辐照的剂量欠响应比较了两种剂量修正方法。利用260 MeV/u的碳离子束通过被动降能得到多种剂量平均LET的碳离子束,利用这些碳离子束进行了胶片剂量响应刻度辐照,选择最佳的拟合公式得到了胶片剂量刻度曲线。使用RE(Relative Efficiency)量化了EBT3胶片随LET的剂量欠响应,并使用RE剂量修正法修正了混合LET辐照胶片的剂量。此外,根据剂量刻度曲线公式中拟合参数随不同LET所占剂量比例的变化规律,提出了拟合参数剂量修正法并修正了混合LET辐照胶片的剂量。最后比较了这两种方法的结果,表明拟合参数方法得到的剂量偏差在5%以内,优于RE方法10%以内的剂量偏差。

Dose Correction Methods of EBT3 Radiochromic Film Irradiated by Mixed-LET Carbon-ion Beams

Two dose correction methods were compared for the under-response of EBT3 radiochromic films to the irradiation of mixed-LET carbon-ion beams. Carbon-ion beam of 260 MeV/u was used to obtain carbon-ion beams with multiple dose-averaged LETs by energy degraders. The films were irradiated by these carbon ion beams, and the optimal fitting formula was selected to fit the film dose response calibration curves. Relative Efficiency(RE) was used to quantify the under-response of EBT3 film with LET, and the doses of the films irradiated by mixed-LET carbon ions were corrected by the RE method. In addition, according to the relation between the fitting parameters of the dose response calibration curve and the dose proportions of different LETs, a new dose correction method was proposed and the doses of the films irradiated by mixed-LET irradiation were also corrected. Finally, the results of the two methods are compared, and it is shown that the dose deviation obtained by the fitting parameter method is less than 5%, which is better than the dose deviation obtained by the RE method less than 10%.