EBT3胶片数字化的横向响应伪影消除方法

Eliminating lateral response artifact for EBT3 radiochromic film digitization

目的:消除EBT3胶片数字化过程中的横向响应伪影,优化EBT3胶片的治疗计划验证结果。方法:覆盖双面镀膜的减反射玻璃进行胶片数字化,通过净光密度与扫描仪不同位置间的抛物线拟合关系来消除横向响应伪影后,借助剂量刻度曲线将胶片净光密度转换为剂量。使用辐照面积较大的治疗计划进行验证,对胶片与计划剂量分布进行γ分析。结果:在3%/3 mm标准下对不小于0.1 Gy的剂量点进行γ分析,消除横向响应伪影后胶片与计划剂量分布的γ通过率为95%,相比未消除横向响应伪影的剂量分布提升了3%的通过率。结论:利用该方法可以有效消除横向响应伪影,提高EBT3胶片治疗计划验证的γ通过率。

Objective To eliminate the lateral response artifact during EBT3 radiochromic film digitization and optimize the treatment plan verification results using EBT3 film.Methods The EBT3 films were digitalized with a scanner covered with a double-side coated anti-reflective glass.The lateral response artifact was eliminated using the parabola function which was obtained by fitting the relationship between the net optical densities and their positions on the scanner window.Then the net optical densities were converted into doses via dose calibration curve.The method was tested with a QA plan with a large irradiation field,and the gamma-index distribution was analyzed.Results The gamma passing rate(3%/3 mm,for dose greater than or equal 0.1 Gy)between planned dose profile and corrected film dose profile was 95%which was 3%higher than the uncorrected film dose profile.Conclusion The proposed method can effectively eliminate the lateral response artifact and improve the gamma passing rate of QA plan verification using EBT3 film.