Spelleken E, Crowe S B, Sutherland B, Challens C, Kairn T
Genesis Cancer Care, Rockhampton, QLD, 4700, Australia.
Cancer Care Services, Royal Brisbane and Women's Hospital, Herston, QLD, 4029, Australia.
Australas Phys Eng Sci Med. 2018 Mar;41(1):117-128. doi: 10.1007/s13246-018-0620-4. Epub 2018 Jan 17.
Gafchromic EBT3 film is widely used for patient specific quality assurance of complex treatment plans. Film dosimetry techniques commonly involve the use of transmission scanning to produce TIFF files, which are analysed using a non-linear calibration relationship between the dose and red channel net optical density (netOD). Numerous film calibration techniques featured in the literature have not been independently verified or evaluated. A range of previously published film dosimetry techniques were re-evaluated, to identify whether these methods produce better results than the commonly-used non-linear, netOD method. EBT3 film was irradiated at calibration doses between 0 and 4000 cGy and 25 pieces of film were irradiated at 200 cGy to evaluate uniformity. The film was scanned using two different scanners: The Epson Perfection V800 and the Epson Expression 10000XL. Calibration curves, uncertainty in the fit of the curve, overall uncertainty and uniformity were calculated following the methods described by the different calibration techniques. It was found that protocols based on a conventional film dosimetry technique produced results that were accurate and uniform to within 1%, while some of the unconventional techniques produced much higher uncertainties (> 25% for some techniques). Some of the uncommon methods produced reliable results when irradiated to the standard treatment doses (< 400 cGy), however none could be recommended as an efficient or accurate replacement for a common film analysis technique which uses transmission scanning, red colour channel analysis, netOD and a non-linear calibration curve for measuring doses up to 4000 cGy when using EBT3 film.
Gafchromic EBT3 薄膜广泛用于复杂治疗计划的患者特异性质量保证。薄膜剂量测定技术通常涉及使用透射扫描来生成 TIFF 文件，这些文件使用剂量与红色通道净光密度（净 OD）之间的非线性校准关系进行分析。文献中介绍的众多薄膜校准技术尚未经过独立验证或评估。对一系列先前发表的薄膜剂量测定技术进行了重新评估，以确定这些方法是否比常用的非线性净 OD 方法产生更好的结果。EBT3 薄膜在校准剂量 0 至 4000 cGy 之间进行辐照，25 片薄膜在 200 cGy 下辐照以评估均匀性。使用两种不同的扫描仪对薄膜进行扫描：爱普生 Perfection V800 和爱普生 Expression 10000XL。按照不同校准技术描述的方法计算校准曲线、曲线拟合的不确定性、总体不确定性和均匀性。结果发现，基于传统薄膜剂量测定技术的方案产生的结果准确且均匀，误差在 1% 以内，而一些非传统技术产生的不确定性要高得多（某些技术超过 25%）。一些不常见的方法在辐照至标准治疗剂量（<400 cGy）时产生了可靠的结果，然而，当使用 EBT3 薄膜测量高达 4000 cGy 的剂量时，没有一种方法可以被推荐为使用透射扫描、红色通道分析、净 OD 和非线性校准曲线的常见薄膜分析技术的有效或准确替代方法。
