Ahmed M F, Shrestha N, Schnell E, Ahmad S, Akselrod M S, Yukihara E G
Physics Department, Oklahoma State University, Stillwater, OK 74078, USA.
Phys Med Biol. 2016 Nov 7;61(21):7551-7570. doi: 10.1088/0031-9155/61/21/7551. Epub 2016 Oct 7.
This work evaluates the dosimetric properties of newly developed optically stimulated luminescence (OSL) films, fabricated with either AlO:C or AlO:C,Mg, using a prototype laser scanning reader, a developed image reconstruction algorithm, and a 6 MV therapeutic photon beam. Packages containing OSL films (AlO:C and AlO:C,Mg) and a radiochromic film (Gafchromic EBT3) were irradiated using a 6 MV photon beam using different doses, field sizes, with and without wedge filter. Dependence on film orientation of the OSL system was also tested. Diode-array (MapCHECK) and ionization chamber measurements were performed for comparison. The OSLD film doses agreed with the MapCHECK and ionization chamber data within the experimental uncertainties (<2% at 1.5 Gy). The system background and minimum detectable dose (MDD) were <0.5 mGy, and the dose response was approximately linear from the MDD up to a few grays (the linearity correction was <10% up to ~2-4 Gy), with no saturation up to 30 Gy. The dose profiles agreed with those obtained using EBT3 films (analyzed using the triple channel method) in the high dose regions of the images. In the low dose regions, the dose profiles from the OSLD films were more reproducible than those from the EBT3 films. We also demonstrated that the OSL film data are independent on scan orientation and field size over the investigated range. The results demonstrate the potential of OSLD films for 2D dosimetry, particularly for the characterization of small fields, due to their wide dynamic range, linear response, resolution and dosimetric properties. The negligible background and potential simple calibration make these OSLD films suitable for remote audits. The characterization presented here may motivate further commercial development of a 2D dosimetry system based on the OSL from AlO:C or AlO:C,Mg.
本研究使用原型激光扫描读取器、开发的图像重建算法和6 MV治疗性光子束，评估了新开发的采用AlO:C或AlO:C,Mg制成的光激励发光（OSL）薄膜的剂量学特性。装有OSL薄膜（AlO:C和AlO:C,Mg）和放射变色薄膜（Gafchromic EBT3）的包装，使用6 MV光子束，以不同剂量、射野大小，在有和没有楔形滤过器的情况下进行照射。还测试了OSL系统对薄膜取向的依赖性。进行了二极管阵列（MapCHECK）和电离室测量以作比较。在实验不确定度范围内（1.5 Gy时<2%），OSLD薄膜剂量与MapCHECK和电离室数据一致。系统本底和最小可探测剂量（MDD）<0.5 mGy，剂量响应从MDD到几个格雷大致呈线性（在~2 - 4 Gy以下线性校正<10%），在30 Gy时未出现饱和。在图像的高剂量区域，剂量分布与使用EBT3薄膜（采用三通道方法分析）获得的结果一致。在低剂量区域，OSLD薄膜的剂量分布比EBT3薄膜的更具可重复性。我们还证明，在研究范围内，OSL薄膜数据与扫描取向和射野大小无关。结果表明，OSLD薄膜具有用于二维剂量学的潜力，特别是对于小射野的表征，因为它们具有宽动态范围、线性响应、分辨率和剂量学特性。可忽略的本底和潜在的简单校准使这些OSLD薄膜适用于远程审核。此处呈现的特性描述可能会推动基于AlO:C或AlO:C,Mg的OSL的二维剂量学系统的进一步商业开发。
