OncoRay-Radiation Research in Oncology, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
Med Phys. 2009 Dec;36(12):5506-14. doi: 10.1118/1.3253902.
The aim of this article is to investigate the energy dependence of the radiochromic film type, Gafchromic EBT-1, when scanned with a flatbed scanner for film readout.
Dose response curves were determined for 12 different beam qualities ranging from a 10 kVp x-ray beam to a 15 MVp x-ray beam and include also two high energy electron beam qualities (6 and 18 MeV). The dose responses measured as net optical density (netOD) for the different beam qualities were normalized to the response of a reference beam quality (6 MVp).
A strong systematic energy dependence of the film response was found. The lower the effective beam energy, the less sensitive the EBT-1 films get. The maximum decrease in dose for the same film response between the 25 kVp and 6 MVp beam qualities was 44%. Additionally, a difference in energy dependence for different doses was discovered, meaning that higher doses show a smaller dependency on energy than lower doses. The maximum decrease in the normalized netOD was found to be 25% for a dose of 0.5 Gy relative to the normalized netOD for 10 Gy. Moreover, a scaling procedure is introduced, allowing the correction of the energy dependence for the investigated beam qualities and also for comparable x-ray beam qualities within the energy range studied.
A strong energy dependence for EBT-1 radiochromic films was found. The films were readout with a flatbed scanner. If the effective beam energy is known, the energy dependence can be corrected with the introduced scaling procedure. Further investigation of the influence of the spectral band of the readout device on energy dependence is needed to understand the reason for the different energy dependences found in this and previous works.
本文旨在研究使用平板扫描仪进行胶片读取时，Gafchromic EBT-1 型光致变色胶片的能量依赖性。
测定了 12 种不同射线质的剂量响应曲线，范围从 10 kVp X 射线到 15 MVp X 射线，还包括两种高能电子射线质（6 MeV 和 18 MeV）。对于不同射线质，测量的净光学密度（netOD）剂量响应归一化为参考射线质（6 MVp）的响应。
发现胶片响应存在强烈的系统能量依赖性。有效束能越低，EBT-1 胶片的灵敏度越低。在相同的胶片响应下，25 kVp 和 6 MVp 射线质之间的剂量最大降低幅度为 44%。此外，还发现了不同剂量的能量依赖性差异，即较高剂量的能量依赖性比较低剂量小。对于 0.5 Gy 的剂量，相对于归一化 netOD 的 10 Gy，归一化 netOD 的最大降低幅度为 25%。此外，引入了一种缩放程序，允许对所研究的射线质以及在所研究的能量范围内可比的 X 射线质的能量依赖性进行校正。
发现 EBT-1 光致变色胶片存在强烈的能量依赖性。胶片使用平板扫描仪进行读取。如果知道有效束能，可以使用引入的缩放程序来校正能量依赖性。需要进一步研究读取设备的光谱带宽对能量依赖性的影响，以了解在本文和以前的工作中发现的不同能量依赖性的原因。
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