Investigation of EBT2 and EBT3 films for proton dosimetry in the 4-20 MeV energy range
Investigation of EBT2 and EBT3 films for proton dosimetry in the 4-20 MeV energy range
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DOI：
10.1007/s00411-014-0581-2
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发表时间：
2015-03-01
影响因子：
1.7
通讯作者：
Parodi, K.
中科院分区：
文献类型：
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作者：
Reinhardt, S.;Wuerl, M.;Parodi, K.
诸如Gafchromic EBT 2或EBT 3膜的辐射变色膜被广泛用于辐射治疗中的剂量确定，因为与任何其他数字剂量测定2D检测器阵列相比，它们提供了上级空间分辨率。检测陡峭剂量梯度的可能性不仅对于使用光子的强度调制放射治疗具有吸引力，而且对于强度调制质子治疗也具有吸引力。他们的特征剂量率独立的响应，使辐射变色薄膜也有吸引力的剂量测定细胞照射实验中使用激光驱动的离子加速器，这是目前正在研究的未来医疗离子加速器。然而，当在离子束中使用这些膜时，必须考虑在布拉格峰附近的能量依赖的剂量响应。在这项工作中，这些薄膜的响应为低能质子进行了研究。为了允许可再现的和无背景的照射条件，将膜暴露于来自静电加速器的单能质子，在4-20 MeV能量范围内。为了比较，还进行了临床光子照射。结果表明，一般而言，EBT 2和EBT 3薄膜表现出相当的性能。例如，能量低至11 MeV的光子和质子的剂量响应曲线几乎没有差异。然而，需要对低于11 MeV的质子能量进行校正。当校正因子与深度剂量测量的平均LET有关时，必须小心，因为只有剂量平均LET才能产生与单能量测量中获得的结果相似的结果。
Radiochromic films such as Gafchromic EBT2 or EBT3 films are widely used for dose determination in radiation therapy because they offer a superior spatial resolution compared to any other digital dosimetric 2D detector array. The possibility to detect steep dose gradients is not only attractive for intensity-modulated radiation therapy with photons but also for intensity-modulated proton therapy. Their characteristic dose rate-independent response makes radiochromic films also attractive for dose determination in cell irradiation experiments using laser-driven ion accelerators, which are currently being investigated as future medical ion accelerators. However, when using these films in ion beams, the energy-dependent dose response in the vicinity of the Bragg peak has to be considered. In this work, the response of these films for low-energy protons is investigated. To allow for reproducible and background-free irradiation conditions, the films were exposed to mono-energetic protons from an electrostatic accelerator, in the 4-20 MeV energy range. For comparison, irradiation with clinical photons was also performed. It turned out that in general, EBT2 and EBT3 films show a comparable performance. For example, dose-response curves for photons and protons with energies as low as 11 MeV show almost no differences. However, corrections are required for proton energies below 11 MeV. Care has to be taken when correction factors are related to an average LET from depth-dose measurements, because only the dose-averaged LET yields similar results as obtained in mono-energetic measurements.