Dosimetric properties of Gafchromic® EBT films in monoenergetic medical ion beams
Dosimetric properties of Gafchromic® EBT films in monoenergetic medical ion beams
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DOI：
10.1088/0031-9155/55/13/011
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发表时间：
2010-07-07
影响因子：
3.5
通讯作者：
Jaekel, Oliver
中科院分区：
文献类型：
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作者：
Martisikova, Maria;Jaekel, Oliver
对于扫描离子束放射治疗中的质量保证测量，例如射束剖面测量和患者计划的剂量验证，需要高空间精度。为此，我们研究了 Gafchromic EBT 薄膜，它是目前可用的 EBT2 薄膜的祖先。与旧类型的放射变色薄膜相比，其出色的空间分辨率和灵敏度的提高使其成为合适的候选者。在这篇文章中，提出了基于绝对剂量的单能光束（平台）剂量响应关系的研究。我们发现薄膜对质子和光子的响应是相当的。对于碳离子，我们观察到相对于光子来说，变暗效率降低了约 30%。这种效应很可能是由离子轨道结构引起的。我们没有发现相对效率对离子束治疗中使用的典型范围内所施加的剂量和能量有任何依赖性。此外，结果表明，离子轨迹重叠对于医用离子束中的 EBT 胶片剂量测定来说不是问题。上述发现使得能够使用在特定离子类型束中校准的 EBT 薄膜来进行任何其他剂量和能量的剂量测量。还讨论了离子束中薄膜变暗测定的不确定性。
For quality assurance measurements in radiotherapy with scanned ion beams, such as beam profile measurements and dosimetrical verification of patient plans, high spatial accuracy is required. We investigated the Gafchromic EBT film, which is the ancestor of the currently available EBT2 film, for this purpose. The excellent spatial resolution and improvements in sensitivity as compared to older types of radiochromic films make it a suitable candidate. In this contribution a study of the dose-response relation for monoenergetic beams (plateau), based on the absolute dose, is presented. We found the film response to be comparable for protons and photons. For carbon ions we observed a decrease in the darkening efficiency of about 30% with respect to photons. This effect is likely to be caused by the ion track structure. We did not find any dependence of the relative efficiency on the applied dose and energy over typical ranges used in ion beam therapy. Furthermore, it is shown that overlaps of ion tracks are not an issue for EBT film dosimetry in medical ion beams. The above findings enable the use of EBT films calibrated in a beam of a particular ion type for dose measurements at any other dose and energy. The uncertainty of the film darkening determination in ion beams is also discussed.