Medical Physics Unit, McGill University, Montréal H3G 1A4, Québec, Canada.
Med Phys. 2010 May;37(5):2207-14. doi: 10.1118/1.3378675.
One of the major drawbacks of the current radiochromic film dosimetry protocols is the postirradiation waiting time. In this article, the authors study the postirradiation time evolution of the absorption spectrum of radiochromic EBT-2 GAFCHROMIC film model.
Postirradiation scanning times range from 3 min to 5 days and a dose range extends from 0 to 6 Gy. The authors compare the results of absorption spectra measurements for the latest GAFCHROMIC EBT-2 film model to the absorption spectra of the previous EBT GAFCHROMIC film model. The authors also describe a method that can establish the time error constraints on the postirradiation scanning time that will still provide an acceptable dose error for clinical applications if the protocol employing the shorter postirradiation scanning time is implemented in the clinic.
The two film models experience the very same dose change in net absorbance with sensitivity of the latest EBT-2 model GAFCHROMIC film being slightly lower than its predecessor. The authors show that for two postirradiation scanning times of 30 min and 24 h, the 1% dose error can be achieved if the scanning time window is less than +/- 5 min and +/- 2 h, respectively.
By comparing the resultant change in net absorbance between the latest EBT-2 and previous EBT GAFCHROMIC film models, the authors conclude that the addition of the yellow marker dye to the sensitive layer does not affect dosimetric properties of the latest film model. The authors also describe a procedure by which one can establish an acceptable time window around chosen postirradiation scanning time protocol that would provide an acceptable dose error for practical purposes.
目前的放射色乳胶剂量测定协议的主要缺点之一是辐照后等待时间。在本文中，作者研究了放射色 EBT-2 GAFCHROMIC 乳胶膜模型的吸收光谱在辐照后的时间演变。
辐照后扫描时间范围从 3 分钟到 5 天，剂量范围从 0 到 6 Gy。作者比较了最新 GAFCHROMIC EBT-2 乳胶膜模型的吸收光谱测量结果与先前 EBT GAFCHROMIC 乳胶膜模型的吸收光谱。作者还描述了一种方法，可以为辐照后扫描时间建立时间误差限制，如果在临床中实施较短的辐照后扫描时间协议，该方法仍可为临床应用提供可接受的剂量误差。
两种膜模型在净吸光度方面经历了相同的剂量变化，最新 EBT-2 模型 GAFCHROMIC 乳胶膜的灵敏度略低于其前身。作者表明，对于 30 分钟和 24 小时的两个辐照后扫描时间，如果扫描时间窗口分别小于 +/- 5 分钟和 +/- 2 小时，则可以实现 1%的剂量误差。
通过比较最新 EBT-2 和先前 EBT GAFCHROMIC 乳胶膜模型之间的净吸光度变化，作者得出结论，在敏感层中添加黄色标记染料不会影响最新膜模型的剂量特性。作者还描述了一种程序，可以在选定的辐照后扫描时间协议周围建立可接受的时间窗口，为实际目的提供可接受的剂量误差。
