Ganapathy K, Kurup P G G, Murali V, Muthukumaran M, Velmurugan J
Department of Radiotherapy, Apollo Specialty Hospital, Chennai, India.
Department of Medical Physics, Anna University, Chennai, India.
J Med Phys. 2013 Oct;38(4):173-7. doi: 10.4103/0971-6203.121194.
Gafchromic films are used as dosimeter for in vivo and in phantom dose measurements. The dose response of Gafchromic EBT2 film under single and repeated exposure conditions is compared in this study to analyze the usability of Gafchromic EBT2 films in cumulative dose measurements. The post-irradiation change in response of the film is studied for up to 4 days after irradiation. The effect of repeated exposure to scanner light on the response of the film is also studied. To check usability of Gafchromic EBT2 films in cumulative dose measurements, three EBT2 films were exposed to a daily fraction dose of 100 cGy, 150 cGy and 200 cGy, respectively, for 4 days. The dose response of the films exposed to cumulative irradiation was compared with the dose measured from films exposed to the same dose but in a single exposure. It is observed that the post-irradiation darkening of the film does not saturate and continue to take place even 4 days after irradiation. The dose measured from the EBT2 films after 4 days from irradiation was around 2% higher than the dose measured from the same films at 24 hours post-irradiation. It was also observed that the repeated exposure to scanner light does not produce any significant change in the film response. The dose response of films exposed to cumulative irradiation agrees with the dose response of films exposed to the same dose in a single irradiation with less than 3% difference. Gafchromic EBT2 films can be used to measure the cumulative dose delivered over multiple fractions, when the delivered dose is uniform across the film.
Gafchromic薄膜用作体内和模体剂量测量的剂量计。本研究比较了Gafchromic EBT2薄膜在单次和重复照射条件下的剂量响应，以分析Gafchromic EBT2薄膜在累积剂量测量中的可用性。研究了辐照后薄膜响应的变化，最长持续到辐照后4天。还研究了重复暴露于扫描仪光对薄膜响应的影响。为了检验Gafchromic EBT2薄膜在累积剂量测量中的可用性，将三张EBT2薄膜分别以每日分次剂量100 cGy、150 cGy和200 cGy照射4天。将累积照射的薄膜的剂量响应与相同剂量单次照射的薄膜测量的剂量进行比较。观察到辐照后薄膜的暗化并未饱和，甚至在辐照后4天仍在继续。辐照4天后从EBT2薄膜测量的剂量比辐照后24小时从相同薄膜测量的剂量高约2%。还观察到重复暴露于扫描仪光不会使薄膜响应产生任何显著变化。累积照射的薄膜的剂量响应与相同剂量单次照射的薄膜的剂量响应一致，差异小于3%。当整个薄膜上的剂量均匀时，Gafchromic EBT2薄膜可用于测量多次分次给予的累积剂量。
