Absorption spectra time evolution of EBT-2 model GAFCHROMIC film.

ABSTRACT

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.