Room: Exhibit Hall | Forum 4
Purpose: To investigate the evolution of the response of the EBT-XD radiochromic films over the course of 96 hours after irradiation.
Methods: EBT-XD film samples were placed between layers of solid water phantoms, and irradiated with a 6 MV flattening-filter-free beam. Four film samples were irradiated at doses in the range 1.5-50 Gy. The net absorption spectra were acquired using a spectrometer and a broadband light source over 400-800 nm spectral range at 0.5, 1, 1.5, 2, 2.5, 3, 6, 9, 12, 24, 48, 72, and 96 hours post-irradiation. Net optical density was measured using a flatbed scanner at the same time intervals.
Results: The net absorption spectra of the EBT-XD films showed two absorption peaks centered on 636 nm and 585 nm, characteristic of the EBT model. The response of the film, measured by the spectrometer and by the scanner, increases at the fastest rate during the first three hours. However, in the window of 3-12 hours the increase in the film response is much slower. There is a small increase in the film response in the window of 12-24 hours. Beyond 24 hours no significant change was observed in the response of the film. Films irradiated with 1.5 Gy did not stabilize over the same time period and showed larger variation in response. Calibration curves were constructed from the red, green, and blue channels after 48 hours. Errors up to ~20% in the calculated dose can occur for films scanned on or before 12 hours post-irradiation.
Conclusion: The rate of polymerization is not constant during the first 24 hours post-irradiation. The net absorbance and the net optical density of the EBT-XD films do not significantly change after 24 hours.