Energy dependence (75 kVp to 18 MV) of radiochromic films assessed using a real-time optical dosimeter

The response of radiochromic film, GafChromic (TM) EBT, was investigated for dependence on x-ray beam energy using a previously reported real-time optical readout approach. X-ray beams of energy from 75 kVp to 18 MV were employed. The dose-induced change in optical density for the EBT film was compared to values obtained for GafChromic (TM) HS and MD-55 films, exposed under the same conditions. All responses were normalized to that obtained for (CO)-C-60 irradiation. While change in optical density for 1 Gy of applied dose as measured with HS and MD-55 films decreased by approximately 40% at low energies, the mean change in optical density of EBT film remained within 3% of that in the Co-60 beam over the entire energy range. (c) 2007 American Association of Physicists in Medicine.