Measurement of energy dependence for XRCT radiochromic film.

Gafchromic XRCT, radiochromic film is assessed over a broad energy range, from kilovoltage to megavoltage x rays for variations in reflected optical density to dose response. A large energy dependence was found with reflected optical density output for the same delivered dose varying from 7.8±0.35 at 25.5keV (50kVp) peaking at 12.1±0.5 at 54keV (125kVp) to 0.975±0.03 at 2300keV (10MV) when normalized to 1 at 1400keV (6MV) energy. The response is constant (within 3%) in the 36-69keV equivalent photon energy range, which corresponds to x-ray tube generating potentials of approximately 100-150kVp. This matches well with beam qualities for diagnostic computed topography applications.