Calorimetric determination of the absorbed dose-to-water beam quality correction factor kQ for high-energy photon beams.

A method has been developed for measuring photon beam quality correction factors kQ using direct transfer with a water calorimeter. kQ values were measured for beam qualities varying between 6 and 23 MV for a Capintec PR-06 and a PTW W30001 cylindrical ionization chamber. Measured values were intercompared with published sets of computed kQ values and agreement was found to be within measurement uncertainty (1%, one standard deviation).