Comparison of dose calibration by ionometric and chemical dosimetry for 6- and 45-MV x-ray beams.

This work reports the results of an experiment carried out to investigate the compatibility of TG-21 ion chamber calibration with Fricke dosimetry near the extremes of the clinically available megavoltage photon energy range. Doses determined from ion chamber measurements and from chemical dosimetry are compared for a 6-MV linear accelerator x-ray beam and 45-MV betatron beam. The Fricke dosimetry was carried out by the National Institute of Standards and Technology. Agreement within 1% between the two techniques was obtained at both photon energies using a currently accepted G-value.