[Water-energy dosage calibration and standard ion dosage calibration--a comparison in ultrahard x-ray radiation]

Ten ionization chambers (PTW), partly of different type, which all have been calibrated in terms of absorbed dose to water, were used to compare the absorbed dose indicated in a reference geometry at 8 MV X-rays. The standard deviation of the mean value of the absorbed dose determined for all chambers was 0.5%. Since 4 chambers have been calibrated in terms of absorbed dose to water and in exposure, the absorbed dose to water was determined from indicated value according to both calibration procedures. The dose values obtained via the energy dose calibration turned out to be about 2.5% less compared to the result when applying the exposure calibration factor.