Memorandum from the British Committee on Radiation Units and Measurements. Quantities for reporting the calibration of therapy-level dosemeters in photon beams.

It is proposed that existing primary standards of exposure continue to be operated as at present; in-air comparison of secondary standards will be used to determine an exposure calibration, quoted in the SI unit C kg-1. A derived calibration factor for absorbed dose will be supplied for use with the secondary-standard chamber in a water phantom under specified conditions. Secondary-standardizing laboratories will be able to calibrate field instruments, scaled in grays, in terms of absorbed dose to water under reference conditions appropriate to the particular radiation quality.