[Measurement procedures for determining the switch-off dose in mammographic equipment]

The usual measurement of the switchoff dose direct on x-ray film plane cannot be employed in mammography equipment without interfering with the switching device, because the chamber for monitoring the automatic exposure is situated behind the film holder and one cannot eliminate the film holder since it is an equipment-specific absorber. We are therefore presenting a method which allows to determine the switchoff dose on x-ray film plane via determination of the attenuating factor of the equipment (influenced by scattered radiation) and the phantom exit dose measured before the compression plate, the film holder having been pushed into position. The ratio of phantom influx to exit dose, standardised for a standard distance, serves additionally to easily recognise major deviations of the x-ray tube voltage from the adjusted value.