The determination of total filtration on mammographic X-ray sets

Data produced by a computer model are presented which allow the amount of molybdenum filtration on a molybdenum target mammographic X-ray set to be estimated from the measurement of the half value layer (HVL) in aluminium. Existing data refer either to tungsten target tubes or to molybdenum target tubes for a single anode angle and a constant potential waveform with the compression plate present. In addition to the tube voltage, the present data take account of the waveform of the tube potential and target angle. The results of an experimental verification of the model are presented and the effect of the geometry used in the experimental set-up discussed. Theoretical predictions of the molybdenum filter thickness made using the data from the model are in good agreement with the measured filter thickness, provided that attention is paid to the experimental geometry.