Additional factors for the estimation of mean glandular breast dose using the UK mammography dosimetry protocol

The UK and European protocols for mammographic dosimetry use conversion fac tors that relate incident air kerma to the mean glandular dose (MGD) within the breast. The conversion factors currently used were obtained by compute r simulation of a model breast with a composition of 50% adipose and 50% gl andular tissues by weight (50% glandularity). Relative conversion factors h ave been calculated which allow the extension of the protocols to breasts o f varying glandularity and for a wider range of mammographic x-ray spectra. The data have also been extended to breasts of a compressed thickness of 1 1 cm. To facilitate the calculation of MGD in patient surveys, typical brea st glandularities are tabulated for women in the age ranges 40-49 and 50-64 years, and for breasts in the thickness range 2-11 cm. In addition, tables of equivalent thickness of polymethyl methacrylate have been provided to a llow the simulation for dosimetric purposes of typical breasts of various t hicknesses.