Average absorbed breast dose in mammography: a new possible dose index matching the requirements of the European Directive 2013/59/EURATOM

BACKGROUND: The new European Directive 2013/59/EURATOM requires that patients are informed about the risk associated with ionising radiation and that detailed information on patient exposure is included in the radiological report. This implies a revision of the routinely used dose indexes to obtain quantities related to individual exposure evaluable from acquisition parameters. Here we propose a new mammography dose index consistent with the average glandular dose (AGD). METHODS: An equation has been developed for calculating the average absorbed breast dose (2ABD). It depends on incident air kerma k(a,i) and on energy absorption coefficient μ(en); k(a,i) can be calculated for each anode-filter combination, based on kVp, mAs, the yield of the tube used Y(tb), and the breast thickness d; μ(en) depends on kVp and has been evaluated for each anode-filter combination. 2ABD has been compared to AGD evaluated by Dance or Wu methods, which represent the reference standards, for 20 patients of our university hospital. RESULTS: The incident air kerma k(a,i), calculated as a function of kVp, mAs, Y(tb) and d, was in good agreement with the same quantity directly measured: the relative uncertainty is < 0.10. The results of the comparison between 2ABD and AGD evaluated by both Dance and Wu methods appear to be consistent within the uncertainties. CONCLUSIONS: 2ABD is easily evaluable for each mammogram from the acquisition parameters. It can be proposed as a new suitable dose index, consistent with AGD, matching the requirements of the 2013 European Directive.