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 ka,i and on energy absorption coefficient μen; ka,i can be calculated for each anode-filter combination, based on kVp, mAs, the yield of the tube used Ytb , and the breast thickness d; μen 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 ka,i , calculated as a function of kVp, mAs, Ytb 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.
Keywords: Average glandular dose; Breast absorbed dose; Dosimetry; Ionising radiation dose index; Mammography.