Dose evaluation of simultaneous breast radiography and mechanical imaging

This study investigates the impact in terms of radiation dose when performing simultaneous digital breast tomosynthesis (DBT) and mechanical imaging (MI) – DBTMI. DBTMI has demonstrated the potential to increase specificity of cancer detection, and reduce unnecessary biopsies, as compared to digital mammography (DM) screening. The presence of the MI sensor during simultaneous image acquisition may increase the radiation dose when automatic exposure control is used. In this project, a radiation dose study was conducted on clinically available breast imaging systems with and without the MI sensor. We have investigated three approaches to analyse the dose increase in DBTMI, using (i) the estimates of average glandular dose (AGD) reported in DICOM headers of radiography images; (ii) AGD measured by a conventional dosemeter; and (iii) AGD measured by optically stimulated luminescence using NaCl pellets. The relative increase in AGD estimated from DICOM headers when using the MI sensor was on average 10.7% and 12.4%, for DM and DBT measurements, respectively. The relative increase in AGD using the conventional dosemeter was 11.2% in DM mode and 12.2% in DBT mode. The relative increase in AGD using NaCl pellets was 14.6% in DM mode. Our measurements suggest that the use of simultaneous breast radiography and MI increases the AGD by 13% on average. The increase in dose is still below the acceptable values in mammography screening recommended by the European Guidelines.