Breast compression thickness and composition affect radiation dose in digital mammography and tomosynthesis

Digital breast tomosynthesis (DBT) improves diagnostic performance compared with full-field digital mammography (FFDM), but concerns remain regarding radiation dose and its variability relative to FFDM under different breast conditions.

To evaluate the effects of breast compression thickness and breast composition on radiation dose in FFDM and DBT, with emphasis on variations in DBT-to-FFDM dose ratios.

This retrospective study included 288 women who underwent paired FFDM and DBT examinations under identical imaging conditions. Exposure parameters, entrance skin exposure (ESE), and average glandular dose (AGD) were extracted from DICOM headers for craniocaudal and mediolateral oblique views. Images were grouped by breast compression thickness and BI-RADS breast composition. Correlation analyses, multivariable linear regression, linear mixed-effects models, and natural spline mixed-effects models were performed to identify independent determinants of radiation dose and DBT-to-FFDM dose ratios.

DBT yielded significantly higher ESE and AGD than FFDM across all imaging views (all P < 0.001). Breast compression thickness was the strongest independent determinant of radiation dose. Absolute dose metrics increased with increasing compression thickness, whereas DBT-to-FFDM ESE and AGD ratios decreased significantly as compression thickness increased (ρ = -0.88 to -0.94, all P < 0.001). In fully adjusted mixed-effects models, greater compression thickness was associated with higher ESE and AGD but lower DBT-to-FFDM dose ratios (all P < 0.001). Breast composition was also independently associated with radiation dose, although its effect was smaller than that of compression thickness. Natural spline analyses showed significant nonlinearity for absolute dose outcomes but not for dose ratios.

Although DBT is associated with higher radiation dose than FFDM, the relative dose increase is not constant and is primarily modulated by breast compression thickness. These findings support individualized dose assessment based on breast characteristics.