Comparison of breast doses for digital tomosynthesis estimated from patient exposures and using PMMA breast phantoms

A proposed European protocol for dosimetry in digital breast tomosynthesis (DBT) has been applied to estimate the average glandular breast dose (AGD) for two different DBT units. AGD was measured for the examination of series of women and for breast-simulating polymethyl methacrylate (PMMA) phantoms, thus assessing the suitability of the phantoms used for dosimetry in 2D mammography for DBT dosimetry. For the first system the mean values of the AGD for breast thicknesses of 21mm, 53mm and 90mm, were 1.21±0.06 (2 s.e.m), 2.12±0.07 and 4.90±0.11 mGy respectively. The corresponding values for the equivalent PMMA thicknesses of 20mm, 45mm and 70mm were 0.92, 2.08 and 4.65 mGy respectively. Similar agreement was found for the second system. It is concluded that the use of standard PMMA phantoms of appropriate thicknesses (as used for 2D dosimetry) to simulate the breast in DBT provides a reasonable estimate of the AGD