A method to compute the Glandular Imparted Energy (GIE) from an estimation of the quantity and localization of glandular tissues in digital breast tomosynthesis (DBT) is proposed and evaluated. The Volumetric Breast Density (VBD) is computed from a single projection of the object, then the DBT voxels are labelled as glandular or adipose depending on whether their values are above or below a threshold computed from the histogram of the DBT volume and ensuring the conservation of the VBD. Finally, the GIE is calculated by Monte Carlo (MC) computation on the resulting tissue-labelled DBT volume. For verification, the method was applied to ten breast-shaped digital phantoms made of glandular spheres of different diameters and positions in an adipose background, and to a digital anthropomorphic phantom. Results were compared to the results of direct computations on the phantoms considered as “ground-truth”. The major limitations in accuracy are those of DBT, in particular the limited z-resolution. However for most phantoms the results can be considered as acceptable.