Comparative study of patient doses calculated with two methods for breast digital tomosynthesis

Abstract

In this study, the average glandular doses ( D_G ) delivered in breast tomosynthesis examinations were estimated over a sample of 150 patients using two different methods. In method 1, the conversion factors air-kerma to D_G used were those tabulated by Dance et al. and in method 2 were the ones from Feng et al. The protocol for the examination followed in the unit of this study consists in two views per breast, each view composed by a 2D acquisition and a tomosynthesis scan (3D). The resulting D_G values from both methods present statistically significant differences ( p = 0.02 ) for the 2D modality and were similar for the 3D scan ( p = 0.22 ). The estimated median value of D_G for the most frequent breasts (thicknesses between 50 and 60 mm) delivered in a single 3D acquisition is 1.7 mGy (36% and 17% higher than the value for the 2D mode estimated with each method) which lies far below the tolerances established by the Spanish Protocol Quality Control in Radiodiagnostic (2011). The total D_G for a tomosynthesis examination (6.0 mGy) is a factor 2.4 higher than the dose delivered in a 2D examination with two views (method 1).