Technical evaluation of a digital breast tomosynthesis system

Abstract

This paper presents results of a technical evaluation of a digital breast tomosynthesis (DBT) system. Projection images were used to assess x-ray focal spot size and lag as a function of detector air kerma (K) during a tomographic scan. Modulation transfer function (MTF), normalized noise power spectrum (NNPS) and detective quantum efficiency (DQE) were used to obtain a quantitative assessment of detector operation, also from the projection image data. Maximum 1st image lag was 4% at 20 mAs/projection. Both edge and wire methods were used to assess MTF; in the direction of tube travel, MTF was reduced by a factor of 0.33 compared to 2D FFDM (static tube). Detector response results showed that detector gain is increased by a factor of 3.6 for DBT operation compared to 2D FFDM mode. DQE measured at 28 kV W/Rh and 2 mm Al added filtration and a typical detector K of 23.8 μGy per projection was 0.5 at 0.5 mm-1, indicating quantum limited performance of the detector for DBT acquisitions. The availability of projection image data enables the evaluation of important aspects of DBT detector performance in the field. © 2010 Springer-Verlag.