A feasibility study of dual-energy digital breast tomosynthesis for three-compartment-breast imaging

Digital breast tomosynthesis (DBT) is a breast imaging modality widely used in clinics. DBT systems obtain multiple projection data within a limited angular range. Reconstructing the acquired projection data provides quasi-3D positional information of the breast anatomy, which is unavailable in conventional digital mammography systems. While breast density is known as one of the critical risk factors of breast cancer, DBT based diagnostic performance is known to have a strong dependence on breast density. As a potential solution to increase the diagnostic performance of DBT, we are investigating dual-energy DBT imaging techniques. An additional shutter-type 2-mm thick aluminum(Al)-filter unit was mounted in front of the x-ray beam outlet of the prototype DBT system. The shutter is electrically synchronized with the scanning sequence so that the Al-filter is placed in the beam when high-energy kVp is used. To reduce scatter, we also installed an anti-scatter grid. The dual-energy DBT system acquired both high- and low-energy projections at each scan angle. For material decomposition, we estimated partial path lengths of an x-ray through water, lipid, and protein from measured projection data and the object thickness information. After material decomposition in the projection domain, we reconstructed material-selective DBT images. The feasibility of the dual-energy DBT scheme has been demonstrated by using the physical phantoms in the prototype dual-energy DBT system, and the proposed method successfully generated quasi-3D compositional images.