Daily quality control for breast tomosynthesis

Breast tomosynthesis is an imaging modality that recently became available for breast examination. For conventional projection mammography quality control procedures are well described. For breast tomosynthesis, on the other hand, such procedures have not yet been established. In this paper we propose a simple method and phantom for daily quality control (DQC). With DQC image quality problems arising after acceptance of the system should be detected. Therefore, the DQC procedure needs to monitor the stability of the most critical components of the system over time. For breast tomosynthesis we assume that the most critical items are the image receptor, X-ray tube and the tomosynthesis motion. In the proposed procedure the image receptor homogeneity and system stability are evaluated using an image of a homogeneous block of PMMA. The z-resolution is assumed to be dependent on the tomosynthesis motion. To monitor this motion the nominal z-resolution using the slice sensitive profile is measured. Shading artefacts that arise due to objects with high attenuation are also typical for tomosynthesis systems. Analysing those artefacts may provide additional information about the tomosynthesis motion. The proposed DQC procedure has been evaluated on two different breast tomosynthesis systems: A multi slit scanning system and a system using a stationary a-Se detector. Preliminary results indicate that the proposed method is useful for DQC, although some minor changes to the phantoms are advised. To verify that this method detects image quality problems sufficiently, more experience with different DBT systems, over longer periods of time are needed.