Investigation of the effect of tube motion in breast tomosynthesis: continuous or step and shoot?

Digital breast tomosynthesis (DBT) is a 3D modality that may have the potential to complement or replace 2D mammography. One major design aspect of DBT systems is the choice of tube motion: continuous tube motion during x-ray exposure or the step and shoot method where the tube is held fixed while x-rays are released. Systems with continuous tube motion experience focal spot motion blurring but a reduced patient motion blurring due to potentially faster total acquisition times when compared to the step and shoot approach. In order to examine the influence of focus motion on lesion detectability, a simulation environment was developed where lesions such as microcalcifications and masses are inserted into different thicknesses of theoretical materials. A version of the power law noise method was employed to approximate realistic anatomical breast volumes. The simulated projection images were reconstructed and appropriate metrics (peak contrast, contrast and signal-difference-to-noise ratio) of the lesions in the two different modes were compared. Results suggest an increase of the peak contrasts in the microcalcification data sets by 8 - 9 % for the step-and-shoot method when compared to the continuous mode (p