1. An imaging system, comprising: a radiation source; a positioner configured to rotate the radiation source along an arc path at a rate that is equal to or less than α/T; an imager in operative position relative to the radiation source, wherein the radiation source and the imager are configured to obtain a plurality of images while the radiation source is at different positions along the arc path; and a processor configured to determine a digital tomosynthesis image using a subset of the plurality of images; where α is an angular spacing between a subset of the images that belongs to a same bin, and T is a period of a physiological motion.