A test-bed system has been developed for imaging phantoms with tomosynthesis and volumetric computed tomography. This system incorporates an amorphous silicon flat panel detector on a movable gantry and a computer-controlled rotational positioning stage. In this paper, an analysis of the sensitivity of reconstructed images to geometrical misalignment is presented. Application of this method to circular digital tomosynthesis is examined, with spatial resolution in the focal plane as the criterion for evaluating the effect of misalignment. A software-based method is presented for correcting data for imperfect system alignment prior to image reconstruction. Experimental results yield reconstructed images with spatial resolution approaching the theoretical limit based on detector pixel size and accounting for data interpolation.