1. A medical tomosynthesis system comprising: a scanner configured for acquiring projection images of a subject volume from a plurality of respective projection angles around said subject volume, said plurality being from among a first set of projection angles at which said scanner is enabled for image acquisition, said acquiring being associated with corresponding fields of view, a part of a medical tomosynthesis apparatus being within a field of view from among said fields of view, said medical tomosynthesis apparatus including a medical tomosynthesis biopsy apparatus; and an image processor configured to: derive geometric data from a three-dimensional (3D) model of said part; derive an actual position of said part; from both said geometric data and said actual position, calculate a plurality of angular positions corresponding to projection angles of said first set in deciding which of said corresponding projection angles are in conflict with an image of a region of interest; and exclude the projection angles decided to be in conflict in forming a second set of allowed projection angles, wherein said system is configured to operate said scanner so as to confine, to projection angles within said second set, acquisition of projection images for use in tomosynthesis reconstruction.