1. A method for producing a medical image of a subject, the method comprising the steps of: a) disposing the subject between a source emitting a divergent beam of x- rays and a detector having an imaging plane configured to receive x-rays emitted by the source; b) acquiring a series of projection images of the subject at a plurality of magnification levels by translating at least one of the source and detector along a central axis substantially normal to the imaging plane of the detector; and c) reconstructing a three-dimensional image of the subject from the series of projection images acquired at the plurality of magnification levels.