1. A method of determining geometry of a tomosynthesis system including a detector and an x-ray source, said method comprising the steps of: arbitrarily identifying at least two markers within an imaged volume, the at least two markers being placed at different relative distances between the detector and the x-ray source, and without having projections located on a straight line for all different source positions; and locating the projections of the markers within at least two images acquired of the imaged volume, said at least two images corresponding to different positions of a focal spot of the x-ray source wherein said step of locating is performed using a computer of the tomosynthesis system.