A method for calibrating medical images is presented. The method includes acquiring (102) a plurality of images of an object from several spatial locations about an axis of rotation passing through a center of the object, selecting (104) a first point (122) and a second point (123) on a first image (120) of the plurality of images, calculating (106) a pixel distance between the first point (122) and the second point (123) on the first image (120), calculating (108) a calibration factor by comparing the pixel distance and a real distance between points in the object corresponding to the first point and a second point, marking (110) the first point or the second point in a new image of the plurality of images, and calculating (112) a new calibration factor from the new image for mapping a three dimensional distance into a two dimensional image.
