1. A method for calibrating a medical imaging apparatus that is capable of acquiring medical images of a region using least two different imaging modalities, comprising the steps of: imaging a multiple point source test phantom using each of said at least two different modalities; calculating centroids of imaged point source data for each of said at least two different modalities; aligning a point source centroid of a first of said at least two different modalities with a corresponding point source centroid of a second of said at least two different modalities so as to obtain a pair of conical generators; determining a pair of lines on intersections of cones generated by said pair of conical generators having an angle therebetween corresponding to the angle between said cones; and adjusting an image plane of one of said at least two modalities by modifying a normal thereof to correspond to said angle.