1. A method for correcting misalignment between a computed tomography (CT) image and a nuclear medical (NM) image in a modular multimodality imaging system, comprising: identifying a difference between an NM patient coordinate system (PCS) with respect to a CT PCS by applying a field of view calibration matrix (FOV-CM) comprising a rotational transformation and a translational transformation of a spatial point that exists in both the NM PCS and in the CT PCS, and aligning the CT image and the NM image based on the difference.