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, and performing a cardiac reconstruction with attenuation correction by adjusting the CT PCS to match the NM PCS, calculating an attenuation map, performing a reconstruction based a CT attenuation map slice, applying the FOV-CM to form an NM reconstruction volume in CT-PCS, rotating, shifting, and masking the NM reconstruction volume in CT-PCS to create an image of standard cardiac orientation, wherein the steps above are performed using at least one processor.