A method and device are provided for matching a patient coordinate system (PCS) of a nuclear medical imaging scanner with a coordinate system of a CT scanner in a multimodality modular imaging system, based on a predefined relationship between a vertical position of a patient bed during the NM scan; an axial position of the patient bed during the NM scan; an axial distance between a gantry of the NM scanner and a gantry of the CT scanner; and a vertical distance between a center of orbit of the NM scanner and a center of rotation of the CT gantry.