A system and method is provided for performing multimodal imaging of an object. The system and method includes performing spatio-temporal detection of transmission CT data of a fan X-ray beam, performing, and simultaneously with the spatio-temporal detection of transmission CT data, spatio-temporal detection of emission nuclear imaging data emitted from the object with a propagation direction across the propagation direction of the fan X-ray beam. The system and method further includes identifying at least two zones in the object based on the transmission CT data, reconstructing an image object from the emission nuclear imaging data under the constraint that respective portions of detected nuclear events are associated with selected zones, and outputting data representative of the image object.