Abstract: Systems and methods for simultaneous acquisition of MRI data and PET data of a subject are disclosed. The system can include a RF coil surrounding the subject and a PET detectors array surrounding the RF coil to generate the MRI data and the PET data of the subject, respectively. The system can include a RF shield positioned between the RF coil and the PET detectors array to prevent an interference between the RF coil and the PET detectors array to thereby allow simultaneous acquisition of the MRI data and the PET data without any one of the RF coil, the PET detectors array or the subject being moved during the imaging. The system can include an analysis unit to generate, based on the simultaneously acquired MRI data and PET data, combined PET-MRI images of the subject that include a spatially and temporally registered structural, functional and/or molecular data acquired under identical physiological conditions.