1. A combined positron emission tomography (PET) and magnetic resonance imaging (MRI) system comprising: PET imaging components forming a PET scanner portion of the combined PET-MRI scanner; MRI components forming an MRI scanner portion of the combined PET-MRI scanner; and a controller in communication with the PET imaging components and the MRI components to control the MRI scanner portion to partition an acquisition of MR data for a MRI field of view over a sequence of PET data acquisitions from smaller PET fields of view and to acquire the MR data for the MRI field of view concurrently with an acquisition of different sets of the PET data.