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; a support structure disposed and moveable with respect to a PET spatial coverage region associated with the PET scanner portion and a MRI spatial coverage region associated with the MRI scanner portion; 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 (FOV) within the MRI spatial coverage region 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; and the controller being configured to control acquisition of PET data and MR data based on a position of the support structure including wherein both the PET data and MR data are acquired continuously as the support structure moves, wherein a single MR image stack is acquired concurrently with the different sets of the PET data, the single MR image stack corresponding to the MRI FOV, the PET spatial coverage region corresponding to the different sets of the PET data, the MRI spatial coverage region larger than the PET spatial coverage region, wherein the different sets of PET data include a first set acquired at a first position of the support structure and a second set acquired at a second position of the support structure, the first and second sets of PET data corresponding to different portions of a patient body, wherein the first position and the second position differ with respect to the PET imaging components and the MRI imaging components, wherein the first position and second position differ with respect to the MRI spatial coverage region, wherein the controller is configured to shift a focus of the MRI FOV with respect to the MRI spatial coverage region to acquire the MR data for the MRI FOV for a same area of the patient body at both the first position and the second position.