1. A magnetic resonance imaging (MM) system, comprising: a magnet system configured to generate a polarizing magnetic field about at least a portion of a subject arranged in the MRI system and free of exogenous contrast agents; a magnetic gradient system including a plurality of magnetic gradient coils configured to apply at least one magnetic gradient field to the polarizing magnetic field; a radio frequency (RF) system configured to apply an RF field to the subject and to receive magnetic resonance signals therefrom in parallel; and a computer system programmed to: control the magnetic gradient system and the RF system to apply at least one radio frequency (RF) saturation pulse to a selected region of the subject to saturate spins of all tissues within the selected region; observe a delay time selected to allow an inflow of unsaturated vascular spins that are free of influence from exogenous contrast agent into the selected region through vascular structures within the selected region; control the magnetic gradient system and the RF system to acquire a sparse dataset formed from a series of spatially-encoded views from the selected region using an undersampled radial k-space trajectory in which the center of k-space is sampled for each view in the series of spatially-encoded views; and reconstruct an image of the vascular structures within the selected region from the sparse dataset, wherein the sparse dataset includes more than one slice acquired in each heartbeat of the subject.