A magnetic resonance imaging (MRI) system is used to produce an image representative of the vasculature of a subject by applying a non-contrast MRI pulse sequence to acquire MRI k-space data from non-stationary nuclei flowing in a selected spatial region of a subject after nuclei within the region have been subjected to spatially non-uniform pre-saturation of nuclear magnetic resonance (NMR) magnetization. Such pre-saturation suppresses subsequent MRI signals emanating from background nuclei located within said region during said pre-saturation, while enhancing MRI signal from flowing nuclei therewithin as a function of speed, slice thickness and elapsed time until image capture as a function of the spatially shaped profile of non-uniform pre-saturation across the imaged volume. Thus, acquired MRI k-space data can then be used to reconstruct an image representing vasculature of the subject.