1. A magnetic resonance imaging (MRI) 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; 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; a computer system programmed to: control operation of the magnetic gradient system and RF system to perform a calibration data pulse sequence to begin acquiring calibration data for use in a parallel imaging reconstruction process after receiving an indication that the subject has received a dose of a contrast agent; discontinue acquisition of the calibration data before the contrast agent reaches a peak concentration within a region of interest (ROI) of the subject; control operation of the magnetic gradient system and RF system to perform an imaging pulse sequence in accordance with a parallel imaging acquisition to begin acquiring image data from the ROI; and reconstruct the image data into an image of the ROI using the calibration data.