Systems and methods are provided for performing a medical imaging. The system includes a main magnet system configured to generate a main static magnetic field about at least a region of interest (ROD of a subject arranged in the main magnet system. The system also includes at least one gradient coil configured to establish at least one magnetic gradient field with respect to the main static magnetic field, The system also includes a radio frequency (RF) system configured to deliver excitation pulses to the subject. The system also includes a polarization magnet system configured to generate a polarization static magnetic field in an at least partially shielded region away from the main magnet system, the polarization magnet system configured to at least partially pre-polarize a blood substitute to be injected to the subject.