1. A method for producing an image of a subject with an MRI system, the steps comprising: performing a prescan to produce a rephasing map, the prescan including: a) acquiring a plurality of pilot images of the subject using an NMR pulse sequence that employs an imaging magnetic field gradient, and wherein the imaging magnetic field gradient is set to different values in the plurality of pilot image acquisitions; b) calculating the optimal imaging magnetic field gradient value for each pixel in the pilot images by examining magnitudes of the corresponding pixels in the plurality of acquired pilot images; c) storing the optimal imaging magnetic field gradient values at corresponding pixel locations in the rephasing map; d) determining an imaging magnetic field gradient setting using the values stored in the rephasing map; and e) performing a scan of the patient using the NMR pulse sequence with the imaging magnetic field gradient setting.