Disclosed herein is a medical system (100, 300). The execution of machine executable instructions (120) causes a processor (104) to: receive (200) measured gradient echo k-space data (122); receive (202) an off-resonance phase map (124); reconstruct (204) an initial magnetization image (126) from the measured gradient echo k-space data; calculate (206) an upsampled phase map (128) from the off-resonance phase map; calculate (208) an upsampled magnetization image (130) from the initial magnetization image; calculating (210) a modulated image (132) by modulating the upsampled magnetization image with the upsampled phase map; calculate (212) a corrected image (134) comprising iteratively. The iterative calculation comprises: calculating (214) updated k-space data by applying a data consistency algorithm (138) to a k-space representation of the modulated image and the measured gradient echo k-space data and calculating (216) an updated image (142) from the updated k-space data. Calculation of the updated image comprises demodulation by the upsampled phase map and applying a smoothing algorithm.