The invention provides for a medical imaging system (100, 400) comprising: a memory (112) for storing machine executable instructions and a processor (106) for controlling the medical imaging system. Execution of the machine executable instructions cause the processor to: receive (200) a preliminary segmentation (124) from a preliminary magnetic resonance image (122) of a region of interest (409), wherein the preliminary segmentation comprises preliminary segmentation edges; reconstruct (202) a first QSM image (124) for the region of interest from QSM magnetic resonance data (122), wherein the reconstruction of the QSM image is at least partially performed using a regularization function, wherein the regularization function is dependent upon the preliminary segmentation edges during reconstruction of the first QSM image; calculate (204) a first segmentation (126) by segmenting the first QSM image using a QSM image segmentation algorithm (134), wherein the first segmentation comprises first segmentation edges; and reconstruct (206) a second QSM image (128) for the region of interest from the QSM magnetic resonance data, wherein the reconstruction of the second QSM image is at least partially performed using the regularization function, wherein the regularization function is dependent upon the first segmentation edges.