The invention provides for a medical imaging system (100, 300, 500, 600) comprising: a memory (110) for storing machine executable instructions (120)； a processor (106) for controlling the medical instrument. Execution of the machine executable instructions causes the processor to: receive (200) MRF magnetic resonance data (122) acquired according to an MRF magnetic resonance imaging protocol of a region of interest (310)； reconstruct (202) an MRF vector (124) for each voxel of a set of voxels descriptive of the region of interest using the MRF magnetic resonance data according to the MRF magnetic resonance imaging protocol； calculate (204, 714) a preprocessed MRF vector (126) for each of the set of voxels by applying a predetermined preprocessing routine to the MRF vector for each voxel, wherein the predetermined preprocessing routine comprises normalizing the preprocessed MRF vector for each voxel； calculate (206, 716) an outlier map (130) for the set of voxels by assigning an outlier score (800) to the preprocessed MRF vector using a machine learning algorithm.
