A medical imaging system (5) includes a data store (12), a clustering module (22), and a display device (32). The data store (12) includes a first imaging data set and a second imaging data set, each data set created with the same imaging device (10) and the same measured value. The measured value of a first and a second tissue type overlap in the first imaging data set. The measured value of the second and a third tissue type overlap in the second data set. The data sets are co-registered, and an external event changes the measured value of the second data set. The clustering module (22) classifies the tissue type based on a fuzzy clustering of the measured value of the first data set and the measured value of the second data set for each location. The display device (32) displays a medical image which contrasts each classified tissue type.