A medical instrument comprising a processor and a memory, wherein the memory contains machine executable instructions, wherein execution of the machine executable instructions causes the processor to: - receive a first magnetic resonance image data set descriptive of a first region of interest of a subject; - receive at least one second magnetic resonance image data set (152, 152') descriptive of a second region of interest of the subject, wherein the first region of interest at least partially comprises the second region of interest; - receive an analysis region within both the first region of interest and within the second region of interest; - construct a cost function comprising an intra-scan homogeneity measure separately for the first magnetic resonance image data set and separately for each of the at least one second magnetic resonance image data set, wherein the cost function further comprises an inter-scan similarity measure calculated using both the first magnetic resonance image data set and each of the at least one second magnetic resonance image data set; - perform an optimization of the cost function by calculating a first intensity correction map for the first magnetic resonance image data set using an intensity correction algorithm within the analysis region and at least one second intensity correction map for each of the at least one second magnetic resonance image data set within the analysis region; - calculate a first corrected magnetic resonance image descriptive of the analysis region using the first magnetic resonance image data set and the first intensity correction map; and - calculate at least one second corrected magnetic resonance image descriptive of the analysis region using the at least one second magnetic resonance image data set and the at least one second intensity correction map. - receive a first magnetic resonance image data set descriptive of a first region of interest of a subject; - receive at least one second magnetic resonance image data set (152, 152') descriptive of a second region of interest of the subject, wherein the first region of interest at least partially comprises the second region of interest; - receive an analysis region within both the first region of interest and within the second region of interest; - construct a cost function comprising an intra-scan homogeneity measure separately for the first magnetic resonance image data set and separately for each of the at least one second magnetic resonance image data set, wherein the cost function further comprises an inter-scan similarity measure calculated using both the first magnetic resonance image data set and each of the at least one second magnetic resonance image data set; - perform an optimization of the cost function by calculating a first intensity correction map for the first magnetic resonance image data set using an intensity correction algorithm within the analysis region and at least one second intensity correction map for each of the at least one second magnetic resonance image data set within the analysis region; - calculate a first corrected magnetic resonance image descriptive of the analysis region using the first magnetic resonance image data set and the first intensity correction map; and - calculate at least one second corrected magnetic resonance image descriptive of the analysis region using the at least one second magnetic resonance image data set and the at least one second intensity correction map.