A method of providing a quantitative volumetric assessment of organ (such as a liver for example) health comprises obtaining a volumetric map 110 of organ health comprising information defining a state of tissue health across at least part of an organ, receiving input defining at least one organ section 125 , determining an assessment organ volume 130 based at least partly on the at least one defined organ section, calculating an organ-viability measure 135 for the assessment organ volume based at least partly on information within the volumetric map defining the state of tissue health across the organ volume, and outputting an indication of the organ-viability measure 150. The method may comprise inputting a user-defined region of interest, and the functional organ model may be based on Couinaud classification. The state of tissue health may be measured at multiple discrete locations within the organ, and these results averaged or interpolated to determine the whole organ health. An apparatus for carrying out the method is disclosed. The method and apparatus are suitable for monitoring conditions such as non-alcoholic fatty liver disease (NAFLD) or non-alcoholic steatohepatitis (NASH), or hepatocellular carcinoma (HCC) and for identifying the functional liver remnant (FLR) prior to removal.
