1. A perfusion imaging data processor, comprising: an agent peak characteristic-time determiner configured to determine two or more agent peak characteristic-times respectively for two or more circulatory sub-systems represented in a same sub-set of voxels of a set of time-series data of perfusion imaging data; an agent peak argument determiner configured to determine an agent peak argument for each of the two or more agent peak characteristic-times; an agent peak argument relation determiner configured to determine a relationship between the agent peak arguments of the two or more agent peak characteristic-times; and a perfusion map generator configured to generate, based on the determined relationship and the perfusion imaging data, at least one perfusion map, wherein the at least one perfusion map includes volumetric image data visually presenting at least one of a relationship or a difference between the two or more circulatory sub-systems.