The present invention relates to a system for measuring a micro-vascular flow distribution of a tissue portion of a mammal comprising means (101) for measuring a first indicator (MTT) for the blood flow through a capillary bed, means (102) for measuring a second indicator (CTTH) of heterogeneity of the blood flow in said capillary bed, and a first processor (110) arranged for using the first and the second indicator to estimate an extraction capacity (EC) of a substance from the blood in said capillary bed.
