We present a one-compartment model with fractional elimination and time-dependent tracer input to estimate perfusion and its heterogeneity with intravascular contrast agent and DCE-MRI. Fractional order elimination leads to residue functions of a simple decreasing Mittag-Leffler type. The technique was validated with animal experiments and also tested clinically in a patient with lower limb sarcoma. Our results suggest that using intravascular contrast agent in combination with a fractional 1-compartment tracer kinetic model allows for the absolute perfusion quantification of low perfused organs like muscles by considering kinetic heterogeneity.