A method for determining functional severity of a stenosis includes: (a) generating a simulated perfusion map from a calculated blood flow (b) comparing the simulated perfusion map to a measured perfusion map to identify a degree of mismatch therebetween, the measured perfusion map representing perfusion in a patient (c) modifying a parameter in a model used in calculating the blood flow when the degree of mismatch meets or exceeds a predefined threshold (d) computing a hemodynamic quantity from the simulated perfusion map when the degree of mismatch is less than the predefined threshold, the hemodynamic quantity being indicative of the functional severity of the stenosis and (e) displaying the hemodynamic quantity. Systems for determining functional severity of a stenosis are described.
