1. A method of image processing to determine blood flow through coronary arteries of a patient, comprising: receiving a 3D image data set of an anatomy comprising at least one or more coronary arteries and myocardial muscle of the patient; receiving a perfusion information data set measured from the patient and corresponding to the 3D image data set; generating a three-dimensional anatomical model depicting the anatomy of the patient's coronary arteries and the myocardial muscle, based on the 3D image data set; subdividing the myocardial muscle into myocardial muscle segments based on which portion of the myocardial muscle is supplied by each of the coronary arteries; determining the blood flow into the respective myocardial muscle segments from said perfusion information data set, by performing a 3-D computational fluid dynamics (CFD) simulation of blood flow using the three-dimensional anatomical model; determining blood flow characteristics at one or more points of a coronary artery of interest, based on the simulated blood flow into all myocardial muscle segments supplied by said coronary artery; determining an estimate of fractional flow reserve in said coronary artery of interest using the blood flow characteristics; and outputting one or more of the determined fractional flow reserve, blood flow characteristics, or the three-dimensional model to an electronic storage medium or display.