1. A method for determining a blood flow characteristic of a patient, comprising: receiving patient-specific image data of the patient at a first physiological state, the first physiological state comprising a state of hyperemia, a state of rest, or a state of exercise; determining boundary conditions based on the patient-specific image data, the boundary conditions corresponding to the first physiological state; performing a patient-specific computational fluid dynamics simulation of blood flow based on the boundary conditions; determining a first value of a blood flow characteristic of the patient at the first physiological state based on the patient-specific computational fluid dynamics simulation of blood flow, the blood flow characteristic representing a medical characteristic of the patient; determining features from the patient-specific image data, wherein the determined features are determined based on the blood flow characteristic determined for the patient; and mapping the first value of the blood flow characteristic of the patient at the first physiological state to a second value of the blood flow characteristic of the patient at a second physiological state based on the determined features, the second physiological state comprising a state of hyperemia, a state of rest, or a state of exercise, the first physiological state being a different physiological state from the second physiological state.