1. A method of determining a required blood flow, the method comprising: obtaining morphological information of a coronary artery in a cardiac image of a user; segmenting the cardiac image into a plurality of myocardial regions based on the morphological information of the coronary artery; calculating a mass of each of the plurality of segmented myocardial regions based on an average myocardial density; determining a myocardial blood flow required for normal myocardial action for each of the plurality of segmented myocardial regions based on the calculated mass of each of the plurality of segmented myocardial regions; adjusting the myocardial blood flow required for normal myocardial action for each of the plurality of segmented myocardial regions based on blood flow distribution information derived from a myocardial perfusion image of the user; and generating a blood flow image of the coronary artery by applying the adjusted myocardial blood flow required for normal myocardial action for each of the plurality of segmented myocardial regions and physiological information of the user to the morphological information of the coronary artery of the user.