Whether coronary CT or coronary angiography, can not directly see the performance of myocardial ischemia, coronary CT to determine the existence of coronary artery stenosis can only judge the epicardial arteries, to determine the presence of obvious plaque in the vessel wall, all of which is a physical assessment of the stenosis of the problem, and can not be directly judged whether there is is ischemia in the myocardial performance. However, it can be combined with it to determine the manifestation of myocardial ischemia, for example, when angina pectoris attack, electrocardiography in the corresponding leads found that myocardial ischemia changes, and the corresponding coronary artery CT suggests that stenosis, at this time, it can be assumed that the stenotic artery contributes to ischemia. Clinical tests to determine myocardial ischemia include exercise load test, coronary flow reserve index, IVUS of coronary artery, and OCT, nuclear magnetic examination of the heart.