Both nuclear myocardial perfusion imaging and CTA and coronary angiography can be used to diagnose coronary artery disease. Myocardial perfusion imaging mainly shows whether there is ischemia in the myocardium and whether the function of myocardial cells is normal. CTA and coronary angiography mainly show whether there is plaque, calcification and stenosis in the coronary arteries. If the rice grows well, it means that the supply of nutrients and water is sufficient, so the farmer does not need to repair the canals. Once the rice in a paddy field withers, it means that the paddy field lacks nutrients, so the farmer only needs to repair the canals that supply the paddy field, but not all of them. Therefore, nuclear myocardial perfusion imaging is to observe the growth of rice (whether there is ischemia in the myocardium), while CTA and coronary angiography are to observe whether there is blockage in the aqueduct (whether there is obstruction in the blood vessels).