The first thing to do is to decide how to look at the CT film according to which part of the patient is being examined, which needs to be combined with the patient’s clinical history. For example, if we take chest CT as an example, there are usually two CT films of the chest, one is the lung window and the other is the mediastinal window. The lung window is the one with white color. The lung window mainly looks at whether the chest is symmetrical, whether the trachea is centered, whether the permeability of the two lungs is uniform, whether the tracheobronchial tubes are open, and whether there are abnormal density shadows in the parenchyma of both lungs. The mediastinal window of the chest is mainly to show whether there are abnormal masses in the mediastinum, whether there are enlarged lymph nodes in the mediastinum and the hilum, whether there is fluid in the pericardium, and whether there are obvious abnormalities in the heart and large blood vessels. The first thing you need to look at on a CT film is the normal tissue structure.