Pneumonia on CT is different depending on the time of the day. In the early stage, only thick lung texture or slightly blurred lung segments or lobes can be seen on CT. As the disease progresses, the alveoli are filled with inflammatory exudate, which is manifested as a large inflammatory infiltrate shadow or solid shadow. In the solid shadows, lumen patency, or bronchial insufflation, can be seen. There may be a small amount of pleural effusion in the costophrenic angle, which is inflammatory exudate. In the dissipation phase, CT shows that the inflammatory infiltrate gradually begins to absorb, and there may be a rapid absorption of flakes, showing the phenomenon of pseudo-cavity, and most cases can not be completely dissipated until 3-4 weeks after the onset of the disease. In most cases, it takes 3-4 weeks for the disease to completely dissipate. In elderly patients, the dissipation may be even slower.