How often ultrasound is done at intervals is defined according to the actual situation. If it is only for physical examination, once every 0.5-1 year is enough. If it is because of disease demand, it is necessary to carry out medically prescribed review according to the actual clinical situation. If a tumor is found to occupy the space or pleural effusion, etc., then the review should be conducted according to the clinical condition, and the interval of review may be longer or shorter. In the case of pleural fluid extraction, the frequency of ultrasound review may be more frequent, possibly within 24-48 hours. Therefore, the interval between ultrasound examinations depends on the actual condition.