The TCD foam test is currently only available in tertiary hospitals, with charges ranging from 200-400 yuan depending on the region.The TCD foam test is mainly used to check for headaches or unexplained cerebral infarction. Clinically, it can check the presence of congenital oval hole in the heart. For the foam test, it is mainly to inject 9 ml of saline and 1 ml of air into the patient, and then use the color ultrasound to monitor whether there is an embolus passing through, to assess the patient’s condition. The fee is not too high, ranging from 200-400 dollars.