MRI DWI sequence is a rapid excitation in the magnetic field to produce oscillatory signal, which can detect the movement of water molecules. In addition to diagnosing tumors, DWI can also diagnose acute stroke and cerebral thrombosis, because brain cells can produce edema after cerebral ischemia and free water between brain cells will be restricted, thus producing high signal; acute cerebral infarction can be diagnosed within 2 hours. MRI is the best diagnostic tool.