The principle of MRI is to use a strong external magnetic field to resonate with the hydrogen nuclei in human tissues. Different tissues will have different contents of hydrogen nuclei due to their different structures, and the external instrument will record the movement of the hydrogen nuclei and then reconstruct the image, which will be reflected as black and white images with different shades of gray. MRI is a commonly used imaging modality in clinical practice, and is often used to examine whether there are lesions in tissues and organs, as well as the extent and severity of the lesions. MRI is clearer than traditional X-ray or CT imaging and is not radioactive. MRI cannot be performed with metal objects, and patients with metal implants in their bodies, such as pacemakers, metal stents, screws, and steel plates, are prohibited from undergoing MRI. MRI is now very common in clinical practice and can be used to diagnose or determine the prognosis of many diseases. Patients should follow the direction of the radiologist when undergoing an MRI to avoid accidents.