The difference between CT and MRI is as follows: 1. The imaging principle is different: CT is an image with different density differences due to the different absorption of X-rays by different tissues after X-rays penetrate the body, while MRI has no radiation and detects the movement of hydrogen protons in the body after the body enters a strong magnetic field, the imaging principle is more complex than CT, and according to the changes in the intensity, angle and interval time of the radiofrequency pulses and other parameters, there will be There are different imaging sequences, and the reconstructed gray-scale images vary in their light and dark changes; 2. The display and diagnostic ability of different organ systems are different: CT is better than MRI for displaying lung texture and small lesions in the lung. Therefore, whether to do CT or MRI examination, we must listen to the doctor’s arrangement according to the specific examination purpose; 3, the time difference: CT examination is fast, and a person with good cooperation usually takes about 5 minutes for plain CT examination. The MRI examination is relatively slow, the general examination also takes about 15-20 minutes, some complex examination may take 30-40 minutes; 4, requirements: Although the CT and MRI examination should be done to remove the metal objects on the body, but the magnetic resonance requirements are higher, all ferromagnetic objects can not enter the examination room, including the accompanying examination personnel should also be removed. Wheelchairs, flat cars, etc. cannot be pushed into the examination room; 5. Equipment thickness: the thickness of the MRI body is much greater than that of CT, so it is necessary to enter a deeper orifice when doing MRI examinations. A few people will experience chest tightness, shortness of breath, dizziness and other uncomfortable symptoms called claustrophobia, while CT examinations do not present such conditions.