Magnetic resonance and CT belong to the same category of medical imaging, but there are essential differences between them. First of all, the working principle is different. MRI uses the nucleus of hydrogen atoms in the human body to resonate and restore energy information in the powerful magnetic field space of the MRI instrument, and then the signal is collected by a high-energy electronic computer system and converted into a magnetic resonance image through digital reconstruction technology; CT uses the X-ray imaging principle to form an image. Secondly, the scope of focus of the two examinations is different. MRI has high resolution for soft tissues, such as synovial membranes, blood vessels, nerves, muscles, tendons, ligaments and transparent cartilage, and CT has advantages in observing bones, lungs and bleeding, etc. The two can complement each other in the examination.