MRI means magnetic resonance imaging and MR means magnetic resonance. In everyday life, MRI and MR are both magnetic resonance scans or magnetic resonance examinations. MRI is the use of radiofrequency electromagnetic waves or energy waves to excite atoms placed in a magnetic field containing non-zero spin, generating echoes, and resonance of the nucleus occurs. The magnetic resonance signal is received with a coil, and both are calculated, processed, reconstructed according to certain mathematical methods, and finally an image is formed. Magnetic resonance is not related to nuclear radiation. Magnetic resonance has the characteristics of multiple imaging parameters and high resolution for soft tissue, especially for the diagnosis of ultra-early brain infarction has very important value. Magnetic resonance can be applied to almost all systems of the body.