Nuclear Magnetic Resonance (NMR) is a physical phenomenon, abbreviated as NMR, or Nuclear Magnetic Resonance, which is scientifically defined as a physical phenomenon that occurs when the nucleus of an atom in a static magnetic field is under the action of another alternating electromagnetic field. NMR is a technology that utilizes the phenomenon of nuclear magnetic resonance to obtain information about the structure of molecules, as well as the internal structure of the human body. This technique is analyzed below. First, not all atomic nuclei are capable of producing this phenomenon, but atomic nuclei are capable of producing NMR because of their nuclear spin. Atomic nuclear spin generates a magnetic moment, and when the nuclear magnetic moment is in a static external magnetic field, it generates an incoming nucleus and energy level splitting. Under the action of an alternating magnetic field, the spin nucleus absorbs electromagnetic waves of a specific frequency and jumps from a lower energy level to a higher energy level, and this process is nuclear magnetic resonance. The MRI we receive in the hospital is accurately called magnetic resonance imaging technology, or resonance imaging for short. It is another major advancement in medical imaging after CT. Resonance imaging has been used since the 1980s and has been growing at a very fast pace ever since. The basic principle of resonance imaging is to place the human body in a special magnetic field, using radio frequency pulses to excite the hydrogen nucleus in the human body, causing the hydrogen nucleus to resonate and absorb energy, after stopping the radio frequency pulses, the hydrogen nucleus sends out radio signals according to a specific frequency and releases the absorbed energy, which is recorded by the receiver outside the body and processed by the computer to obtain an image. The amount of information provided by MRI technology is not only greater than many other imaging techniques in medical imaging, but also different from existing imaging techniques. Therefore, it has great potential superiority for the diagnosis of diseases. It can directly make cross-sectional, sagittal, coronal and various oblique images of the body, and does not produce artifacts in the CT test; does not need to be injected into the contrast agent; no ionizing radiation, less adverse effects on the body. Resonance imaging is very effective in detecting intracerebral hematoma, extracerebral hematoma, brain tumor, intracranial aneurysm, arteriovenous vascular malformation, cerebral ischemia, intravertebral tumors, spinal cord cavernous disease, and spinal cord hydrocele. At the same time, it is also effective in the diagnosis of lumbar intervertebral disc posterior protrusion, primary liver cancer and other diseases. Of course, resonance imaging has its shortcomings. Its spatial resolution is not as good as CT, and patients with pacemakers or parts with certain metal foreign bodies cannot receive this examination. This site has briefly explained the circumstances that cannot receive MRI examination and whether tattoos can do MRI in the article of “Whether tattoos on the body can do MRI”, which is welcome to refer to. On the other hand, MRIs are relatively expensive.