What is the principle of nuclear magnetic resonance

Currently, many hospitals are gradually incorporating MRI into routine physical examinations. Since the diagnostic results of MRI are more accurate, it can increase the chances of discovering medical conditions during physical examinations. Many people do not understand what MRI is and are somewhat resistant to this new diagnostic and treatment technology. In fact, MRI is very safe and its working principle is in line with modern medical safety standards.

Nuclear magnetic resonance (NMR) is a physical process in which an atomic nucleus with a non-zero magnetic moment undergoes Zeeman splitting of its spin energy levels under the action of an external magnetic field and resonates to absorb radio frequency radiation of a certain frequency. Nuclear magnetic resonance spectroscopy is a branch of spectroscopy. Its resonance frequency is in the radio frequency band, and the corresponding transition is the transition of nuclear spin on the nuclear Zeeman energy level.

Nuclear magnetic resonance is widely used as an analytical method in physics, chemistry, biology and other fields. It was not until 1973 that it was used in medical clinical testing. Magnetic resonance imaging (MRI) is another major advancement in medical imaging after CT. Since its application in the 1980s, it has developed at a very fast speed.

The basic principle of magnetic resonance imaging (MRI) is to place the human body in a special magnetic field and use radio frequency pulses to excite the hydrogen nuclei in the human body, causing the hydrogen nuclei to resonate and absorb energy. After the radio frequency pulse is stopped, the hydrogen nuclei emit radio signals at a specific frequency and release the absorbed energy, which is received by receivers outside the body and processed by a computer to obtain an image. This is called magnetic resonance imaging.

The amount of information provided by MRI is not only greater than many other imaging techniques in medical imaging, but also different from existing imaging techniques. Therefore, it has great potential advantages in the diagnosis of diseases. It can directly produce cross-sectional, sagittal, coronal and various oblique tomographic images without producing artifacts seen in CT detection; it does not require injection of contrast agents; it has no ionizing radiation and has no adverse effects on the body. MRI is very effective in detecting common brain diseases such as intracerebral hematoma, extracerebral hematoma, brain tumors, intracranial aneurysms, arteriovenous malformations, cerebral ischemia, intraspinal tumors, syringomyelia and hydromyelia. It is also very effective in diagnosing diseases such as lumbar disc herniation and primary liver cancer.