What are the applications of magnetism in modern medicine?

The application of magnetism in medicine has a long history. In the Historical Records of the Western Han Dynasty (about 90 BC), Biography of Cang Gong said that the King of Qi used five kinds of mineral medicines (called five stones) to treat diseases. These five mineral drugs are magnetite (Fe3O4), cinnabar (HgS), realgar (As2O3), alum (potassium aluminum sulfate) and cyanine (2CuCo3).

Later generations recorded the application of magnets to treat diseases. For example, in Shennong Materia Medica in the Eastern Han Dynasty (about the 2nd century AD), it was said that cold and warm stone was used to treat rheumatism, joint pain, fever, deafness and other diseases. Tao Hongjing in the Southern and Northern Dynasties (AD 5 10) wrote a medical book "Records of Famous Doctors", which said that magnets can tonify the kidney, strengthen the spine, dredge joints, reduce swelling and relieve pain. Sun Simiao, a famous doctor in the Tang Dynasty, also talked about honey pills made of magnets in Qian Jin Fang (AD 652), which can improve eyesight if taken frequently. Sheng Huifang (A.D. 1046) written by He Xiying in the Northern Song Dynasty also mentioned that a magnet can cure children from swallowing needles by mistake, that is, a magnet the size of a jujube pit is polished and put in the throat, and then the swallowed needles are sucked out. Fang Jisheng (AD 1253), a medical book strictly used in the Southern Song Dynasty, also talked about using magnets to treat ear diseases with poor hearing. This is to put a bean-sized magnet in the ear with new cotton, and then put a pig iron in the mouth to improve the hearing of the sick ear. Compendium of Materia Medica, written by Li Shizhen, a famous pharmacist in Ming Dynasty, has a rich and summative description of medical magnets. It describes in detail the shape of the magnet, the name of the main treatment, the preparation method of the medicine and various applications. For example, diseases treated by magnets include kidney deficiency deafness, deafness of the elderly, frailty of the elderly, blindness cataract, epilepsy of children, uterine failure, proctoptosis of large intestine, intestinal abscess, abscess bleeding and so on. Drugs made of magnets include Cizhu Pill, Zi Xue Powder and Erlong Zuo Ci Pill.

Generally speaking, the medical books of various dynasties often recorded that magnets were used to treat many diseases.

The Dictionary of China Medicine published by China 192 1 (edited by Xie Guan) records several kinds of Chinese patent medicines with magnets as important raw materials, such as magnet pills, magnet pills, magnet hair, magnet sheep kidney pills, magnet wine, magnet powder and magnet bead pills. 1935 first edition, 1956 revised "China Pharmaceutical Dictionary" recorded in detail the types, preparation methods, usage, indications and historical records of magnets, and listed more than 10 applications of magnets in medicine. In the Pharmacopoeia of People's Republic of China (PRC) published by the Ministry of Health 1963, several Chinese patent medicines with magnets as important components are listed, such as Erlong Zuo Ci Pill, Zi Xue Powder and Cizhu Pill.

An important application of magnetism in biology and medicine is magnetic resonance imaging (MRI), also known as magnetic resonance CT(CT is the abbreviation of computed tomography). This is a nuclear nuclide, that is, the concentration distribution image of chemical elements of this nuclide obtained by nuclear magnetic resonance method and computer processing technology.

The basic principle of nuclear magnetic resonance imaging technology is that the nucleus is positively charged and spins. Usually, the arrangement of nuclear spin axes is irregular, but when it is placed in an external magnetic field, the spatial orientation of nuclear spin changes from disorder to order. The magnetization vector of the spin system increases gradually from zero, and when the system reaches equilibrium, the magnetization reaches a stable value. If the nuclear spin system is acted by external force at this time, for example, a certain frequency of radio frequency excites the nuclear, it can cause * * * vibration effect. After the RF pulse stops, the nuclei excited by the spin system can not maintain this state, and will return to their original arrangement in the magnetic field, and at the same time release weak energy into radio signals. These signals are detected and spatially resolved, and the distribution images of moving nuclei are obtained. The characteristic of NMR vibration is that the flowing liquid does not produce signal, which is called flow effect or flow blank effect.

So blood vessels are gray-white tubular structures, while blood is black and has no signal. This makes blood vessels easily separated by soft tissue. Normal spinal cord is surrounded by cerebrospinal fluid, which is black and has white dura mater set off by fat, which makes the spinal cord show white strong signal structure. Nuclear magnetic resonance (NMR) vibration has been applied to imaging diagnosis of various systems in the whole body. The best results are the brain and its spinal cord, cardiac blood vessels, joint bones, soft tissues and pelvic cavity. For cardiovascular diseases, we can not only observe the anatomical changes of various heart cavities, great vessels and valves, but also analyze the ventricles, make qualitative and semi-quantitative diagnosis, and make several high-spatial resolution sectional views to show the whole picture of the heart and lesions and their relationship with surrounding structures.

At present, nuclear magnetic resonance tomography of hydrogen is used. This kind of tomography has more advantages than X-ray tomography (also called X-ray CT). For example, X-ray tomography is the density distribution image of the imaging object, while nuclear magnetic resonance tomography is the distribution image of the nuclear density of the imaging object. At present, although it is limited to the density distribution image of hydrogen nuclei, hydrogen is the main chemical element that constitutes human body and organism. Therefore, the hydrogen distribution image obtained from nuclear magnetic resonance tomography has more information about human body and organism than that obtained from X-ray density distribution image. For example, the density of skull outside the human head is high, while the density of brain tissue inside is low, so it is difficult to obtain a clear image of human brain tissue from X-ray tomography of human head. However, from the MRI of the human head, we can clearly see the distribution of hydrogen nuclei in the brain tissue of the head, so we can see whether the brain tissue is normal or not. For another example, when there is no obvious difference between the initial tumor patient and the normal tissue, no abnormality can be seen from X-ray tomography, but abnormality can be seen from nuclear magnetic resonance tomography. Brain tumors can be detected by magnetic resonance tomography, but not by X-ray tomography. At present, although only one nuclear element hydrogen nucleus is used in nuclear magnetic resonance tomography, it can be predicted that more nuclear elements will appear, such as carbon nuclei and nitrogen nuclei, and nuclear magnetic resonance tomography will also enter the application.

Magnetism can not only diagnose, but also help treat diseases. Magnets were used blindly in ancient medicine in China. Now people use the magnetic differences of different components in blood to separate red blood cells from white blood cells. In addition, the interaction between magnetic field and human meridians can realize magnetotherapy, which has a unique role in treating many diseases and has been applied to magnetic therapy pillows, magnetic therapy belts and so on.