It is the specialized technician who operates the MRI **** vibration machine.
Medical applications of MRI
The purpose of the examination
1, detection and diagnosis of heart diseases, cerebrovascular accidents and vascular diseases
2, detection and diagnosis of diseases of the thoracic cavity and the abdominal cavity
3, diagnosis and evaluation, tracking of tumors and functional disorders
MRI has been widely used in the diagnosis of sports-related injuries, including soft tissues near the bones and around the bones, including ligaments and muscles. MRI is widely used in the diagnosis of sports-related injuries. It can present clear images of the soft tissues near and around bones, including ligaments and muscles, and is therefore a very sensitive test for spine and joint problems.
Because there is no risk of radiation exposure, MRI is often used to detect and diagnose disorders of the reproductive system, breasts, pelvis, and bladder.
Overview
Hydrogen nuclei are the preferred nuclei for imaging the human body: The human body contains a large amount of water and hydrocarbons in various tissues, so hydrogen nuclei have high MRI **** vibration flexibility and strong signals, which is the reason why they are preferred as the imaging element for the human body.
NMR signal strength and the density of hydrogen nuclei in the sample is related to the human body between the various tissues containing different proportions of water, i.e., the number of hydrogen nuclei containing the number of different, there is a difference in the intensity of the NMR signal, the use of this difference as a characteristic quantity, to separate the various tissues, which is the density of hydrogen nuclei of the NMR * * * vibration image.
The differences in the three parameters of hydrogen nuclei density, relaxation time T1 and T2 between different tissues of the human body, normal tissues and diseased tissues in that tissue are the most important physical basis for MRI to be used for clinical diagnosis.
When a radiofrequency pulse signal is applied, the hydrogen nuclear energy state changes, and after the radiofrequency has passed, the hydrogen nuclei return to their initial energy state, and the electromagnetic waves generated by *** vibration are emitted.
The small differences in the vibration of the nucleus can be detected precisely, and after further computer processing, it is possible to obtain a three-dimensional image of the chemical composition of the reactive tissue, from which we can obtain information including differences in the water content of the tissue and the movement of water molecules. In this way, pathological changes can be recorded.
2/3 of the body's weight is water, and such a high percentage is the basis for magnetic **** vibration imaging to be widely used in medical diagnostics. The water in organs and tissues in the human body is not the same, and the pathology of many diseases can lead to changes in the water pattern, which can be reflected by the magnetic **** vibration image.
The images obtained by MRI are very clear and detailed, which greatly improves the diagnostic efficiency of doctors and avoids the need for a thoracotomy or cesarean section for diagnostic surgery. Since MRI does not use X-rays, which are harmful to the human body, or contrast agents, which are prone to allergic reactions, there is no damage to the human body.
MRI can image various parts of the body from multiple angles and planes, and with its high resolution, it can show the anatomical tissues and adjacent relationships in the human body more objectively and concretely, and can better localize and characterize the lesions. It is of great value for the diagnosis of systemic diseases, especially for the diagnosis of early tumors.
Expanded Information
Imaging Principle
Nuclear Magnetic **** vibration imaging principle: The atomic nucleus is positively charged, and the nuclei of many elements, such as 1H, 19FT and 31P, undergo spin motion. Normally, the arrangement of the spin axis of the nucleus is irregular, but when it is placed in an applied magnetic field, the nuclear spin space orientation transitions from disorder to order.
In this way, the spinning nucleus simultaneously spins around the applied magnetic field vector at an angle between the spin axis and the vector direction of the applied magnetic field, a spinning called Larmor spinning, like the rotation of a spinning gyroscope under the Earth's gravity. The magnetization vector of a spin system grows gradually from zero, and when the system reaches equilibrium, the magnetization strength reaches a stable value.
If at this time the nuclear spin system is subject to external effects, such as a certain frequency of radio frequency excitation of the nucleus can cause *** vibration effect. In this way, the spin nucleus also want to spin in the direction of radio frequency, this superposition of the spin state is called chapter action. In the radio frequency pulse stops, the spin system has been excited nuclei, can not maintain this state, will return to the magnetic field in the original arrangement of the state, at the same time to release a weak energy, become a radio signal, the many signals detected, and make it possible to carry out the spatial resolution of the room, you get the distribution of the nuclei in the movement of the image.
After the cessation of the radio frequency pulse, the spin system has been excited nuclei, can not maintain this state, will return to the magnetic field in the original arrangement of the state, at the same time releasing a weak energy into the radio signal, the many signals detected, and make it possible to carry out the spatial resolution of the room, you get the distribution of nuclei in the movement of the image.
The process in which the nucleus returns to an equilibrium arrangement from an excited state is called the relaxation process. The time it takes is called relaxation time. There are two types of relaxation time i.e. T1 and T2, T1 is spin-dot-dot or longitudinal relaxation time and T2 is spin-spin or transverse relaxation time.
Baidu Encyclopedia - MRI
Baidu Encyclopedia - Magnetic **** Vibrational Imaging