Medical imaging MRI applications:
1, craniocerebral lesions: cerebrovascular disease, intracranial tumors, intracerebral inflammatory lesions, craniocerebral trauma, congenital craniocerebral malformations, cerebral degenerative diseases and cerebral white matter lesions, nasal, orbital lesions.
2, spine and spinal cord lesions: spinal cord cavernous disease, spinal cord injury, spinal cord tumor.
3. Neck: lymph node lesions, laryngeal lesions, thyroid tumors and so on.
4. Chest: mediastinal and hilar masses, thymic lesions, late lung cancer, pleural lesions, etc.
5. Abdominal region: liver cyst, cirrhosis, liver tumor, cholecystitis, etc.
6. Pelvis: uterine and ovarian tumors, prostate hypertrophy, prostate tumors and spermatic cord lesions.
7, musculoskeletal system: bone trauma, tumors, knee and meniscus injuries, and so on.
Question 2: What is called "nuclear magnetic **** vibration" nuclear magnetic **** vibration (MRI), also known as magnetic **** vibration imaging technology. Is following the CT after medical imaging is another major progress. Since its application in the 80's, it has been developed at an extremely fast pace. Its basic principle: the human body is placed in a special magnetic field, radio frequency pulse excitation of hydrogen nuclei in the body, causing hydrogen nuclei **** vibration, and absorption of energy. After stopping the radio frequency pulse, the hydrogen nucleus sends out radio signals at a specific frequency and releases the absorbed energy, which is recorded by the receiver outside the body and processed by an electronic computer to obtain an image, which is called nuclear magnetic **** vibration imaging.
Magnetic moments are caused by the internal angular momentum, or spin, that many atomic nuclei have, and techniques for studying magnetic moments have been developed since 1940. The foundation for this work was laid by physicists working on the fundamentals of nuclear theory, and the first rough determination of the magnetic moments of nuclear particles was made in 1933 by G. O. Stern and I. Estermann. The laboratory of I. I. Rabi (born 1898) in Columbia, U.S.A., made progress in this field of research. These studies played a great role in the development of nuclear theory.
When a beam of atoms accelerated by a strong magnetic field is subjected to a weakly oscillating magnetic field of known frequency, the nucleus has to absorb energy at certain frequencies and at the same time jump to a higher sublayer of the magnetic field. By determining the intensity of the atomic beam in a magnetic field of gradually varying frequency, the magnitude of the absorption frequency of the nucleus can be determined. This technique was initially used for gaseous substances, but was later extended to liquids and solids through the work of F. Bloch (Bloch b. 1905) at Stanford and E. M. Purcell (Puccell b. 1912) at Harvard. Bloch's group made the first determination of the *** vibrational absorption of protons in water, while Puccell's group made the first determination of the *** vibrational absorption of protons in solid chain alkanes. Since these studies were performed in 1946, the field has rapidly gained momentum. Physicists have used the technique to study the properties of atomic nuclei, while chemists have used it for identification and analytical work during chemical reactions, as well as for the study of complexes, hindered rotation, and defects in solids, etc. In 1949, W. D. Knight demonstrated that the *** vibration frequency of the nucleus of a given atom in an applied magnetic field is sometimes determined by the chemical form of that atom. For example, protons in ethanol can be seen to display three separate peaks corresponding to several protons in the CH3, CH2 and OH bonds. This so-called chemical shift is related to the shielding effect that valence electrons have on the applied magnetic field.
(1) Nuclear magnetic **** vibration techniques have played an extremely important role in the elucidation of the structure of organic matter, especially the structure of natural products, since the 1970s. At present, the use of chemical shifts, cleavage constants, H-′HCosy spectra, etc. to obtain the structural information of organic matter has become a routine means of testing. In the last 20 years nuclear magnetic **** vibration technology has made tremendous progress in spectrometer performance and measurement methods. In terms of spectrometer hardware, due to the development of superconductivity technology, the magnetic field strength of the magnet is increased by an average of 1.5 times every 5 years, and by the end of the 1980s 600 megaweeks of spectrometer has begun to be practical, and due to the development of a variety of advanced and complex radio frequency technology, the excitation and detection of nuclear magnetic **** vibration technology has been greatly improved. In addition, with the development of computer technology, not only can the excitation of nuclear *** vibration of the pulse sequence and data acquisition for strict and fine control, but also to get a large number of data for a variety of complex transformations and processing. The most prominent technological progress in the software of the spectrometer is the development of two-dimensional nuclear magnetic **** vibration (2D-NMR) method. It has fundamentally changed the way NMR technology is used to solve complex structural problems, greatly improving the quality and quantity of information provided by NMR technology about molecular structure, and making NMR technology the most important physical method for solving complex structural problems.
① 2D-NMR technology can provide a wide variety of correlation information between various nuclei in a molecule, such as spin-coupling correlation between nuclei through chemical bonding, dipole-coupling (NOE) correlation through space, coupling correlation between homologous nuclei, coupling correlation between heterologous nuclei, and direct correlation and remote correlation between nuclei and nuclei. Based on this correlation information, it is possible to connect the atoms in a molecule to each other through chemical bonds or spatial relationships, which not only greatly simplifies the process of analyzing the molecular structure, but also makes it a direct and reliable method of logical reasoning.
② The development of 2D-NMR not only greatly improves the separation of a large number of *** vibration signals, reducing the overlap between the *** vibration signals, and can provide a lot of 1D-NMR spectra can not provide structural information, such as overlapping *** vibration signals of each group of letters ...... >>
Question 3: What is the difference between CT and NMR **** vibration principles, and what is the scope of application CT scanners can be used for full body scanning of the human body, while NMR **** vibration scanners are mainly used for scanning the soft tissues of the human body. Through these two instruments, the doctor can obtain a detailed three-dimensional image of the human body, clearly see the subtle changes in human tissue, to provide strong evidence for scientific diagnosis.CT scanner and nuclear magnetic **** vibration scanner appearance is very similar, they obtain three-dimensional image is also very similar, but it should be pointed out that the imaging principle of these two instruments is completely different. CT scanner principle is relatively simple, it is the use of different densities of human tissue on the X-ray has a different absorption rate of the principle and design. As we all know, X-rays are a kind of electromagnetic wave with short wavelength, which propagates along a straight line, and because of its high energy, it can penetrate all tissues of the human body. Since different tissues of the human body have different densities, they have different absorption rates of X-rays. If X-rays are sent through the body in parallel or at an angle, and then exposed to photographic film, the distribution of bones, ribs and soft tissues of the body can be clearly seen. This is the basic principle of X-ray fluoroscopy, which was invented in the early twentieth century and has provided an extremely important source of information for medical diagnosis. Unfortunately, X-ray is a flat image, and because of the overlapping of body tissues, which causes a superimposed effect on the absorption of X-rays, many details are not visible in the X-ray picture. In order to understand some three-dimensional details, it is necessary to perform X-ray fluoroscopy from different angles, and it is impossible to obtain a three-dimensional image of the human body. In order to obtain the details of human tissue, in order to obtain a three-dimensional image of human tissue, which can only rely on the modern CT scanner and nuclear magnetic **** vibration scanner. CT scanner was invented in 1971 by Hounsfield (Hounsfield), Hounsfield and thus won the Nobel Prize in 1979. CT scanner and X-ray fluoroscopy have a lot of the same place, but there are many different places. CT scanners and X-ray fluoroscopy have a lot in common, but they also have a lot of differences. The same is that they are both based on the basic principle that organs of different densities in human tissue have different absorption rates of X-rays. The ray source they use can be the wavefront surface X-ray surface source, can also be the wavefront surface is a spherical dispersion of the X-ray point source. The difference between them is that 1) the receiving device for X-ray fluoroscopy is a piece of film, whereas CT scanners use a set of garden-arc-shaped electronic receiving devices, which are generally composed of crystals separated by a collimator. This electronic receiver is located directly opposite the X-ray source. 2) X-ray fluoroscopy work its ray source and film are in a fixed position, while CT scanning in the work of not only the body scanned in the scanner's garden hole will be moved back and forth, and the X-ray source and the electronic receiver will be in the CT scanner's garden ring of high speed rotation. These two directions of motion are monitored by sophisticated encoders on the CT scanner.3) The final difference between the two instruments is that X-ray fluoroscopy does not require computer processing, whereas the CT scanner requires a computer to perform more complex calculations and processing of the image to form a detailed three-dimensional image of the human body tissues. In order to understand the principles of the CT scanner, it is necessary to understand the absorption of X-rays. If a material has an absorption coefficient of , then the transmission of X-rays through the material after a certain distance is . When the plane of the X-film or receiver is parallel to the plane of X-ray emission, the distribution of X-rays after absorption by various parts of the body, the transmittance of X-rays at various points on the film is: (1) The product of the transmittance and the source intensity of the X-rays is the energy of the X-rays arriving at the photographic film or receiver. Assuming that the wavefront of X-rays is a plane, the original intensity of X-rays is , taking into account the background noise in the receiver is , if the absorption coefficient of the medium is discretized, for the length of each discrete point in the medium, then the radiation intensity of the corresponding point that finally falls on the receiver is: (2) Taking into account the scattering of X-rays and other factors, the formula is a simple transformation of the: (3) Note that when the X-rays for the dispersion of propagation, we must also note that the intensity of X-rays in the propagation of their own strength will continue to decay. X-rays of their own strength and X-rays propagate the distance of the square is inversely proportional to the square. From the above formula, X-rays in the absorption coefficient of different structures after the information generated can form a linear system of equations. CT scanner general ...... >>
Question 4: What is nuclear magnetic **** vibration? The phenomenon of nuclear magnetic **** vibration arises from the progression of the spin angular momentum of the atomic nucleus in the presence of an applied magnetic field.
Nuclear magnetic *** vibration
According to quantum mechanics, the atomic nucleus, like electrons, also has spin angular momentum, the specific value of the spin angular momentum of the atomic nucleus by the spin quantum number of the decision, the experimental results show that different types of nuclei spin quantum number is also different:
The mass number and the number of protons are even number of nuclei, the spin quantum number of 0, i.e. I = 0, such as 12C,16C,16C,16C,16C. Nuclei with an odd number of masses and a half-integer spin quantum number, such as 1H,19F,13C, etc., have a non-zero spin quantum number and are called magnetic nuclei. Nuclei with an even number of masses and an odd number of protons have an integer spin quantum number, and such nuclei are also magnetic. But so far, only the spin quantum number equal to 1/2 of the atomic nucleus, its nuclear magnetic **** vibration signal can be used by people, often used by people for the atomic nucleus are: 1H, 11B, 13C, 17O, 19F, 31P , due to the atomic nucleus carries an electric charge, when the atomic nucleus spin, it will be generated by the spin of the atomic nucleus, a magnetic moment, this magnetic moment of the direction of the atomic nucleus with the same direction of the spin direction, the size with the The direction of this magnetic moment is the same as the spin direction of the nucleus, and the size is proportional to the spin angular momentum of the nucleus. The nucleus will be placed in the applied magnetic field, if the magnetic moment of the nucleus and the direction of the applied magnetic field is different, then the magnetic moment of the nucleus will rotate around the direction of the external magnetic field, this phenomenon is similar to the gyroscope in the process of rotating the axis of rotation of the swing, known as the into motion. This phenomenon is similar to the oscillation of the rotating axis of a gyroscope during the rotation process, which is called in motion.
The frequency of the atomic nucleus into action by the strength of the applied magnetic field and the nature of the nucleus itself, that is to say, for a particular atom, in a certain strength of the applied magnetic field, the frequency of its atomic nucleus spin into action is fixed.
The energy of the atomic nucleus is related to the magnetic field, the magnetic moment of the nucleus, and the angle between the magnetic moment and the magnetic field. According to the principle of quantum mechanics, the magnetic moment of the nucleus and the angle between the applied magnetic field is not continuously distributed, but is determined by the magnetic quantum number of the nucleus, and the direction of the magnetic moment of the nucleus can only be jumped between these magnetic quantum numbers, but not smooth changes, which creates a series of
The magnetic moment of the nucleus is the same as the magnetic field of the atom, but the magnetic field is the same as the magnetic field. /p>
Nuclear magnetic **** vibrational hydrogen spectrum
energy levels. When an atomic nucleus receives energy input from another source in an applied magnetic field, an energy level jump occurs, which means that the angle between the magnetic moment of the nucleus and the applied magnetic field changes. This energy level jump is the basis for obtaining the nuclear magnetic **** vibration signal.
In order to make the energy level jump in the nuclear spin evolution, the nucleus needs to be provided with the energy required for the jump, and this energy is usually provided by an applied radio frequency field. According to the principle of physics, when the frequency of the applied RF field and the frequency of the atomic nucleus spin progress is the same, the energy of the RF field can be effectively absorbed by the atomic nucleus, to provide assistance for the energy level jump. Therefore, a particular nucleus, in a given applied magnetic field, only absorbs the energy provided by the RF field at a particular frequency, thus forming a nuclear magnetic **** vibration signal.
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Technical Applications
NMR, or Nuclear Magnetic **** Vibration Spectroscopy, is a technique that applies the phenomenon of nuclear magnetic **** vibrations to the determination of molecular structures. NMR plays a very important role in the structure determination of organic molecules, and NMR, together with ultraviolet spectroscopy, infrared spectroscopy and mass spectrometry, has been called the "four famous spectra" by organic chemists. At present, the study of NMR spectra mainly focuses on the 1H and 13C atomic nuclei of the two types of maps.
For isolated nuclei, the same nucleus in the same strength of the external magnetic field,
NMR***Vibration Carbon Spectrum
only sensitive to a particular frequency of the radio frequency field. But in the molecular structure of the nucleus, due to the molecular distribution of the electron cloud and other factors, the actual felt strength of the external magnetic field tends to change to a certain extent, and is in the molecular structure of the nucleus in different positions, the felt strength of the applied magnetic field is also different, this molecular electron cloud on the strength of the applied magnetic field will lead to the molecules of different positions of the nucleus of the nucleus of a different frequency of the This effect of the electron cloud in the molecule on the strength of the applied magnetic field causes the nuclei at different locations in the molecule to be sensitive to different frequencies of the radio frequency field, which leads to differences in the NMR*** vibration signals. The distribution of chemical bonds and electron clouds in the vicinity of the nucleus is called the chemical environment of the nucleus, and the change in the frequency and position of the NMR signal due to the chemical environment is called the chemical shift of the nucleus.
The coupling constant is another important information provided by the NMR*** vibration spectra in addition to the chemical shift. The so-called coupling refers to the interaction of the spin angular momentum of the neighboring nuclei, and this interaction of the spin angular momentum of the nuclei will change the energy level distribution of the nuclei's spin in the external magnetic field. ...... >>
Question 5: What can nuclear magnetic **** vibration check? Magnetic *** vibration imaging (MRI) is also known as nuclear magnetic *** vibration, the English abbreviation for MRI. Its basic principle is in the role of a strong magnetic field, recording the atomic nucleus of hydrogen atoms in the tissue and organs of the movement of the nucleus, calculated and processed to obtain the image of the examination site.
Purpose of the examination: cranial and spinal column and spinal cord lesions, pentacameral diseases, cardiac diseases, mediastinal masses, bone, joint and muscle lesions, lesions of the uterus, ovaries, bladder, prostate, liver, kidneys, pancreas and other parts of the body.
Advantages: 1. MRI has no damage to the human body;
2. MRI can obtain a three-dimensional image of the brain and spinal cord, unlike CT, which scans one layer at a time and may miss the lesion;
3. It can diagnose cardiac pathology, which is difficult for CT to do because of its slow scanning speed;
4. It can be better than other tests for the bladder, rectum, uterus, ***, bones, joints and muscles.
Disadvantages: 1. Like CT, MRI is also a diagnostic imaging, and many lesions are still difficult to diagnose by MRI alone, unlike endoscopy, which can be used to obtain diagnosis of both imaging and pathology;
2. The examination of the lungs is not superior to X-ray or CT, and the examination of the liver, pancreas, adrenal glands, and prostate is not superior to CT, but the cost is much more expensive;
3. The cost is much higher;
3. Gastrointestinal lesions are not as good as endoscopy;
4. MRI is not recommended for those who have metal objects in their bodies.
Precautions: 1. Before the examination, you must remove all metal-containing objects, such as metal watches, eyeglasses, necklaces, dentures, eye prostheses, buttons, belts, and hearing aids, etc.;
2. Patients with pacemakers are prohibited from undergoing the examination. Patients with pacemakers are prohibited from doing MRI examination;
3. When doing pelvic area examination, the bladder needs to be full, and no urination is allowed before the examination. Metal birth control ring must be removed to carry out;
4. The body has shrapnel residue, generally can not do MRI;
5. Surgery left after the metal silver clip patients, whether to do MRI examination to the doctor to carefully decide;
6. Thorax and abdominal examination, to maintain stable breathing, do not check during the coughing or swallowing action;
7. MRI has no special requirements for diet and medication;
8. Bring other examination materials that have already been done, such as the report of ultrasound, X-ray, and CT, to the examination.
Question 6: What is magnetic **** vibration imaging Magnetic **** vibration imaging (MRI) is a new examination technique based on the principle that the nucleus of an atom with a magnetic distance can produce leaps between energy levels under the action of a magnetic field, MRI helps to check the energy state of the brain and cerebral blood flow of patients with epilepsy, and is of great value in the diagnosis of degenerative diseases.MRI is achieved through the action of a high-frequency magnetic field outside of the body by the body's material Radiation energy to the surrounding environment to generate signals to achieve, the imaging process and image reconstruction and CT is similar, except that MRI does not rely on the external radiation, absorption and reflection, nor does it rely on radioactive substances in the body of the γ radiation, but the use of external magnetic fields and object interaction to imaging, high-energy magnetic field is harmless to the human body. Therefore, MRI examination is safe. MRI examination is commonly used in clinical practice to find out the brain structural changes of secondary epilepsy. if the clinical classification of epilepsy syndrome is unknown, MRI can clarify whether the patient is caused by brain structural changes. intracranial tumors often cause epilepsy, and the diagnostic confirmation rate of MRI for intracerebral low-grade astrocytomas, ganglion, neurogliomas, arteriovenous malformations, and hematomas is extremely high. mri can clearly show brain atrophy in patients with epilepsy, the The visualization of brain parenchyma and cerebrospinal fluid is excellent.
The main advantages of MRI over CT are:
① Ionized radiation has no radioactive damage to brain tissue and no biological damage.
② It can directly make cross-sectional, sagittal, coronal and various oblique images of the body.
③ There is no ray hardening and other artifacts in CT images.
④ It is not interfered by the bone image, and can satisfactorily display the small lesions at the base of the posterior cranial recess and the brain stem, etc. It has high diagnostic value for the top of the skull and the sagittal sinus, the structure of the lateral fissure, and widely metastasized tumors.
⑤ It can show the pathologic process of the disease more widely and the structure more clearly than CT. It can detect isodense lesions that are completely normal on CT, especially demyelinating diseases, encephalitis, infectious demyelination, ischemic lesions and low-grade gliomas.
Question 7: What is the nuclear magnetic **** vibration examination Nuclear magnetic **** vibration examination:
First, the whole body soft tissue lesions: no matter from the nerves, blood vessels, lymphatic vessels, muscles, connective tissue tumors, infections, degenerative lesions, etc., can be made to make a more accurate localization, qualitative diagnosis.
Second, bone and joint: bone infection, tumor, trauma diagnosis and the scope of the lesion, especially for some subtle changes such as bone contusion has a greater value, intra-articular cartilage, ligament, meniscus, synovium, synovial bursa and other lesions and bone marrow lesions have a higher diagnostic value.
Third, thoracic lesions: mediastinal masses, lymph nodes and pleural lesions, etc., can show the relationship between the masses in the lungs and the larger airways and blood vessels.
Fourth, pelvic organs; uterine fibroids, other tumors of the uterus, ovarian tumors, qualitative localization of pelvic masses, rectum, prostate and bladder masses.
V. Abdominal organs: diagnosis and differential diagnosis of hepatocellular carcinoma, hepatic hemangioma and hepatic cysts, diagnosis and differential diagnosis of intra-abdominal masses, especially retroperitoneal lesions.
Sixth, neurological lesions: cerebral infarction, brain tumors, inflammation, degenerative diseases, congenital malformations, trauma, etc., for the earliest application of the human body system, and has accumulated a wealth of experience in the localization of lesions, qualitative diagnosis of the lesion is more accurate and timely, can be found in the early stage of the lesion.
VII, cardiovascular system: can be used for heart disease, cardiomyopathy, pericardial tumors, pericardial effusion, and attached wall thrombus, endothelial slice of the stripping and other diagnostics.
Question 8: What is the meaning of magnetic **** vibration? The original called nuclear magnetic **** vibration, is in your body to impose a magnetic field, so that your body's hydrogen nuclei are directed toward the direction of the magnetic field, and then withdraw this magnetic field, to capture these nuclei to return to the original state of the energy released, which will know the distribution of water in your body, because the water content of the different organs are enameled the same, so you can clearly distinguish between the different organs, to put it bluntly is a water imaging.