1 Principle of diagnostic measures
The investigation of internal organs, based on the absorption or emission of energy by any substance, was the basis for diagnosis by MRI.The nuclei of atoms in the same molecules can radiate different frequency signals. This change is due to the chemical shift, it is this difference from the standard parameters that formed the basis for studying the molecules of which internal organs and tissues are composed. The diagnostic method, which was based on obtaining the image emitted by the nuclei of the atoms that make up the molecules, was called nuclear, but not due to some kind of radiation or activity. Later on this name was forced to be abandoned due to low awareness and literacy of people in this area.
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The study of the structure of internal organs during the examination is done by creating a strong electromagnetic field. The reaction and change in the behavior of atomic nuclei, motion and frequency radiation emitted under the influence of magnetic disturbance, are fixed by sensors and allow the image of internal organs to be obtained. This method proved most effective in the examination of the head and brain, without interference and the use of X-ray studies.
Opportunities and application of the study allow to obtain a picture of the condition of the internal organs, the brain and spinal cord, the indications of all the main functions, diseases, pathological changes in the body.
For functional examination of the brain, areas and areas, a functional MRI is used. This method is based on monitoring the change in the strength of blood flow in various areas of the brain. The ability to capture changes in the physical state of atoms or their heating in various parts of the body, internal organs and tissues formed the basis for measuring temperature with the help of MRI.Thus, it is possible to easily determine the effectiveness of treatment, diagnose diseases of internal organs, and also to reveal tumor formations of various nature.
Obtaining the general condition of the cerebral vessels can be very effectively accomplished by contrasting the action of the magnetic field and signals of different frequencies. The method is good in that it excludes the introduction of various drugs into the body. But in some cases, to obtain a clearer image, the introduction of substances based on rare-earth metal oxides - gadolinium - is permissible. The method of investigation was called "angiography", meaning "contrast study".
The main way of brain research is functional magnetic resonance diagnostics or tomography. In this case, a routine MRI scan is combined with a FFRI obtained during brain work. Thus, the increase in blood flow makes it possible to identify changes or general features of the sites controlling speech, vision, memory and movement.
To assess and determine changes in tissues and organs that can develop as a result of the effects of diseases, an MRS method is used that is a spectroscopy based on magnetic resonance. To detect this way the disease and its consequences can be at the very beginning of development, long before the appearance of the main symptoms and signs.
The equipment and location for conducting diagnostics using magnetic resonance equipment must meet certain requirements and causes some limitations. Inadequate to the necessary characteristics and the degree of stability of instruments installed or brought into the field of action of the field, the results of their operation may be disabled or distorted.
But there are a number of limitations for such studies, the cause of which are various contraindications to MRI.This can be caused by various features of the body, psychological disorders, the presence of pacemakers, foreign bodies or implants.
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2 Purpose for examination
Due to the high degree of effectiveness of such diagnostics, the use of magnetic tomography has been widely used, and indications for MRI of the brain can be very different. These are urological diseases, oncology, diseases of blood supply systems, inflammatory processes in lymphatic vessels. Such studies have the widest range of indications for the study of many human systems and organs.
The power characteristics of the magnetic field during the MRI study is quite large and differs from the usual natural indicators. There are MRI and contraindications.
3 General limitations of
- Among the limitations in the appointment of tomography are isolated in people with diabetes who use an insulin pump. Various stimulants, implants of the inner ear, not made of iron, prosthetic heart valves, designed to eliminate dysfunctions. The established hemostatic clips, except the cerebral vessels, are common contraindications, and the clips placed on the vessels in the brain are absolute, the MRI in this case can cause bleeding.
- It is impossible to pass the study to people suffering from heart diseases, in whom the stage of heart failure has reached the last form - decompensated. In this case, the heart is no longer able to completely provide all the tissues and organs with the necessary amount of blood. Such patients are prescribed a magnetic tomography only after consulting a doctor, but with the sufficiency and effectiveness of other methods of examination it is better to abstain.
- Women in the first trimester of pregnancy are not recommended to assign a resonance tomography. Although at the moment there is insufficient information on the possible influence of the magnetic field on the development of the embryo. The fetus is particularly sensitive during the period from 18 to 60 days, so it is better to transfer the MRI to a later time. As for the general negative effect on the mother and her unborn child, the diagnosis with magnetic resonance is safe in comparison with the X-ray method, computed tomography. Whether there is a teratogenic effect from the magnetic field created by the MRI equipment is currently unknown.
- People suffering from claustrophobia, fear of enclosed space and similar phobias, panic attacks while in the tunnel of the device may not allow to conduct a study. It is better to be safe and try to conduct a different kind of research.
- For patients who need to be physiologically monitored, it is better not to apply magnetic research.
- With special care and at the discretion of the treating doctor, diagnose inadequate patients. But this is only in extreme cases, when other methods of diagnosis are ineffective.
- Severe and extremely severe conditions of the patient, both in primary and in concomitant disease, can lead to the rejection of diagnosis by MRI.
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4 To whom the procedure
is not fully recommended. To absolute contraindications, in which an MRI is unacceptable, there are several factors. Among them, the presence of a pacemaker in the patient, a strong magnetic field, changes in its action during the study can mimic the heart rhythm. Established in the middle ear, implants are another contraindication to CT.
Iron implants, metal parts present in the body, or their fragments, exclude such a method of examination. If a person has an Ilizarov device, which is made of iron alloys, magnetic resonance imaging is inadmissible in this case.