Medical research and diagnostics

Magnetic resonance imaging (MRI) of cerebral vessels

The brain is the main organ of the central nervous system of the human body. It consists of an enormous number of neurons, between which synaptic connections are established. It is the interaction of neurons that forms complex electrical impulses that allow us to process information, feel emotions and just live, because the brain is also responsible for the functionality of the organs.

The body is divided into different departments, but the system functions as a whole. Her slightest failure can cause abnormalities in both the physiological and emotional spectrum. MRI is used to track brain lesions. What you need to know about the procedure, how exactly it is carried out and what risks should the patient be aware of?

What you need to know about the scanned area?

The brain is the main part of the central nervous system. The weight of the body is about 2% of the total weight of the human body. It is enclosed in a durable shell of the skull, and on top is additionally covered with layers of connective tissue. Between the shell and the surface of the brain is liquor (a special protective fluid). The body consists of several structures - the cortex, stem, cerebellum, thalamus, ganglia, which are combined by nerve fibers.

The functioning of the neurons of the brain requires significant energy costs that the brain receives through the blood supply. The body is fed from the basin of three large vessels - two internal carotid and one main artery. If the activity of neurons increases (for example, when a new skill is acquired or another strong mental load), then the blood supply in one of the departments increases.

Changes in the activity of different parts of the brain can be tracked using magnetic resonance imaging.

What are the functions of the brain? The organ is responsible for processing sensory information from the senses. The brain controls movements, decision making, planning, positive and negative emotions, attention and memory. At the expense of the brain, the generation and perception of speech becomes possible, as well as the highest function - thinking.

The organ is subject to many pathologies - from mechanical injuries to inflammatory / oncological / neurological processes. Magnetic resonance imaging is used to study the anatomical structures of the brain. This is a non-invasive research method, through which you can get a three-dimensional image of the brain and sections of the smallest parts of the body at any angle. MRI allows you to track the activation of the cortex, to find cancer, aneurysm and other vascular diseases.

How does magnetic resonance equipment work?

The MRI machine is a large magnet. In addition to creating a powerful magnetic field, it can capture, process and transform information into a detailed three-dimensional image. The human body consists of water, and water contains protons. If you place the protons in a strong magnetic field, the elementary particles will begin to emit radio waves. The frequency and intensity of these radio waves may vary, depending on the location of the proton. Particles that are located in different parts of the brain emit different radio waves that cannot be repeated.

How does this happen in practice? The patient (proton source) is placed in an MRI apparatus (a source of a strong magnetic field). Protons react to the change of the usual environment and begin to emit radio waves. The device captures each radio wave determines its frequency / intensity and by mathematical calculations finds a proton that emits it. After all the elementary particles are found, the computer converts the information into a layer-by-layer three-dimensional image.

Functional MRI

Functional MRI or fMRI is one type of magnetic resonance imaging. During diagnosis, hemodynamic reactions caused by the neural activity of the brain / spinal cord are measured.

Hemodynamics - the movement of blood through the vessels. It depends on the specific area of ​​the circulatory system, since each of them has a different pressure. Under hemodynamic reactions imply changes in blood flow.

The method is based on the relationship between neuron activity and cerebral blood flow. The higher the activity of a certain part of the brain, the greater the need for blood supply. Such situations arise when heightened mental activity, mastering a new skill, learning songs or solving logic problems. Tomography captures the activation of the brain during rest, standard functioning, under the influence of physical factors (for example, active body movements) and during various pathological processes.

During the diagnosis, the patient will be offered a set of specific actions and tasks that he will have to perform. During a particular activity, certain parts of his brain will work more intensively, which means that the blood circulation in this zone will increase. The device records the activation of the brain, processes the information, and then superimposes the formed image on the standard tomogram of the brain.

The fMRI is recognized as one of the most actively developing branches of neuroimaging. This is a common name for methods that visualize the structure, functional and biochemical characteristics of the brain. Neuroimaging is a relatively new branch of medicine that is closely related to psychiatry, neurosurgery and neurology. Magnetic resonance imaging is ahead of other methods due to the absence of radiation, relatively wide availability and maximum information content.

Indications / contraindications to the study
IndicationsRelative contraindicationsAbsolute contraindications
Cancer neoplasms regardless of the nature and stageProstheses, pumps, clips, implants, stimulants and devices (provided that they do not affect the magnetic field and do not distort the results)Pacemaker
Stroke (acute violation of cerebral circulation, accompanied by paralysis and frequent loss of consciousness)Braces and DenturesFerromagnetic device Ilizarov
Infectious diseases (for example, encephalitis or meningitis)Tattoos (if the dye includes metallized compounds)Electronic / ferromagnetic middle ear implants
Congenital and acquired organ malformationsClaustrophobia, mental illness or psycho-emotional disorders
Hydrocephalus or "dropsy" (impaired brain development due to excessive accumulation of fluid in the body)Early pregnancy
Systemic pathologies of the nerves (for example, multiple sclerosis)Decompensated myocardial dysfunction
Violation of the functionality of the organs of vision or hearingTemporary deterioration
Brain hemorrhage due to trauma
Diagnosing the causes of epilepsy
Impaired pituitary function
Vascular pathologies (for example, venous thrombosis, aneurysm, vascular occlusion)

How is the brain diagnosed?

Magnetic resonance imaging looks like a massive cylindrical tube, placed in a round magnet. This cylindrical tube serves as a retractable table on which the patient is located. The scanning ring is placed above the diagnostic area. In our case, just over the patient's head.

There are open scanners. In them, the scanning ring does not completely surround the patient, but only from above and below. The space left and right remains free. This option is especially good for patients with claustrophobia or overweight. The lack of an open-type apparatus is the relatively low power of the magnetic field, which affects the information content of the procedure.

Preparing to scan

Before diagnosis, the patient should change into special medical clothes or leave their own, if it does not contain metal elements. Metallic parts of the decor can affect the magnetic field, distorting the final result. When conducting a standard scan, no specific preparation is provided. Before contrasting MRI should refrain from food for 5-6 hours before the procedure. This will help to avoid such side effects as vomiting, nausea, pain in the abdominal cavity.

Before tomography medical documentation should be transferred to the laboratory technician. It should contain the direction of diagnosis, allergy testing (with contrast scanning), a preliminary diagnosis, and specific recommendations to the laboratory technician.

The medical officer helps the patient to sit on the extendable table, offers to fasten the body with soft straps or take a sedative. Do not take the pills by yourself before the procedure. The need for them can determine the doctor or technician, assessing your condition and the safety of the drug. When conducting a contrast procedure, a specialist introduces gadolinium intracutaneously, monitors the patient's response, waits for the drug to spread and proceeds to diagnosis. As soon as all the preparatory manipulations are completed, the laboratory technician leaves for the adjacent office. From there, he monitors the progress of the scan and monitors the patient's condition.

The patient can stop diagnostics at any time by pressing the alarm button. The location of the button before the procedure should inform the laboratory.

Methodology

After starting the scanner, the coils located inside the ring or around the patient emit / receive radio waves. Information about radio waves enters the computer, which captures, processes the signal and generates sections of the brain. From a series of sections, a three-dimensional image of the organ is gradually formed, which is displayed on the screen. The total duration of tomography is 20-25 minutes. When using a contrast agent, the time is increased to 45 minutes. During the procedure, the person does not feel pain or discomfort. Perhaps a feeling of heat in the scanned area (head), but this is a temporary phenomenon that should not cause concern. The main thing - to relax and maintain complete immobility.

After the procedure does not require adaptation or recovery for many hours. The magnetic field does not affect the course of physiological processes, so the patient can immediately return to the usual rhythm of life. The first thing is to eat better, because the body has felt hunger and stress for the last 5-6 hours. Side effects after the procedure are extremely rare. Most often it is a local pain at the injection site of contrast, dizziness, nausea / vomiting, itching, or a specific allergic reaction.

Advantages and disadvantages of diagnostics

The main advantage of MRI is safety. The magnetic field, in contrast to X-ray radiation, does not affect a person in any way, does not accumulate in the body, and cannot cause serious pathologies. At the end of the scan, the patient can immediately return to the usual rhythm of life. MRI is allowed for the most vulnerable patients - babies, pregnant and lactating women, people of the older age category. Magnetic resonance imaging is best suited for prophylactic and multiple diagnostics. The only caveat is the high price, which is justified by the cost of the equipment and the need for its maintenance.

Do not self-medicate. Even standard routine check-ups are best done as directed by a doctor.

Possible side effects after MRI are associated with contrast or sedatives (relaxing) drugs. The first are necessary to increase the information content of the image, the second - to relax the patient. Malaise, nausea / vomiting, dizziness, and other symptoms are usually easily controlled with medicines. If you feel a deterioration of the condition - immediately inform the laboratory technician or your doctor.

Specific restrictions are provided for nursing mothers. Doctors advise not to attach the baby within 24-48 hours after the administration of medicines.

MRI is an informative and safe procedure, but only with a conscious and professional approach. Do not try to find and prevent brain cancer with a monthly MRI. To begin with, regularly (1-2 times a year) visit a general practitioner, lead a healthy lifestyle and protect yourself from stress. Use the benefits of modern medicine, feel the measure and be healthy!

Watch the video: Which diagnostic test is best for imaging of arteriovenous malformations ? Better Health Channel (January 2020).

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