Contents
The brain is the main organ of the central nervous system of the human body. It consists of a huge 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 simply live, since the brain is also responsible for the functionality of organs.
The body is divided into various departments, but the system functions as a whole. Its slightest failure can cause pathologies of both the physiological and emotional spectrum. MRI is used to track pathological changes in the brain. What do you need to know about the procedure, how exactly is it performed, and what are the possible risks that the patient should be aware of?
What you need to know about the scanned area?
The brain is the main division of the central nervous system. The weight of the organ is approximately 2% of the total mass of the human body. It is enclosed in a strong shell of the skull, and on top it is additionally covered with layers of connective tissue. Between the shell and the surface of the brain is cerebrospinal fluid (a special protective liquid). The organ consists of several structures – the cortex, trunk, cerebellum, thalamus, ganglia, which are combined by nerve fibers.
The functioning of brain neurons requires significant energy costs, which the brain receives through the blood supply. The organ is fed from the pool 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 coming from the sense organs. The brain controls movement, decision making, planning, positive and negative emotions, attention and memory. Due to the brain, the generation and perception of speech, as well as the highest function – thinking, becomes possible.
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 technique, thanks to which it is possible to obtain a three-dimensional image of the brain and sections of the smallest details of the organ at any angle. MRI allows you to track the activation of the cortex, find cancerous growths, aneurysms 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 is made up of water, and water contains protons. If you place protons in a strong magnetic field, elementary particles will begin to emit radio waves. The frequency and intensity of these radio waves can vary, depending on the location of the proton. Particles that are in different parts of the brain emit different radio waves that cannot be repeated.
How does it work in practice? The patient (source of protons) is placed in the MRI machine (source of strong magnetic field). Protons respond to a change in their familiar environment and begin to emit radio waves. The device captures each radio wave, determines its frequency / intensity and, through mathematical calculations, finds the proton that emits it. After all elementary particles are found, the computer converts the information into a layered three-dimensional picture.
Functional MRI
Functional MRI or fMRI is a type of magnetic resonance imaging. During diagnosis, hemodynamic responses induced by neuronal activity in the brain/spinal cord are measured.
Hemodynamics is the movement of blood through the vessels. It depends on the specific area of the circulatory system, since each of them has different pressure. Hemodynamic responses refer to changes in blood flow.
The method is based on the relationship between neuronal activity and cerebral blood flow. The higher the activity of a particular part of the brain, the higher the need for blood supply. Similar situations arise with increased mental activity, mastering a new skill, learning songs or solving logical problems. Tomography captures the activation of brain regions during rest, normal 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 this or that activity, certain parts of his brain will work more intensively, which means that blood circulation in this area will increase. The device captures the activation of brain regions, processes the information, and then superimposes the generated image on a standard tomogram of the brain.
fMRI is recognized as one of the most actively developing branches of neuroimaging. This is the general name of 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.
| Показания | Relative contraindications | Absolute contraindications |
|---|---|---|
| Cancer neoplasms, regardless of nature and stage | Prostheses, pumps, clips, implants, stimulators 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) | Bracket systems and dentures | Ilizarov ferromagnetic apparatus |
| Infectious pathologies (for example, encephalitis or meningitis) | Tattoos (if the dye contains metallized compounds) | Electronic/ferromagnetic middle ear implants |
| Congenital and acquired organ malformations | Claustrophobia, mental illness or psycho-emotional disorders | |
| Hydrocephalus or “dropsy” (impaired development of the brain due to excessive accumulation of fluid in the organ) | Early pregnancy | |
| Systemic nerve pathologies (for example, multiple sclerosis) | Decompensated myocardial dysfunction | |
| Violation of the functionality of the organs of vision or hearing | Temporary deterioration | |
| Cerebral hemorrhage due to trauma | ||
| Diagnosis of the causes that provoked epilepsy | ||
| dysfunction of the pituitary gland | ||
| Vascular pathologies (for example, venous thrombosis, aneurysm, vascular occlusion) |
How is the brain diagnosed?
An MRI scanner looks like a massive cylindrical tube placed in a round magnet. This cylindrical tube serves as a sliding table on which the patient is located. The scanning ring is placed above the diagnostic zone. In our case, just above the patient’s head.
There are open tomographs. In them, the scanning ring does not completely surround the patient, but only from above and below. The space on the left and right remains free. This option is especially good for patients with claustrophobia or excessive body weight. The disadvantage 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 the diagnosis, the patient should change into special medical clothing or leave his own if it does not contain metal elements. Metallized parts of the decor can affect the magnetic field, distorting the final result. When conducting a standard scan, no specific preparation is provided. Before a contrast MRI, you should refrain from eating 5-6 hours before the procedure. This will help avoid side effects such as vomiting, nausea, and abdominal pain.
Before the tomography, medical documentation should be handed over to the laboratory assistant. It should contain a referral for diagnostics, an allergy test (with contrast scanning), a preliminary diagnosis, and specific recommendations to the laboratory assistant.
The health worker helps the patient to sit on a sliding table, offers to fix the body with soft straps or take a sedative. Never take the tablets yourself before the procedure. The need for them can be determined by a doctor or laboratory assistant, assessing your condition and the safety of the drug. During the contrast procedure, the specialist injects gadolinium intradermally, monitors the patient’s reaction, waits for the drug to spread, and proceeds to the diagnosis. As soon as all the preparatory manipulations are completed, the laboratory assistant goes to the adjacent room. From there, he monitors the progress of the scan and monitors the patient’s condition.
The patient can stop the diagnosis at any time by pressing the alarm button. The laboratory assistant must inform about the location of the button before the procedure.
Method of conducting
After the tomograph is started, 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 brain slices. From a series of slices, 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 increases to 45 minutes. During the procedure, a person does not feel pain or discomfort. You may feel warmth in the scanned area (head), but this is temporary and should not cause concern. The main thing is to relax and remain completely still.
After the procedure, adaptation or many hours of recovery is not required. The magnetic field does not affect the course of physiological processes, so the patient can immediately return to the usual rhythm of life. First of all, it is better to eat, because the body has felt hunger and stress for the last 5-6 hours. Side effects after the procedure are extremely rare. Most often, this is local pain at the site of contrast injection, dizziness, nausea / vomiting, itching, or a specific allergic reaction.
Advantages and disadvantages of diagnostics
The main advantage of MRI is safety. The magnetic field, unlike X-rays, 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 categories of patients – infants, pregnant and lactating women, people of the older age category. It is magnetic resonance imaging that is best suited for preventive 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 preventive examinations are best done as prescribed by a doctor.
Possible side effects after MRI are associated with contrast or sedative (relaxing) drugs. The former are necessary to increase the information content of the picture, the latter to relax the patient. Malaise, nausea/vomiting, dizziness and other symptoms are usually easily relieved with medication. If you feel a deterioration in the condition, immediately inform the laboratory assistant or the attending physician.
Specific restrictions are provided for nursing mothers. Doctors advise not to apply the baby within 24-48 hours after the administration of medications.
MRI is an informative and safe procedure, but only with a conscious and professional approach. Don’t try to find and prevent brain cancer with monthly MRIs. 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!