Functional mri. Functional magnetic resonance imaging is an effective method for examining the brain. Functional MRI

The effectiveness of the treatment of the disease depends on the stage at which it is started - the sooner, the better and faster the result will be. A neglected disease can give more serious consequences even if procedures are being carried out to eliminate it. As for the brain, it is very difficult to identify the initial stages of pathologies here, because. they are not visible from the outside. For this, functional MRI is used - an indispensable tool in surgery and neurology.

Functional MRI of the brain: how is it different from conventional diagnostics?

The functional type of tomography differs from the classical one in that the indicators are taken not in a calm state, but in the process of active brain activity.

In the process of physical activity, the brain cells are better saturated with oxygen, the overall blood flow increases. This is picked up by the tomograph scanner. Registration of activity occurs due to an increase in tissue magnetization - it depends on the additional oxidation of glucose.

A more intense signal is compared with the values obtained in the normal, quiet mode. A specialist with the help of a computer program overlays one three-dimensional image on another.

The result is a complete map, which captures the entire cerebral cortex, because. blood in an active state allows you to view even the smallest and most distant areas. The tomogram shows parts having a diameter of half a millimeter. If necessary, you can enlarge them on the screen.

Signals from different cortical and subcortical structures are registered and differentiated:

Basal ganglia.
Belt bark.
Thalamus.
All types of tumors - not only their size and contours, but also the degree of penetration into the gray and white medulla.

Using functional MRI, you can compare the behavior of brain cells:

At rest.
During mental work.
During physical, motor activity.

The functional type of tomography makes it possible to accurately determine the location and size of all brain centers:

Sensory.
Motor.
Rechevykh and others.

If a more accurate study is required, the patient is additionally injected with glucose.

Possibilities of functional MRI diagnostics

Diagnostics is used as a supplement to the classical type of magnetic resonance imaging - in order to clarify an unclear diagnosis, it is better to look at one or another brain section, tissue or blood vessels.

Options for using the results of functional tomography:

Surgery. Before brain surgery, an exact action plan is drawn up using a tomographic map - it clearly shows the damage that needs to be repaired. This avoids errors in actions and complications.
Radiology. Tomographic data make it possible to calculate the amount of radiation needed to treat cancer.
Neuropsychology. The study of failures in the work of memory, speech apparatus, attention.
Identification of epileptic foci.
Ischemic areas are visible at an early stage - to prevent a stroke.
Recognition of the initial processes of Alzheimer's and Parkinson's diseases.
The method allows you to find a connection between brain activity and dizziness,.

A specialist in radiation diagnostics can fully decipher the data obtained as a result of the study.

When Not to Do a Functional MRI

Since a powerful magnet is involved in the case and at the same time it is necessary to lie quietly for an hour, being inside a cylindrical device, there are contraindications:

Pregnancy in the early stages.
Claustrophobia.
Metal parts inside the body and on the body are implants and prostheses that cannot be removed.
Mental illness, due to which the patient cannot be immobile for at least thirty minutes.

Tattoos with a metal component, small fillings and any non-magnetic materials are not dangerous, but you need to warn the doctor about them in order to compensate for the deviations of the magnetic field caused by these objects and, accordingly, data distortion.

The research methodology has undoubted advantages:

High quality map of the brain.
Image resolution is more than three millimeters.
A convenient way to study the brain in a calm and active state.
No harm to the body - the procedure does not lead to cell death and other negative consequences.
Availability of the method - for this you do not need to go abroad.

Informative fMRI in Moscow at a bargain price

Changes in blood flow activity are recorded by functional magnetic resonance imaging (fMRI). The method is used to determine the localization of the arteries, to assess the microcirculation of the centers of vision, speech, movement, the cortex of some other functional centers. A feature of mapping is that the patient is asked to perform certain tasks that increase the activity of the desired brain center (read, write, talk, move their legs).

At the final stage, the software generates an image by summing up conventional layered tomograms and images of the brain with functional load. The complex of information displays a three-dimensional model. Spatial modeling allows specialists to study the object in detail.

Together with MRI spectroscopy, the study reveals all the features of the metabolism of pathological formations.

Principles of functional brain MRI

Magnetic resonance imaging is based on recording the altered radio frequency of hydrogen atoms in liquid media after exposure to a strong magnetic field. The classic scan shows soft tissue components. To improve the visibility of blood vessels, intravenous contrasting with paramagnetic gadolinium is performed.

Functional MRI records the activity of individual areas of the cerebral cortex by taking into account the magnetic effect of hemoglobin. The substance, after the return of the oxygen molecule to the tissues, becomes a paramagnet, the radio frequency of which is picked up by the device's sensors. The more intense the blood supply to the brain parenchyma, the better the signal.

Tissue magnetization is additionally increased by glucose oxidation. The substance is necessary to ensure the processes of tissue respiration of neurons. The change in magnetic induction is recorded by the device's sensors and processed by the software application. High-field devices create a resolution of a high degree of quality. On the tomogram, a detailed image of details with a diameter of up to 0.5 mm in diameter can be traced.

Functional MRI study registers a signal not only from the basal ganglia, cingulate cortex, thalamus, but also from malignant tumors. Neoplasms have their own vascular network, through which glucose and hemoglobin enter the formation. Signal tracking allows you to study the contours, diameter, depth of penetration of the tumor into the white or gray matter.

Functional diagnostics of MRI of the brain requires the qualification of a doctor of radiation diagnostics. Different zones of the cortex are characterized by different microcirculation. Saturation with hemoglobin, glucose affects the quality of the signal. The structure of the oxygen molecule, the presence of alternative substitutes for atoms should be taken into account.

A strong magnetic field increases the half-life of oxygen. The effect works when the power of the device is more than 1.5 Tesla. Weaker settings cannot fail to investigate the functional activity of the brain.

The metabolic intensity of the blood supply to the tumor is best determined using high-field equipment with a power of 3 Tesla. High resolution will allow you to register a small focus.

The effectiveness of the signal is scientifically called the "hemodynamic response". The term is used to describe the speed of neural processes with an interval of 1-2 seconds. The blood supply to tissues is not always sufficient for functional studies. The quality of the result is improved by the additional administration of glucose. After stimulation, the saturation peak occurs after 5 seconds, when the scan is performed.

Technical features of the functional study of MRI of the brain

The functional diagnostics of MRI is based on an increase in the activity of neurons after stimulation of brain activity by performing a certain task by a person. An external stimulus causes stimulation of sensory or motor activity of a certain center.

To track the area, the gradient echo mode is activated based on the impulse echoplanar sequence.

Analysis of the core signal on MRI is done quickly. Registration of one tomogram is performed at an interval of 100 ms. Diagnosis is performed after stimulation and during the rest period. The software uses tomograms to calculate foci of neuronal activity, superimposing areas of amplified signal on a 3D model of the brain at rest.

For attending physicians, this type of MRI provides information about pathophysiological processes that cannot be tracked by other diagnostic methods. The study of cognitive functions is necessary for neuropsychologists to differentiate mental and psychological diseases. The study helps to verify epileptic foci.

The final mapping map shows more than just areas of increased functional stimulation. The pictures visualize the zones of sensorimotor, auditory speech activity around the pathological focus.

The construction of maps of the location of brain channels is called tractography. The functional significance of the location of the visual, pyramidal tract before planning surgery allows neurosurgeons to correctly plan the location of the incisions.

What does fMRI show?

High-field MRI with functional tests is prescribed according to the indications, when it is necessary to study the pathophysiological foundations of the functioning of the motor, sensory, visual, and auditory areas of the cerebral cortex. Neuropsychologists use research in patients with impaired speech, attention, memory, and cognitive functions.

Using fMRI, a number of diseases are detected at the initial stage - Alzheimer's, Parkinson's, demyelination in multiple sclerosis.

Functional diagnostics in different medical centers is performed on different units. He knows what the MRI of the brain shows, the doctor-diagnostician. Consultation with a specialist is mandatory before the examination.

High quality results are achieved by scanning with a strong magnetic field. Before choosing a medical center, we recommend that you find out the type of device installed. The qualification of a specialist is important, who must have knowledge of the functional, structural component of the brain.

The future of functional MRI diagnostics in medicine

Functional research has recently been introduced into practical medicine. The possibilities of the method are not used enough.

Scientists are developing techniques for visualizing dreams, reading thoughts using functional MRI. It is supposed to use tomography to develop a method of communication with paralyzed people.

neural excitability;
mental activity;
Degrees of saturation of the cerebral cortex with oxygen, glucose;
The amount of deoxylated hemoglobin in the capillaries;
Areas of expansion of blood flow;
The level of oxyhemoglobin in the vessels.

Advantages of the study:

High-quality temporary picture;
Spatial resolution above 3mm;
Ability to study the brain before and after stimulation;
Harmlessness (when compared with PET);
No invasiveness.

The mass use of functional brain MRI is limited by the high cost of equipment, each single examination, the impossibility of directly measuring neuronal activity, which cannot be done in patients with metal inclusions in the body (vascular clips, ear implants).

Registration of the functional metabolism of the cerebral cortex is of great diagnostic value, but is not an accurate indicator for the dynamic assessment of changes in the brain during treatment, after surgery.

Functional magnetic resonance imaging of the brain is a type of study that allows you to measure the hemodynamic reactions of blood flow caused by the functioning of the organ.

In modern medicine, this is one of the main methods for studying brain processes.

Principles of functional brain MRI

Functional MRI will help to identify pathologies in significant areas of the brain. The principle of operation of the device is quite simple: the brain consumes energy and the more active this process, the more nutrients and oxygen it needs to receive. All this enters the body with the bloodstream. It is MRI that helps to see areas with slow and increased blood circulation and understand how the brain copes with a particular problem.

Diagnostic measures related to nuclear magnetic resonance, including functional tomography, have the following advantages:

The image on the device screen is very clear. The study is considered not only one of the ultra-precise, but also gives a picture of the highest quality.
Short study time. The magnetic field has a high intensity, which makes it possible to significantly reduce the diagnostic time. This is especially convenient for people suffering from neurodegenerative pathologies, mental illness (BAD).
High accuracy of results. If surgery is required on the organ, it is important for the doctor to obtain reliable information about the condition and localization of the tumor, which will allow to exclude motor, speech, visual and other disorders after its excision. With the help of functional MRI, the risk of such consequences can be accurately assessed and the final decision on the operability of the tumor can be made.

According to what are the features of the changes revealed by functional magnetic resonance imaging, it is possible to determine the prognosis of a particular disease, the effectiveness of the treatment.

Technical features

The magnetic resonance imaging apparatus consists of:

table for placing the patient;
a computer with a monitor to which the image is fed;
radio frequency and gradient system;
magnet.

A constant magnetic field with a force expressed in Tesla (T) is supplied from the magnet. Given the strength, the apparatus is divided into low-field, medium-field, high-field, ultra-high-field. In modern medicine, a high-field tomograph with a power of 1.5 T is considered the most popular.

Given the design, the apparatus is divided into closed and open. The first is presented in the form of a tunnel in which a table with a bedridden patient is placed. There is no tunnel in open devices, which makes it possible to prescribe diagnostics to people who have a phobia of confined spaces.

Indications and contraindications for fMRI

Classification of MRI on a functional basis allows us to divide the study into several types:

examination of the brain: with the help of it, a detailed image of the hemispheres, the trunk is obtained for the presence of neoplasms, infectious and inflammatory lesions, congenital anomalies;
research: using MRI, they study the internal structure of the brain, detect tumor-like neoplasms in the gland;
examination of the head (including MRI of the cervical spine with functional tests, MRI of the temporomandibular joints with functional tests): in this case, it is possible to diagnose the cause if it did not give an accurate result.

In addition, diagnostics are prescribed to identify foci, determine the cause of a violation of such functions as memory, speech, attention. Functional MRI is an effective way to identify some pathologies that occur at stage 1, for example, to identify areas with, diagnose diseases and.

Despite the prevalence of the method, it has contraindications to the appointment, which are divided into absolute and relative. Among the first:

the presence of a pacemaker;
the presence of ferromagnetic or electronic implants in the middle ear;
the presence of a ferromagnetic Ilizarov apparatus.

Relative contraindications include:

the presence of a non-ferromagnetic implant in the inner ear;
the presence of hemostatic clips;
development of heart failure in the stage of decompensation;
pregnancy in the 1st trimester;
fear of being in an enclosed space (phobia);
severe mental disorder or general condition;
the presence of a tattoo, which is made using a dye containing metal compounds;
the presence of dentures and braces.

Tomography using a contrast agent is not performed with concomitant hemolytic anemia, hypersensitivity to contrast, with chronic liver failure, during pregnancy.

Procedure steps

Before fMRI, a blood test for creatinine, its quantitative indicator, is necessary. You need to take your passport, a referral from a doctor and the results of previous diagnostic measures with you to the office.

There are no physical sensations or other discomfort during the procedure. There is only noise that can not be heard by wearing special earplugs or headphones.

A person must remove all metal objects from himself, leave them in a specially designated place. Next, the subject lies down on the table of the apparatus, puts on earplugs (or headphones). If necessary, the necessary part of the body is fixed.

In exceptional cases, if a person is unable to remain still, he is given general anesthesia. Intravenous contrast may be needed to improve the information content of the results.

The duration of the study varies from 10 to 30 minutes. You can get diagnostic results in a few minutes.

Where can I get a functional MRI and how much does it cost?

Computed tomography devices are installed in many private and public medical institutions. The cost of the study starts from 4-5 thousand rubles. If a contrast analysis is required, the price rises to 7-8 thousand rubles.

Functional magnetic resonance imaging is an effective method for diagnosing the brain, which allows you to examine the organ in detail for specific pathologies. However, before it is carried out, it is necessary to weigh all the pros and cons, as well as to exclude contraindications. This is the only way to get reliable results.

Functional magnetic resonance imaging(fMRI) is an MRI technique that measures the hemodynamic response (change in blood flow) associated with neuronal activity. fMRI does not allow to see the electrical activity of neurons directly, but does it indirectly, due to the phenomenon of neurovascular interaction. This phenomenon is a regional change in blood flow in response to the activation of nearby neurons, since when their activity increases, they need more oxygen and nutrients brought with the blood stream.

Basic principles of fMRI. fMRI is a neuroimaging technique that uses oxyhemoglobin and deoxyhemoglobin in blood vessels as an endogenous contrast agent. This uses the principle of BOLD-contrast (blood oxygenation level-dependent contrast - contrast depending on the degree of blood oxygen saturation), discovered by Seiji Ogawa in 1990. BOLD contrast is the difference in MR signal on images using gradient sequences depending on the percentage of deoxyhemoglobin. The BOLD-fMRI technique is as follows: an increase in neuronal activity causes a local increase in oxygen consumption. This leads to an increase in the level of the paramagnetic deoxyhemoglobin, which reduces the level of the fMRI signal. But after a few seconds, neuronal activity also causes an increase in cerebral blood flow and blood volume, which leads to an increase in arterial blood flow and, consequently, an increase in oxyhemoglobin, which increases the level of the fMRI signal. For unknown reasons, the amount of oxygenated blood that comes in response to neuronal activity greatly exceeds metabolic oxygen consumption. This kind of overcompensation of oxyhemoglobin leads to a change in the ratio of oxyhemoglobin to deoxyhemoglobin, which is measured and is the basis for the BOLD fMRI signal.

There are two main methods for performing fMRI: [ 1 ] with the measurement of the functional activity of the cerebral cortex when performing a specific task compared with its activity at rest/with a control task (the so-called task-fMRI); [ 2 ] with the measurement of the functional activity of the cerebral cortex at rest (the so-called resting state fMRI - RS-fMRI).

When conducting an fMRI study with the implementation of a certain paradigm, the tasks that the subject performs can be different: motor, visual, cognitive, speech, etc. After fMRI, the obtained functional data are subjected to statistical analysis. The result is information about activation zones in the form of color maps superimposed on anatomical data, and the same data can be presented in digital format indicating the statistical significance of the activation zone, its volume and coordinates of its center in stereotaxic space. However, in the last 10 years, resting fMRI (fMRIp) has attracted increasing interest from researchers. The principle of its operation remains the same as in classical fMRI (task-fMRI). The only difference is the absence of any paradigms (i.e., active tasks or actions presented to the patient) during fMRIp. During fMRI, the subject is at rest in the MRI scanner and is instructed to relax as much as possible and not think about anything in particular. In various works, there are different views on whether the subject to be examined should close his eyes or not. Proponents of leaving the eyes open argue that it prevents the subject from falling asleep.

When is fMRI performed??

Firstly, for purely scientific purposes: this is the study of the normal brain and its functional asymmetry. This technique has revived the interest of researchers in mapping brain functions: without resorting to invasive interventions, one can see which areas of the brain are responsible for a particular process. Perhaps the greatest breakthrough has been made in understanding higher cognitive processes, including attention, memory, and executive functions. Such studies have made it possible to use fMRI for practical purposes far from medicine and neuroscience (as a lie detector, in marketing research, etc.).

Secondly, fMRI is beginning to be actively used in practical medicine, in particular, for preoperative mapping of the main functions (motor, speech) before neurosurgical interventions for brain tumors or incurable epilepsy. As a rule, motor zones for the arms and legs, tongue, as well as speech zones - Broca and Wernicke - are assessed: their presence, location relative to the lesion, the presence of homologues in the healthy hemisphere, compensatory increased activation in the opposite hemisphere of the brain or secondary zones. This information helps neurosurgeons assess the risk of postoperative neurological deficit, choose the most convenient and least traumatic approach, and suggest the extent of resection.

Thirdly, researchers are also trying to introduce fMRI into routine clinical practice in various neurological and psychiatric diseases. The main goal of numerous works in this area is to evaluate changes in the functioning of the brain in response to damage to one or another of its areas - loss and (or) switching of zones, their displacement, etc., as well as dynamic observation of the restructuring of activation zones in response to ongoing drug therapy. therapy and/or rehabilitation measures. Ultimately, fMRI studies performed on patients of various categories can help determine the prognostic value of various variants of functional cortical rearrangement for the restoration of impaired functions and develop optimal treatment algorithms.

More information on fMRI:

article "Advanced technologies of neuroimaging" M.A. Piradov, M.M. Tanashyan, M.V. Krotenkova, V.V. Bryukhov, E.I. Kremneva, R.N. Konovalov; FGBNU "Scientific Center of Neurology" (magazine "Annals of Clinical and Experimental Neurology" No. 4, 2015) [read];

article "Functional magnetic resonance imaging" E.I. Kremneva, R.N. Konovalov, M.V. Krotenkov; Scientific Center of Neurology of the Russian Academy of Medical Sciences, Moscow (magazine "Annals of Clinical and Experimental Neurology" No. 1, 2011) [read];

article "The use of functional magnetic resonance imaging in the clinic" Belyaev A., Pek Kyung K., Brennan N., Kholodny A.; Memorial Sloan-Kettering Cancer Center, Functional MRI Laboratory, Department of Radiology, New York, USA (Russian electronic journal of radiology, No. 1, 2014) [read];

article "Functional magnetic resonance imaging at rest: new opportunities for studying the physiology and pathology of the brain" E.V. Seliverstova, Yu.A. Seliverstov, R.N. Konovalov, S.N. Illarioshkin Federal State Budgetary Institution "Scientific Center of Neurology" RAMS, Moscow (magazine "Annals of Clinical and Experimental Neurology" No. 4, 2013) [read];

article "Functional magnetic resonance imaging at rest: possibilities and future of the method" Yu.A. Seliverstov, E.V. Seliverstova, R.N. Konovalov, M.V. Krotenkova, S.N. Illarioshkin, Scientific Center of Neurology, Russian Academy of Medical Sciences, Moscow (Bulletin of the National Society for the Study of Parkinson's Disease and Movement Disorders, No. 1, 2014) [read];

article "Functional magnetic resonance imaging and neuroscience" M.B. Shtark, A.M. Korostyshevskaya, M.V. Rezakova, A.A. Savelov; Institute of Molecular Biology and Biophysics SB RAMS, Novosibirsk; Institute "International Tomographic Center" SB RAS, Novosibirsk; SPF "Computer systems of biofeedback", Novosibirsk (magazine "Successes of physiological sciences", No. 1, 2012) [read]