MRI 0.3 tesla and 1.5 which is better. What is the principle of operation of MRI

Is it true that a 3-tesla apparatus is twice as good as a 1.5-tesla apparatus? If we take into account only the field strength - of course. In the world of marketing sales, too. However, in terms of visualization, throughput in terms of earnings is absolutely not. Before investing more in opening a center with a 3-tesla device, you should think about what you are going to do with it, how it can be useful to you and what it can not.

Cost effective systems

Without imposing a percentage, it's safe to say that a 1.5 Tesla MRI machine is suitable for most MR scans. The short tunnel 1.5 T remains the standard, most used MRI machine. This does not mean that 3-Tesla systems have not “taken root”, but here you should consider return on investment, throughput, staffing, and other factors. Shut down the noise or turn the volume down? In an MRI scan, there is always noise in the image. Most of this noise is created by the patient's body, as well as the electronics of the MRI machine itself. It is important to get the "signal" that creates the image, and not the "noise" that can affect the quality of the image. 1.5 and 3-tesla devices cope with this, but in varying degrees. Small children tend to be very noisy. If they get together, for example for a birthday party, the excitement makes them even more noisy. Games can keep them busy for a while until the party is over. On this occasion, if you want to play musical chairs, you have two options to get everyone to hear the music:

Make sound louder

soothe the children

Job 3- Tesla MRI machine much like a stereo system playing music for children at maximum volume. In fact, in this way, you get more signal - the higher the field strength, the more molecules resonate, drown out the noise. The 1.5-Tesla multi-coil system works more like a "baby-calming" system. The coil elements allow the examination to be carried out closer to the body, which reduces the amount of noise in the image.

Clarity, speed, need

Two parameters come to mind when talking about 3-tesla machines: clarity and scan time. Simply put, 3-Tesla systems, having a higher field strength, increase the signal (creating the image), and hence the clarity of the image, at a certain scan rate. However, you can't get all the best all at once, so MRI scans represent a trade-off between scan time and image quality. Thus, depending on the technology, your bandwidth needs, and other factors, the advantage is in one direction or another. The bottom line is that you will still get good images on a 1.5 Tesla system using multi-coil technology - but the scan time will be longer than 3T. Conversely, you can reduce the scan time on a 1.5 Tesla machine, but the image quality will be slightly worse. It all depends on the type of research.

Demand Offer

If you are doing research that requires the smallest details (complex brain work is one of the categories where a 3T machine is really needed), or you have a need to see the maximum number of patients per day, you tend to purchase a 3-tesla system, then you should plan everything in advance. Such devices are expensive - even in the secondary market you can pay twice as much for them than for 1.5T, and yet they are difficult to find. Take the time to find the system, make sure your space is suitable for it. Remember: the strength of the electromagnets that are used to lift cars in junkyards is about the same as a 1.5 tesla machine. And in a 3-tesla system, the force magnetic field twice as much! Make sure all safety measures are in place! If your research is less detailed, or the pace is less strenuous, the 1.5-Tesla system may give you everything you need. These systems are much more readily available, as are spare parts for them, as well as service engineers to maintain them. As with the 3 tesla magnet, you must make sure your room is ready to place the machine. Failure to take proper precautions can result in costly damage and serious injury.

According to experts, the use of 3 Tesla is much better than, say, 1.5 Tesla. What are the advantages of such seemingly super-powerful devices and do they have a harmful effect on the human body? We will find out what characteristics such a device has, what can be seen with the help of a 3 Tesla MRI and why a three-tesla tomograph is better.

Any tomographs differ in the voltage of the magnetic field they create.

Thus, a low-field tomograph generates a magnetic field up to 0.5 T, a mid-field tomograph up to 1.5 T, and a high-field tomograph up to 3 Tesla. Devices with magnetic field strength up to 0.5 T are not used. As a rule, devices that create magnetic fields in the range from 1.5 to 3 Tesla are used in clinics and diagnostic centers.

The operation of such an apparatus is due to the fact that it generates a stronger field and, accordingly, produces more noise. High field generating systems produce high definition images and reduce scan times. Of course, a less powerful magnetic coil can also be used. But in this case, to obtain a high-quality image, you have to increase the scanning time. By reducing it at a lower power, you can get not such high-quality pictures as on a three-tesla device.

A device with such power is ideal for scanning the smallest details - for example, when performing an MRI of the brain. Such devices cost incomparably more money. So when choosing them, it is necessary to provide for the premises, the intensity of work, and so on. Careful observance of all safety measures when working with powerful tomographs is necessary. If you do not do this, then magnetic resonance imaging can cause dangerous consequences.

The devices for conducting the examination are outwardly very similar, however, there is a difference, namely, in the strength of the magnetic field and the accuracy of the image, however, the lower the field voltage, the lower the cost of the examination.

What allows you to see such a tomograph

This device opens up many new possibilities for doctors. So, it gives the prospect of detecting the smallest details in all the studied tissues of the body:

visualize small structures of the brain;
it is good to see the shells of the organ;
diagnose the state of the vessels with which the head is rich;
obtain tissue sections with a thickness of less than 1 millimeter (and not only the brain, but also other tissues of the body);
diagnose the smallest foci of neoplasms when other methods of their determination do not give the desired result;
build a high-quality three-dimensional image of the organ or tissue under study;
see the topography, the ratio of structures;
perform brain tomography in emergency cases in a short time (for example, if a patient with a traumatic brain injury is admitted to the clinic);
obtain an image with high split precision;
to avoid obstacles from possible motor interference as much as possible (this is especially true when MRI is done to children or patients with mental disabilities);
to diagnose in patients with Parkinson's syndrome or with uncontrolled muscle tremor;
apply perfusion, diffusion and tractography techniques for early diagnosis of cerebral circulatory disorders;
to detect pathologies in the parts of the brain directly adjacent to the spinal parts.

Such devices create a sufficiently strong magnetic resonance, which allows them to be used for almost any diagnostic purposes.

Such devices with a power of 7 Tesla are no longer used for examining patients. Such units are used only for scientific purposes.

Advantages of three-tesla devices

Today, such devices are increasingly used in diagnostic practice. What are the advantages of these devices?

Improving the quality of visualization of organs and tissues.
You can get high-quality sections with their minimum thickness (in some cases - even up to 0.5 millimeters). So you can determine the presence of the smallest pathological changes in the patient.
Significantly reduces the time spent by the patient in the magnetic field.
The accuracy of visualization of the conductive structures of the head and spinal cord.
The quality of diagnostics of cerebral microcirculation improves, and this can be achieved without the use of special magnetic contrast preparations.
Increases the accuracy of assessing the functional state of the brain.
There is a possibility of diagnostics in patients with claustrophobia and overweight.
The doctor may apply in the study Newest technologies diagnostics.
To date, there are practically no shortcomings in such a survey.
The fact is that the magnetic field, in contrast to x-ray radiation used, say, in computed tomography, is harmless to health.

Limitations and contraindications for this type of examination are practically the same as when using weaker devices. So modern technologies meet the needs of doctors and patients, allowing them to make better images of organs.

If the patient is concerned about increased noise during the diagnosis, the doctor puts on headphones and ear plugs. Noise is associated with the operation of the device and cannot adversely affect the functioning of the body. Undoubtedly, the use of a 3 Tesla apparatus is much better.

Are there more powerful devices?

All such devices are high-field. To date, the use of tomographs capable of producing a magnetic field strength of 7 Tesla and even more is known. Such high power devices are rarely used today. They detect malignant neoplasms in humans at an early stage.

With this examination, much less time is spent to determine the condition of the patient's organs and tissues. On given time such devices - units. In the future, the prospects for the use of super-powerful MR devices are not yet clear.

So, the use of 3 Tesla tomographs is justified in modern medical practice. They allow you to get high-quality images of organs and tissues in very clear resolution. More and more clinics diagnostic centers powerful tomographs are used for such purposes.

Magnetic resonance imaging (MRI) is a widely used non-invasive diagnostic method in medicine that uses magnetic resonance. The action of the magnetic field does not pose a danger to human health. The strength of the magnetic field is measured in Tesla - in honor of Nikola Tesla, who won world fame for his research on magnetism and electricity.

Power of tomographs

For diagnostic studies, MRI of various power can be used. On this basis, they are divided into the following groups:

low-field - with a magnetic field strength of up to 0.5 T;
mid-field - from 0.5 to 1 T;
high-field - 1.5-3 T.

Ultra-high-field devices over 3 T are used only in scientific and technical laboratories and diagnostics are not carried out on them.

The capabilities of the tomograph depend on the strength of the magnetic field. The lower the tension, the lower the quality of the images and the more time spent on diagnostics. When examining the same organ, the time indicators are as follows:

1 T - 15-20 minutes;
1.5 T - 10-15 minutes;
3 T - 5-10 minutes.

Examination on low-field tomographs is cheaper, but can only be used for preliminary diagnosis and to answer the question of whether there is a tumor or not. If there is a tumor, then an additional study on a more powerful device will be required to establish its size and boundaries.

Which is more effective: MRI 1.5 Tesla or 3 Tesla

For most MRI scans, the 1.5 T machine is the standard and is most commonly used to assess the condition of blood vessels, detect metastases, and examine small structures. In terms of visualization quality and throughput, the 1.5 T tomograph is almost as good as the 3 T tomograph.

3T MRI machines are almost 2 times more expensive than 1.5 T MRI machines and require more thorough preparation of the room and compliance with safety measures when working with strong electromagnets. Spare parts and service maintenance more powerful tomographs are also more expensive.

The use of a powerful 3Tl tomograph is justified in cases where it is required to study the work of the brain with the smallest details. A higher examination speed is justified with a large influx of patients or diagnosing children and seriously ill patients. In all other cases, the use of a 1.5 T tomograph for medical institutions is more accessible and justified.

MRI is a modern and most accurate research method in medical practice. This method is non-invasive, i.e. without interfering with the human body, which is an absolutely safe method for health.

The intensity or power of the magnetic field of the MR tomograph is measured in units of Tesla (1 T). The power value is named after the scientist Nikola Tesla.

This brilliant man made a huge breakthrough in science at the beginning of the 20th century. And he received world fame for research in such areas of science as electricity and magnetism.

All MRI machines (tomographs) are divided into the following types:

Low field - 0.23-0.35 Tesla
Midfield - 1 Tesla
High field - 1.5-3 Tesla.

The results obtained by medical professionals using these types of devices are different. The stronger the magnetic field, the higher the quality of the results.

Nowadays, clinics conduct research on devices with a power of 1 to 3 Tesla, and devices of 5 Tesla and above are used exclusively for scientific research.

Thus, the power of the tomograph is the main indicator of the accuracy of the study of MR tomography. The higher the power, the higher the diagnostic accuracy. The maximum power of MRI machines that are used today in medicine is 3 Tesla.

MRI 1.5 Tesla and MRI 3 Tesla

The quality of the images obtained on tomographs with a magnetic field of 1 - 1.5 Tesla is high, and on a 3 Tesla device it is the highest. Also, an important factor is that the greater the power of the magnetic field of the MRI machine, the less time is required to obtain images. For example, an examination on a tomograph with a magnetic field of 1 Tesla will last about fifteen minutes, and on an MRI machine with a magnetic field of 1.5 Tesla, it will take from 10 to 12 minutes, and if you take a tomograph with a strength of 3 Tesla, the procedure will take no more more than 5 minutes. The duration of the procedure can be critical in cases such as, for example, or an injured patient with severe injuries.

Also, an MRI machine with a power of 3 Tesla is used to study the finest structures and tissues that are not visible on an MRI of 1.5 Tesla and below.

That is, a study conducted using a 3 Tesla MRI tomograph has important advantages, in contrast to a study using an MRI machine with a power of 1.5 Tesla:

Less research time
Get more accurate pictures with more high quality and resolution
High-precision display of small , and

However, sometimes the use of lower intensity tomographs is more than justified. Such a survey is less expensive both technically and financially, because its cost is cheaper. MRI less than 1 Tesla is usually used for preliminary diagnostic purposes, for example, to detect or not. However, you should be aware that in this case, the quality of the images is lower than on a tomograph from 1.5 to 3T.

Often, data from a low-field tomograph is not enough to make a more detailed diagnosis. In these cases, it is necessary to perform a secondary examination on a device with a power of 1.5 to 3 Tesla. And in order not to overpay for a similar procedure, it is better to immediately undergo an examination on an MRI machine with a capacity of 1.5 Tesla or more.

Thus, the power of the magnetic field of the tomograph is an essential indicator for making a decision in choosing a study. We recommend that you agree with the doctor on the need to undergo an MRI examination, specifying the power of the tomograph on which you will be examined.

Magnetic resonance imaging (MRI) is one of the most modern diagnostic methods that allows you to study almost any system of the body. The most important characteristic of an MRI machine is the magnetic field strength, which is measured in Tesla (T). The quality of visualization directly depends on the field strength - the higher it is, the better quality images, and, accordingly, the diagnostic value of MR examinations is higher.

Depending on the power of the device, there are:

At the moment, all major manufacturers produce MR scanners with a field of 3 T, which differ little in size and weight from standard systems with a field of 1.5 T.

Safety studies in MR imaging have not shown any negative biological effects of magnetic fields up to 4 T used in clinical practice. However, it should be remembered that the movement of electrically conductive blood creates an electrical potential, and in a magnetic field it will create a small voltage through the vessel and cause an elongation of the T wave on the electrocardiogram, therefore, in studies in fields above 2 T, ECG monitoring of patients is desirable. Physical studies have shown that fields above 8 T cause genetic changes, charge separation in liquids, changes in permeability cell membranes.

Unlike the main magnetic field, gradient fields (magnetic fields perpendicular to the main, main, magnetic field) are switched on at certain time intervals in accordance with the chosen technique. Rapid switching of gradients can induce electric currents in the body and lead to stimulation of the peripheral nerves, causing involuntary movements or tingling in the limbs, but the effect is not dangerous. Studies have shown that the threshold for stimulation of vital organs (for example, the heart) is much higher than for peripheral nerves, and is about 200 T/s. When the threshold [rate of change of gradients] dB/dt = 20 T/s is reached, a warning message appears on the operator console; however, since the individual threshold may differ from the theoretical value, constant monitoring of the patient's condition is necessary in strong gradient fields.

Metals, even non-magnetic ones (titanium, aluminium), are good conductors of electricity and will heat up when exposed to radio frequency [RF] energy. RF fields induce eddy currents in closed circuits and conductors, and can also create significant stress in elongated open conductors (for example, a rod, wire). The length of electromagnetic waves in the body is only 1/9 of the wavelength in air, and resonance phenomena can occur in relatively short implants, causing their ends to heat up.

Metallic objects and external devices are generally erroneously considered safe if they are non-magnetic and labeled "MP compatible". However, it is important to make sure that objects that are scanned inside the working area of the magnet are immune to induction. Patients with implants are only eligible for MR examination if the implants are both non-magnetic and small enough to heat up during scanning. If the object is longer than half the length of the RF wave, a high heat resonance may occur in the patient's body. The limiting dimensions of metal (including non-magnetic) implants are 79 cm for a field of 0.5 T and only 13 cm for 3 T.

Switching gradient fields creates a strong acoustic noise during an MR examination, the value of which is proportional to the power of the amplifier and the field strength and according to regulatory documents should not exceed 99 dB (for most clinical systems is about 30 dB).

based on the article "Possibilities and limitations of high-field magnetic resonance imaging (1.5 and 3 Tesla)" A.O. Kaznacheeva, National research university information technologies, mechanics and optics, St. Petersburg, Russia (journal "Radial diagnostics and therapy" No. 4 (1) 2010)

read also the article "Safety of magnetic resonance imaging - the current state of the issue" by V.E. Sinitsyn, Federal State Institution "Treatment and Rehabilitation Center of Roszdrav" Moscow (Journal "Diagnostic and Interventional Radiology" No. 3, 2010) [read]

MRI DURING PREGNANCY - IS IT SAFE?

Currently, MRI is a widely used method of radiation diagnostics, which is not associated with the use of ionizing radiation, as in X-ray examination (including CT), fluorography, etc. MRI is based on the use of radio frequency pulses (RF pulses) in a high magnetic field. The human body consists mainly of water, consisting of hydrogen and oxygen atoms. At the center of each hydrogen atom is a small particle called a proton. Protons are very sensitive to a magnetic field. Magnetic resonance imaging scanners use a constant strong magnetic field. After the object under study is placed in the magnetic field of the tomograph, all its protons line up in a certain position along the external magnetic field, like a compass needle. An MRI scanner sends a radio frequency pulse to the part of the body being examined, causing some of the protons to move out of their original state. After turning off the radio frequency pulse, the protons return to their previous position, emitting the accumulated energy in the form of a radio frequency signal that reflects its position in the body and carries information about the microenvironment - the nature of the surrounding tissue. Just as a million pixels form an image on a monitor, the radio signals from millions of protons, after complex mathematical processing, form a detailed image on a computer screen.

However, certain precautions must be strictly observed when performing an MRI. Potential hazards for patients and staff in MRI rooms may be related to factors such as:

Due to the "youth" of the methodology, a small (worldwide) amount of accumulated safety data, the FDA (Food Control Administration and medicines, USA) together with the World Health Organization impose a number of restrictions on the use of MRI, due to the possible negative impact of a strong magnetic field. The use of a magnetic field up to 1.5 T is considered acceptable and absolutely safe, except for cases when there are contraindications for MRI (MR tomographs up to 0.5 T - low-field, from 0.5 to 1.0 T - medium-field, from 1.0 - 1.5 T and more - high-field).

Speaking about long-term exposure to constant and alternating magnetic fields, as well as radio frequency radiation, it should be noted that there is no evidence of the existence of any long-term or irreversible effects of MRI on human health. So, female doctors and radiologists are allowed to work during pregnancy. Monitoring of their health showed that no abnormalities were noted in their health or in their offspring.

In magnetic resonance imaging of women of childbearing age, it is necessary to obtain information about whether they are pregnant or not. There is no evidence of the harmful effects of magnetic resonance imaging on the health of pregnant women or the fetus, but it is strongly recommended to perform MRI for women in position only with obvious (absolute) clinical indications, when the benefits of such an examination clearly outweigh the risks (even if very low).

If there are only relative indications for MRI, then doctors recommend abandoning this study in the first three months (up to 13 weeks of gestation, I trimester) of pregnancy, since this period is considered fundamental for the formation of the internal organs and systems of the fetus. During this period, both the pregnant woman and the child itself are very sensitive to the effects of teratogenic factors that can cause disruption of the embryogenesis process. In addition, according to most doctors, the first three months, the pictures of the fetus are not clear enough due to their small size.

Moreover, during the diagnosis, the tomograph itself creates a background noise and emits a certain percentage of heat, which can also potentially affect the fetus in early pregnancy. As mentioned above, MRI uses RF radiation. It can interact both with body tissues and with foreign bodies in it (for example, metal implants). The main result of this interaction is heating. The higher the RF frequency, the more large quantity heat will be released, the more ions are contained in the tissue, the more energy will be converted into heat.

To evaluate the thermal effects of RF radiation, specific absorption rate - SAR (specific absorbtion rate), displayed on the display screen of the device, helps. It increases with increasing field strength, RF pulse power, decreasing slice thickness, and also depends on the type of surface coil and patient weight. MRI systems are protected to prevent the SAR from rising above a threshold, which could result in tissue heating of more than 1°C.

During pregnancy, MRI can be used to diagnose pathology either in a woman or in a fetus. At the same time, MRI is prescribed according to ultrasound diagnostics when certain pathologies are detected in the development of the unborn child. The high sensitivity of MRI diagnostics makes it possible to clarify the nature of the deviations and helps to make an informed decision on whether to continue or terminate the pregnancy. MRI becomes especially important if it is necessary to study the development of the fetal brain, diagnose malformations of cortical development associated with a violation of the organization and formation of brain convolutions, the presence of areas of heterotopia, etc. Thus, the reasons for MRI can be:

■ various developmental pathologies of the unborn child;
■ deviations in the activity of internal organs, both the woman herself and the unborn child;
■ the need to confirm indications for artificial termination of pregnancy;
■ as evidence or, conversely, refutation of a previously diagnosed diagnosis based on tests;
■ the lack of the possibility of ultrasound due to the obesity of the pregnant woman or the inconvenient location of the fetus in the last stage of pregnancy.

Thus, in the first trimester of pregnancy (up to 13 weeks of gestation), an MRI is possible for health reasons on the part of the mother, since organo- and histogenesis has not yet been completed, and in the second and third trimesters of pregnancy (after 13 weeks) - the study is safe for the fetus.

On the territory of Russia, there are no restrictions on MRI in the first trimester, however, the Commission on Ionizing Radiation Sources at WHO does not recommend any exposure to the fetus, which may in any way affect its development (despite the fact that studies have been carried out during which children under 9 years of age were observed, subjected to MRI in the first trimester of intrauterine development, and no deviations in their development were found). It is important to remember that the lack of information about negative impact MRI on the fetus does not mean the complete elimination of the harm of this type of study for the unborn child.

note: pregnant [ !!! ] it is forbidden to conduct an MRI with intravenous administration of MR contrast agents (they penetrate the placental barrier). In addition, these drugs are excreted in small amounts with breast milk, so the instructions for gadolinium drugs indicate that when they are administered, breastfeeding should be stopped within a day after the administration of the drug, and the milk secreted during this period should be expressed and poured out. .

Literature: 1. article "Safety of magnetic resonance imaging - the current state of the issue" V.E. Sinitsyn, Federal State Institution "Therapeutic and Rehabilitation Center of Roszdrav" Moscow; journal "Diagnostic and interventional radiology" Volume 4 No. 3 2010 pp. 61 - 66. 2. article "MRI diagnostics in obstetrics" Platitsin I.V. 3. materials of the site www.az-mri.com. 4. materials from the site mrt-piter.ru (MRI for pregnant women). 5. materials from the site www.omega-kiev.ua (Is MRI safe during pregnancy?).

From the article: "Obstetric aspects of acute cerebrovascular disorders during pregnancy, childbirth and the postpartum period (literature review)" R.R. Harutamyan, E.M. Shifman, E.S. Lyashko, E.E. Tyulkina, O.V. Konysheva, N.O. Tarbaya, S.E. Flock; Department of Reproductive Medicine and Surgery, FPDO, Moscow State University of Medicine and Dentistry. A.I. Evdokimova; City Clinical Hospital №15 named after O.M. Filatov; Department of Anesthesiology and Intensive Care FPC MR Russian University Friendship of Peoples, Moscow (magazine "Problems of reproduction" No. 2, 2013):

“MRI does not use ionizing radiation, and no harmful effects on the developing fetus have been noted, although long-term effects have not yet been studied. A recently published guideline from the American Radiological Society states that MRI should be performed on pregnant women if the benefit of the study is clear and the necessary information cannot be obtained by safe methods (for example, using ultrasound) and cannot be waited until the end of the patient's pregnancy. MRI contrast agents easily cross the uteroplacental barrier. No studies have been conducted on the removal of contrast from amniotic fluid, just as their potential toxic effects on the fetus are not yet known. It is assumed that the use of contrast agents for MRI in pregnant women is justified only if the study is undeniably useful for making a correct diagnosis in the mother [read source].”

From the article"Diagnostics of acute disorders of cerebral circulation in pregnant women, puerperas and women in childbirth" Yu.D. Vasiliev, L.V. Sidelnikova, R.R. Arustamyan; City Clinical Hospital №15 named after O.M. Filatov, Moscow; 2 SBEE HPE "Moscow State University of Medicine and Dentistry named after A.I. A.I. Evdokimov" of the Ministry of Health of Russia, Moscow (magazine "Problems of reproduction" No. 4, 2016):

"Magnetic resonance imaging (MRI) - modern method diagnostics, which allows to identify a number of pathologies that are very difficult to diagnose using other research methods.

In the first trimester of pregnancy, MRI is performed according to vital indications on the part of the mother, since organo- and histogenesis has not yet been completed. There is no evidence that MRI has a negative effect on the fetus or embryo. Therefore, MRI is used for research not only in pregnant women, but also for fetography, in particular, for examining the fetal brain. MRI is the method of choice in pregnancy if other non-ionizing medical imaging methods are insufficient, or if the same information is needed as with x-rays or computed tomography (CT) but without the use of ionizing radiation.

There are no restrictions on MRI during pregnancy in Russia, however, the Commission on Non-Ionizing Radiation Sources at WHO does not recommend any exposure to the fetus from the 1st to the 13th week of gestation, when any factor can in any way affect its development.

In the II and III trimesters of pregnancy, the study is safe for the fetus. Indications for MRI of the brain in pregnant women are: [ 1 ] stroke of various etiologies; [ 2 ] vascular diseases of the brain (anomalies in the development of blood vessels of the head and neck); [ 3 ] trauma, bruises of the brain; [ 4 ] Tumors of the brain and spinal cord; [ 5 ] paroxysmal conditions, epilepsy; [ 6 ] infectious diseases of the central nervous system; [7 ] headache; [8 ] violations of cognitive functions; [ 9 ] pathological changes in the sellar region; [ 10 ] neurodegenerative diseases; [ 11 ] demyelinating diseases; [ 12 ] sinusitis.

For MR angiography in pregnant women, the introduction of a contrast agent in most cases is not necessary, in contrast to CT angiography, where it is required. Indications for MR angiography and MR venography in pregnant women are: [ 1 ] cerebrovascular pathology (arterial aneurysms, arteriovenous malformations, cavernomas, hemangiomas, etc.); [ 2 ] thrombosis of large arteries of the head and neck; [ 3 ] thrombosis of venous sinuses; [ 4 ] identification of anomalies and variants of development of the vessels of the head and neck.

There are few contraindications for the use of MRI in the general population, and in pregnant women in particular. [ 1 ] Absolute contraindications: artificial pacemaker (its function is disturbed in the electromagnetic field, which can lead to the death of the examined patient); other electronic implants; periorbital ferromagnetic foreign bodies; intracranial ferromagnetic hemostatic clips; conductive pacemaker wires and ECG cables; pronounced claustrophobia. [ 2 ] Relative contraindications: I trimester of pregnancy; serious condition of the patient (an MRI is possible when the patient is connected to life support systems).

In the presence of heart valves, stents, filters, the study is possible if the patient provides the accompanying documents of the manufacturer, which indicate the possibility of an MRI indicating the magnetic field strength, or an epicrisis of the department where the device was installed, which indicates the permission conducting this survey” [read source].