Types of tomographs: what power MRI machine is better to choose for diagnostics? Which MRI machine to choose based on field power, type of diagnostic tasks Disadvantages and advantages of closed and open machines

Ultra-high-field expert-class MR system with a magnetic field strength of 3 Tesla, with a full set of high-tech MR coils for all localizations without exception (head, breast, joints and “whole body”). In the MAGNETOM Verio MR system we managed to implement the incompatible:

on the one hand, the largest aperture diameter (70 cm) and the shortest length of the 3T system (173 cm), which reduces the discomfort associated with the study, allows you to provide assistance to overweight patients (table load capacity is up to 200 kg) and patients with disabilities ; the need and frequency of sedation in patients with signs of claustrophobia is reduced;

on the other hand, the method has unprecedented information content due to the high magnetic field power of 3 Tesla. In clinical practice, the use of such a magnetic field allows the system to be used in functional neurology, orthopedics, breast studies, angiology and cardiology at a fundamentally new level.

The innovative technologies underlying the MAGNETOM Verio MR system provide tangible superiority over other MR tomographs, which can be formulated in a number of postulates:

• the current minimum duration of the study,
• smaller slice thickness without loss of quality and resolution, which allows visualization of organs and tissues more thoroughly,
• high signal-to-noise ratio, which in turn also guarantees high-quality images, even if the patient’s weight exceeds 100 kg,
• the ability to use 3D modeling, which provides additional diagnostic information due to visualization of the pathological process in absolutely any plane,
• The use of Tim™ (Total imaging matrix) technology eliminates additional repositioning of the patient and coils, which allows us to, for example, perform Examination of the entire central nervous system in less than 10 minutes!

MAGNETOM Verio's advanced field homogeneity and wide range of unique clinical applications make this system unrivaled for high-end diagnostic MP examinations at the highest level. Innovative technologies from Siemens expand the clinical capabilities of the method, creating a variety of so-called clinical applications that allow the use of the MR technique based on a specific clinical problem, taking into account the characteristics of a given patient.

Siemens MAGNETOM Avanto 1.5 T, A Tim + Dot System

The most advanced and powerful MP ​​system in the class of 1.5 Tesla scanners with unique “zero helium evaporation” technology. Leader in image quality, clinical capabilities and speed of MP examinations. MP system equipped with a unique Tim and Dot technology that allows you to work at a fundamentally higher level both in terms of the quality of the obtained diagnostic images and the range of clinical problems solved. Matrix coil technology allows you to examine any part of the body without the need to reposition the patient and without reinstalling the coils (up to a full body scan of 205 cm in length).

Tim technology (Total imaging matrix) represents a revolutionary development of the RF path, RF coils, and reconstruction algorithms using parallel imaging techniques. Tim - the first implementation in the history of MRI of the concept of a surface coil of the whole body of the patient and a multi-channel radiofrequency system to create a single imaging matrix. Tim - This is in some way an analogue of multi-slice (multi-slice) CT technology. Tim makes MP examination more flexible, more accurate and faster.

Siemens has developed technology performance optimization Dot (Day optimizing throughput) , which applies to all stages of work. Basic operating principle Dot - the maximum possible automation of the process of setting up and selecting optimal MP scanning parameters (in each specific case, for each specific patient) with one goal - obtaining an MP image of expert quality. The actions of medical personnel are focused on choosing from the options offered by the system those items that characterize this particular patient. Dot allows you to select the optimal cardiac scanning mode 50% faster, taking into account the anatomical and physiological characteristics of the patient, speed up MP studies in the field of neurology by 30%, and simplify preparation for expert studies. Dot expands and enriches technology Tim , providing additional stability in image quality, reducing the risk of possible diagnostic errors.

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

Cost effective systems

Without imposing a percentage, it is safe to say that a 1.5 Tesla MRI machine is suitable for most MR scans. The 1.5 T short bore machine remains the standard, most used magnetic resonance imaging scanner. This does not mean that 3 Tesla systems have not caught on, but return on investment, throughput, staffing, and other factors should be taken into account. Silence the noise or turn down the volume? During an MRI scan, there is always noise in the image. Much of this noise comes from the patient's body, as well as from the electronics of the MRI machine itself. It is important to get the "signal" that creates the image, not the "noise" that can affect the quality of the image. 1.5 and 3 tesla devices cope with this, but to varying degrees. Young children tend to be very noisy. If they get together, for example for a birthday, the excitement makes them even noisier. Games can keep them occupied for a while until the party is over. For the occasion, if you want to play musical chairs, you have two options to make everyone hear the music:

Make the sound louder

Calm the children

Work 3- Tesla MRI machine much like the operation of a stereo system playing music for children at maximum volume. Essentially, this way you get more signal - the higher the field strength, the more molecules resonate, drowning out the noise. The 1.5 Tesla system with a multi-channel coil works largely on the principle of “calming children”. 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 thinking 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 therefore the clarity of the image at a certain scanning speed. However, you can't get the best of everything at once, so MRI studies present a trade-off between scan time and image quality. Thus, depending on the technology, your bandwidth needs, and other factors, the advantage may be in one direction or another. The bottom line is that you will still get quality images on a 1.5T system using multi-coil technology - but the scan time will be longer than 3T. Conversely, you can reduce 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 a maximum number of patients in a day, you are inclined to purchase a 3 Tesla system, then you should plan everything in advance. Such devices are expensive - even on the secondary market you can pay twice as much for them as 1.5T, and yet they are difficult to find. Take the time to find a system and 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 that of a 1.5 Tesla machine. And a 3 Tesla system has twice the magnetic field strength! Make sure to follow all safety precautions on site! If your research is less detailed, or the pace is less strenuous, a 1.5 Tesla system may give you everything you need. These systems are much more accessible, as are spare parts for them, as well as service engineers to maintain them. As with the 3 Tesla magnet, you must ensure that your facility is ready to accommodate the machine. Failure to take proper precautions can result in costly damage and serious injury.

Magnetic resonance imaging (MRI) is one of the ways to diagnose diseases and study tissues and various human organs. It is based on the spectroscopy method and the principles of nuclear magnetic resonance.

MRI allows specialists to find out the necessary information about the tissues and organs being examined, because this diagnostic method has such advantages as excellent resolution, good contrast of images, and the ability to obtain sections in various planes.

In addition, magnetic resonance imaging is characterized by the absence of gamma radiation exposure to humans.

Magnetic resonance imaging is performed using special MRI scanners.

They are formed by several components:
a system that receives, processes and transmits information;
magnet;
cooling system;
shimming, gradient and radio frequency coils;
shielding system.

However, this does not mean that all existing diagnostic devices are the same. Experts have created several different classifications of devices.

Types of MRI machines

Depending on the design, a magnetic resonance imaging scanner can be closed or open. The first device has an annular part, open at the foot and head ends. This is where the person coming for the examination is placed. The open type device is not closed from the sides.

If we take into account the source of the main magnetic field, then diagnostic devices can be divided into the following types:
resistive;
permanent;
hybrid;
superconducting.

In resistive systems, electric current passes through a coil. Due to this, a magnetic field with a power of about 0.6 Tesla is formed. These devices require a large amount of electricity. They also need a good cooling system. Now this type of medical equipment is practically not used.

In tomographs with permanent magnets, the field is formed between the poles. The advantages of these devices are that they do not require additional electric current or cooling. Cons - the generated magnetic field is inhomogeneous, and its power reaches only 0.3 Tesla.

In hybrid systems, a magnetic field is generated through the use of current-conducting coils and permanently magnetized material. But in superconducting devices it is created by current in a wire made of a special material. Regarding the field power, it is worth noting that it turns out to be more than 0.5 Tesla.

Classification of devices based on power

Depending on the strength of the main magnetic field, medical equipment is divided into the following types:
more than 2 Tesla is ultra-high field;
from 1 to 2 T – high-field;
about 0.5 T – mid-field;
from 0.1 to 0.4 T – low-field;
less than 0.1 T – ultra-low.

MR imaging companies primarily produce medium-field models. Ultra-high-field devices are used only in research laboratories, since the power of the main magnetic field of more than 2 Tesla is considered potentially dangerous.

Regarding low-field systems, it is worth noting that they have fewer contraindications for people undergoing examination and specialists performing MRI. However, such devices are rarely used, because they have one drawback. It lies in the low signal-to-noise ratio and the fact that it takes more time to examine and obtain good quality images.

Low-field tomograph

Disadvantages and advantages of closed and open devices

Many medical institutions have closed-type tomographs. They have good power, making them suitable for complex examinations. However, closed tomographs have a significant drawback. It lies in the fact that the diameter of the annular part is about 70 cm. Accordingly, closed tomographs are not suitable for those people who suffer from obesity and claustrophobia.

The open type device has many advantages. Firstly, such a tomograph is suitable for patients diagnosed with claustrophobia or other mental illnesses. You can examine children in an open apparatus (they tend to panic when they find themselves in a closed space). Secondly, this tomograph allows you to examine certain parts of the body. At the same time, there is no effect on other areas and organs.

What to consider when choosing an MRI machine?

Purchasing medical equipment requires a serious approach. When choosing a tomograph for MRI, you should pay attention not only to its price, but also to its characteristics. First of all, you should think about what type of device to choose - open or closed type. For example, if you plan to install a tomograph in a children's medical facility, then it is best to buy an open device.

Another selection criterion is power. It determines how high quality the resulting images will be. Thus, to diagnose complex diseases, more powerful devices should be chosen. But it must be taken into account that this figure should not exceed 5 Tesla. Ultra-high-field tomographs are not used in clinics.

In conclusion, it is worth noting that magnetic resonance imaging is a highly informative diagnostic method. Tomographs used in MRI allow specialists to identify serious diseases and pathologies in patients. The question regarding which MRI machine is better is quite relevant. When purchasing a specific tomograph, it is very important not to make a mistake with the choice, because the examination results depend on the device.

After the invention of the magnetic resonance imaging scanner, the popularity of such a device rose to a high level. This is due to the fact that such devices can diagnose all human organs and tissues, excluding the development of serious diseases. The basis of the MRI procedure is the corresponding equipment, presented in the form of a tomograph. The tomograph is a large capsule with free space inside. Such a unit saves not hundreds, but thousands of people around the world every day, providing the opportunity to make accurate diagnoses. What types of tomographs are there, as well as the influence of MRI power on diagnostic procedures.

Characteristics of the tomograph

Patients often have a question about which tomograph is best to choose for MRI so that the results are as accurate as possible? The power of the unit, as well as its structural structure, plays a significant role. The main characteristics of MRI include the following factors:

1. Power. This value for tomographs is measured in Tesla. Tomographs are divided into four types according to their power: low-field, mid-field, high-field and ultra-high-field. We will look at the capacities of the units in more detail below.
2. Research time. The duration of the study is influenced by factors such as the power of the tomograph. The more powerful the unit, the faster the diagnostics are carried out.
3. Possibility of using contrast agents. If an MRI examination procedure is performed without the use of contrast agents, the final result will not be as accurate as when contrast is used.
4. Possibility of diagnostics of various organs and systems. Depending on what part of the body needs to be examined, appropriate devices are selected.
5. Types of tomographs. There are two types of tomographs: open and closed. The open type is intended primarily for overweight people, as well as patients suffering from claustrophobia.
6. Patient's weight. The patient’s weight is essential, since standard ones are designed for weights from 80 to 200 kg. For patients with larger body weights, special veterinary devices are used.
7. Manufacturer of the product. The most popular tomograph models are brands such as Siemens and Philips.

What parts of the body can be diagnosed on an MRI?

Using magnetic resonance procedures, it is possible to examine the following human organs and systems:

• head;
• vascular system;
• bone tissue;
• joints;
• spine.

It should be noted that the MRI procedure allows for diagnostics of the entire body, identifying all pathologies and abnormalities. But here it is important to note that the more organs are examined in one session, the less effective the device is. Let us consider in more detail how the units differ depending on their power.

Low-field tomographs

Low-floor units have a power limit of 0.3 to 0.5 Tesla. These are quite good units, the main advantage of which is significant energy savings. The cost of the examination procedure on low-field tomographs is several times lower than on high-field ones. That's all of the advantages of low-field tomographs.

Low-field units produce low-quality images, which significantly affects the information content of the results. With such devices, small tumors may not be noticed, which will lead to the need to carry out diagnostics again. A low-field magnetic tomograph is used to perform tractography of brain tracts, as well as dynamic angiography.

It is important to know! Low-field devices do not allow diagnosing tumors and aneurysms in the brain, so it is recommended to use more powerful equipment.

Mid-field tomographs

The power of mid-field devices varies from 0.5 to 1 Tesla. The devices are found mainly in state-run medical institutions. In private clinics, such units are not installed, since they practically do not differ from low-power ones, and their cost is similar to high-field types.

It is important to know! Mid-field tomographs have gained less popularity than low-power ones, so they can only be found in budget clinics.

High-power MRI machines

The magnetic field strength of high-field units ranges from 1 to 1.5 Tesla. Experts recommend that it is better to do MRI using high-voltage tomographs. To cool such units, a special type of cooler is used, presented in the form of a cryogenic helium substance.

Equipment of this type is one of the most popular, therefore it is used not only in the Russian Federation, but throughout the world. When asked about which device is better to carry out MRI diagnostics, we can safely say that these are high-field tomographs. Such units make it possible to diagnose any human organs and systems from the brain to the feet.

The scanning time of tomographs of this type is 1.5-2 times less than that of low-field units. Devices with the “Tim” function are capable of diagnosing all human organs from head to toe. This type of equipment costs between $350 and $500.

Ultra-high-field devices

The power of such units ranges from 3 to 7 Tesla. These are sufficiently high power levels that allow MRI of the spine to be performed in the most detailed form. The scope of application of such units is research complexes. It is not rational to install such machines in private clinics, since the cost of the procedure will increase 3-4 times, which will affect the number of people wishing to undergo examination.

A high degree of information content is a very important indicator when conducting diagnostics. Typically, the need for diagnostics using ultra-high-field devices arises when there is a need for a detailed study of the brain.

It is important to know! The doctor may prescribe an MRI for the patient if he suspects a casuistic disease.

To summarize, it should be noted that in comparison with computed tomography, MRI is the most accurate, painless and safe way to diagnose human internal organs. From the above it follows that the power of the devices is an important factor that affects the accuracy of the final results. Before consenting to undergo an MRI, patients must ensure what type of equipment is installed in the room. Many patients resort to diagnostics using low- or medium-power devices, due to the low cost of the procedure. In order for the doctor to make a correct and accurate diagnosis, the MRI procedure must be performed on a high-field unit.

Today, diagnosing diseases with MRI machines is considered the most informative, although quite expensive, procedure. The work of tomographs is based on the use of the phenomenon of nuclear magnetic resonance. MRI machines of 3 Tesla and higher provide the creation of a super-powerful magnetic field, which allows you to obtain higher-quality images of the examined area. Does such a diagnosis harm the body?

The essence of the scanning technique

The examination does not require intervention in the body (non-invasive method), and for its implementation, equipment is used that generates a certain magnetic field strength. MRI research uses the phenomenon of magnetic waves that change the behavior of the nuclei of hydrogen atoms that make up the cells of the human body. The result of this action is photographs of the surveyed areas.

The essence of the technique is to register emitted radio signals, which in whole and healthy cells differ significantly from the emission of structures damaged by disease. After the result is processed by a computer, the doctor receives a series of images with well-visualized changes.

Modern MRI machines are capable of generating fields of varying powers, which are measured in teslas (T). The unit of measurement of magnetic intensity was named after the brilliant experimental scientist of the last century, who surprised the world with inventions in the field of electricity. Based on the intensity of the created magnetic field, the classification of tomographs is as follows:

• for low-floor devices – 0.25-0.35 tesla;
• for mid-field – 1.0 Tesla;
• for high-field ones - 1.5-3.0 tesla.

The magnitude of the field strength depends on the properties of the magnet installed in the apparatus. However, it should be taken into account that superconducting magnets have a higher cost than low-tension magnets. It makes no sense to use less expensive MRI devices with a power below 1 Tesla; their data will not be accurate and reliable.

What are the advantages of a 3 Tesla device compared to a low power tomograph:

• the research will require less time;
• the resulting images will be of higher quality due to high resolution;
• small structures (vessels, joints, etc.) will be displayed with high accuracy.

It is important to know: despite the power of the equipment, a short time spent by a person within the range of a magnet does not harm health. Therefore, diagnostics can be performed more than once. The appearance of unpleasant sensations is associated only with the use of contrast.

How tomographs of various powers are used

• 1 Tl. The power of mid-field devices of this magnetic field strength is only sufficient for preliminary diagnostics. Tomographs help determine the presence of a tumor or metastases, but with low quality images without displaying fine structures and tissues.
• 1.5 Tesla Tomographs of this class can be used to assess the condition of blood vessels, review small problem areas, and identify the border of the metastasis zone. Only such tasks guarantee reliable results.
• 2 Tl. The devices are not particularly popular because a power of 1.5 Tesla is sufficient to detect tumors and abnormal organ development. Despite the good image quality and high accuracy, the details necessary for treatment are not visualized.
• 3 Tesla. Thanks to the high-field tomographs of this group, it is possible to better identify structures that are indistinguishable when examined with low-field devices. In this case, scanning is much faster, which is important for injuries, especially of the skull.
• Diagnostics are not performed on tomographs of 4 Tesla and more powerful; the devices are used for scientific research. MRI rooms are equipped mainly with 1.5 Tesla tomographs; for special types of scanning, 3 Tesla tomographs are used.

Important. As a result of scanning the body with MRI devices, layer-by-layer images of the selected area (slices) are obtained. The thinner the sections can be obtained, the more detailed the morphological picture of the tissues will be. The key to accurate diagnosis is a more powerful magnetic field, which shortens the procedure time.

Advantages of 3 Tesla tomographs

Despite the presence of a magnetic field in the area of ​​influence, the patient does not receive a dangerous radiation load and does not feel any particular discomfort, except for the need to lie still. To study pathologies, two types of tomographs are used - open and closed. True, the power of open complexes that provide tomography of a body area immersed in a camera is somewhat lower than the power of closed devices, which affects the quality of the resulting sections.

Study of the head area

To examine brain structures, 1.5 Tesla is often sufficient, so MRI of the brain is performed with high-field devices of minimal power. But if it is necessary to clarify the picture and obtain highly accurate results, the doctor may prescribe an MRI using a 3 Tesla machine. What information does a tomogram performed on this tomograph provide to the doctor:

• visualization of small brain structures with higher contrast than on a 1.5 Tesla device;
• a detailed overview of the membranes of the organ being studied, the condition of the blood vessels;
• information about the smallest foci of neoplasms thanks to the thinnest (less than 1 m) tissue sections;
• high-precision topography of head structures after traumatic brain injury;
• detailed information about brain pathologies in areas adjacent to the spinal zone.

Among the important advantages of 3 Tesla complexes is increased quality of sections with high accuracy of the information obtained about the functioning of the brain. This can be achieved even without the use of contrast, and tomography is more informative than computer diagnostics, is faster, and does not expose the patient to x-rays.

How long will the MRI procedure take? When examined on a 1.5 Tesla device, the magnetic diagnostic time will last 12-15 minutes. The duration of an MRI on a 3 Tesla tomograph will be reduced to 5 minutes.

Spine overview

To examine the spinal column, magnetic resonance imaging with a 3 tesla tomograph is prescribed for back injuries to detect structural anomalies and progressive pathologies. The use of high-field tomographs is important for examining small patients and people with severe injuries, when the speed of the procedure is important.

For what purposes will you need to undergo an MRI of the spine using a 3 Tesla machine:

• detection of congenital defects, intervertebral disc injuries;
• diagnosing areas of narrowing of the spinal canal;
• identifying tumors and their nature, metastases from other organs affected by cancer;
• fixing areas with insufficient blood flow, damage to nerve structures.
• identifying the consequences of osteochondrosis, the condition of intervertebral hernias.

Disadvantages of 3 Tesla devices

• Some patients are intolerant of the confined space of high-field tomographs. If mild sedation is not sufficient, the study will have to be abandoned.
• MRI equipment with field strengths above 1.5 Tesla has limited tunnel dimensions where the table with the patient is located. Therefore, particularly obese people will not be able to undergo diagnosis.
• With high pain syndrome affecting the back and neck, the patient will not be able to remain motionless for a long time. This is especially true when using a contrast agent.

If the organ being examined allows, a person can undergo MRI diagnostics using an open (low-field) tomograph or turn to alternative examination methods. True, they do not guarantee high reliability and accuracy of the results.

Thanks to innovative technologies, today high-power devices have been created that provide higher resolution images. However, tomographs with a power of up to 7 Tesla are used quite rarely, only for detecting malignant tumors, since the equipment is extremely expensive. To obtain detailed sections about the state of the examined area, high magnetic field tomographs with an intensity range of 1.5-3 tesla are sufficient.