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 MRI machine - tension magnetic field, which is measured in Tesla (T). The quality of visualization directly depends on the field strength - the higher it is, the better the image quality, and, accordingly, the higher the diagnostic value of the MR study.
Depending on the power of the device, there are:
■ low-field tomographs - 0.1 - 0.5 T (Fig. 1);
■ high-field tomographs - 1 - 1.5 T (Fig. 2);
■ ultra-high-field tomographs - 3 Tesla (Fig. 3).
Currently, all major manufacturers produce MR scanners with a field of 3 Tesla, which differ little in size and weight from standard systems with a field of 1.5 Tesla.
Safety studies of MR imaging have shown no negative biological effects magnetic fields up to 4 Tesla, used in clinical practice. However, it should be remembered that the movement of electrically conductive blood creates electric potential, and in a magnetic field will create a slight voltage through the vessel and cause an elongation of the T wave on the electrocardiogram, therefore, when studying in fields above 2 Tesla, ECG monitoring of patients is desirable. Physical studies have shown that fields above 8 Tesla cause genetic changes, charge separation in liquids, and 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. Rapidly switching gradients can induce electrical currents in the body and lead to stimulation 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 value [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, monitoring of the patient's condition is constantly necessary in strong gradient fields.
Metals, even non-magnetic ones (titanium, aluminum), are good guides electricity and radio frequency [RF] energy will become hot. RF fields cause eddy currents in closed loops and conductors, and can also create significant stress in extended open conductors (eg, rod, wire). Length electromagnetic waves in the body is only 1/9 of the wavelength in air, and the phenomenon of resonance can occur in relatively short implants, causing their ends to heat up.
Metal objects and external devices are usually mistakenly considered safe if they are non-magnetic and labeled as "MR-compatible". However, it is important to ensure that the objects being scanned within 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 generate heat during scanning. If the object is longer than half the RF wavelength, resonance may occur in the patient's body with high heat generation. Limit dimensions 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 amplifier power and field strength and regulatory documents should not exceed 99 dB (for most clinical systems is about 30 dB).
based on materials from the article “Possibilities and limitations of high-field magnetic resonance imaging (1.5 and 3 Tesla)” by A.O. Kaznacheeva, National Research University information technologies, mechanics and optics, St. Petersburg, Russia (magazine “Radiation diagnostics and therapy” No. 4 (1) 2010)
read also the article “Safety of magnetic resonance imaging - current state question" V.E. Sinitsyn, Federal State Institution “Treatment and Rehabilitation Center of Roszdrav” Moscow (magazine “Diagnostic and Interventional Radiology” No. 3, 2010) [read]
MRI DURING PREGNANCY - IS IT SAFE?
Currently, MRI is a widely used method radiology diagnostics, which does not involve the use of ionizing radiation, as with X-ray examination(including CT), fluorography, etc. MRI is based on the use of radiofrequency pulses (RF pulses) in a high-intensity magnetic field. The human body is composed primarily of water, made up of hydrogen and oxygen atoms. At the center of each hydrogen atom is a small particle called a proton. Protons are very sensitive to magnetic fields. 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 are aligned in a certain position along the external magnetic field, like a compass needle. An MRI scanner sends a radiofrequency pulse to the part of the body being examined, causing some protons to move from their original state. After the radio frequency pulse is turned off, the protons return to their previous position, emitting the accumulated energy in the form of a radio frequency signal, reflecting its position in the body and carrying information about the microenvironment - the nature of the surrounding tissue. Just as a million pixels form an image on a monitor, radio signals from millions of protons, after complex mathematical computer processing, form a detailed image on a computer screen.
However, certain precautions must be strictly observed when performing MRI. Potential hazards for patients and staff in MRI rooms may include factors such as:
■ constant magnetic field generated by the tomograph magnet;
■ changing magnetic fields of the device (gradient fields);
■ RF radiation;
■ devices and substances included with the tomograph, such as cryogens (liquid helium) and electrical cables.
Due to the “youth” of the technique and the small (worldwide) volume of accumulated safety data, the FDA (Food and Drug Administration, USA) together with the World Health Organization impose a number of restrictions on the use of MRI due to possible negative effects strong magnetic field. The use of a magnetic field up to 1.5 Tesla is considered acceptable and absolutely safe, except in cases where there are contraindications for MRI (MRI scanners up to 0.5 Tesla are low-field, from 0.5 to 1.0 Tesla are mid-field, from 1.0 - 1.5 Tesla 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. Thus, female doctors and x-ray technicians are allowed to work during pregnancy. Monitoring of their health showed that no abnormalities were noted in their health or in their offspring.
When performing a magnetic resonance examination of women of childbearing age, it is necessary to obtain information about whether they are pregnant or not. There is no evidence of a harmful effect of magnetic resonance examinations on the health of pregnant women or the fetus, but it is strongly recommended that pregnant women undergo MRI only when there are clear (absolute) clinical indications, when the benefits of such an examination clearly outweigh the risks (even 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, first trimester) of pregnancy, since this period is considered fundamental for the formation internal organs and fetal systems. During this period, both the pregnant woman and the child himself are very sensitive to the effects of teratogenic factors that can cause disruption of the process of embryogenesis. In addition, according to most doctors, during the first three months, photographs of the fetus are not clear enough due to its small size.
Moreover, during diagnostics, the tomograph itself creates a background noise and emits a certain percentage of heat, which can also potentially affect the fetus. early stages pregnancy. As stated 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 frequency of RF radiation, the more heat will be generated, the more ions contained in the tissue, the more energy will be converted into heat.
The specific absorption rate (SAR), displayed on the device display screen, helps to evaluate the thermal effects of RF radiation. It increases with increasing field strength, RF pulse power, decreasing slice thickness, and also depends on the type of surface coil and the weight of the patient. Magnetic resonance imaging systems are protected to prevent the SAR from rising above a threshold that could result in tissue heating of more than 1°C.
During pregnancy, MRI can be used to diagnose pathology in either the woman or the fetus. In this case, MRI is prescribed based on ultrasound diagnostic data when certain pathologies in the development of the unborn child are identified. High sensitivity MRI diagnostics allows you to clarify the nature of the abnormalities and helps make an informed decision about maintaining or terminating the pregnancy. MRI becomes especially important when it is necessary to study the development of the fetal brain, diagnose malformations of cortical development associated with disruption of the organization and formation of brain convolutions, the presence of areas of heterotopia, etc. Thus, the reasons for performing MRI may be:
■ various pathologies of development of the unborn child;
■ deviations in the activity of internal organs, both of the woman herself and the unborn child;
■ the need to confirm the indications for artificial termination of pregnancy;
■ as evidence or, conversely, a refutation of a previously made diagnosis based on tests;
■ the inability to conduct an ultrasound due to the obesity of the pregnant woman or the inconvenient position of the fetus in the last stage of pregnancy.
In Russia, there are no restrictions on MRI in the first trimester, however, the WHO Commission on Ionizing Radiation Sources does not recommend any exposure to the fetus that could in any way affect its development (despite the fact that studies have been conducted , during which children under 9 years of age were observed and exposed to MRI in the first trimester of intrauterine development, and no abnormalities in their development were found). It is important to remember that the lack of information about the negative impact of MRI on the fetus does not mean that this type of examination is completely harmful to the unborn child.
note: pregnant [ !!! ] it is prohibited to perform MRI with intravenous administration MR contrast agents (they penetrate the placental barrier). In addition, these drugs are excreted in small quantities and with breast milk, therefore, the instructions for gadolinium drugs indicate that when they are administered, breastfeeding should be stopped within 24 hours after administration of the drug, and milk secreted during this period should be expressed and poured out.
Literature: 1. article “Safety of magnetic resonance imaging - current state of the issue” by V.E. Sinitsyn, Federal State Institution “Treatment 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 from 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 postpartum period(literature review)” R.R. Arutamyan, E.M. Shifman, E.S. Lyashko, E.E. Tyulkina, O.V. Konysheva, N.O. Tarbaya, S.E. Flocka; Department reproductive medicine and surgery FPDO Moscow State Medical and Dental University named after. A.I. Evdokimova; City Clinical Hospital No. 15 named after. O.M. Filatova; Department of Anesthesiology and Reanimatology, Faculty of Advanced Training of the Medical Sciences, Peoples' Friendship University of Russia, Moscow (magazine "Problems of Reproduction" No. 2, 2013):
“MRI does not use ionizing radiation and there are no harmful effects on the developing fetus, although long-term effects have not yet been studied. Recent guidelines published by the American Society of Radiology state that pregnant women can undergo MRI if the benefit of the test is clear and the necessary information cannot be obtained through safe methods (for example, using ultrasound) and cannot wait until the patient is pregnant. MRI contrast agents readily penetrate the uteroplacental barrier. There have been no studies on the removal of contrast agents from amniotic fluid, just as their potential toxic effect on the fetus is not yet known. It is assumed that the use of contrast agents for MRI in pregnant women is justified only if the study is undoubtedly useful for making a correct diagnosis in the mother [read source].”
From the article"Diagnostics of acute disorders cerebral circulation in pregnant women, postpartum women and women in labor" Yu.D. Vasiliev, L.V. Sidelnikova, R.R. Arustamyan; City Clinical Hospital No. 15 named after. O.M. Filatova, Moscow; 2 State Budgetary Educational Institution of Higher Professional Education “Moscow State Medical and Dental University named after. 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, allowing 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 studying the fetal brain. MRI is the test of choice in pregnancy if other non-ionizing medical imaging techniques are insufficient, or if you want to obtain the same information as radiography or computed tomography (CT), but without the use of ionizing radiation.
In Russia there are no restrictions on MRI during pregnancy, however, the WHO Commission on Non-Ionizing Radiation Sources does not recommend any exposure to the fetus from the 1st to the 13th week of gestation, when any factor may in any way affect its development.
In the second and third 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 brain (anomalies in the development of blood vessels in the head and neck); [ 3 ] injuries, bruises of the brain; [ 4 ] tumors of the brain and spinal cord; [5 ] paroxysmal conditions, epilepsy; [ 6 ] infectious diseases central nervous system; [7 ] headache; [8 ] cognitive impairment; [ 9 ] pathological changes sellar region; [ 10 ] neurodegenerative diseases; [ 11 ] demyelinating diseases; [ 12 ] sinusitis.
To perform MR angiography in pregnant women, the administration of a contrast agent in most cases is not necessary, unlike CT angiography, where this is mandatory. 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 the venous sinuses; [ 4 ] identification of anomalies and variants of development of the vessels of the head and neck.
There are few contraindications to the use of MRI in the general population, and in pregnant women in particular. [ 1 ] Absolute contraindications: artificial driver rhythm (its function is disrupted in the electromagnetic field, which can lead to the death of the patient being examined); other electronic implants; periorbital ferromagnetic foreign bodies; intracranial ferromagnetic hemostatic clips; pacemaker conductive wires and ECG cables; severe claustrophobia. [ 2 ] Relative contraindications: I trimester of pregnancy; the patient's serious condition (an MRI may be performed when the patient is connected to life support systems).
If there are heart valves, stents, filters, the study is possible if the patient provides accompanying documents from the manufacturer, which indicate the possibility of performing an MRI with an indication of the magnetic field voltage, or an epicrisis of the department where the device was installed, which indicates the permission conducting this survey" [read source].
Regardless of the type of MRI device, the principle of their operation is the same. The magnetic field of the tomograph makes hydrogen atoms in the human body move, or rather “vibrate”. Water contains the largest number of hydrogen atoms, which is why MRI is best for visualizing soft fabrics, rather than the skeletal system. This vibration is picked up by the detectors of the device, and the image becomes contrasting due to the unequal water content in the tissues.
To improve the image, volumetric radiofrequency coils are used that are installed in the area of interest. There are coils:
- head (birdcage type)
- cervical
- humeral
- saddle knee
- breast scanning coils
- pelvic examination coil
- intracavital coils (intrarectal, intravaginal)
- abdominal coil
The purpose of such coils is to reduce unwanted connections during scanning between the area of interest and surrounding areas; avoiding excessive RF losses; improves the signal-to-noise ratio and resolution, which significantly reduces scanning time.
What types of MRI machines are there?
Depending on the type of source of the main magnetic field, tomographs are distinguished:
- permanent
- resistive
- superconducting
- combined
Devices with permanent magnets are the most affordable, as they do not require additional costs for electricity and cooling. Their induction force does not exceed 0.35 Tesla. Tomographs with resistive magnets are more expensive to maintain, but their power is not much higher than that of devices with a permanent magnet - a maximum of 0.6 Tesla. Modern devices contain superconducting magnets; they are the most expensive to maintain (therefore, the price of research in them is higher), their induction force is at least 0.5 Tesla.
Depending on the magnetic field strength, tomographs are:
- ultra-low (less than 0.1 Tesla)
- low-floor (0.1-0.4 Tesla)
- mid-field (0.5-1.5 Tesla)
- high-field (1.5-3 Tesla)
- ultra-high field (more than 3 Tesla, not used for diagnostics)
Low-field machines use permanent or resistive magnets, and these also include seated MRI machines for examining extremities. The advantage of such tomographs is that they are open and, therefore, more comfortable for the patient. The disadvantage is the low signal-to-noise ratio (low image quality), as well as the long scanning duration.
The optimal power of an MRI machine ranges from 1 to 3 Tesla. This power provides an optimal signal-to-noise ratio to ensure sufficient image quality.
Which MRI machine is more accurate and why?
The resolution of MRI devices depends on their power (induction force). The greater this power (measured in Tesla), the higher the signal-to-noise ratio and the faster the examination. The optimal signal-to-noise ratio ensures high contrast between tissues of different densities; this condition is met when using devices with a power of at least 1.5 Tesla. At the same time, you will not see significant differences between 1.5 and 3 Tesla MRI images; The main reason why 3 Tesla tomographs are used is that they are relatively high speed scanning and the ability to conduct specialized MR diagnostic methods (for example, diffusion tensor imaging, functional MRI).
Low-field scanners, having low power, lose in image clarity, however, this is also their advantage. The fact is that the use of high-field scanners is impossible if there are ferromagnetic (capable of magnetization) elements in the body; they will heat up significantly and tend to the source of the magnet. Low-field tomographs do not cause such an effect; the only possible interference is that if the metal is located directly in the scanning area, it may produce minor artifacts in the image. If the metal element is located far from the area of interest, then this will not affect the scanning in any way.
At the moment, an MRI machine with a field of 3 Tesla has the maximum power; devices with higher power are used only in research laboratories (they are not used to study pathologies not because they are dangerous, but because they are extremely expensive, and the quality of the images is not good). differs from those obtained on high-floor machines).
What is the difference between open and closed MRI?
The main difference between closed and open type MRI is the power of such devices. Open tomographs are low-field, usually their field strength does not exceed 0.6 Tesla. This undoubtedly affects the quality of the images; the contrast of the examined tissues will be lower than in images obtained on 1.5 Tesla scanners.
The advantage of open scanners is that this is an MRI without a weight limit, while the permissible weight for an MRI on a closed machine should usually not exceed 130 kg (it is worth noting that new closed-type MRI machines with an expanded aperture are now widely used, allowing examination patients who have overweight up to 200kg).
In addition, unlike high-field closed scanners, open low-power scanners allow scanning with metal objects in the body; they are magnetized slightly and do not affect scanning; they can only cause artifacts if they are located directly in the area of interest.
What does an MRI machine look like?
Tomographs closed type They are a pipe in the form of a tunnel. The patient is placed on the table and then moved into the aperture of the device. Their limited internal space can be a problem for patients who suffer from claustrophobia and are significantly overweight.
Open tomographs have a wide open design, such as C-shaped scanners with two large disks between which the person being examined is placed. They are comfortable for performing MRI scans for people of any size. It is also possible to scan patients in vertical position(Upright™).
It is rare to find semi-open tomographs with a short tunnel length and flared ends.
Where can I get an open and closed tunnel MRI?
MRI on an open tomograph in St. Petersburg, as well as in a closed one, is carried out by several dozen clinics, including state ones. Remember that the choice of the type of tomograph should be based on the indications. Conventional (routine) examinations can be carried out on low-field open scanners, high-precision studies - on high-field closed scanners of 1.5 Tesla, high-precision specialized types of scanning should be carried out on MRI machines of 3 Tesla - in St. Petersburg and Moscow, these devices are presented by leading manufacturing companies.
Why is the MRI machine noisy?
Acoustic noise is caused by the way the MRI machine works. It occurs when the magnetic field of the gradient coil interacts with the main magnetic field. The noise level depends on the power of the scanner - the higher it is, the louder the noise. All modern scanners are equipped with a noise reduction system, which provides completely acceptable conditions for the patient.
Which machine is better for doing MRI of the spine?
The readings determine which MRI machine to choose and how much Tesla should be in it. To study degenerative diseases and changes in the spinal axis, the power of an open tomograph is sufficient. For infectious, inflammatory, and traumatic lesions, it is worth choosing a closed high-field device of 1.5 Tesla. The study of the spinal cord, blood vessels, tumors and metastases must be carried out using powerful 3 Tesla MRI machines.
Contraindications for MR scanning
Absolute contraindication is the presence of pacemakers, ferromagnetic and electronic implants with an induction force of more than 5 Gauss. If there is a pacemaker, the magnetic field of the tomograph induces currents in its circuits, causing it to stop working. If a ferromagnetic alloy is present in the body (clipped vessels, fragments, bullets, middle ear implants, endoprostheses, stents, etc.), then under the influence of the field they can move, causing severe injury to the patient. Also, there should be no ventilators, oxygen cylinders, etc. in the room with the magnet. When scanning on a low-field machine, the presence of metal is allowed.
Relative contraindications: the first 12 weeks of gestation, the patient’s heavy weight, claustrophobia, epilepsy (rhythmic noise can trigger an attack). These contraindications disappear when using an open scanner. There are also modern closed-type devices with an expanded aperture that allow MRI to be performed for patients weighing over 130 kg, as well as for those suffering from claustrophobia.
Modern medicine can no longer imagine existence without magnetic resonance imaging, but due to the availability of a wide range of equipment, it is difficult to understand which MRI device is best to use in a particular case. Computer diagnostics provides information regarding organs and tissues being diagnosed. After the examination, the specialist receives an informative and accurate report due to the high detail of the image, good resolution and the ability to obtain images in different planes. MRI is better than CT or X-ray because it is known to be safe due to the absence of negative gamma radiation.
The types of tomographs for MRI differ from each other, but in their design they have:
- shielding systems;
- sensors for receiving, processing and transmitting data;
- coils of different frequencies;
- magnet;
- cooling system.
All pieces of equipment, regardless of the type of MRI machines, are highly technical equipment that only a specialist can handle. For example, the best one for today displays not only bones and tissues, but also blood vessels or the nervous system.
Types of tomography equipment
Initially, all types of diagnostic MRI devices can be divided into closed or, conversely, open. The first option is a horizontal ring-type pipe in shape, which is open only at two ends, from the legs and head.
There are open devices that are most often used for people who suffer from a fear of closed spaces and small children. The device is not closed on the sides.
MRI machines can be divided into 4 types according to the source of the magnetic field:
- superconducting;
- resistive;
- hybrid;
- constant.
Each type of MRI scanner has its own unique characteristics, advantages, disadvantages and is relevant for a particular diagnosis. An experienced technician must choose between a specific magnetic field source to obtain more accurate information.
The tomograph should be selected based on power depending on the organ being examined; the most common are 3 Tesla MRI devices
Power classification
Based on the tension between magnetic fields, medical tomographs can be divided into the following types:
- ultra-low;
- low-floor;
- mid-field;
- high-field;
- ultra-high-field.
Among MRI devices, mid-field devices are more common. As for devices with ultra-high fields, they can only be found in specialized research laboratories. It's all their fault high level power, which often exceeds the best option at 3 Tesla and is potentially dangerous.
As for low-field systems, they can only be found in medical institutions government type or with weak funding. Even the best unit of this class will not give the same result as a mid-field one. This is due to the low signal-to-noise ratio, which is why the process of examining and obtaining data is very long. Although such devices also have an advantage - a reduced number of contraindications for use. Therefore, only a specialist should decide which device is best to conduct the examination.
Which MRI machine is better: open or closed?
It is impossible to clearly determine which MRI machine is better, closed or open type. As for the first resonance tomograph, it can be found more often in medical institutions. It has sufficient power, so it is relevant for conducting examinations of any type.
But such devices also have one drawback - the diameter of the annular part is approximately 70 cm, so such equipment is not suitable for people who are overweight; it is better for them to do MRI in open-type machines.
Such units are also not without advantages and are ideal for people with mental disorders(the same claustrophobia). Open tomograph. Adults who need an examination of a specific part of the body are also diagnosed there. In this case, there will be no unnecessary impact on other organs.
Which tomograph is better?
The purchase of an MRI machine must be approached with the utmost responsibility. When choosing a tomograph, you need to consider not only its cost, but also its technical functionality. First of all, you need to decide which types will be most relevant: open or closed type. Naturally, for installing the unit in a children's clinic, the first option would be better.
Don't forget about the power of the device. This selection criterion is very important, because it directly affects the quality of the resulting images. To diagnose serious illnesses, you need to look at more powerful units. However, in this case, the power of the device should not be higher than 3 Tesla; such devices are not used in clinical hospitals.
Based on the direction of the MRI, it is determined which device will do a better job of diagnosing a particular organ. A tomograph helps to identify serious pathologies and make the correct diagnosis at the initial stage. When choosing a specific device, it is very important not to make a mistake, because the final diagnostic result and many lives of patients depend on it, so it is better pay attention to the characteristics and power of the equipment:
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 in 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 1.5 Tesla 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 leaning towards purchasing 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. Absence appropriate measures precautions may result in costly damage and serious injury.
