The maintenance of more powerful magnets is expensive, so the passage of an MRI of 3 T is much more expensive. However, when the issue of health is acute, many patients prefer the more expensive option, so as not to go through the entire operation of receiving a tomogram twice.
At the same time, they save their money, because it’s cheaper to go through one expensive procedure than one cheap and one expensive one.
The high power of the magnetic field allows you to get the most informative tomography of human organs, on which it is possible to detect formations and abnormalities that an MRI of 1.5 Tesla could simply miss. In other words, the resolution of MRI devices directly depends on the power of the magnetic field that they are capable of creating.
The time of exposure to a magnetic field on a person is also reduced. If at 1.5 T, the length of stay inside the MRI apparatus is on average 20-30 minutes, then on an MRI with a capacity of 3 T the same procedure will take no more than 10-15 minutes. This is very important if the patient is a small child who cannot be forced to lie still for almost half an hour or an elderly person for whom staying in a fixed position for a long time is a real punishment.
In the 1980s, a large-scale study was conducted by a number of oncologists aimed at identifying the general trend in the development of cancer. To their horror, they found that over the past few years (meaning the 80s of the 20th century), the number of people with a terrible diagnosis of cancer has grown rapidly.
Naturally, the grumbling of opponents of global industrialization immediately rose, which blamed this dubious “merit” on the general deterioration of the environmental situation in the world.
But there were sensible people, mainly from the world of medicine, who directly pointed out the rapid development of methods for detecting oncology. Not the least role in this was played by the method of magnetic resonance imaging, whose appearance occurred precisely in this period of time.
Power 1.5
The first samples of MRI devices had a capacity of only a few thousandths of a ton (up to 0.005 Tesla), which did not always allow making high-quality images. As a working element, they used permanent magnets, unable to create a sufficiently strong magnetic field. However, the development of progress does not stand still and high-field devices with a capacity of up to 1.5 T have already appeared, in which electromagnets have already played the role of the workhorse.
Power 3
It seems that it was time to stop at that, the limit has been reached and further increase in power does not make sense. But no, capricious doctors and no less inquisitive scientists sought to obtain more powerful devices that would use electromagnets with superconducting conductors immersed in liquid helium. Therefore, devices began to appear with ultra-high magnetic field strengths of up to 3 Tesla, or even higher. Such an effort to increase power is explained that the principle underlying MRI is used not only in medicine, but also in other fields of science.
General characteristics
In general, the method of magnetic resonance imaging has a rather long history, and on its way from an idea to an embodiment it has come a few decades and several Nobel Prizes.
The method itself is more correctly called NMR – nuclear magnetic resonance, but due to the widespread fear of everything connected with the word “nuclear”, the term has been replaced by another.
So what is the essence of this method?
Each atom consists of a nucleus and electrons rotating around it. In turn, the nucleus consists of protons with a positive electric charge and neutrons that do not have an electric charge. Thus, in general, an atom has an electric charge, and if we take into account its rotation, then it has an alternating magnetic field (though only those atoms with an odd number of protons and neutrons). For ease of perception, imagine this atom in the form of a charged ball that rotates very quickly around its axis.
Now, if you act on this ball with a very powerful magnetic field, then the ball will begin to swing and its axis of rotation will begin to describe the circle (remember the children’s top). This means that the ball absorbs the energy of an external magnetic field, moving to a higher energy level. But such a resonance will be observed only when the magnetic fields of the atoms and the external magnet coincide.
When atoms transition to their previous state, the energy is released again, a kind of “surge” is observed on the recording devices.
Modern MRI devices create powerful magnetic pulses that act on the most common atom – hydrogen. The content of hydrogen atoms in human tissues is not the same, therefore, the magnetic field generated by the action of an external field will also be inhomogeneous.
By the way, the unit of magnetic field strength is called “Tesla” and is named after the genius Serbian scientist Nikola Tesla. But not in honor of the car manufactured by businessman Ilon Mask.
Areas of use
Among the main advantages of the MRI method from others, three can be distinguished:
- Non invasiveness. It is not necessary to carry out complex operations to obtain information about the internal structure of a person and the state of his internal organs.
- Security. MRI can be prescribed even for pregnant women, this method is so safe. In this case, there are absolutely no side effects.
- Informational content. That case when the patient “in full view.” Indeed, few other diagnostic methods can argue with MRI in the visibility of the information provided.
Of course, the high cost of the procedure imposes its limitations and referral to MRI is given by a doctor only in strictly specified cases. In the end, this is still not a blood test, although its availability could significantly increase the diagnosis of diseases that are almost asymptomatic.
As mentioned above, an MRI of 3 T is prescribed in cases where it is necessary to diagnose the patient as accurately as possible, in the remaining cases, the scanning procedure is performed on devices of 1.5 T or lower.
