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The most powerful MRI scanners in the world and what is right for us in the future in the field

About twenty subjects experienced an MRI 5 times stronger than the ones available today in Minneapolis. Ofer Ben Hurin explains why this is a breakthrough

The most powerful MRI device in the world. PR photo
The most powerful MRI machine in the world in Minneapolis. PR photo

About a year ago, after four years of animal experiments, Adam entered Al Research Center in Minneapolis, Minnesota in the United States, headed by the director of the center, Kamil Ugurbil, in order to perform an MRI to test the cartilage of the hip joint in the most powerful MRI scanner that exists today in the world - with a power of 10.5 Tesla. This scanner, which was built at a cost of about 14 million dollars, weighs 3 times as much as a Boeing plane, the tunnel is 4 meters long, surrounded by 110 tons of magnet and 600 tons of iron protecting the magnet. This is the first subject among the twenty subjects approved to perform an MRI scan with this magnet.

The most common scanners in the world today are scanners with strengths of 1.5 or 3 stella. There are research scanners with powers of 7 Tesla (the first went into operation in 1999) and in the last year 7 Tesla scanners were approved for clinical use in the United States and Europe.

 

the scannersMRI The strongest in the world

 

In the world today there are three MRI scanners that pass the 10 Tesla. The first is, as written, the University of Minnesota scanner with a power of 10.5 Tesla. The other two scanners have a power of 11.7 Tesla - the first one is a huge scanner for the whole body at the NeuroSpin Center At CEA Saclay which is outside Paris. The other scanner is a smaller scanner for brain scans only located at the US National Institutes of Health (NIH) in Bethesda, Maryland. These days, Germany, China and South Korea, each on their own, are considering building human scanners with powers of 14 Tesla.

The reason there is a lot of competition to build large scanners is to get larger field strengths. The greater the strength of the magnetic field, the greater the signal-to-noise ratio and thus you can get a better quality image, with a higher resolution, or the same image as you get today - only much faster. MRI scanners with a power of 3 tesla can sample the brain at the level of one millimeter. With a 7 Tesla scanner, it is already possible to reach half a millimeter - which is already enough to demonstrate a functional unit within the cortex and perhaps see, for the first time, how information flows between the clusters of neurons in the brain.

The race to achieve higher field strengths poses a wide variety of challenges - the scanners are larger, more expensive and technically more demanding. They also require more safety attention. Despite all this, they lead to significant achievements, both in the field of neuroscience research and in clinical applications. Doctors can see much better where to place electrodes in the brain, detect diseases at an earlier stage and model the human brain in a way never seen before.

It is important to note that the basic idea of ​​the MRI has not changed since the mid-seventies. There is a tube-like conducting magnet, which produces a strong static electromagnetic field. As a result, a relative excess of hydrogen protons is created within the water molecules, which are in a state parallel to the magnet, and which are not canceled out by the hydrogen protons that are in a state antiparallel to the magnet. This excess is acted upon by radio pulses sent at a specific frequency (Larmor frequency), in order to tilt and oscillate those protons. When the radio pulse ends, the movement of these protons back to their normal state releases energy, some of which returns in the form of a faint echo, the magnetic resonance signal, which is picked up by receiver coils and thus the image of the anatomy of the brain and other tissues is presented. The stronger the magnetic field, the greater the excess of protons used in the magnetic resonance process, and the amount of energy between them and the protons in the other state increases - these enable a stronger magnetic resonance signal and then a better image quality.

 

Scanner advantages and disadvantages MRI have intensities of 7 tesla and above

 

The advantages of the T7 scanners are many, such as the ability to scientifically identify areas of the brain related to different mental functions, the better ability to map links between neurons in the brain (brain connectivity), the ability to more accurately insert electrodes for deep stimulation (a procedure used to treat, for example, Parkinson's patients ) without causing damage to blood vessels, better identification of pathologies in the brain, such as diagnosis of multiple sclerosis in its initial stages and more.

Another advantage that is important to note is that when it comes to scanners with strengths of 7 Tesla or higher, it is also possible to receive a magnetic resonance signal not only from hydrogen nuclei, but also from atomic nuclei of heavier elements (such as sodium, potassium, phosphorus and fluorine), which have a much lower internal sensitivity to resonance magnetic than hydrogen nuclei - this expands the possibilities of imaging and research to areas that we have not yet seen before (for example A study done at New York University Led by Gregory Chang, he demonstrated the ability to diagnose the amount of sodium with the help of a 7 Tesla scanner in people with osteoarthritis in very early stages and then it was possible to provide them with preventive treatment for the future).

From experiments that have been done, the transition from T3 scanners to T7 scanners causes side effects to the subjects, even if temporary, such as dizziness, a metallic taste in the mouth during the examination, flashes of white light in the eyes and involuntary eye movements called nystagmus. In addition to these, the danger of the subject's tissues heating up increases, so all kinds of tactics have been developed in order to facilitate this (such as the production of the pulses by transmitter rings around the patient that are adjusted separately). Another significant challenge in jumping to scanners with a higher Tesla is the matter of moving. Any small movement can damage the scan - for example, even stretching the toes can cause the brain to move because they are connected to it through the spinal cord - these disturbances damage the quality of the test and cause artifacts.

 

Scans over 7 Tesla

 

The most powerful MRI scanner in the world It sits in the US National High Magnetic Field Laboratory and has a power of 21.1 Tesla. The problem is that the diameter of his tunnel is about 10.5 centimeters, which makes it too small for use on humans. This is a research scanner that, for example, is used to test sodium in tumors in the brains of mice for the purposes of the effect of chemotherapy.

Scanners above 7 Tesla require many regulations and approvals, they are also more prone to malfunctions and problems. The scanner at the NeuroSpin Center in France with a power of 11.7 Tesla is expected to produce the first scans of a living human brain in 2022.

The scanner from Minnesota, with whom we opened the article, received approval from the US Food and Drug Administration in August 2017 to scan 20 people with his 10.5-T MRI (the subject last December was his first, after conducting experiments for 4 years on animals). He will perform his first human brain scan in 2019.

The images currently produced from it are nothing short of amazing, but right now scans with this field strength are at the point where researchers are not looking to answer biomedical questions, but are simply checking to see if the process has side effects.

The competition is in full swing, but of course there is a limit to how many Teslas you can reach without damaging your body. Some researchers have estimated that scanners operating above 14 Tesla can, in addition to excessive heating, cause the formation of nerve conduction, stimulate peripheral nerves or cause damage to DNA (although to date no such effects are seen in animals that have been scanned with very powerful scanners) - so that at the end of the competition will stop.

 

Bibliography and for further reading

 

An article about the MRI research center website in Minnesota, United States

The European scanner at the NeuroSpin Center at CEA Saclay outside Paris

The most powerful MRI scanner in the world - 21.1 Tesla

The world's strongest MRI machines are pushing human imaging to new limits

Reproducibility of subregional trabecular bone micro-architectural measures derived from 7-Tesla magnetic resonance images

 

 

7 תגובות

  1. Completely by chance, yesterday I had a conversation with a well-known doctor in his field who undergoes dozens of MRI examinations a day. The conversation was about the vulnerability of tiny blood vessels around half a millimeter in size. According to him, if all the best for the resolution even. A flat done under full anesthesia will not reduce the blurring resulting from tiny movements such as heartbeats and blood flow in the arteries, etc. How to overcome this is the question...

  2. Is it not possible to simply take several images in a normal MRI and then combine the images using algorithms to achieve high resolution?
    Maybe by machine learning and neural networks...

  3. Sabdarmish, the description of the prostheses finally finished me. magnificent!!
    The technique of hydrogen mobilization has not yet reached exhaustion, certainly not in biology in general, but it will not be far today that a medical application of the technology in humans will no longer be sufficient. We have been waiting since the seventies for the next field.

  4. from experience
    Even so, as we know, there are not enough MRI facilities in the country, so it is better to settle for smaller and cheaper MRIs. The existing strength already sticks the dentures to your smile so that a strength 4 times greater than the existing one may be problematic today. Also, in a person who has undergone surgery, metal pins may be found, which can be problematic in a high-power MRI. The excessive need to be motionless is also not a trivial matter. It is almost impossible to be motionless for half an hour or even an hour. I prefer the PET CT to the MRI tests. This is done faster and in my opinion the resulting photograph is more detailed. from experience.
    The main thing is that we be healthy.
    Yehuda

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