magnetic resonance scan MRI

Magnetic resonance scans: a medical miracle

Neurology @en

We have all probably seen news stories with titles like: this is how your brain looks when meditating. Or: this is your brain in love. It almost seems like soon, magnetic resonance scans will be able to read our thoughts.

This type of brain scan is called a“functional” MRI scan, which is a newer type of the basic MRI scan. The main purpose of the basic MRI scan is to look for structural problems in the brain or other parts of the body. They are especially useful when looking for tumors. When you understand a little bit about how the MRI works, you will see that this technology is a medical miracle, and why this technology won the Nobel Prize.

The first MRI scan was done in 1977. Then, the machines were painfully slow and prohibitively expensive. But now, MRI machines are much faster and less expensive. They are standard equipment in most hospitals. An MRI scan basically takes pictures based on the actual atoms in our tissues! After taking these pictures, sophisticated computer software assembles the pictures into the amazing 3D images.

How a magnetic resonance scan is made

The MRI machine itself is basically 2 large magnets, cooled to a very low temperature to work properly. A current is passed through the magnets, and a strong force is created, so strong that it realigns the very atoms in our tissues. One magnet aligns the atoms in one direction, then the other magnet sends a signal in the opposite direction to allow the atoms to fall back to their normal position.

Different tissues have atoms that react in different ways as they re-align from the magnetic forces. For example, the atoms in fat cells react different than the atoms in muscle cells, and the atoms in a tumor react differently than the tissues surrounding the tumor. It is this difference that shows up on the individual pictures, or “slices” that are taken during the scan. The software then analyzes this information and reconstructs the images we see.

It might sound scary that these magnets temporarily move our atoms. But fortunately, this has not been shown to cause any physical damage. The atoms all fall back into their original position. Note that an MRI scan is a much different than a computerized tomography (CT) scan.

Magnetic resonance scan vs. CT scan

A CT scanner also takes multiple images, which are reconstructed later by the computer, but the main difference is that CT scanners use standard Xrays instead of moving our atoms with magnetic forces. An advantage of the MRI scan (compared with the CT scan), is that MRI scans do not expose us to the sort of radiation that could lead to burns, or other problems.

A person that undergoes many many CT scans may have an increased risk of developing a cancer from all the Xray exposure, but that’s not a risk with an MRI scan. Another advantage of the MRI scan is that the images created are typically clearer and more detailed.

Magnetic resonance scan disadvantages

But MRI scanning is not perfect. MRI equipment is much more expensive than a CT machine, and the MRI scan takes longer to perform. Also, most MRI machines require the person to enter a rather confined tube, which may be problematic for the person with claustrophobia. Further, because the MRI scan uses strong magnets, a person who has metallic implants may not be able to undergo an MRI, since the magnets will pull on the metal.

Newer MRI scans machines are less confining, and there are now techniques so that most people with metallic implants can undergo scans.

The MRI scan is truly a medical miracle that has revolutionized doctor’s diagnostic abilities. In our next post we will explain how a “functional” MRI scan is different, and about the controversy that has erupted in the medical community about these scans. Stay tuned.

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Read also in ProcuraMed:

What you should know about CT scans

Esta postagem também está disponível em: Portuguese (Brazil)

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