A of the human body.”[1] The inventor

 

A life without illness has always been one of the main
goal for the human species. At the start of our existence it was discovered
that natural remedies helped alleviate some of symptoms of various illnesses.
Naturally, as humans evolved so did our ways of medical treatments. While
medicine is inherently mostly a biological science the machinery used to
perform the tasks rely mostly on computer science and physics.

Physics has made major discoveries in the last
centuries that have made our lives unimaginably easier and safer. Modern
physics is the basis of MRI. “Magnetic
resonance imaging (MRI) is an imaging technique used primarily in medical
settings to produce high quality images of the inside of the human body.”1 The
inventor of the first MRI machine was Raymond Vahan Damadian. His studies about
living cells dove him to his first tries with NMR. Damadian found that tumors
and ordinary tissue can be discerned by the way their signals change with time.
This led him to propose the initial full body magnetic resonance scanner and he
was the first one to play out a full body scan in 1977.2
The first scan took about 5 hours to produce one image with was very elementary
compared to today’s scans.3 MRI
relies upon the benchmarks of nuclear magnetic resonance (NMR), a spectroscopic
system used by specialists to get physical information about particles. The procedure was called MRI rather
than nuclear magnetic resonance in light of the negative implications related
with the word nuclear in those years.4
The difference between MRI and the similar computer tomographic (CT) scans is
that MRI does not incorporate the usage of x-rays and thus is seen as the more
superior option. However, MRI’s compared to CT scans are much longer and
louder, anything metal has to be removed before entering the machine and this
may cause problems to people with pacemakers.5It
is also a very closed off device and for the patients that have claustrophobia
it is needed to use a different kind of “open” scanner.

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The way MRI works is that the scanner contains two
intense magnets, these are the most critical parts of the gear. The human body
is to a great extent made of water particles, which are contained hydrogen and
oxygen molecules. An atom is made out of electrons and a nucleus which consist
of protons and neutrons. Protons have a positive charge and because of that are
sensitive to magnetic fields. When performing the MRI scan a person is placed
inside the scanner which then creates a magnetic field around the body.
Normally the protons are scattered randomly across the body and do not follow
any kind of pattern but the when the magnet is turned on the protons strain to
re-align themselves either north or south. Then the magnet is shut down and
goes through the series again. The particles when going from an excited state
to their normal one emit radio waves. The scanner measure how the signals
change in time in the whole body and stores the information. Different types of
tissues have different response signals and as Raymond Vahan Damadian noticed
tumor tissue has a significantly different response signal than normal, healthy
tissue.

The MRI scan image is then processed and developed
with high (bright) to low (dark) signal parts. The image can be processed in
two different ways – T1-weighted or T2-weighted. The difference between them is
in the areas that have high signals. In a T1-weighted scan only the fat parts
would appear bright. That is what makes it very useful when scanning the brain.
In a T2-weighted scan the parts that would appear bright are fat and fluids.6
That makes it more useful when identifying inflammation. When needed toc create
a higher quality image contrasting liquids may be put in use. Usually they are
injected into the veins or straight into the joint in the event when making an
MRI of a joint.

As written before, the main component of the magnetic
resonance imaging scanner is the magnet. They come in various shapes although
the most reliable and popular one would be the C shaped magnet. It is usually a
permanent magnet made out of a ferromagnetic material, even though the most
common magnet used in today’s MRI machine would be the superconducting
electromagnet. It is the most expensive one but also the most reliable one with
the highest accuracy out of all of the possible choices. The main factor in the
magnet that determines the quality of the image scan is the magnetic field
strength. It is measured in teslas (T). 1-3 T would be considered a high
magnetic field MRI scanner and different strength are used for different parts
of the body. 7
Another important part of the scanner would be the shims. The magnetic field
created by a magnet is not useful by itself. It need to be completely stable
and the same all throughout the procedure. “A
shim is a thin and often tapered or wedged piece of material, used to fill
small gaps or spaces between objects8.”
When the subject is placed in the magnetic field it loses its homogeneity
and the shim coils restore it.

MRI technology is extremely useful is nowadays
medicine. It has marginally helped us understand the working of the brain and
helped us diagnose brain traumas more easily. It is a completely non-invasive
way to diagnose a tumor, abnormalities in the spinal cord, cysts and other
major illnesses. It has also provided
more insight into how various mental illnesses affect the brain. Functional
magnetic resonance imaging allows us to monitor the activity of neurons in
different brain sections, which then allows us to compare various brain scans
and see if there are any differences between patients with different diagnoses.
Researches have been interested in the physical symptoms of various mental
illnesses that cannot be seen outside our bodies. A new study in 2017 by the Radiological
Society of North America discovered a relation between the abnormalities of the
brain when suffering from major depressive disorder and social anxiety disorder
that might explain why those two illnesses often come hand-in-hand. 9

While as mentioned before, MRI scans are considered very
safe and reliable because of the fact that they do not expose people to
possibly harmful ionising radiation like CT scans do there are still some risks
that need to be taken into account. The scanner is essentially a huge and
extremely powerful magnet and it will attract anything metal to it, so a patient
needs to be screened thoroughly and the room should be checked thoroughly
before beginning the procedure to limit the risk of any metal objects becoming
projectiles. The procedure itself is extremely loud and combined with a person
being in a very small confined space can cause anxiety. This makes it very hard
to stay still during the procedure, which is vital for the image to develop
clearly. Some people with claustrophobia might have the option to use an open
MRI scanner but it cannot perform all the tasks a closed one can. In the case
where a patient is not able to stay still for the period of time needed or is
an infant sedation might be needed. This, of course, bring in another set of
risk that are not limited to MRI scanner but still might cause problems and
complications. Any patient with metal implants in their body or artificial
limbs will most likely not be able to go through the MRI procedure and will
have to look for an alternative method.10
All in all, while this is a evolutionally device that has made modern medicine
advance in an even faster pace it does come with its own, in comparison small,
disadvantages.

 

 

1 https://www.cis.rit.edu/htbooks/mri/inside.htm

2 https://armenianweekly.com/2013/11/07/2003-nobel-prize-for-mri-denied-to-raymond-vahan-damadian/

3 https://en.wikipedia.org/wiki/Raymond_Damadian

4 https://www.cis.rit.edu/htbooks/mri/inside.htm

5 https://en.wikipedia.org/wiki/CT_scan

6https://www.ole.bris.ac.uk/bbcswebdav/institution/Faculty%20of%20Health%20Sciences/MB%20ChB%20Medicine/Radiology/MRI%20e-tutorial/page_04.htm

7 http://www.teslasociety.com/mri.htm

8 http://www.merriam-webster.com/dictionary/shim

9 https://www.sciencedaily.com/releases/2017/11/171120085448.htm

10 https://www.medicinenet.com/mri_scan/article.htm