How Do MRI, PET and CAT Scans Work?

In the field of healthcare there have
been major advancements in medical imaging techniques. Their ability to
create visual representations of internal structures and organs of the
body allow these imaging techniques that have major clinical applications. Today,
we discuss three of the most commonly used imaging techniques: the MRI, CT scan
and the PET scan. This is Michael. Michael suffered a knee injury while playing
basketball last week. After an appointment with his doctor Michael
finds out he will be needing an MRI scan to determine if he needs surgery. Well what exactly is an MRI? An MRI which stands for magnetic resonance imaging is
a technique used to generate an image of one’s body non-invasively. When
undergoing an MRI scan a patient lies on a moveable bed which is surrounded by
the MRI scan and a circular magnet. Radio waves 10,000 to 30,000 times stronger
than the magnetic field of Earth are sent through the body. As we all know, our
bodies are mainly composed of water which contain hydrogen atoms these waves
cause the nuclei of the atoms to change position. As the nuclei move back into
their original positions they emit their own radio waves which the scanner picks
up and ultimately turns into a picture that is seen on a computer. For the most
part this procedure is painless and risk-free. It should be noted that
pregnant women or anyone with a pacemaker or any sort of metal implant
cannot do an MRI scan due to its powerful magnetic force. After finishing
his MRI scan Michael meets Sarah who just underwent a
CT scan for her severe abdominal pain. A computerized tomography scan produces
detailed images of the body mainly through the use of x-rays. Several beams
of x-rays all from different angles are sent through the body during a CT scan.
Each angle provides a picture of a thin slice of the area being analyzed. The
data is saved on a computer which takes these two-dimensional pictures and
creates a 3d cross-sectional picture of the area. In some CT scans a dye called
contrast material is taken by the patient through injection, solution or inserted rectally. This dye makes structures and organs
easier to see on the pictures. Because of the extreme accuracy and detail of these
pictures CT scans are used for a myriad of the body’s internal situations
including internal injuries from trauma, muscle and bone disorders, detecting lung and liver diseases, and also detecting different types of cancer. CT scans
provide advantages in comparison to an MRI scan as they provide higher
resolution pictures, however they do pose some risks as well. The ionizing
radiation from the x-rays has been linked to increased risk of cancer,
although it is a low possibility. The most common risk of CT scans is a
reaction to the contrast material which is generally mild and results in hives
or itchiness. Similar to MRIs, pregnant women should not undergo CT scans in
order to avoid radiation exposure to the fetus. Finally, meet Claire. Claire has a
history of coronary artery disease so her doctor advises her to undergo a PET
scan. A Positron Emission Tomography scan is performed by using a special dye that
has radioactive tracers. The patient injects this tracer and it is
subsequently absorbed by organs and tissues in the body. The PET scanner can
highlight these traces and see how well organs and tissues are performing. PET
scans can therefore measure blood flow, oxygen use, and glucose metabolism. A
major difference between PET scans and the two previous scans is the ability of a
PET scan to show problems and complications at a cellular level.
The resolution might not be as clear as an MRI or CT scan, however, it gathers
more functional information. To prepare for a PET scan, the patient must notify
their doctor about any medical conditions and if they are pregnant. In
some instances it is advised that the patient does not eat for 8 hours prior
to the scan. Risks associated with a PET scanner similar to those of a CT scan
including exposure to radiation and allergic reactions to the injected tracer. The MRI, CT scan, and PET scan are three of the most commonly used
techniques for medical imaging. We learned the benefits associated with
each, such as the high-resolution provided by the CT scan or the
functional information given by the PET scan. Furthermore, we also learned about
the disadvantages and risks associated with these scans such as the possibility
of an allergic reaction to the tracers in a PET scan or the exposure to high
radiation in CT scans. In conclusion, the benefits outweigh the risks in all three
of these scans as they provide essential information for patients and healthcare
providers in need of help. Thank you for watching! you

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18 Responses

  1. Dandon Family says:

    I was pregnant in 2014, and I did MRI scan for my little boy inside me.

  2. D M says:

    MRI is safe for pregnancy

  3. zun netor says:

    your music background like noise !

  4. Medium Approach Medium Productions says:

    did they seriously use goanimate

  5. AIRMAN BEAR says:


  6. Eric Yates says:

    man u this aint helping

  7. aci12lin says:

    In this video an allergic reaction to the PET-tracer is mentioned. After 6 years in nuclear medicine I never have seen any reaction to a PET-Tracer. Why? In most cases we use Glucose (FDG-PET) – there is no life without Glucose so allergy is reasonably uncommon. Usually the amounts of substance we need for Imaging are are far below the amounts  to induce an allergic reaction. E.g. to perform a radioablation of the thyroid gland after oncologic resection  we need at max twice the physiologic amount of iodine which is deliverd with normal eating every day . So if someone suffers from the most horrific anaphylaxis against iodine, we still are on the safe side to perform therapy without even thinkin about anaphylaxis. The normal Ingestion of iodine per day in salt should be roughly around 200 micrograms (depending on iodination of salt by authorities). In case of proven anaphylaxis a factor of around 1000 times more of iodine than internationally used for radioablation has been administered (contrast agent, amiodarone). So there are no reports of anaphylaxis in radioablation with iodine131. Still we ask our radiophycicists to calculate the absorbed dose.

  8. Fizz Whizz says:

    It would have been helpful to have someone who speaks clearly or at least not use background music as I had to replay some parts over again to try to decipher what was being said.

  9. giorgosntoulos2 says:

    Voxels why can't we reduce the size to 10^-50 yoctometres or something really small like 1 pm, which is less than Helium radius. In order to maximise spatial resolution
    I get that Intensity given and the intensity received will differ very little but why would that make the computer calculate the attenuation factor wrong?
    Unless we make the size 0 could the equation not be solved?

  10. Cathy Bobathy says:

    MRI does not use dangerous ionizing radiation(xrays) like PET and CAT scans. All xrays are extremely dangerous.

  11. AdminOf Bootikeman says: nice information here

  12. N1k says:

    0:54 radiowaves in MRI aren´t 10,000-30,000 times stronger than the magnetic field of earth. They only have a magnitude of 10^-4 tesla, which is around two times stronger than the magnetic field of earth. You confused the static magnetic field B_0 (this one is more than 10,000 times stronger) with the time dependend magnetic field B_1 which is in the frequency domain of radiowaves.

  13. RaMed Education says:

    what is cat scan ??
    they didnt talk about it

  14. Aisha VP says:

    Just for clarification. According to Neurology Book (Adams and Victor's Principles of Neurology), a study shows that there were no discernible adverse effects found on fetus.

  15. Mahdi Abu AL-Saud says:

    It’s a good video but unfortunately many mistakes were said for each type of those imaging modalities.

  16. John Klein says:

    There are implanted metal devices that can be compatible with MRI use, now.

  17. Róbert Dan says:

    But what is SPECT scan?

  18. stickvortex says:

    Why does the narrator sound like his dog died this morning?

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