Medical Imaging Flashcards
What different types of medical imaging are there?
X-rays Ultrasound MRI CT PET Fluorscopy
Briefly explain X-ray.
Radiation goes through the body and hits a receiver on the other side. Some radiation is absorbed and some scatter. Scattered and absorbed radiation appear as lighter on the scans.
This means that more dense tissue appear lighter.
X-ray can go from anterior to posterior or posterior to anterior. Which is the favoured way?
Posterior to anterior. However this is not always possible if the patient is lying down and can’t get out of bed or rotate.
What are some advantages of X-ray?
It’s fast (2-3 minutes)
It is cheap
It shows dense tissue well
It uses low levels of radiation
What are some disadvantages of X-ray?
It doesn’t show soft tissue very well (less dense)
It only shows a picture in 2 dimensions
Briefly explain CT-scanning.
CT scanning uses X-ray. However it is rotating the X-ray to create a 3 dimensional picture.
In what plane is CT usually done?
In transverse plane. From the feet looking up.
What are some advantages of CT scanning?
It is still fairly fast (3-7 minutes)
It is fairly cheap but more expensive than X-ray
It shows a 3 dimensional picture
It shows dense tissue well
What are some disadvantages of CT scanning?
It shows soft tissue poorly
The patient is exposed to a lot of radiation.
Briefly explain fluoroscopy.
It is essentially an X-ray movie.
X-ray pictures are taking in rapid succession.
A contrast is introduce to a tissue to see how the flow of blood for example works in the tissue to see if there is for example a blockage.
“Shows the dynamic flow through a system in the body.”
Briefly explain PET scan.
Scanning done by nuclear medicine.
Radioactively labelled substance is injected. This is usually glucose.
Tissue that has a high glucose uptake appear brighter on the scan than other tissue. This is for example the brain but also tumours.
This is usually coupled with CT scan to make a 3D picture.
Briefly explain MRI.
Concerned with the spin of hydrogen ions.
This is normally random but in a MRI machine which is a powerful magnet the orientation of the spins pair up into half up and half down.
Some ions are not matched up together and point the same way instead, these are the important ones.
The MRI applies a radio frequency pulse which gives the unmatched ions energy so they flip the other way. When they flip back again they emit energy.
This energy is detected.
What is T1 and T2 concerning MRI?
T1 and T2 are two different images which you will always get when doing an MRI.
T1 is a black image
T2 is a white image
T1 and T2 show different tissues differently well.
What are some advantages with MRI?
Shows soft tissue very well
No radiation at all
3 dimensional
What are some disadvantages with MRI?
Expensive It takes a long time (30-45 min) It's noisy and can appear claustrophobic Shows bone poorly Cannot be used for some patients with metal implants
