Lecture 7 - Diagnostic Imaging Flashcards
What are the 3 principles behind X-rays?
- Electromagnetic waves of short wavelength (photons) are capable of penetrating some thickness of matter
- As X-rays pass through the body they are attenuated by the tissues (the denser the tissue, the more attenuation)
- As X-rays pass through the tissues, they interact with the photographic film behind the body
Magnitude of X-ray wavelengths?
10^(-10) m
In what way do X-rays exit the machine?
They flare out (diverge)
How can we interpret the colors on X-rays?
- Less dense: more black because X-rays can easily get to the photographic film
- More dense: more white because X-rays cannot get through to the photographic film
List air, fat, bone, and water in order of X-ray attenuation.
- Air
- Fat
- Water
- Bone
What is the most often broken bone in the body?
Clavicle
What is the hardest bone to break in the body?
Femur
How to describe subject placement in radiography?
First the side receiving the rays first
Then the side next to the film
Where do you put the part of the body you want to see in radiography? Why?
Closest to the photography film so that it does NOT appear larger because the X-rays diverge as they come out (you want a better representation of the organ)
What are the 2 types of X-ray positioning?
- AP = anterior posterior
2. PA = posterior anterior
How to see structures on an X-ray that are normally not dense enough to show up?
Fill them with contrast agents that will attenuate X-rays more than usual
What contrasting agent should you use to see bowels?
Barium sulfate
What is important to ensure when using contrast agents?
That they are non-toxic
What are the 2 ways of administering barium sulfate? How to pick between the two?
- Oral: to see foregut and midgut
2. Enema: to see large intestine and hindgut
What contrasting agent should you use to see arteries and veins?
Iodine
How is iodine cleared by the body?
Kidneys
When is subtraction angiography used?
When the vessels you are trying to see are around bones or other dense structures
How does subtraction angiography work?
- Images are obtained before the injection of the media
- Contrast is injected and new images are obtained of the vessels
- First set of images are subtracted from the second, producing a solitary image of contrast only