Imaging of the Abdomen 1 Flashcards
What does the absorption of an x-ray beam in tissue depend on?
The thickness of the tissue, the density of the tissue and the atomic number of the tissue
What is the order of structures in the body from least absorptive to most absorptive?
Air, fat, soft tissue, bone
What is the atomic number of some different elements in the body?
hydrogen -1, carbon - 6, oxygen - 8, calcium -20, tin - 50
To what power does the atomic number influence absorption?
to the 4th power
How does introducing a contrast medium change an x-ray?
makes the structure more opaque
What contrast medium is used to look at the bowels?
A barium meal or enema
What is an endoscopic retrograde cholangio-pancreatography?
A contrast to look at the bile and pancreatic ducts
What is a percutaneous transhepatic cholangiography?
A needle of contrast injected into the bile duct
Why do the kidneys look more opaque with an iodine intravascular contrast medium?
Because the kidneys concentrate the contrast
What is an angiography?
An intra-arterial contrast
What is an intravenous contrast with biliary excretion?
Where the contrast is tagged with something similar to bilirubin so is excreted by the liver - used to see the gall bladder and bile duct
What is the hounsfield scale?
A scale to quantitatively describe radiodensity
What is radioisotope imaging?
Where radioisotopes are attached to particular molecules and introduced to the body and then emit gamma rays which are picked up by a camera
Why is a gel required in ultrasound?
To exclude air
What is the doppler effect?
A change in frequency when there is relative movement between source of wave and observer of wave - allows you to look at blood flow in an ultra sound
