week 8: contrast barium Flashcards
1
Q
what 4 things affects the contrast of an image
A
tissue density
tissue atomic number
thickness
exposure factors
2
Q
Barium solphate
A
- positive contrast
- will increase atomic number and density of tissue
- must be mixed with water, forming a suspension (must be mixed)
- insoluble
- used for GI tract
- Atomic =56
- barium toxic by itsen
3
Q
contradictions for BaSo4
A
- oesophagus/GI tract perforation
- colon obstruction
- recent rectum biopsy
- hypersensitivity
- previous reactions
- infants,
4
Q
WHat is thin barium/ used for?
A
- one part barium/ 1 part water
- entire GI tract
- speed depends on:
temp, (warm=yuck), consistency of it.
5
Q
what type of exposure we use with barium?
A
use high. to make use of comptom scattert.
this will penertrate barium and lower radiographic contrast
6
Q
what is thick barium/ used for?
A
3 part barium, 1 part water
- good for upper oesphagus (moves slower down GI tract)
- coats moucosal lining better.
7
Q
Water soluble (iodinated contrast)
A
- travels much faster then barium (good for delayed imaging)
- readily absorbed by peritoneal cavity if leaked
z= 53 - will change atomic number of tissue, but not phyical density (unlike barium)
8
Q
C02 as a contrast
A
- negative
- swallowed/rectum
- will reduce physical density/ atomic number of tissue (oposite to barium)
9
Q
what type of exposure do we use for iodianted contrast?
A
use lower KVp to make use of photoelectric effect.
10
Q
what is subject contrast
A
difference of attenuation by different structures.
contrast media can enhance subject contrast
