23 - Contrast Media in Radiology Flashcards
What is contrast media used for?
Helps in better differentiation of tissues
What is the difference between a positive and negative contrast medium? Give some examples.
Positive - high density (high attenuation) - e.g. barium, iodine and gadolinium
Negative - low density (usually gases) - e.g. air, CO2 and water
What are the ideal properties of contrast media?
- Low osmolality and viscosity
- High water solubility
- Biologically inert
- Safe
- Heat and chemical stability
- Cost effective
By what methods can a contrast medium be administered?
- Oral
- Rectal
- IV
- Intra-articular (IA) - into a joint cavity
- Filling a space or cavity (e.g. bladder, intrathecal space, gall bladder etc.)
How are contrast media excreted?
- Glomerular filtration (95%)
- Half-life is 30-60 mins
Before giving contrast media, what should always be checked to ensure it is safe to do so?
Kidney function
Good kidney function is required so excrete the contrast media by glomerular filtration.
What are some common side effects of contrast media?
- Reactions due to osmolality
- Endothelial damage
- Thrombosis or thrombophlebitis (thrombosis due to inflammation)
- Vasodilation
- Vascular pain
How long after administering a contrast medium would you start to see any unusual side effects (idiosyncratic reactions)?
Within 20 minutes
Delayed reactions to contrast media can take longer to manifest. How long after having contrast media could a patient experience side effects?
30 minutes to 7 days.
What are the different projections that can be used for a chest X-ray?
- PA (most common)
- AP
- Lateral
