Principles of radiological interpretation Flashcards
What is radiographic conrast media?
Media that is administered to the patient and is either more radioopaque or radiolucent than the surrounding tissue.
What 5 things does contrast media provide?
- shape
- size
- position
- internal structure
- sometimes function
What appearance do negative contrasts have?
Radiolucent appearance –> low radiographic opacity e.g. air and gases
What appearance do positive contrasts have?
Radiopaque appearance e.g. barium, meglumine, iohexol, diatrozoate. This type of media has a high atomic number.
What is a downfallof contrast media?
Can have adverse effects.
What are the 7 properties of ideal contrast agents?
- differ from tissue under examination in terms of ability to absorb x-rays
- non-irritant, non-toxic
- accurately delineate the body part being examined
- persist for the duration of the study
- be totally eliminated afterwards
- be easily administered
- be cost effective.
What do you always need to do before taking a contrast radiograph?
Take a plain (survey) radiograph first.
What is another rule in terms of taking images when using contrast?
Need to take enough images!
1. need to take 4 images, one in each plane of the body e.g RLR, LLR, VD and DV
Is it worth taking another image after the contrast has left the animal?
Yes, because the contrast might be stuck in something that was previously missed.
where are negative contrast agents most commonly used?
In the bladder and GIT.
What is a double contrast study?
It is when a negative contrast agent is used with a positive contrast agent
what are the advantages of using negative contrast study?
It is cheap, quick and convenient.
It is also relatively safe.
What is a benefit of using double contrast study, what does it enable us to see?
Gives good margins.
What are three disadvantages of using negative contrast alone?
- poor mucosal detail if used alone
- air will be slowly eliminated from the body and therefore will confuse later studies.
- chance of air embolus in the blood - safer to use carbon dioxide as more soluble.
why is carbon dioxide safer to use?
Because it is more soluble therefore less likely to form an embolus.
What is an example when you would use barium sulphate studies?
GI contrast studies.
Name 5 advantages of using barium sulphate?
- low toxicity
- inert
- excellent MUCOSAL DETAIL
- may be therapeutic
- relatively cheap
How is barium sulphate administered?
As a suspension, paste, or mixed with food
What are the two disadvantages of using barium sulphate?
- careful with aspiration (do not administer under GA)
2. becomes quite an irritant if enters body cavities therefore need to be careful with suspected perforations!
Name 8 reasons for using a water soluble iodine preparation?
- myelography
- Cardiovascular system
- urinary tract
- joints
- salivary glands
- tear ducts
- fistulas/ sinuses
- GIT
What are the two types of water soluble iodine preparations?
- Ionic
2. Non-ionic
How is ionic administered?
Suitable for IV or direct administration (but NOT myelography) e.g. meglumine diatrozoate
How is non-ionic administered?
Suitable for myelography and any other use e.g. iohexol.
Which type of water soluble iodine preparations are recommended and why?
non-ionic as fewer side-effects.