Radiography Flashcards
(21 cards)
What are the roentgen signs?
Number Location Size Shape Margination Radiopacity (Internal architecture) (function)
When can you not GA a patient for radiographs?
If you are doing an oral barium contrast study
How can you decrease movement blur?
Increase mA and decrease the exposure time
How can you tell if an image is perpendicular?
The caudodorsal rib heads will be superimposed
How many unexposed boarders should a cassette have?
4
This is described as 0/25/50/75/100% of each 4 borders)
How do grids work?
Consist of strips of plastic and lead that filter out x-ray photons that are not passing in a straight line
This reduced the scattered radiation reading the x-ray cassette
When should you use a grid?
Body regions greater than 10-15cm thick
What must you compensate with when using a grid?
The grid absorbs a proportion the primary beam so you must increase the exposure (higher mA’s) This is defined as the ‘grid factor’ and can be x2 or x3
What do negative contrast media look like?
Low density - low radiographic opacity so have a radiolucent appearance eg. gas
What do positive contrast media look like?
high density - high radiographic opacity so have a radiopaque appearance eg. barium
Before doing a contrast study what should you do first?
Take enough plain radiographs
Where are negative contract medias used?
Mostly used in the bladder and GI tract
What are the advantages and disadvantages of negative contrast media?
A: cheap, quick and convenient. Relatively safe
D: Poor mucosal detail, Slowly eliminated from the body (can confuse further studies) , theoretical risk of air embolus (Co2 is more soluble and therefore safer)
Where is barium sulphate used in contrast studies?
GI tract administered as a paste or mixed with food
What are the advantages and disadvantages of barium sulphate as a contract media?
A: Low toxicity, inert, excellent mucosal details, relatively cheap
D: care with aspiration (not use under GA), Irritant if it enters the body cavity (don’t use if suspect perforation
When are water soluble iodine preparations used as contrast media?
Imagine the CVS, urinary tract, joints, salivary glands, tear ducts, sinuses, Gi tract and myelography
What are the types of water-soluble iodine contrast media available?
Ionic: suitable for IV but not myelography
Non-ionic: Suitable for myelography and any other use (reccomened as it has fewer side effects)
GI preparations
What are the advantages and disadvantages of water soluble iodine preparations as a contract media?
A: Versatile and rapidly absorbed if it leaks into body cavities
D: Hyperosmolar (unpleasant side effects if conscious eg. nausea/vomiting), Irritant if injected perivascularly, large does are toxic, contraindicated Iv if the patient is hypovolaemic/hypotension and cardiac or renal failure
What are the A&D of CT and MRI?
A: avoids superimposition, good for surgical planning
D: animal needs restraint for long periods of time and costly
Where is CT appropriate?
NAsal cavities Middle ear Some joints Pharynx, lungs Thoracic and abdominal masses
Where is MRI appropriate?
Nervous system
Middle ear
Soft tissue masses
