Radiological Interpretation Flashcards
Define contrast media
• Substances which are administered to the patient which are either more radiopaque or more radiolucent than the surrounding tissue.
How can contrast media improve radiographic imaging?
• Provide detail of organ size, shape, position, internal detail and sometimes function
Describe negative contrast (include examples and where it is most commonly used)
• Negative contrast media have a low physical density low radiographic opacity
– Radiolucent appearance on radiographs
– e.g. air, gases
– Mostly used in the bladder and GI tract
Give 2 advantages of negative contrast use
- Cheap, quick and convenient
* Relatively safe
Give three disadvantages of negative contrast studies
- Poor mucosal detail if used alone
- Air slowly eliminated from the body (may confuse later studies)
- Theoretical risk of air embolus in blood stream (C02 is more soluble and therefore safer)
Describe positive contrast (include examples )
• Positive contrast media have a high atomic number high radiographic opacity
– Radiopaque appearance on radiographs
– E.g. barium, meglumine diatrozoate, iohexol
Describe the use of barium sulphate as a contrast medium
- Used for GI contrast studies
* Administer as suspension, paste or mixed with food
Give advantages of using barium sulphate as a contrast medium
• Advantages: Low toxicity, Inert, Excellent mucosal detail, May be therapeutic, Relatively cheap
Give disadvantages of using barium sulphate as a contrast medium
• Disadvantages: Care with aspiration (NOT under GA), Irritant if enters body cavities – care with suspected perforation
Describe the use of Water soluble iodine as a contrast medium (include types and where they are used)
- Imaging of cardiovascular system, urinary tract, joints, salivary glands, tear ducts, fistulas/sinuses, gastrointestinal tract, myelography
- Types:
- Ionic: suitable for IV or direct administration (but NOT myleography) e.g. meglumine diatrozoate (can interfere with the nervous system)
- Non-ionic: suitable for myelography and any other use – e.g. iohexol. Recommended for all applications as fewer side effects. Gastro-intestinal preparations – specifically for GI studies
Give an advantage of using water soluble iodine as a contrast medium
Versatile – can be injected IV or directly administered, Rapidly absorbed if leak into body cavities
Give disadvantages of using water soluble iodine as a contrast medium
- Hyperosmolar (ionic) unpleasant side effects if conscious (nausea, vomiting, etc.)
- Irritant if injected perivascularly (ionic)
- Large doses of iodine are toxic
- Contra-indicated IV in hypovolaemia, hypotension and cardiac or severe renal failure (stabilise first)
- Rarely may cause iodine-induced acute renal failure
Define Positive contrast cystography
– Positive contrast cystography (infusion of positive contrast into bladder)
Define Pheumocystography
– Pneumocystography (infusion of air into bladder)
Define double contrast cystography
– Double contrast cystography (infusion of positive contrast followed by air into bladder)