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)
Why would you take a plain radiograph before completing a contrast one?
o Assess adequate technique o Contrast media contra-indicated? o May give a diagnosis o Assess patient preparation o Decide on suitable technique o Compare with subsequent films
Give 4 advantages of CT/MRI
o Avoid superimposition
o Superior contrast/soft tissue detail compared to radiography
o Superior to radiography and ultrasonography for some conditions
o Very useful for surgical planning (e.g. oncology)
Give 4 disadvantages of CT/MRI
o Radiography and ultrasonography may be more efficient
o Long periods of restraint needed (particularly with MRI)
o Cost
o Availability
Give three locations that can be imaged using CT
Nasal cavity
Middle ear
Thoracic and abdominal masses
Give three locations that can be imaged using MRI
Nervous system
Middle Ear
Soft tissue masses e.g. in the brain
Describe the purpose of a radiological report
• Sufficient to enable someone else to be able to look at the radiograph and understand what you are talking about, without you being present to point it out
Describe the process of a radiological report
- Focus on important points
- Use Radiographic (Roentgen) signs for accurate descriptions
- Structures considered normal should be mentioned to confirm they have been evaluated
- All abnormalities listed and prioritised in terms of likely significance
- Differential diagnoses ordered in terms of likelihood
- Consider further diagnostic tests necessary
- Follow the standard format
- Be systematic and try not to jump to conclusions or miss out stages
- Be succinct and concentrate on most significant information
Describe a technical assessment of a radiograph
– Whole point of this is to decide if the image is good enough to use for diagnosis; so need to specify this!
– Comment on aspects which are poor enough to affect quality and interpretation (don’t be overly critical)
Describe an image assessment of a radiograph
– Concentrate on the abnormalities - use Radiographic (Roentgen) signs to describe
– Don’t let your clinical suspicion affect your observations!!
– Comment briefly on normal anatomy
– If you are struggling to work out what is happening, start by simply describing what you see
– Beware the effect of superimposition (e.g. pulmonary blood vessels crossing ribs vs. lung nodules; kidney overlap vs. additional structure)
– How visible is the border of the structure being evaluated?
Describe the conclusion of a radiological report
– Summarise all your observations from all the images before producing your differentials / diagnosis
– Diagnosis/differential diagnosis
– These should lead on from your conclusions
– List in order of likelihood
– Don’t include those that you can eliminate as a result of your study
