Principles of radiographic interpretation Flashcards
How do different body tissues appear on a radiograph?
Air = black Fat = dark grey Soft tissue/fluid = grey Mineral (bone) = light grey Metal = white
Apparent opacity of a tissue depends on which 3 factors?
Atomic number
Physical density
Thickness
Radiographs are systematically evaluated according to which 5 radiographic signs?
- Number
- Size
- Shape
- Location
- Opacity
What are the steps involved in interpreting a radiograph?
- deviation from normal appearance recognised
- lesions described in a systematic fashion
- formulation of differential diagnosis
How must the completeness/quality of a study be assessed before diagnosis?
- Ensure study is of correct patient and required regions are imaged
- Ensure study is complete (two orthogonal views)
- Identify views and check labelling
- Assess technical quality of image
What factors can change the quality of the image?
- Exposure
- Collimation
- Positioning
- Contrast
- Artefacts/errors
How should shape be described when analysing a radiograph?
- Overall shape (nodule, multilobulated…)
- Shape of margins (regular/irregular)
- Definition of margins (well marginated, poorly circumscribed…)
- Overall shape of lesion
How should location be described when analysing a radiograph?
- Need to use anatomical landmarks if possible
- Can be more general (“cranioventral thorax”) or relate to other structures (“ventral to the left kidney”)
- As well as simply documenting location important to anatomically localise
- Sometimes location itself is the primary abnormality
What is sclerosis?
Increased opacity
What is lucency?
Decreased opacity
Soft tissue nodules must be at least what size to appear on a radiograph?
at least 4mm
If a soft tissue nodules is less than 4mm in size how does it appear?
As mineralisation
What can act as a contrast opacity?
Gas
- e.g. placing gas inside the bladder to see it more clearly
What is the mass effect?
If something changes in size its going to have an effect on the surrounding tissues – displacement of other structures
What is effacement?
- Loss of normal contrasting opacity and so borders are lost
- Ability to see structures is lost/weakened
