Radiographic contrast

Radiographic contrast is the difference in image appearance between adjacent areas. In a radiograph, it helps make a change in material thickness, composition or internal condition distinguishable from its surroundings.

What it means in an examination

Image contrast alone does not establish whether an examination can reveal the required discontinuity. Spatial resolution, noise, geometry, exposure conditions and viewing conditions also affect interpretation. A strongly contrasted image can still fail to show a small or unfavourably oriented discontinuity.

Important distinctions

Keep object contrast separate from the contrast produced by the film or digital imaging system and its display. Digital windowing can change how an image looks; it does not recreate information that was never captured. Evaluate the image using the procedure and the required image-quality evidence, rather than visual attractiveness.

Using the term correctly

For an actual examination, record the technique and retain the relevant image-quality checks with the image. The responsible interpreter applies the specified acceptance criteria. Contrast is an image characteristic, not an acceptance limit by itself.

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