Revision 36 for 'Mosaic attenuation pattern in lung'

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Mosaic attenuation pattern in lung

Mosaic attenuation is the description given to the appearance at CT where there is a patchwork of regions of differing attenuation.  It is a non-specific finding, which may be seen in any of the following:

Differentiating the cause

This term "mosaic attenuation" is non-specific, and best used where the differentiation between mosaic perfusion (or mosaic oliagemia) and ground-glass opacity cannot be confidently made.

However, ascertaining the underlying cause for mosaic attenuation is often possible on the basis of clinical information, combined with the assessment of other lung features on HRCT 2,5:

  1. peripheral vessels: if vessels in hypoattenuated regions of the lung are smaller than in the other regions, the pattern is due to mosaic perfusion (i.e. airways or vascular disease rather than ground-glass)
  2. central vessels: pulmonary hypertension, reflected as dilatation of the central pulmonary arteries, suggests a vascular cause
  3. small airways: the presence of abnormally dilated or thick walled airways in the relatively lucent lung confirms underlying airway disease, see small airways disease
  4. parenchymal changes: ground glass opacity is the likely cause for mosaic attenuation if other features of infiltrative disease are present, such as reticular opacities (i.e. crazy paving pattern) or nodules
  5. air trapping: refers to regions of lung which following expiration do not show the normal increase in attenuation, or show little change in cross-sectional area 5 (i.e. this is an expiratory HRCT finding); the presence of air trapping suggests airway disease

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