Mosaic attenuation pattern in lung

Mosaic attenuation is a descriptive term used in describing a patchwork of regions of differing pulmonary attenuation on CT imaging.  It is a non-specific finding, although is associated with the following:

The term is best used where the differentiation between mosaic perfusion, mosaic oligaemia, and ground-glass opacity cannot be confidently made.

Differentiating the cause

Although "mosaic attenuation" is non-specific, a radiologist should search for ancillary imaging findings which may help identify the underlying process in order to help guide clinical management.

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 the infiltrative disease are present, such as reticular opacities (i.e. crazy paving pattern) or nodules
  5. air trapping: refers to regions of the 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
Inspired signs

Article information

rID: 9087
System: Chest
Section: Gamuts, Signs
Tag: lungs, hrct
Synonyms or Alternate Spellings:
  • Mosaic perfusion
  • Mosaic oligemia
  • Mosaic oligaemia
  • Mosaic attenuation pattern
  • Mosaic attenuation
  • Mosaic perfusion pattern

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Cases and figures

  • Figure 1: photograph: Roman mosaic
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  • Case 1: mild - background bronchiectasis also present
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  • Case 2: bronchiolitis
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  • Case 3
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  • Case 4: probably due to pulmonary hypertension
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  • Case 5: mosaic perfusion and air trapping
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  • Case 6: bronchiolitis obliterans
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