000 Mosaic Attenuation Pattern

Mosaic attenuation is an
- imaging pattern
  - variable lung attenuation
  - results in a heterogeneous appearance of the parenchyma.
  - sometimes it is caused by air trapping
  - sometimes by perfusion abnormalities
  - sometimes normal

Nutshell Buzz

patchwork

differing pulmonary attenuation

What is it:

Mosaic attenuation refers to a patchy or uneven pattern of lung attenuation seen on CT imaging.

It usually appears as areas of
- normal lung density adjacent to areas of
- decreased lung density This pattern can be caused by several different factors, such as:

Airway Disease
1. Small Airway Disease: Mosaic attenuation can be associated with diseases affecting the small airways, such as
  1. chronic obstructive pulmonary disease (COPD) or
  2. bronchiolitis obliterans
  3. hypersensitivity pneumonitis
2. Air Trapping: In conditions like asthma or other obstructive lung diseases, air may be trapped in certain lung regions during exhalation, leading to areas of hyperinflation
Blood Vessel Disease
1. Pulmonary Embolism: Blood clots in the pulmonary arteries can lead to mismatched lung perfusion and cause mosaic attenuation patterns.
2. Pulmonary Edema: Fluid accumulation in the lungs due to heart failure or other causes can result in mosaic attenuation.
Infection and Inflammation: Certain lung infections and inflammatory conditions can also contribute to mosaic attenuation.
- What is it:
  - Mosaic attenuation refers to a patchy pattern of varying lung density seen on CT imaging.
  - It represents alternating areas of low and high attenuation due to differences in lung aeration or perfusion.
- Etymology:
  - Derived from the Latin word mosaicus, referring to a patterned or tiled appearance.
- AKA:
  - Mosaic perfusion (in perfusion-related cases).
- How does it appear on each relevant imaging modality:
- Recommendations:
  - Further evaluation:
    - Perform expiratory CT to differentiate air trapping (obstructive disease) from vascular or parenchymal causes.
    - Pulmonary function tests (PFTs) for assessing small airway or obstructive disease.
    - Ventilation/perfusion (V/Q) scan or CT pulmonary angiography for vascular evaluation.
  - Clinical correlation:
    - Consider patient history, such as exposure to allergens (hypersensitivity pneumonitis), smoking (COPD), or embolic risk factors (vascular causes).
- Key considerations and pearls:
  - Expiratory CT is crucial for detecting air trapping, confirming small airway disease as a cause of mosaic attenuation.
  - Mosaic perfusion (vascular cause) shows regions of hypoperfused, low-attenuation lung due to reduced blood flow.
  - Ground-glass opacities superimposed on mosaic attenuation suggest parenchymal lung disease.
  - Mosaic attenuation requires a multidisciplinary approach to differentiate between obstructive, vascular, and parenchymal diseases.
This structured format ensures clarity in understanding, diagnosing, and managing mosaic attenuation in the lungs.