Case 28

Section 1

Images 1 and 2 were obtained at full inspiration. Images 1a and 2a were obtained at end-expiration.

Image 1--End-inspiration

In images 1 and 1a, compare the size of the vessels in regions of dark lung with that of the vessels in regions of lighter lung.

What is the significance of the vessel size?

Answer

darksmall1lightlargedarksmall2

Image 1a--End-expiration

Image 2--End-inspiration

Note similar findings in images 2 and 2a.

Image 2a--End-expiration

Section 2

Image 1--End-inspiration

Find 2 areas of dark lung with small vessels in the right lung.

Find an area of light lung with larger vessels in the right lung.

Find the same areas on the expiratory image below. (They are not marked.)

What happens to the regions of dark and light lung on the expiratory images 1a and 2a compared to the inspiratory images?

Answer

Image 1a--End-expiration

Section 3: Mosaic Perfusion

Mosaic Perfusion in Airway Disease

Causes of Mosaic or Inhomogeneous Perfusion

  • Small airway disease with a physiologic decrease in perfusion in regions of air-trapping
  • Primary stenosing vascular disease

End-expiratory images help to determine whether mosaic perfusion is caused by air-trapping or primary vascular disease.

Note: The contrast between light and dark is accentuated on the expiratory image.

Note: The contrast between light and dark is not accentuated on the expiratory image.

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Case 28--Continued

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The vessels are smaller in regions of dark lung and larger in regions of lighter lung. This finding known as mosaic perfusion indicates that the dark lung has decreased perfusion, while the lighter lung has relatively more perfusion.

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The light lung becomes lighter and the dark lung stays relatively dark, resulting in a greater contrast between light and dark lung on the end-expiratory images compared to the inspiratory images. The significance is that the mosaic perfusion in this case is caused by air-trapping of small airway disease. Air-trapping is sometimes evident only on expiratory images.

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Dark lung with small vessels

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Light lung with larger vessels than dark lung

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