The Common Vein

Ground Glass and the Lungs

• GGO is characterized by increased lung attenuation
• with preserved bronchial and vascular markings.
• Differentiation from Consolidation: Unlike consolidation, where alveoli are completely filled (leading to obscuration of vessels),
• GGO represents
  • • partial filling,
    • mild alveolar collapse.or
    • interstitial thickening,

• Why Do We See Things?
  Because they are different!

• 

Ground Glass Opacification or Consolidation?
Black White or Gray is the question

 

Contrast of bronchioles and lungs in the
normal situation

• In the normal situation,
  • when the
    • black of the thin walled bronchioles
      • (walls imperceptible because of their size) is
  • positioned alongside  the
    • black of the air-filled alveoli
    • they cannot be perceived since we have a
      • black on black situation with
      • no contrast between the 2 structures

Normal
Black Bronchiole Aside Black Alveoli

Consolidation
Black Bronchiole Aside White Alveoli
Result = Distinct Air Bronchogram

Contrast of bronchioles and lungs in the
alveoli filled with fluid situation

• • When the alveoli are filled with fluid
    • they become white
    • HU range: ~ 0 to +100 HU
  • and therefore the
    • black of the airways against the
    • white of the alveoli results in
      • a clear distinction of the airways known as
      • air bronchograms

Contrast of bronchioles and lungs in the
alveoli half filled with fluid situation

• • When the alveoli are for example half filled with fluid
    • they become gray
    • HU range: ~ -200 to -600 HU
  • and therefore the
    • black of the airways against the
    • gray of the alveoli results in
      • a hazy opacity overlying the still visible airways

With the knowledge that
We only see things when they are different
and the more different they are
The better we see them

Ground Glass and the Airways and
Consolidation and the Airways

 

• 

  Silhouetting

  

  Airways in GGO and Consolidation

  

   

  Blood Vessels on a Non Contrast Study in
  GGO and Consolidation

  

   

• Feature	Ground-Glass Opacities (GGOs)	Consolidation
  Definition	Areas of increased lung attenuation with visible underlying structures.	Homogeneous increase in lung attenuation with obscured underlying structures blood vessels but greater clarity of airways (air bronchogramns).
  Visibility of Airways	Airways (air bronchograms) are visible but indistinct  through the hazy opacity.	Airways (air bronchograms) are prominent and easier to identify.
  Visibility of Blood Vessels	Blood vessels are visible through the hazy opacity.	Blood vessels are obscured  due to dense opacification.
  Associated Conditions	Inflammatory or fibrotic processes, early infection, interstitial lung diseases.	Pneumonia, organizing pneumonia, advanced infection, pulmonary edema.

Causes of GGO’s
When the net density of the lungs is Gray

HU range: ~ -200 to -600 HU

• This occur when
  • alveoli are half filled with
    • fluid
    • cells
  • alveolar walls are
    • inflamed
  • bronchioles ore
    • filled with fluid
    • are inflamed
  • alveoli are
    • fibrosed
  • bronchioles are
    • fibrosed

Ground Glass Causes

GGO Caused by
The Half Filled Alveoli

When The Half Filled Alveoli have
Fluid Content

The net density of the affected region of the lung
= gray
and gray density in the affected region
= GGO

Fluid Content in the Alveoli Can Take Many Forms

GGO Caused by
The Half Filled Alveoli
When The Half Filled Alveoli have
Cellular Content

 

GGO Caused by
Congested Alveolar Walls

The net density of the affected region of the lung
= gray
and gray density in the affected region
= GGO

In moderate to severe CHF
there are 2 hits
Fluid in the Alveoli
Congestion in the Alveolar Walls

The net density of the affected region of the lung
= gray
and gray density in the affected region
= GGO

 

GGO Caused by
Inflammed  Alveolar Walls

The net density of the affected region of the lung
= gray
and gray density in the affected region
= GGO

 

In Patients with
Alveolitis
Inflammed  Alveolar Walls
will result in
Edema in the Alveolar Walls which
will result in
an increase in density

The net density of the affected region of the lung
= gray
and gray density in the affected region
= GGO

In patients with
Eosinophillic Pneumonia
Cellular infiltration in the
Small Airways and
Alveoli
will result in a increase in density of the
affected regions of the lung
The net density of the affected region of the lung
= gray
and gray density in the affected region
= GGO

In patients with
fibrosis of the alveolar walls (septa)
For example in NSIP
will result in a increase in density of the
affected regions of the lung

The net density of the affected region of the lung
= gray
and gray density in the affected region
= GGO

Interstitium Fibrosed Causing
Net Density of Gray = Ground Glass

 Alveoli Half Filled with Cells

The Story in Bottles

 

:

#	Category	Common Causes	Key Features
1	Edema-related	– Cardiogenic pulmonary edema	Perihilar “bat-wing” GGO, Kerley B lines, cardiomegaly
		– Non-cardiogenic pulmonary edema (ARDS, TRALI)	Diffuse or perihilar GGO, acute onset, normal heart size
2	Infectious	– Viral pneumonia (Influenza, COVID-19, RSV)	Diffuse or perihilar GGO, fever, systemic symptoms
		– Pneumocystis jirovecii pneumonia (PJP)	Bilateral perihilar GGO, seen in immunocompromised patients
		– Mycoplasma pneumonia	Atypical pneumonia, patchy perihilar GGO
3	Inflammatory/Autoimmune	– Hypersensitivity pneumonitis (acute phase)	Perihilar GGO, ground-glass nodules, exposure history
		– Diffuse alveolar hemorrhage (DAH)	Bilateral GGO, hemoptysis, seen in vasculitis or lupus
		– Eosinophilic pneumonia (acute or chronic)	Peripheral and perihilar GGO, eosinophilia
4	Interstitial Lung Disease	– Non-specific interstitial pneumonia (NSIP)	Bilateral GGO, lower lung predominance, seen in autoimmune disease
		– Cryptogenic organizing pneumonia (COP)	Patchy perihilar GGO, associated with migratory opacities
5	Neoplastic	– Lymphangitic carcinomatosis (early stage)	Subtle perihilar GGO, interstitial thickening, history of malignancy
6	Toxic and Drug-related	– Amiodarone toxicity	Bilateral GGO, lung fibrosis in chronic exposure
		– Methotrexate, checkpoint inhibitors	Drug-induced pneumonitis, perihilar GGO, fibrosis in chronic cases
7	Miscellaneous	– Pulmonary alveolar proteinosis (PAP)	“Crazy paving” pattern, bilateral GGO, alveolar filling disorder

Bilateral Upper Lobe GGO