000 Ground Glass Infiltrates and Opacities

In a Nutshell

The Reason We See Things

HOW MANY SQUARES 3 OR 4?
Courtesy Ashley Davidoff

How many squares
Ashley Davidoff thecommonvein.net notes scale music-0019-low resb

Filled and Half-Filled Alveoli – Differences in Appearance on CT
When the alveoli are fully filled with fluid, tumor, or pus for example, the overall net density will be white, and when adjacent to air filled airways, air bronchograms are visible (left side of image)
When the alveoli are only partially filled, the density of the fluid added to the density of the air results in an overall gray density, and when positioned next to air filled bronchi, there is insufficient contrast to create an air bronchogram and sufficient to enable visualization of the blood vessels. This is called ground glass opacification
Ashley Davidoff
TheCommonVein.net lungs-00681

Hazy areas of increased opacity or areas of increased attenuation with

preserved bronchial and vascular margins

Why is it called ground-glass?

Not black, not white but gray

Technique in glassmaking during which the surface of the glass is blasted by sand. This technique gives the glass a hazy white or frosted appearance.

Ground Glass
“Ground glass is glass whose surface has been ground to produce a flat but rough (matte) finish, in which the glass is in small sharp fragments.
Ground glass surfaces have many applications, ranging from ornamentation on windows and table glassware to scientific uses in optics and laboratory glassware.”
Wiki

The term has its origins in the way old movies shot their flashback scenes, through a ground-glass lens that gave the film a hazy appearance

Chest radiologists adopted it in the 1980s, with a first appearance in the Fleischner Society Glossary of Terms for Thoracic Radiology in 1984

Gray areas of increase density arising from
- Disease in the
  - airways
  - alveoli
  - inter-alveoalar septa
  - interstitium

AIR BRONCHOGRAMS AND GROUND GLASS
TheCommonVein.net

The collage provides a perspective of disease of the small airways and the alveoli that results in ground glass appearance on Xray. A process that increases the density of the lungs to a net “gray” regional density will result in a ground glass opacity whether it is inflammation of the walls ((second column) fluid within the lumen of the small air ways and alveoli (3rd column) or whether it is fibrosis in the walls of the small airways or alveolar septa (last column alveoli. The net result on CT is a ground glass opacity (bottom row). In fibrosis there are secondary changes which include bronchiolectasis in this case, but other associated changes may include reticulations or centrilobular nodules
Ashley Davidoff MD TheCommonVein.net lungs-0733

Types of Fluid Accumulations and Appearance as Ground Glass Infiltrates
Ashley Davidoff MD TheCommonVein.net lungs-0702d- lo res

Ground Glass Opacity and Adenocarcinoma with Lepidic Growth
The Ground Glass Opacity (GGO) in this case is caused by partial filling of the alveolus with malignant cells Ground glass opacification may be caused by partial filling of the alveolus with cellular material resulting in partial replacement of air with solid material. The net density is gray rather than white in the situation where the alveolus is fully replaced with cells or fluid. There is blending of the black of the subtending airways and the white of the vessels with the gray density of the cellular infiltrate and hence the normal vessels are not visualized in ground glass opacities.
Ashley Davidoff MD TheCommonVein.net 134375b01

Ground Glass Nodules and Pneumonic Infiltrate and Air Bronchograms
Ashley Davidoff
TheCommonVein.net

Normal Structure

Anatomy of the Distal Airways in Color and in the Black and White of Radiology
The subsegmental medium sized airways give rise to the terminal bronchiole (tb) which gives rise to the membranous airways. These include in order, the respiratory bronchiole (rb), alveolar duct (ad) and alveolar sac (as)
Ashley Davidoff TheCommonvein.net

Ground Glass Changes May result from Disease in the
- Small Airways
- Alveoli
- Interalveolar Septa
- Interstitium

The collage provides a persepective of disease of the small airways and the alveoli that results in ground glass appearance on Xray. A process that incereases the densityof the lungs to a net “gray”regional density will result in a ground glass opacity whether it is inflammation of the walls ((second column) fluid within the lumen of the small aireways and alveoli (3rd column) or whether it is fibrosis in the walls of the small airways or alveolar septa (last column alveoli. The net result on CT is a ground glass opacity (bottom row). In fibrosis there are secondarychanges which include bronchiolectasis in this case, butother associated changes may include reticulations or centrilobuar nodules
Ashley Davidoff MD TheCommonVein.net lungs-0733

Origin in the Alveoli

Types of Fluids that Can Partially Fill in the Alveoli

Application to Radiology

Concept of the Fully Filled Alveolus with Net “White Density”
vs.
Half Filled Fluid Alveolus with a Net of “Gray” Density

Acute Ground Glass Infiltrates Caused by partial Filling of the Alveoli with Fluid

Radiological Application This an eample of acute diffuse ground glass change where thenet density of the alveoli is gray caused by partial filling of the alveoli with fluid
Ashley Davidoff MD TheCommonVein.net
lungs-0708d- lo res

CHF

Acute CHF
50 year old female with diabetes, chronic renal failure with congestive heart failure. CT in the coronal plane shows diffuse ground glass changes, Kerley B lines at the right base,
Ashley Davidoff MD TheCommonvein.net 50-003-CT

50 year old female with diabetes, chronic renal failure with congestive heart failure. CT in the coronal plane shows diffuse ground glass changes, Kerley B lines peribronchial cuffing in the right upper lobe and right lower lobe
Ashley Davidoff MD TheCommonvein.net 50-004-CT

50 year old female with diabetes, chronic renal failure with congestive heart failure. CT in the axial plane shows diffuse ground glass changes, thickening of the interlobular septa, centrilobular nodules peribronchial cuffing mosaic attenuation in the right lower lobe, associated with a complex right sided effusion
Ashley Davidoff MD TheCommonvein.net 50-010-CT

Types of Cells that Can Partially Fill in the Alveoli

Examples include Langerhans Cells, Macrophages, Eosinophils and Malignant Cells

Half Filled Cellular Accumulation in the Alveolus Type of Cells include Langerhans Cells Macrophages and Malignant Cells
Ashley Davidoff MD TheCommonVein.net lungs-0707a

Ground Glass Opacity (GGO) Caused by Cellular Accumulation with Partial Filling of the Alveolus Type of Cells include Langerhans Cells Macrophages and Malignant Cells
Ground glass opacification may be caused by partial filling of the alveolus with cellular material with partial replacement of air with solid material with the net density being gray rather than white if the alveolus were fully filled. The black of the airway nor the white of the vessels may blend with the gray density and hence they are not visualised in ground glass opacities. ore is usually lood vessels and airway walls The replacement may be due to cellular infiltration including inflammatory ,benign or malignant cells without or with fluid.
Ashley Davidoff MD TheCommonVein.net lungs-0707ad

Eosinophils in Acute Eosinophilic Pneumonia

Infiltration of eosinophils and exudation into the alveoli and interalveolar septa and interstitium
Ashley Davidoff TheCommonVein.net
lungs-0756b01

Application to Radiology

Concept of the Fully Filled Alveolus with Net “White Density”
vs.
Half Filled Fluid Alveolus with a Net of “Gray” Density

Ground Glass as a result of Cellular Accumulations in the Alveoli
When there are extensive cellular accumulations in the alveoli, such as adenocarcinoma with lepidic growth, Langerhans cells or other macrophages, the overall net density of the region of involvement will be gray, and when adjacent to the black air filled airways, a ground glass appearance will be apparent
Ashley Davidoff
TheCommonVein.net
ssb = subsegmental bronchiole
tb = terminal bronchiole
rb = respiratory bronchiole
as = alveolar duct
as = alveolar sac
is = interalveolar septum
lungs-00682-lo res

Difference Between Consolidation and Ground Glass

GGO -(Nodule) in Adenocarcinoma with Lepidic Growth

GGO with Origins in the Interstitium

Ground Glass as a result of Interstitial Disease –
When there are extensive interstitial fibrotic changes in the interstitial compartments of the lung which include the and the interalveolar septa, and the supporting interstitium of the lung between the acini and small airways, the overall net density of the region of involvement will be gray, and when adjacent to the black air filled airways, a ground glass appearance will be apparent
Ashley Davidoff
TheCommonVein.net
ssb = subsegmental bronchiole
tb = terminal bronchiole
rb = respiratory bronchiole
as = alveolar duct
as = alvelar sac
is = anteralveolar septum
lungs-00682-lo res

Ground Glass from Interlobular Septal Fibrosis

Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net

Combination of Elements resulting in ground Glass Changes

In Acute Eosinophilic Pneumonia Changes include;
Alveolar, and Interalveolar Interstitial Infiltration with Eosinophils and Inflammatory Exudate

The ground glass changes are a combination of the cellular and exudative inflammatory response in the small airways, alveoli, interalveolar septa and interstitium, and thickened alveolar septum

Alveolar and Interalveolar Interstitial Infiltration with Eosinophils and Inflammatory Exudate – Ground Glass Changes
The ground glass changes are a combination of the cellular and exudative inflammatory response in the small airways, alveoli, interalveolar septa and interstitium, and thickened alveolar septum
The diagram shows the abnormal secondary lobule (a) The involved components include the small airways(b) alveoli and interalveolar interstitium (c) and the thickened interlobular septum (d) surrounding the secondary lobule due to an inflammatory process, cellular infiltrate and congestion of the venules and lymphatics in the septum. An anatomic specimen of a secondary lobule from a patient with thickened interlobular septa and interstitial thickening is shown in image e, and is overlaid in red (f) . A magnified view of an axial CT of the lungs in a patient with acute eosinophillic pneumonia shows thickened interlobular septa and centrilobular nodules (g) The inflammatory changes in the aforementioned structures result in an overall increase in density of the lung manifesting as ground glass changes (g) and overlaid in red (h)
Ashley Davidoff MD The CommonVein.net lungs-0762

Infiltration of eosinophils and exudation into the alveoli and interalveolar septa and interstitium
Ashley Davidoff TheCommonVein.net
lungs-0756b01

Ground Glass Opacity
On HRCT, ground glass opacity appears as hazy areas of increased opacity or attenuation with preserved anatomy, including bronchial and vascular margins.7 In comparison, ground glass opacity is less opaque than consolidation.7

- A region of ground glass opacity on CT with it’s incidental correlation on T2 weighted MRI showing that in this instance it is composed of water
  Ashley Davidoff MD
  TheCommonvein.net
Diseases Associated with GGO
Types of GGO

There are several types of GGO. These include:
- - Nodules
  - Focal
  - Diffuse
    - - Subsegmental
      - Segmental
      - Lobar
      - Patchy
      - Central
  - Halo
  - Reversed Halo
  - Head Cheese
  Focal
  - Nodules and Nodular: This type can indicate both benign and malignant conditions. GGO that persists over several scans may indicate either premalignant or malignant growths.
    - Centrilobular: This type appears within one or several lobules of the lung. Lobules are the hexagonal divisions of the lung. The connective tissue between the lobules is unaffected.
    - 41-year-old man with subacute hypersensitivity pneumonitis. High-resolution CT image shows bilateral poorly defined centrilobular nodules and ground-glass opacities. Also evident are lobular areas (arrows) of decreased attenuation.
      
      Intralobular
    - WEGENER’S GRANULOMATOSIS WITH POLYANGIITIS, GPA,VASCULITIS AND MICROINFARCTION
      81-year-old male with weight loss, renal failure, and hemoptysis
      CT axial view (a) shows multiple peripheral wedge shaped ground glass densities subtended by distended feeding vessels (a,b,c, red arrowheads) reflecting areas of microinfarction due to vasculitis that affects both the arterioles and venules.
      Priscilla Slanetz MPH MD
      TheCommonVein.net
      - 26 male SOB s/p RFA ablation for atrial fibrillation lung pulmonary let upper lobe pulmonary vein thrombosed secondary lobule interlobular septa are thickened secondary lobule due to congestion and hemorrhage dx pulmonary vein thrombosis secondary to radiofrequency ablation therapy iatrogenic CTscan Courtesy Ashley Davidoff MD Scott Tsai MD ground glass changes pulmonary infarction venous infarction
        TheCommonVein.net
    - Diffuse:
      - Diffuse opacities show up in multiple lobes of one or both lungs. This pattern occurs when the air in the lungs is replaced with fluid, inflammation, or damaged tissue.
        
        Segmental
        
        Subsegmental
        
        Lobar
    - Subsegmental
      - COVID 19
        55-year-old male presents with a fever and a cough.
        CXR findings reveal vague peripheral, bibasilar, “ground glass” changes in the lower lung zones.
        The CT scan confirms the presence of bilateral, predominantly basilar, nodular, and peripheral mixes ground glass and consolidative opacifications consistent with the diagnosis of COVID 19. Differential diagnosis however includes other viral pneumonias, allergic alveolitis and other multifocal and organizing pneumonias.
        Courtesy Kevin Chang MD
        TheCommonVein.net
        
        PET Positive Adenocarcinoma in a Background of Multicentric Adenocarcinoma with Lepidic Growth
        The CT is from a 51 year old male who is a smoker who shows a ground glass opacity (GGO) mixed with a solid mass (arrow in a) and multicentric BAC in a lower cut (b) characterised by three areas in the right lower lobe of partial alveolar opacification. Ground glass appearance is the result of partial opacification of the alveoli. Two of the GGOs measure close to 2cms each and the third more anterior measures about 8mms. In this instance a PET scan was positive in the area (green ring in d) It is likely that the solid component in image a represents the transformation of BAC – (really a carcinoma in situ) into adenocarcinoma.
        Courtesy Ashley Davidoff MD
        TheCommonVein.net
        87769c02b.8s
- Subsegmental
  - HEAD CHEESE SIGN, GROUND GLASS, MOSAIC PATTERN
    SARCOIDOSIS, STAGE IV, PTX, ENCASEMENT
    Ashley Davidoff MD
    
    SLE AND PE
    24 year old male with SLE presented with chest pain and dyspnea and initial CT showed occlusive pulmonary emboli to the right lower lobe (a,b, red arrowhead) with total occlusion of the right lobe artery extending into posterior basal segmental vessels (red ring d compared with normal vessels surrounded by white rin (d). An associated wedge shaped ground glass region is noted (e,f red arrowhead) representing either hemorrhage or early infarction
    Ashley Davidoff MD
    
    Ground Glass Nodules with ? Lymphangitic Spread
    Ashley Davidoff
    TheCommonVein.net
    
    60 year old female who presents with hemoptysis. Ct scan shows a focal region of ground glass change in the superior segment of the left lower lobe, abutting the fissure, likely reflecting hemorrhage
    Ashley Davidoff MD TheCommonVein.net
    
    Segmental
    - LEFT PTX (green arrow) , ENCASEMENT OF AIRWAYS (red arrows) and GROUND GLASS (blue arrows)
      SARCOIDOSIS, STAGE IV, PTX, ENCASEMENT
      Ashley Davidoff MD
  - - - Lobar or Almost Lobar
      - 44-year-old male presents with history of sarcoidosis manifesting as diffuse ground glass involving the upper lobes and lower lobes sparing the middle lobe and lingula to some extent.
- SARCOIDOSIS, STABLE DIFFUSE GROUND GLASS AND ADENOPATHY OVER 9 YEARS
  Ashley Davidoff MD
  
  SARCOIDOSIS, STABLE DIFFUSE GROUND GLASS AND ADENOPATHY OVER 9 YEARS
  Ashley Davidoff MD
- Multilobar

BASILAR GROUND GLASS INFILTRATES
Axial CT through the base of the lungs show diffuse ground glass density, with some segmental sparing in the middle lobe and lingula characterized by increased density without obscuring the airways and vessels
Ashley Davidoff MD TheCommonVein.net

- CHF
DIFFUSE GROUND DISEASE WITH REGIONS OF NORMAL LUNG
CHF, INTERSTITIAL EDEMA KERLEY A and B
Ashley Davidoff MD TheCommonVein.net
- Diffuse Multilobar with Mosaic Attenuation : This pattern develops when small arteries or airways within the lung are blocked. The opaque areas vary in intensity.
- Hypersensitivity Pneumonitis
  High-resolution CT: increase in density in areas of ground glass and air trapping in lower lobes in patients with hypersensitivity pneumonitis
  Courtesy Mluisamtz11
  
  SECONDARY PULMONARY LOBULE
  lung pulmonary lobule secondary lobule arteriole venule interlobular septa bronchovascular bundle mosaic pattern air trapping fx ground glass XCTscan
  Davidoff MD
- Diffuse Multilobar with Crazy paving: Crazy paving shows up as a linear pattern. It can occur when the spaces between the lobules widen.
- CRAZY PAVING
  57-year-old female with progressive dyspnea.
  CXR shows bilateral, diffuse alveolar opacities having a perihilar and basal distribution with sparing of the apices
  CT shows diffuse ground glass change with crazy paving morphology characterized by bilateral diffuse ground-glass opacities (GGO) with interlobular and intralobular septal thickening. There is a geographical distribution .
  Differential diagnosis
  ARDS
  PCP pneumonia
  CHF
  Alveolar Hemorrhage
  UIP
  Hypersensitivity Pneumonitis
  XRT pneumonitis
  COP
  Chronic Eosinophilic
  Lymphangitis
  Veno-Occlusive Disease
  Ashley Davidoff MD
  TheCommonVein.net
- Crazy-paving sign. Axial CT of the chest shows thickening of the intralobular and interlobular septa with a superimposed background of ground-glass opacity in a patient with pulmonary alveolar proteinosis.
  Source
  Signs in Thoracic Imaging
  Journal of Thoracic Imaging 21(1):76-90, March 2006.
  
  Congestion of the Venules in the Interlobular Septa

Halo Sign in Angioinvasive Aspergillosis

Halo
Reversed Halo
Head Cheese
- HEAD CHEESE SIGN, GROUND GLASS, MOSAIC PATTERN
  SARCOIDOSIS, STAGE IV, PTX, ENCASEMENT
  Ashley Davidoff MD

Focal Wedge Shaped

ANCA VASCULITIS WITH PULMONARY INFARCTION AND MYOCARDIAL INFARCTION CT scan of a 67 year old female with anca vasculitis shows regions of dystrophic calcification in the lateral aspect of the right lower lobe (white arrow, a and b) )with focal nodular parenchymal consolidation, that likely reflects a site of prior small vessel infarct. Dystrophic calcification in the LV myocardium (blue arrows c) and a suggestion of fatty dysplasia in the left ventricular apex red arrow d) suggest changes from small vessel infarct. Ashley Davidoff MD

Multicentric Mixed

ACUTE ALVEOLAR PNEUMONITIS
PA and lateral chest X-ray of a 54 year old female with SLE shows bibasilar ground glass infiltrates.
The heart is slightly enlarged and the region of the IVC on the lateral examination is also enlarged
Ashley Davidoff MD
key word
acute pneumonitis
SLE

ACUTE ALVEOLAR PNEUMONITIS
CT scan through the 4 chambers of the heart using lung windows is from a a 54 year old female with SLE. Recent CXR showed bibasilar ground glass infiltrates.
The scan shows basilar multicentric infiltrates with elements of ground glass change and small airway wall thickening (red circles in the right lower lobe middle lobe and lingula, as well as interlobular septal thickening (green circle) in the lateral basal segment of the left lower lobe. A small pericardial effusion is present (yellow arrowhead)
Ashley Davidoff MD

GROUND GLASS MORPHOLOGY IN ILD
Ground glass infiltrates are one of the features of the interstitial disease with increased density without obscuring the airways and vessels

- Focal Associated with Other Diseases
- Halo sign:
- This type of opacity fills the area around the nodules.
- WEGENER’S GRANULOMATOSIS WITH POLYANGIITIS, GPA, HALO SIGN AND AIR BRONCHOGRAMS
  81-year-old male with weight loss, renal failure, and hemoptysis
  CT axial view (a) shows a 2 cm solid nodule in the RUL surrounded by A HALO SIGN OF GROUND GLASS CHANGES AND RETICULAR CHANGES (a,b, red arrowheads), indicating surrounding hemorrhage, and subtle air bronchograms (a,b,c, teal arrowheads) best appreciated in c with narrowed windows.
  Priscilla Slanetz MPH MD
- HEMORRHAGE, GROUND GLASS, HALO SIGN, AIR BRONCHOGRAM AND CHEERIO SIGN, WEGENER’S GRANULOMATOSIS WITH POLYANGIITIS, GPA.
  57 year old male presents with a history of hemoptysis and dyspnea.
  Axial CT scans show multicentric nodular consolidations with air bronchograms (red arrowheads a ,b, c), ground glass infiltrate (black arrowheads, a,b,c) halo sound around nodules and masses in the RLL (a,e, green arrowheads) and in the LLL 9a,f, blue arrowheads). Lastly there is a cheerio sign (a,d, white arrowheads) either representing granulomatous mass surrounding an airway, or central cavitation of a nodule.
  Ashley Davidoff MD.
  57 year old male presents with a history of hemoptysis and dyspnea.
  Axial CT scans show multicentric nodular consolidations with air bronchograms (red arrowheads a ,b, c), ground glass infiltrate (black arrowheads, a,b,c) halo sound around nodules and masses in the RLL (a,e, green arrowheads) and in the LLL 9a,f, blue arrowheads). Lastly there is a cheerio sign (a,d, white arrowheads) either representing granulomatous mass surrounding an airway, or central cavitation of a nodule.
  Ashley Davidoff MD TheCommonVein.net
- Reversed halo sign: A reversed halo sign is an area that is almost totally surrounded by liquid-filled tissue.
Hemorrhage

Pre and Post Biopsy – Hemorrhage and Pneumothorax Post Biopsy of an Adenocarcinoma
Ashley Davidoff MD TheCommonVein.net
70m – adenocarcinoma-
Diffuse Disease

CAUSES

- normal expiration
- partial filling of air spaces
- partial collapse of alveoli
- interstitial thickening
- inflammation
- edema
- fibrosis
- lepidic proliferation of neoplasm

References and Links

Radiopedia

Wiki

TCV
- Ground Glass Opacities – Introduction
- Diseases Associated with GGO
- Cases of Ground Glass

Segmental

Lobar or Almost Lobar

Halo Sign in Angioinvasive Aspergillosis

Halo

Reversed Halo

Head Cheese

Focal Wedge Shaped

Multicentric Mixed

CAUSES

References and Links