Computed Tomography in Chest Diseases

Dr. Rikin Hasnani

• Developmental Anomalies• Airway Diseases• Pulmonary infection & Pneumonias• Neoplastic diseases• Disease of mediastinum , Pleura & Chest Wall• Diffuse Lung Diseases

Patterns In HRCT

Secondary Pulmonary Lobule Anatomy• The secondary pulmonary lobule represents the smallest discrete portion of

lung surrounded by connective tissue. It is polyhedral, averages 1.0–2.5 cm in size, is supplied by a terminal bronchioles, and contains 5–15 pulmonary acini. • Central core structures include the centrilobular bronchus and its accompanying

pulmonary artery and lymphatics that course along the bronchovascular bundle toward the center of the SPL. • Diseases affecting the airways involve this portion of the SPL (i.e., aspiration,

centrilobular emphysema, hypersensitivity pneumonitis, infection, inhalational diseases, and respiratory bronchiolitis).• Peripheral structures include the interlobular septa, which are continuous with

the pleural surface, pulmonary veins, and lymphatics. • Diseases affecting the pulmonary veins or lymphatics involve this portion of the

SPL (i.e., pulmonary edema, sarcoidosis, and lymphangitic carcinomatosis).

Disease Patterns• 4 different patterns are observed.• 1) reticular opacities (i.e., interlobular, intralobular, smooth, or

nodular); • (2) nodules (e.g., centrilobular, perilymphatic, or random) • (3) areas of increased attenuation (i.e., ground glass and

consolidation) and • (4) areas of decreased attenuation (e.g., emphysema, cystic lung

disease, bronchiectasis, and honeycombing)

Reticular Opacities Interlobular Intralobular • Pulmonary edema Idiopathic pulmonary fibrosis• Viral infections Pulmonary edema• Lymphangitic carcinomatosis Atypical infections• Acute eosinophilic pneumonia• Sarcoidosis• Amyloidosis• Kaposi sarcoma

• Smooth Nodular• Pulmonary edema Sarcoidosis• Lymphangitic carcinomatosis Lymphangitic carcinomatosis• Lymphoma Lymphoma• Pulmonary alveolar proteinosis Silicosis

Nodules • Centrilobular nodules are evenly spaced and

spare the outer 3–5 mm of lung along the costal pleura. This pattern suggests airway dissemination of disease.• Perilymphatic nodules are located along the

costal pleura, fissural surfaces, and bronchovascular bundles. Such nodules do not spare the outer 5 mm of lung.• Random nodules occur everywhere and may

occur in association with centrilobular and perilymphatic nodules.

Tree In Bud• Tree-in-bud represents a specific centrilobular nodular pattern.• Impaction of centrilobular bronchus with mucous, pus, or fluid,

resulting in dilation of the bronchus, with associated peribronchiolar inflammation .• Dilated, impacted bronchi produce Y- or V-shaped structures• This produces a characteristic pattern with Centrilobular dots (impacted

mucus) and linear branching opacities (Dilated bronchioles) known as Tree In Bud pattern.• Normal lobular bronchioles (< 2 mm ) cannot be seen on CT. Diseased

bronchioles can be seen.

Causes of Tree-In-Bud Pattern• Infections• Bacterial – MTB, NTM, Staph, H.

influenza • Fungal – invasive Aspergillosis• Viral – CMV

• Congenital disorders• Cystic fibrosis• Kartagener syndrome

• Idiopathic disorders Obliterative bronchiolitis Diffuse panbronchiolitis

• Aspiration or inhalation of foreign substances• Immunologic disorders -

ABPA• Peripheral pulmonary vascular

disease – Tumor emboli

• Connective tissue disorders• Rheumatoid arthritis• Sjögren syndrome

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Centrilobular nodulesWith tree-in-bud opacity Without tree-in-bud opacity

• Typical and atypical mycobacteria infections• Bacterial pneumonia• Diffuse panbronchiolitis• Bronchiolitis• Aspiration • ABPA• Cystic fibrosis• Endobronchial-neoplasms

(particularly broncho alveolar carcinoma)

• All causes of tree-in-bud opacity• Hypersensitivity

pneumonitis• Organzing Pneumonia• Pneumoconioses• Langerhans’ cell

histiocytosis• Pulmonary edema• Vasculitis• Pulmonary hypertension

Perilymphatic nodule

• sarcoidosis• Silicosis, • Coal-worker's pneumoconiosis

and • Lymphangitic spread of

carcinoma.

Random Nodules

• Hematogenous metastases• Miliary tuberculosis• Miliary fungal infections• Langerhans cell histiocytosis

(early nodular stage)• Wegener granulomatosis• Sarcoidosis (when very

extensive)

Patterns of Increased Attenuation• Ground glass creates areas of increased attenuation with preservation of

underlying bronchovascular bundles and can be differentiated from mosaic perfusion by comparing relative vessel diameters in affected and unaffected regions . • The pulmonary vessels are similar in size with the former but discrepant with

the latter. • Mosaic perfusion results from differential blood flow and may occur with

vascular obstruction (e.g., chronic pulmonary thromboembolic disease) and small airways disease. • Air trapping on expiratory images differentiates the small airway disease from

embolic disease. • Consolidation causes increased attenuation that obscures visualization of

underlying bronchovascular bundles and in many cases is a further progression of diseases that cause ground glass , that is, replacement of intra-alveolar air by pus, fluid, blood, tumor, or fibrosis.

• Ground Glass opacification Consolidation

• Crazy paving is a specific pattern of increased attenuation created by a combination of ground glass with superimposed interlobular septal thickening

• It is seen in:• Alveolar proteinosis• Sarcoid• NSIP• Organizing pneumonia (COP/BOOP)• Infection (PCP, viral, Mycoplasma, bacterial)• Neoplasm (lepidic Adenocarcinoma)• Pulmonary hemorrhage• Edema (heart failure, ARDS, AIP)

Patterns of Decreased Attenuation• (1) Emphysema it can be Centrilobular emphysema, paraseptal

emphysema, or panlobular emphysema, • (2) Lung cysts, which vary in size and shape, and demonstrate a thin

perceptible wall (≤4 mm) but no centrilobular artery. • Cavities, alternatively, have more irregular-appearing walls >4 mm in

thickness.• (3) Honeycombing, which represents replacement of normal lung by 0.3–

1.0 cm juxtapleural cystic spaces in several contiguous layers whose walls are composed of varying amounts of fibrous tissue. Honeycombing is associated with varying degrees of architectural distortion.• (4) Bronchiectatic airways, which vary in size and shape, have definable

walls, and parallel an accompanying artery.

Interstitial Lung Diseases

Acute Interstitial Pneumonia• Geographic pattern of diseased and

normal lung • Bilateral ground glass opacities or

Consolidation ; patchy or diffuse or occasionally peripheral with focal sparing of lung lobules.• Smooth septal thickening and

intralobular lines superimposed on ground glass opacities (“crazy paving” pattern) • Lymphadenopathy and pleural

effusion; uncommon

Non Specific Interstitial Pneumonia• Ground glass opacities often with basal and peripheral predominance • Associated irregular linear or reticular opacities (50–100%) with or without fibrosis, traction

bronchiolectasis, interlobular septal thickening, intralobular septal thickening, irregular interfaces

• Honeycombing; mild involving <10% of parenchyma (10–30%)• Centrilobular nodules; uncommon• Abnormalities may be diffuse; lower lung zone predominant (60–90%); peripheral lung (50–

70%); relative sparing of immediate juxtapleural dorsal lung in lower lobes (64%)• Mediastinal lymph node enlargement (80%)• 10–15 mm short axis diameter• Usually involves one or two nodal stations, most commonly lower right paratracheal (4R) and

subcarinal(7)

NSIP

Pulmonary Alveolar Proteinosis• X ray • Bilateral, symmetric, patchy, and diffuse ground glass opacities and

consolidations• Nodular or reticular opacities• Lower lobe predilection• Relative sparing of costophrenic angles and apicesCT Crazy Paving Pattern with Areas of affected lung sharply demarcated from adjacent uninvolved lung.

Desquamative Interstitial Pneumonia (DIP)• Chest Radiography• Normal (3–22% of patients)• Bilateral, symmetric ground glass

opacification• Bibasilar, irregular linear

opacities• Lower lung zone predominance• Preserved lung volumes• Nodules and honeycombing

• MDCT /HRCT• Diffuse ground glass opacity

(100%) • Subpleural and lower lobe

predominance.• Traction bronchiectasis,

honeycombing uncommon• Small cysts (microcysts) (32–

75%)

The combination of ground glass opacity and small cysts is suggestive of DIP

Lymphocytic Interstitial Pneumonia (LIP)• X RAY• Preserved lung volume• Non-specific bilateral reticular-

nodular and ground glass opacities with or without consolidation

• Lower lung zone predilection• Nodular pattern and

lymphadenopathy more common in AIDS patients

• pleural effusions –rare

• MDCT /HRCT• Diffuse, bilateral, patchy areas of

ground glass opacity and/or poorly defined centrilobular nodules (100%)

• Small juxtapleural nodules (86%) • Peribronchovascular bundle thickening

(86%)• Mild interlobular septal thickening

(82%) • Thin-walled cystic airspaces (68%)• Larger nodules, 1–3 cm diameter- rare

LIP

Cryptogenic Organizing Pneumonia (COP)CT Alveolar pattern• Patchy, bilateral, often

symmetrical GGO/Consolidation, juxtapleural or peribronchial .

• May range from few cm to whole lung.

• Reverse Halo sign or Atoll sign.• Centrilobular nodules

• It may present as Mass lesion• Larger nodules or masses; two to eight per

patient• 8 mm to 5 cm diameter• Irregular (88%) or spiculated (35%) margins• Air bronchograms (45%)• Pleural tails (50%)• Vessels converge on lesion edge (80%)• Upper lung zone predilection (60%)• Juxtapleural (40%); peripheral

bronchovascular (33%); peripheral (30%)• Satellite nodules (55%)

COP

Sarcoidosis Intrathoracic lymphadenopathy• 80% of patients at presentation, typically bilateral

and symmetric• Classic triad of right paratracheal and bilateral

hilar lymphadenopathy, so-called 1-2-3 sign or Garland triangle

• Bilateral hilar lymphadenopathy with or without mediastinal lymphadenopathy (95%)

• Aortopulmonary window lymphadenopathy (76%)• Common involvement of 4R, 5, 7, 10R, 11R, 11L

lymph node stations; • Calcified lymph nodes with chronicity of disease;

20% after 10 years ; may demonstrate eggshell pattern of calcification

Pulmonary involvement• Bilateral, symmetric small nodular and

reticular opacities with a predilection for the upper and middle lung zones

• Nodular (so-called alveolar or nummular) sarcoidosis: multi-focal nodules and/or masses with or without air bronchograms

• Focal opacity, pleural effusion, pneumothorax, atelectasis, cavitation -rare

• Central upper lobe–predominant fibrosis with volume loss, hilar retraction, and cystic change;

• may be complicated by mycetoma.

CT• Nodules – Perilymphatic or random (Milliary)• Ground glass opacities, large nodules, and masses with perilymphatic

distribution; may exhibit air bronchograms• Sarcoid galaxy sign—large nodular opacities with satellite

micronodules• Mosaic attenuation and air trapping on expiratory images• Lymphadenopathy: bilateral, symmetric; may exhibit amorphous,

punctate, and eggshell pattern of calcification

Stage I

Sarcoidosis stage I: left and right hilar and paratracheal adenopathy (1-2-3 sign)

There is hilar and paratracheal adenopathy and no sign of pulmonary involvement.

Stage II

lymphadenopathy hilar and small nodules along bronchovascular bundles (yellow arrow) and along fissures (red arrows)

Stage II

.

Always look for small nodules along the fissures, because this is a very specific and typical sign of sarcoidosis

Fibrosis in Sarcoidosis.• Progressive fibrosis in sarcoidosis may lead to peribronchovascular

(perihilar) conglomerate masses of fibrous tissue.• The typical location is posteriorly in the upper lobes, leading to

volume loss of the upper lobes with displacement of the interlobar fissure.

• Other diseases that result in this appearance are:• Tuberculosis• Silicosis• Talcosis

Stage IV

Alveolar Sarcoidosis. 

Hypersensitivity Pneumonitis • Acute and Subacute• Patchy or diffuse bilateral ground glass opacities (100%) with associated poorly defined

subcentimeter nodules and mosaic perfusion (80%) • Fuzzy or ill-defined centrilobular nodules (70%) • Most prominent mid- to lower lungs; costophrenic angles commonly spared (or less severely

involved)• Air trapping on expiratory imaging (95%)• Lobular areas of hypoattenuated lung parenchyma • Head cheese sign: geographic ground glass attenuation + normal lung + mosaic perfusion + air

trapping• Thin-walled lung cysts (10%); nearly always seen in conjunction with diffuse ground glass opacities• Mediastinal lymphadenopathy (50%); nodes <20 mm short axis diameter• Pleural effusion rare

Chronic HP• Background of subacute findings• Centrilobular nodules (60%); usually ground glass attenuation• Mosaic perfusion (60%)• Lung cysts (30%); nearly always seen in association with ground glass

opacitiesFibrosis• Irregular linear opacities (40%)• Traction bronchiectasis (20%) • Honeycombing (50%)

Usual Interstitial Pneumonia • Patchy, predominantly peripheral, predominantly, subpleural, and

bibasilar reticular opacities.• Fibrosis and progressive lung parenchyma architectural distortion)• Traction bronchiectasis and bronchiolectasis • Honeycombing• Predominance of paraseptal, peribronchiolar, basal, and juxtapleural

abnormalities • Reduction in lung volume

Usual Interstitial Pneumonia • Common mild mediastinal lymph node enlargement• 4R and 7 node stations, most commonly• Short axis diameters range between 10 and 21 mm• More prevalent with severe lung disease; associated with progression of fibrosis• Foci of ground glass correlate with active alveolitis (70% of cases) or fibrosis

beyond the resolution of the CT scan• Rarely, punctate calcified nodules (pulmonary ossification) within the areas of

fibrosis.• The presence of subpleural honeycombing, traction bronchiectasis, and

thickened interlobular septae increases the specificity of the CT scan for diagnosing IPF.

Thank You