High-Resolution Lung CT: Key Findings and What They Mean W. Richard Webb MD.

High-Resolution Lung CT:High-Resolution Lung CT:Key Findings andKey Findings andWhat They MeanWhat They Mean

W. Richard Webb MDW. Richard Webb MD

High-Resolution Lung CT:High-Resolution Lung CT:Key Findings andKey Findings andWhat They MeanWhat They Mean

W. Richard Webb MDW. Richard Webb MD

Key HRCT Findings of Lung DiseaseKey HRCT Findings of Lung Disease

• interlobular septal thickeninginterlobular septal thickening• honeycombinghoneycombing• irregular reticular opacitiesirregular reticular opacities• traction bronchiectasistraction bronchiectasis• nodules (3 patterns)nodules (3 patterns)• ““tree-in-bud”tree-in-bud”• consolidationconsolidation• ground-glass opacityground-glass opacity• emphysemaemphysema• lung cystslung cysts• mosaic perfusion and air trapping mosaic perfusion and air trapping

High-Resolution Lung CT:High-Resolution Lung CT:TechniqueTechnique

High-Resolution Lung CT:High-Resolution Lung CT:TechniqueTechnique

• thin collimation (1 mm)thin collimation (1 mm)

• spaced scans (1-2 cm) spaced scans (1-2 cm)

• prone scans (1-2 cm)prone scans (1-2 cm)

• inspirationinspiration

• expiratory scans (3-5 levels) expiratory scans (3-5 levels)

• MDRCT: volumetric (spiral) scans MDRCT: volumetric (spiral) scans

• 1-2 cm in diameter

Secondary Pulmonary LobuleSecondary Pulmonary Lobule

• interlobular septa(a few visible in nls)

• centrilobular artery(normally visible) and bronchiole(normally invisible)

courtesy H. Itoh

Pulmonary LobulePulmonary Lobule

.

interlobular septa: pulmonary lobules

Interlobular Septal ThickeningInterlobular Septal Thickening

• septal veins

.

• centrilobular artery

• lines outline lobules ofcharacteristic size andshape

Interlobular Septal Thickening: significance

Interlobular Septal Thickening: significance

• ignore IST unless it is a predominant finding ignore IST unless it is a predominant finding

• smooth - interstitial infiltrationsmooth - interstitial infiltration» lymphangitic spread of neoplasm» lymphangitic spread of neoplasm» pulmonary edema» pulmonary edema» rare diseases» rare diseases

• nodular - “perilymphatic pattern”nodular - “perilymphatic pattern”» lymphangitic spread of neoplasm » lymphangitic spread of neoplasm » sarcoidosis» sarcoidosis

• irregular (lung distortion) - fibrosisirregular (lung distortion) - fibrosis» other findings of fibrosis present» other findings of fibrosis present

smooth septal thickening

.

Lung carcinoma: lymphangitic spread.

Lung carcinoma: lymphangitic spread.

. interstitial pulmonary edema

Erdheim-Chester Disease

.

Erdheim-Chester Disease

.

.

nodular septal thickening

sarcoidosis

neoplasm

UIP/IPF

.

asbestosis

.

HoneycombingHoneycombing

• cystic lucencies• air containing• 3-10 mm in diameter

• early: isolated cysts• late: several layers• cysts share walls when numerous

• subpleural

.

UIPUIP(IPF)(IPF)

Honeycombing: differential diagnosisHoneycombing: differential diagnosis

• usual interstitial pneumonia (UIP) usual interstitial pneumonia (UIP)

• idiopathic pulmonary fibrosis (IPF)idiopathic pulmonary fibrosis (IPF)

• rheumatoid arthritis, scleroderma, other CVD rheumatoid arthritis, scleroderma, other CVD

• drugs drugs

• chronic hypersensitivity pneumonitischronic hypersensitivity pneumonitis

• asbestosis (uncommon)asbestosis (uncommon)

• end-stage sarcoidosis (uncommon)end-stage sarcoidosis (uncommon)

• fibrotic NSIPfibrotic NSIP

Rheumatoid lung disease

.

Honeycombing: significanceHoneycombing: significance

• a very important finding in practicea very important finding in practice

• fibrosis is presentfibrosis is present

• UIP is likely the histologic patternUIP is likely the histologic pattern

• in the absence of a known disease, IPF very likely in the absence of a known disease, IPF very likely

• lung biopsy is uncommonly performed iflung biopsy is uncommonly performed ifsignificant honeycombing is visiblesignificant honeycombing is visible

UIP(IPF)

.

.

UIP(IPF)

honeycombing?

paraseptal emphysema

. honeycombing?

.

UIP(IPF)

honeycombing?

honeycombing?

.

UIP(IPF)

honeycombing?

.

????

.

honeycombing?

Honeycombing and window settings

Irregular reticular opacitiesIrregular reticular opacities

• reticular opacities not representingreticular opacities not representinginterlobular septal thickening or honeycombinginterlobular septal thickening or honeycombing

• nonspecificnonspecific

• fibrosis or interstitial infiltrationfibrosis or interstitial infiltration

• ground-glass opacity: likely infiltrationground-glass opacity: likely infiltration

• honeycombing also present: likely fibrosishoneycombing also present: likely fibrosis

• traction bronchiectasis: likely fibrosis traction bronchiectasis: likely fibrosis

Nonspecific interstitial pnuemonia (NSIP)

inflammation fibrosis

.

Traction BronchiectasisTraction Bronchiectasis

• bronchiectasis resulting from fibrosis

• associated with other findings of fibrosis (e.g. reticulation or honeycombing)

• corkscrew appearance• mucous plugging absent• bronchioles may be involved

.

traction bronchiectasistraction bronchiectasis

traction bronchiolectasistraction bronchiolectasis

.

UIP(IPF)

.

.

fibrotic NSIP

.

NSIP

fibrosis

Traction Bronchiectasis:significance

Traction Bronchiectasis:significance

• fibrosis is very likely presentfibrosis is very likely present

• useful in diagnosis when a reticular abnormalityuseful in diagnosis when a reticular abnormalityis unassociated with honeycombingis unassociated with honeycombing

• UIP and IPF are common causesUIP and IPF are common causes

• other causes of fibrosis (i.e. sarcoidosis, HP, NSIP) other causes of fibrosis (i.e. sarcoidosis, HP, NSIP)

are more likely than when honeycombing presentare more likely than when honeycombing present

• biopsy often indicated unless the patient hasbiopsy often indicated unless the patient hasa C-V diseasea C-V disease

Nodules - anatomic distribution (Colby)

Nodules - anatomic distribution (Colby)

• lymphatic distribution -lymphatic distribution - along lymphatics along lymphatics

• random distribution -random distribution - random relative to lung structuresrandom relative to lung structures

• bronchiolocentric -bronchiolocentric - centrilobular airways centrilobular airways

• angiocentric -angiocentric - in relation to small vessels in relation to small vessels

Nodules - anatomic distribution (HRCT)

Nodules - anatomic distribution (HRCT)

• perilymphatic distribution perilymphatic distribution

• random distributionrandom distribution

• centrilobular distributioncentrilobular distribution

• subpleural nodules• peribronchovascular nodules

Perilymphatic nodules

• septal nodules• patchy distribution

• nodules in relation to lymphatics

Perilymphatic Nodules: differential diagnosis

Perilymphatic Nodules: differential diagnosis

• sarcoidosissarcoidosis

• lymphangitic spread of tumor lymphangitic spread of tumor

• silicosis and CWP (uncommon) silicosis and CWP (uncommon)

• amyloidosis (rare)amyloidosis (rare)

• LIP (rare)LIP (rare)

Sarcoidosis

Sarcoidosis

Sarcoidosis

.

Sarcoidosis

.

Sarcoidosis

.

lymphangitic spread of carcinoma.

55 year-oldwoman

withdyspnea

Lymphangitic spread:breast cancer

.

Simple Silicosis

Perilymphatic Nodules: significance

Perilymphatic Nodules: significance

• sarcoidosis or lymphangitic carcinoma very likelysarcoidosis or lymphangitic carcinoma very likely

• clinical history may be sufficient for diagnosisclinical history may be sufficient for diagnosis

• bronchoscopy will likely provide diagnostic bronchoscopy will likely provide diagnostic materialmaterial

• random distribution relative to lung structures

Random nodules

• subpleural nodules• uniform distribution

Random Nodules: differential diagnosisRandom Nodules: differential diagnosis

• miliary TBmiliary TB

• miliary fungal infectionsmiliary fungal infections

• hematogenous metastases hematogenous metastases

• sarcoidosis (uncommon)sarcoidosis (uncommon)

Miliary TB

Miliary TB

. 65 year-old with cough

. Miliary Coccidioidomycosis in AIDS

.

Random Nodules:significance

Random Nodules:significance

• metastases or TB very likely, depending on historymetastases or TB very likely, depending on history

• bronchoscopy will likely provide diagnostic bronchoscopy will likely provide diagnostic materialmaterial

• occur in relation to centrilobular bronchiole or artery

Centrilobular nodules

• centered 5-10 mm from pleura• evenly spaced• diffuse or patchy

no pleural nodulesno pleural nodulesno pleural nodulesno pleural nodules

Multiple NodulesMultiple NodulesMultiple NodulesMultiple Nodules

perilymphaticperilymphaticdistributiondistribution

perilymphaticperilymphaticdistributiondistribution

diffuse anddiffuse anduniformuniform

diffuse anddiffuse anduniformuniform

subpleural nodulessubpleural nodulessubpleural nodulessubpleural nodules

patchy orpatchy ornonuniformnonuniformpatchy orpatchy or

nonuniformnonuniform

centrilobularcentrilobulardistributiondistribution

centrilobularcentrilobulardistributiondistribution

randomrandomdistributiondistribution

randomrandomdistributiondistribution

sarcoidosissarcoidosissilicosissilicosis

lymphangitic carclymphangitic carc

sarcoidosissarcoidosissilicosissilicosis

lymphangitic carclymphangitic carc

miliary TBmiliary TBhematogenous methematogenous met

miliary TBmiliary TBhematogenous methematogenous met

diseases involvingdiseases involvingsmall airwayssmall airways

or vesselsor vessels

diseases involvingdiseases involvingsmall airwayssmall airways

or vesselsor vessels

Hypersensitivity Pneumonitis

.

Centrilobular Nodules: differential diagnosisCentrilobular Nodules: differential diagnosis

• bronchiolitis, e.g. infectious, inflammatory bronchiolitis, e.g. infectious, inflammatory

• endobronchial spread of TB, MACendobronchial spread of TB, MAC

• bronchopneumonia (any cause)bronchopneumonia (any cause)

• hypersensitivity pneumonitishypersensitivity pneumonitis

• endobronchial spread of tumor (BAC) endobronchial spread of tumor (BAC)

• pneumoconiosis (e.g. silicosis)pneumoconiosis (e.g. silicosis)

• organizing pneumonia, i.e. BOOP (rare)organizing pneumonia, i.e. BOOP (rare)

• histiocytosis (rare)histiocytosis (rare)

• edema or vasculitis (uncommon)edema or vasculitis (uncommon)

TB

Viral pneumonia

.

aspiration

.

BAC

Pulmonary hypertension

Pulmonarycapillaryhemangiomatosis

centrilobularnodules

..

Centrilobular branching opacities in talcosis

metastatic calcification

Tree in bud:diagnosis

Tree in bud:diagnosis

• dilatation and impaction of centrilobular airways dilatation and impaction of centrilobular airways

• resembles a budding treeresembles a budding tree

• centered 5 - 10 mm from the pleural surfacecentered 5 - 10 mm from the pleural surface

• more conspicuous than normal branching vesselsmore conspicuous than normal branching vessels

• often associated with centrilobular nodulesoften associated with centrilobular nodules

“tree-in-bud”• dilated, impacted centrilobular bronchioles• clustered centrilobular nodules or rosettes

.

AIDS-related airways disease

.

Tree-in-bud: differential diagnosisTree-in-bud: differential diagnosis

• endobronchial spread of TB, MAC endobronchial spread of TB, MAC

• bronchopneumonia (any cause)bronchopneumonia (any cause)

• bronchiectasis or bronchitisbronchiectasis or bronchitis

• cystic fibrosiscystic fibrosis

• panbronchiolitis (rare)panbronchiolitis (rare)

• aspiration (rare)aspiration (rare)

• ABPA or asthma (rare)ABPA or asthma (rare)

• BAC (rare)BAC (rare)

pseudomonas bronchopneumoniapseudomonas bronchopneumonia

.

Tree-in-bud:significanceTree-in-bud:significance

• a very characteristic appearancea very characteristic appearance

• almost always infectionalmost always infection

• the diagnosis is in the sputum the diagnosis is in the sputum

• if not, bronchoscopy should be diagnostic if not, bronchoscopy should be diagnostic