33rdrd Seed Program / Shanghai 2015 Seed Program / Shanghai 2015

HRCT of the Lungs: HRCT of the Lungs: Anatomy Basis and Imaging PatternsAnatomy Basis and Imaging Patterns

Gerald F. Abbott MDGerald F. Abbott MD

Harvard Medical School / Massachusetts General HospitalHarvard Medical School / Massachusetts General Hospital

High Resolution CTHigh Resolution CTHRCTHRCT

Developed in 1989Developed in 1989

Optimized for lung parenchymaOptimized for lung parenchyma

High spatial resolution algorithmHigh spatial resolution algorithm

Thin collimation (1-1.5 mm)Thin collimation (1-1.5 mm)

1989: single-slice technique1989: single-slice technique

Today: multidetector techniquesToday: multidetector techniques

HRCTHRCT Scanning ProtocolScanning Protocol

SupineSupine

Full inspirationFull inspiration

Optional Optional

Prone (interstitial lung disease)Prone (interstitial lung disease)

Expiration (air-trapping)Expiration (air-trapping)

InspirationInspiration ExpirationExpiration

Posterior Posterior Tracheal WallTracheal Wall

Inspiration vs ExpirationInspiration vs Expiration

Expiration with atelectasisExpiration with atelectasis(ground-glass opacity)(ground-glass opacity)

Ground Glass Opacity

Ground glass opacity (GGO)

Increased opacity

Does not obscure

underlying anatomy

Ground Glass Opacity

Ground glass opacity (GGO)

Increased opacity

Does not obscure

underlying anatomy

Consolidation

Increased opacity

Does obscure underlying anatomy

Ground Glass Opacity

Non-specific CT finding

May represent Airspace disease

(partial filling of air spaces)

or Interstitial disease

(thickening of interstitium)

NSIP

PCP pneumonia

Sharp pleural interfacesSharp pleural interfaces

Fissures sharp or ground-glass Fissures sharp or ground-glass

HRCTHRCTNormalNormal

Broncho-Arterial PairsBroncho-Arterial PairsNormalNormal

Diameter of Diameter of

normal normal bronchusbronchus

equal to paired equal to paired

pulmonary arterypulmonary artery

HRCTHRCTNormalNormal

No airways visibleNo airways visible

in outer 1/3 of lungin outer 1/3 of lung

BronchiectasisBronchiectasis3 Degrees of Severity3 Degrees of Severity

Cylindrical Cylindrical (mild)(mild)

Varicose Varicose (moderate)(moderate)

Cystic Cystic (severe)(severe)

NormalNormal

BronchiectasisBronchiectasis Degrees of Severity Degrees of Severity

Cylindrical Varicose Cystic Cylindrical Varicose Cystic

Interstitial Network of LungInterstitial Network of Lung

AxialAxialPeribronchovascularPeribronchovascular

Interstitial Network of LungInterstitial Network of Lung

PeripheralPeripheralSubpleural / fissuresSubpleural / fissuresInterlobular septa Interlobular septa ((Kerley B linesKerley B lines))

Extend along theExtend along the

Interstitial NetworkInterstitial Network

PeribronchovascularPeribronchovascular

Subpleural (includes fissures)Subpleural (includes fissures)

Interlobular septaInterlobular septa

Basis for theBasis for the

Perilymphatic PatternPerilymphatic Pattern

Pulmonary LymphaticsPulmonary Lymphatics

Secondary Pulmonary LobulesSecondary Pulmonary Lobules

Key to HRCTKey to HRCT

Lobular Core StructuresLobular Core Structures

Pulmonary arteryPulmonary artery

Bronchiole Bronchiole

LymphaticsLymphatics

Interlobular septa Interlobular septa

Pulmonary veinsPulmonary veins

LymphaticsLymphaticsWebb et al. HRCT of the LungWebb et al. HRCT of the Lung

Secondary Secondary Pulmonary Pulmonary LobuleLobule

AnatomyAnatomyin 3-stepsin 3-steps

3. Interstitium3. Interstitium

2. Vessels2. Vessels

1. Airways1. Airways

Secondary Secondary Pulmonary Pulmonary LobuleLobuleAirwaysAirways

Terminal bronchioleTerminal bronchiole

Respiratory bronchioleRespiratory bronchiole

Alveolar sacsAlveolar sacs

Alveolar ductAlveolar duct

Secondary Secondary Pulmonary Pulmonary LobuleLobuleVesselsVessels

Capillary networkCapillary network

Veins and LymphaticsVeins and Lymphaticsin in interlobular septainterlobular septa Pulmonary Pulmonary

ArteryArtery

Secondary Secondary Pulmonary Pulmonary LobuleLobule

LymphaticsLymphaticsPeribronchovascularPeribronchovascular

Interlobular septaInterlobular septa

SubpleuralSubpleural

Interlobar fissuresInterlobar fissures

Secondary Secondary Pulmonary Pulmonary LobuleLobule3. Interstitium3. Interstitium

InterstitiumInterstitium

Loose connective tissueLoose connective tissue

HRCTImaging Patterns

Reticular opacities

Nodular opacities

Increased lung opacity

Decreased lung opacity

Cystic lung lesions

Honeycombing

Abnormal airways

HRCTHRCTDistribution of Lung DiseaseDistribution of Lung Disease

Upper / Mid / Lower zonesUpper / Mid / Lower zones

Central / PeripheralCentral / Peripheral

Diffuse / PatchyDiffuse / Patchy

Relationship to Secondary Pulmonary LobuleRelationship to Secondary Pulmonary Lobule

(Centrilobular, Perilobular)(Centrilobular, Perilobular)

Relationship to lymphatic pathwaysRelationship to lymphatic pathways

(Perilymphatic)(Perilymphatic)

Core region of Core region of

Secondary Pulmonary LobuleSecondary Pulmonary Lobule

Pulmonary artery, bronchiole, lymphaticsPulmonary artery, bronchiole, lymphatics

HRCT: HRCT: In center of SPLIn center of SPL

5-10 mm from pleural surface5-10 mm from pleural surface

Not related to interlobular septaNot related to interlobular septa

CentrilobularCentrilobularDefinedDefined

Centrilobular Nodules

Evenly spaced

5-10mm from

pleural surface

Soft-tissue

Ground-glass

Tree-in-bud

Centrilobular Nodules

Evenly spaced

5-10mm from

pleural surface

Soft-tissue

Ground-glass

Tree-in-bud

Centrilobular Nodules

Evenly spaced

5-10mm from

pleural surface

Soft-tissue

Ground-glass

Tree-in-bud

Tree-in-Bud OpacitiesTree-in-Bud Opacities

Resembles budding treeResembles budding tree

Small airway diseaseSmall airway disease

(cellular bronchiolitis)(cellular bronchiolitis)

Centrilobular Nodules

Tuberculosis (tree-in-bud)

Hypersensitivity pneumonitis(ground-glass nodules)

Perilymphatic Nodules

Distribution:Distribution:

PeribronchovascularPeribronchovascular

SubpleuralSubpleural

(including fissures)(including fissures)

Interlobular septaInterlobular septa

Sarcoidosis

Lymphangitic carcinomatosis

Perilymphatic Nodules

Perilymphatic / Septal Pattern

Perilymphatic / Septal Pattern

Pulmonary edema

Lymphangitic carcinomatosis

Lymphangitic carcinomatosis

Pulmonary alveolar proteinosis

Random Nodules

Randomly distributed

Not related to SPL

Abut fissures, septa, vessels

Lower zone predominance

Hematogenous spread

DDx:

Miliary infection (TB, fungal)

Metastases (hematogenous)

Septic emboli

Random NodulesMetastases

Abut fissures,

septa, vessels

Lower zone

predominance

Hematogenous

Random NodulesDisseminated Fungal Infection

Abut fissures,

septa, vessels

Lower zone

predominance

Hematogenous

Nodules: Random Distribution

Metastases

Miliary tuberculosis

Hematogenous pattern

of spread to the lungs

Reticular Pattern

Steel Wool

Irregular intersecting lines

Interlobular / Intralobular

Pulmonary fibrosis

Pulmonary Fibrosis

UIP

Advanced UIP Coarse reticular Loss of volume

Early UIP Fine / medium

reticular opacities

Baseline 3 years later

HoneycombingEnd-stage fibrosis

Cystic air spaces 3mm to 3cmCystic air spaces 3mm to 3cm

Thick, clearly defined wallsThick, clearly defined walls

Multi-tieredMulti-tiered

Peripheral, subpleuralPeripheral, subpleural

End-stage lung / Advanced fibrosisEnd-stage lung / Advanced fibrosis

Cystic Pattern

Thin walled

Thick walled

Single tier

Multi-tiered

Cystic Pattern

Thin walled

Thick walled

Single tier

Multi-tiered

DDx:Centrilobular

Emphysema=

imperceptible walls

Cystic Pattern

Lymphangioleio-myomatosis LAM

Centrilobular emphysema

Honeycombing

Honeycombing Associated Findings of Fibrosis

Reticulation(interlobular/ intralobular)

Traction Bronchiectasis

Honeycombing(subpleural;

multi-tiered)

Mosaic Attenuation (Inspiration) Air trapping (Expiration)

Patchwork / ”geographic”

Regions of differing attenuation

Follow outlines of lobules

Inspiratory CT images

Mosaic Attenuation (Inspiration) Air trapping (Expiration)

Patchwork / ”geographic”

Regions of differing attenuation

Follow outlines of lobules

Inspiratory CT images

Constrictive bronchiolitis

Patchy interstitial disease

Occlusive vascular disease

Mosaic AttenuationMosaic AttenuationDifferential DiagnosisDifferential Diagnosis

54-year old woman trapped in a house fire

Inspiration: mosaic attenuation

Constrictive Bronchiolitis from smoke inhalation

Concentric rings of fibrosis around small airways

Expiration: air-trapping

33rdrd Seed Program / Shanghai 2015 Seed Program / Shanghai 2015

HRCT of the Lungs: HRCT of the Lungs: Anatomy Basis and Imaging PatternsAnatomy Basis and Imaging Patterns

Gerald F. Abbott MDGerald F. Abbott MD

Harvard Medical School / Massachusetts General HospitalHarvard Medical School / Massachusetts General Hospital