lung hrct patterns
TRANSCRIPT
HRCT PATTERNS
Secondary lobule
• It is the basic anatomic unit of pulmonary structure and function.
•
It is the smallest lung unit that is surrounded by connective tissue septa.
1-2 cm and is made up of 5-15 pulmonary acini
Supplied by a small bronchiole (terminal bronchiole) in the center, that is parallelled by the centrilobular artery.
Pulmonary veins and lymphatics run in the periphery
Two lymphatic systems: central network peripheral network
Raoof, S. , CHEST 2006; 129:805
6
terminal bronchioles
7
Accompanying pulmonary arterioles
8
Surrounded by lymph vessels
9
Pulmonary veins
10
Pulmonary lymphatics
11
12
Connective Tissue StromaConnective Tissue Stroma
Increased attenuationDecreased attenuation
interlobular septal thickening
Irregular smooth nodularLung distortion
Honey lymphangitic tumor
Combing DDs sarcoidosis Sarcoidosis,asbestosis
smooth
Thick septa predominant ground glass predominant
Lymphangitic tumor crazy paving DDs
Pulm oedemaHaemorrhageAmyloid(rare)
Peribronchovascular interstitial thickening
Lymphangitic spread of carcinomaLymphomaLeukaemiaLIPInterstitial edemaSarcoidosis
Interlobular septal thickening
Focal septal thickening in lymphangitic carcinomatosis
Septal thickening and ground-glass opacity with a gravitational distribution in a patient with cardiogenic pulmonary edema.
Notice the nodules along the fissures indicating a perilymphatic distribution (red arrows).
The majority of nodules located along the bronchovascular bundle (yellow arrow).
Nodular septal thickening
Parenchymal bands
Non tapering reticular opacity,1-3 mm in tickness and 2 to 5 cm in length
Often peripheral and contacts the pleural surface
Represent contiguous thickened interlobulsr septa,peribronchovascular fibrosis,scars or atelectasis
DD’S
AsbestosisSarcoidosisSilicosisTB
Subpleural line
Curvilinear opacity,few mm or les in thickness,prallelling the pleura and less than 1 cm from the pleural surface.
Represent fibrosis / localized alveolar collapse / atelectasis.
Commonly seen in asbestosis
Size, Distribution, AppearanceNodules and Nodular Opacities
28
SizeSize
Small Nodules: <10 mm Micro - <3 mmSmall Nodules: <10 mm Micro - <3 mm
Large Nodules: >10 mm Masses - >3 cmsLarge Nodules: >10 mm Masses - >3 cms
AppearanceAppearance
Interstitial opacity: Well-defined, homogenous,Soft-tissue densityObscures the edges of vessels or adjacent structure
Interstitial opacity: Well-defined, homogenous,Soft-tissue densityObscures the edges of vessels or adjacent structure
Air space: Ill-defined, inhomogeneous.Less dense than adjacent vessel – GGOsmall nodule is difficult to identify
Air space: Ill-defined, inhomogeneous.Less dense than adjacent vessel – GGOsmall nodule is difficult to identify
Based on distribution
Perilymphatic
Centrilobular
Random
Sarcoidosis
The majority of nodules located along the bronchovascular bundle (yellow arrow).
Centrilobular nodules
5 to 10mm away from the pleural surfaceEvenly spacedAssociated with pumonary artery branchesIf air filled centrilobular bronchiole----lucency
within the nodule
Causes
Bronchiolar and peribronchiolarVascular and perivascular
Bronchiolar and peribronchiolar
Endobronchiolar spreadHSPBronchiolitis obliteransRespiratory bronchiolitisCystic fibrosisBronchiectasis
Vascular and perivascular
Pulmonary edemaVasculitisPulmonary hemorrhagePulm HTN
Tree-in-bud
44
Centrilobular nodules m/b further characterized by presence or absence of ‘‘tree-in-bud.’’
Tree-in-bud -- 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 finding is almost always seen with pulmonary infections.
Tree-in-bud
Typical Tree-in-bud appearance in a patient with active TB.
Random nodules
Hematogenous metsMiliary TBMiliary fungal infectionsSarcoidosis ( extensive)LCH
Langerhans cell histiocytosis: early nodular stage before the typical cysts appear.
Parenchymal opacification
GGOConsolidationLung calcification and high attenuation
opacities
Ground glass opacity
Hazy increase in lung opacity not associated with obscuration of underlying vessels or bronchial margins
Significance of GGO
Acute symptoms---asociation with active disease
Subaute or chronic---active disease / fibrosis
Crazy paving pattern
Superimposition of reticular pattern on GGOPAPAcute silicosisPulmonary edemaPulmonary haemorrhageARDSP.Carnii pneumonias
Consolidation
Increased lung attenuation with obscuration of underlying vessels
Lung calcification and high attenuation opacities
Multifocal calcification (often with nodules) T.B, Histoplasmosis, varicella pneumonia,
sarcoidosisDiffuse and dense calcification Metastatic calcification (due to
hypercalcemia ,in patients with CRF, Hyperparathyroidism) – calcification mainly interstitial.
Disseminated pulmonary ossification Alveolar microlithiasis (posterior and lower
lobe predominance
Low attenuation
Lung cysts,emphysema and bronchiectasis
Honey combingLung cystsEmphysemaBullaePneumatocoelesCavitary nodulesBronchiectasis
HONEYCOMBING67
Defined as - small cystic spaces with irregularly thickened walls composed of fibrous tissue.
Predominate in the peripheral and subpleural lung regions
Subpleural honeycomb cysts typically occur in several contiguous layers. D/D- paraseptal emphysema in which subpleural cysts usually occur in a single layer.
Honey combing
Air filled cystic spacesSeveral mm to cms in diameterPeripheral and subpleuralDefinable walls,1 to 3 mm in thicknessAssociated with findings of lung fibrosis
69
Causes
Lower lobe predominance : 1. UIP or interstitial fibrosis 2. Connective tissue disorders 3. Hypersensitivity pneumonitis 4. Asbestosis 5. NSIP (rare)
Upper lobe predominance : 1. End stage sarcodosis 2. Radiation 3. Hypersensitivity Pneumonitis 4. End stage ARDS
Honeycombing
Typical UIP pattern with in a patient with idiopathic pulmonary fibrosis
Lung cysts
Well defined rounded or circumscribed lesion with a wall that may be uniform or varied in thickness ( < 2-3 mm)
LAMLCHLIPBullaePneumatocoelesHoneycombingCystic bronchiectasis
Langerhans cell histiocytosis
HRCT Appearances LAM
Numerous thin-walled cysts, surrounded by normal parenchyma. Round in shape and more or less uniform.
Mediastinal or hilar adenopathy .Chylous Pleural effusions (40%).Recurrent pneumothorax (40%)
Multiple thin-walled cysts of roughly uniform
size.
Unlike LCH, the cysts in LAM tend to be
rounded and uniformly distributed throughout
the parenchyma with no regional sparing.
There is a conspicuous absence of nodules.
Lymphangiomyomatosis complicated by pneumothorax
Emphysema
Permanent abnormal enlargement of air spaces distal to terminal bronchiole accompanied by destruction of walls of involved air spaces
CentrilobularParaseptalPanlobularIrregular / cicatricalBullous
Centrilobular emphysema Most common type Upper lobe predominance Strongly associated with smoking.
Centrilobular emphysema 81
Manifests as multiple small areas of low attenuation without a perceptible wall, producing a punched-out appearance.
Often the centrilobular artery is visible within the centre of these lucencies.
Centrilobular emphysema due to smoking. The periphery of the lung is spared (blue arrows). Centrilobular artery (yellow arrows) is seen in the center of the hypodense area.
Panlobular emphysema Affects the whole secondary lobule
Lower lobe predominance In alpha-1-antitrypsin deficiency, but also seen in smokers with advanced emphysema
PANLOBULAR EMPHYSEMA
84
Panlobular emphysema
Paraseptal (distal acinar) emphysema86
Affects the peripheral parts of the secondary pulmonary lobule
Produces subpleural lucencies.
Paraseptal emphysema
Paraseptal emphysema v/s honeycombing
Centrilobular emphysema and lung cysts
Bullae and blebs
Bulla : sharply demarcated area of emphysema measuring 1cm or more in diameter with a wall that is < 1 mm.
Bleb: focal thin walled lucency contigous with pleura usually at lung apex
Pneumatocoele
Thin walled gas filled space within the lung,usually assosciated with pneumonia
Appearance similar to cyst or bulla and cannot be differentiated
Cavitary nodules
• Thicker and irregular walls than cysts• LCH• TB• Fungal infections• Sarcoidosis• Rheumatoid lung disease• Mets• wegeners
Bronchiectasis
Localized irrevesible bronchial dilatation with thickening of the bronchial wall.
CylindricalVaricoseCysticTraction
• localized bronchial dilatation. (signet-ring sign) bronchial wall thickening lack of normal tapering with visibility of airways
in the peripheral lung mucus retention in the broncial lumen
ABPA: glove-finger shadow due to mucoid impaction in central bronchiectasis in a patient with asthma.
Signet-Ring Sign
A signet-ring sign represents an axial cut of a dilated bronchus (ring) with its accompanying small artery (signet).
Tram Tracks
Mosaic perfusion and attenuation
Due to airway diseaseDue to vascular diseaseInfiltrative process adjacent to normal lung
Inhomogenous lung opacity
Decreased vessel size Uniform sized vessels
Some regions too lucent Some regions too dense
No reticulation Associated reticulation,
No Nodules Nodules
Mosaic perfusion Ground glass opacity
Inhomogenous lung opacity
Decreased size of vessels uniform sized vessels
(suspect mosaic perfusion) (suspect GGO)
No air trapping air trapping no air trapping
Vascular disease obstructive disease infiltrative disease
Chronic PE small airways disease GGO DD’s
large airways disease
Air trapping on expiration
Diagnosis of air trapping in obstructive lung disease
Diagnosis of airway diseases with normal inspiratory scan
Distinguishing mosaic perfusion from GGOAllowing the diagnosis of mixed infiltrative
and obstructive diseases
Nodular pattern
1.Hypersensitivity pneumonitis:2.Miliary TB: random nodules 3.Sarcoidosis4.Hypersensitivity pneumonitis
Low Attenuation pattern
Lymphangiomyomatosis (LAM)LCH
Honeycombing Centrilobular emphysema
Thank you
Mosaic perfusion
Pulmonary hypertension Abnormal airwaysLarge areas of lucency Lobular lucencies
Vascular disease Obstructive disease
Chronic PE small airways disease
lareg airways disease