ct chest imaging · 2018-06-14 · ct •1-5mm slice thickness • 0.5-1mm slice thickness •...
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CT CHEST IMAGING
Sahar Ahmad, MD
Division of Pulmonary and Critical Care
Stony Brook Medicine
OBJECTIVES
• CT and HRCT basics and indications
• Lung anatomy
• How to describe CT findings
• Clinical correlations
CT
• 1-5mm slice thickness • 0.5-1mm slice thickness
• Sharp high spatial frequency reconstruction algorithm
Benefits:
Less volume averaging
- better estimation of nodule/mass volume (SPN)
- better estimation of bronchial wall diameter (bronchiectasis)
- better estimation of vessel diameter
HRCT
CT: BASICS
However:
vessels can look like nodules
(short segments are caught in the scan plane)
5mm cuts better to follow vessels
CT CHEST
• Lung cancer screening
• SPN, multiple nodules monitoring
• Follow up of indiscrete parenchymal
findings
• CTPA: diagnose PE
• SPN, multiple nodules
• Monitor over time
• Guide for TBBx or TTFNA
• Navigational bronchoscopy
• Virtual Bronchoscopy
• Interstitial lung disease
• Bronchiectasis
• Discrete findings followed over time
HRCT CHEST
CT, HRCT CHEST: INDICATIONS
AXIS PLANES
OBJECTIVES
• HRCT basics and indications
• Lung anatomy
• How to describe CT findings
• Clinical correlations
• Airways
• Vasculature
• Mediastinum
• Lymph Nodes
• Heart
• Pleura
• Lung Parenchyma
• Name abnormality
• Distribution
• Clinical data
LUNG ANATOMY:THE SECONDARY PULMONARY LOBULE
• smallest unit of lung structure
• marginated by connective
tissue septa
• 5-12 acini in SPL
LUNG ANATOMY: THE ACINUS
• Acinus: portion of lung distal to a terminal bronchiole
• supplied by a first-order respiratory bronchiole(s).
• 6 -10 mm diameter
• HRCT basics and indications
• Lung anatomy
• How to describe CT findings
• Clinical correlations
RETICULAR OPACITIES
CT FINDINGS: RETICULAR OPACITIES
INTERLOBULAR SEPTA
http://www.radiologyassistant.nl
Smooth interlobular septal thickening
clinical correlation: Pulmonary edema, lymphangitic spread;
hemorrhage, or veno-occlusive disease; lymphangiomatosis;
amyloidosis; pneumonia; alveoloar proteinosis
Nodular (beaded) interlobular septal
Thickening
clinical correlation:
Sarcoid
Lymphagitic spread of CA
Lymphoproliferative disease
(eg, lymphocytic interstitial pneumonia),
Silicosis, coal worker’s pneumoconiosis,
amyloidosis
BRONCHIECTASIS
• irreversible localized or diffuse bronchial dilatation
• identification of bronchi within 1 cm of the pleural surface
• bronchi do not taper
• Airway caliber on cross section is larger than that of associate vessel
Signet ring
DDX: BRONCHIECTASIS
Diffuse-central- ABPA- cartilage deficiency syndr
peripheral upper lung- CF- sarcoid- post XRT
peripheral low- idiopathic- chronic aspir- fibrotic lung disease
- XP rejection (BOOP)- hypoganmmaglob- HIV
Focal to a lobe-
lingula, middle lobe- MAC- immotile cilia
Other Focal-- mechanical obstruction
FBO, airway mass
other stenosis
extrinsic compression
- congen bronchial atresia- Other congenital syndromes (rare)
Diffuse bilateral bronchiectasis in Cystic Fibrosis
Focal- lobar bronchiectasis of MAI, post- infection, or endobronchial obstruction
NODULES
CT FINDINGS: NODULES
Tree in bud
RANDOM NODULES
• do not follow a particular pattern of involvement with respect to the pulmonary architecture and the secondary pulmonary lobule.
• Can be at fissures, peribronchovascular structures and the center of the secondary pulmonary nodules
Ddx.
• hematogenous metastastic disease
• miliary spread of tuberculosis
• miliary fungal infections
• Langerhans cell histiocytosis
PERILYMPHATIC NODULES
• Trace pleural surfaces, interlobular septa, bronchovascular interstitium, subpleural, at fissure.
Ddx.
• sarcoidosis (especially peri-bronchovascular and fissures)
• lymphangitic spread of carcinoma
• pneumoconiosis: silicosis, coal worker's lung
• amyloidosis (rare)
• lymphoid interstitial pneumonitis (rare)
CENTRILOBULAR NODULES
• appear at the center of the secondary pulmonary lobules;
• represent engorgement of the pulmonary arteriole and/or
occlusion of the centrilobular bronchiole.
• do not touch the pleural surfaces or fissures
Ddx.
• - infection
- hypersensitivity pneumonitis
- respiratory bronchiolitis in smokers (RB-ILD)
- bronchioloalveolar carcinoma
- pulmonary edema
- vasculitis
SMALL AIRWAY NODULES: TREE IN BUD
Ddx.
• Infectious bronchiolitis, esp viral
(often unilateral/ lobar)
• pan- bronchiolitis (bilateral/ diffuse)
ATTENUATION PATTERNS
ATTENUATION PATTERNS
• Increased attenuation
• Consolidation: Dense, white
• Atelectasis: Dense White
• Ground Glass Opacity (GGO): Light Grey
• underlying vasculature still visible, alveoli not obliterated
• Decreased Attenuation: Dark Grey- Black
• air trapping
• Emphysema
• cystic lung disease
• Pneumothorax
CONSOLIDATION
INCREASED ATTENUATION PATTERN: CONSOLIDATION, INFILTRATE
Air bronchogram distinguishes infiltrate from atelectasis.
Ddx. PNA, other infiltrative diseases
INCREASED ATTENUATION PATTERN: ATELECTASIS
• RML atelectasis.
• Smooth border
• Lack of air bronchogram
INCREASED ATTENUATION: PARENCHYMAL OPACITIES
INCREASED ATTENUATION PATTERN: GGO
nonspecific
Alveolitis or interstitial pneumonitis
- HSP, IPF (early). Sarcoid
- Pulmonary edema, DAH
- Resolving PNA
GGO
GGO: CRAZY PAVING
• Ddx: PAP, PCP, DAH, Lipoid PNA, drug or xrt induced pneumonitis,
mucinous adenocarcinoma
June 2007 Radiology, 243,905-906
Interlobular septal
thickening superimposed
on a background of GGO,
resembling irregularly
shaped paving stones.
DECREASED ATTENUATION PATTERN: EMPHYSEMA
Paraseptal emphysema:
Thin walled air pockets
Along the periphery including mediastinal edge
Associated with bullae formation and pneumothorax
Panacinar/Panlobular Emphysema::
Generalized diffuse over- lucency of the lung parenchyma
Centrilobular Emphysema:
Multiple small lucencies
absence of discrete walls
DECREASED ATTENUATION PATTERN: CYSTS
UIP/IPF
Findings: Reticular opacities/fibrosis, traction bronchiectasis, honeycomb cysts
Distribution: posterior, low lobes, peripheral
• Honeycomb cysts
PLCH
• Irregular, bizarre shaped cysts
• Nodules often present
LAM
• Female patient
• Diffuse, small, regular cysts
CYSTIC BRONCHIECTASIS
• Dilated airways
• Cyst formation
• Volume loss
• RML, Lingula
DIFFUSE PARENCHYMAL LUNG DISEASES
UIP (IPF)
Distribution:
Peripheral, Low lobes
Honey comb cyst
Traction bronchiectasis
Reticulations
Minimal focal GGO
NSIP
Distribution:
Peripheral
Without upper-lower gradient
GGO
Minimal: reticulations, micronodules, cysts
NODULES AND MASSES
NODULE
• Any pulmonary, pleural, or
mediastinal rounded opacity
• Well or poorly defined
• Solid and Ground glass components:
depending on dominant component,
managed differently
• <3cm diameter at largest plane
MASS
• Any pulmonary, pleural, or
mediastinal opacity
• Solid or partly solid.
• >3 cm in diameter (without
regard to contour, border, or
density characteristics)
SUMMARY
• Describe Distribution
• Right, left bilateral
• Diffuse, focal
• Upper, lower lobe dominant
• Peripheral, central
• Describe Finding
• Reticular opacities
• Nodule patterns
• Attenuation patterns
• Emphysema pattern
• Cysts
• Nodule, Mass
Consider clinical data to arrive at Ddx
REFERENCES AND FURTHER READING
• http://www.radiologyassistant.nl
• Fleischner Society: Glossary of Terms for Thoracic Imaging
• High Resolution CT of the Lung. Webb, Muller, Naidich. Lippincott. 2009.
• Thin-Section CT of the Secondary Pulmonary Lobule: Anatomy and the Image— The 2004
Fleischner Lecture
• What every Radiologist Should Know About Interstitial Pneumonias.
Radiographics Volume 27 ● Number 3
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