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