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93 SUNDAY Society of Thoracic Radiology Annual Meeting and Postgraduate Course Back to Basics: Lateral Chest Radiograph Back to Basics: Lateral Chest Radiograph March 11, 2012 Huntington Beach, California Christopher Lee, M.D. Cardiothoracic Imaging Department of Radiology Keck School of Medicine of USC Disclosures • None Acknowledgements Robert Suh, M.D. (UCLA Medical Center) Introduction Education and clinical importance of the lateral chest radiograph have diminished as CT has become more popular Ease of requesting (and recommending) a chest CT when questionable abnormality seen on frontal CXR Radiology trainees, in particular, have considerable difficulty in recognizing and interpreting the subtleties of the lateral Learning objectives Review fundamental anatomy, variations, and spaces routinely revealed on the lateral CXR Correlate the perspective the lateral view Correlate the perspective the lateral view provides with that provided by multiplanar CT Reinforce an appreciation of the value of the lateral chest radiograph Outline • Trachea Retrotracheal space (Raider triangle) Large airways At i d i Arteries and veins “Three clear spaces” Inferior hilar window Back to Basics: Lateral Chest Radiograph Christopher Lee, MD

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93

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Society of Thoracic Radiology

Annual Meeting and Postgraduate Course

Back to Basics: Lateral Chest RadiographBack to Basics: Lateral Chest Radiograph

March 11, 2012

Huntington Beach, California

Christopher Lee, M.D.

Cardiothoracic Imaging

Department of Radiology

Keck School of Medicine of USC

Disclosures

• None

Acknowledgements

• Robert Suh, M.D. (UCLA Medical Center)

Introduction

• Education and clinical importance of the lateral

chest radiograph have diminished as CT has

become more popular

– Ease of requesting (and recommending) a chest CT

when questionable abnormality seen on frontal CXR

• Radiology trainees, in particular, have

considerable difficulty in recognizing and

interpreting the subtleties of the lateral

Learning objectives

• Review fundamental anatomy, variations, and

spaces routinely revealed on the lateral CXR

• Correlate the perspective the lateral viewCorrelate the perspective the lateral view

provides with that provided by multiplanar CT

• Reinforce an appreciation of the value of the

lateral chest radiograph

Outline

• Trachea

• Retrotracheal space (Raider triangle)

• Large airways

A t i d i• Arteries and veins

• “Three clear spaces”

• Inferior hilar window

Back to Basics: Lateral Chest RadiographChristopher Lee, MD

94

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Trachea

• Easily recognizable

• Anterior tracheal stripe

– Appreciated only on occasionAppreciated only on occasion

• Mediastinal fat

• Air/lung

– May not be visibly altered even in the presence of

extensive pretracheal pathology

Trachea

• Posterior tracheal stripe

– Outlined posteriorly by air in right lung or esophageal

lumen and anteriorly by air in tracheal lumen

– Variable appearance, 1-5 mm

• Posterior tracheal wall only: thin line

• Posterior tracheal wall, intervening tissue,

collapsed esophagus: thicker stripe or band

Trachea

• Posterior tracheal stripe

– Outlined posteriorly by air in right lung or esophageal

lumen and anteriorly by air in tracheal lumen

– Abnormal appearance

• > 5.5 mm

• Persistently thickened on serial radiographs

Trachea

• Posterior tracheal stripe

– Outlined posteriorly by air in right lung or esophageal

lumen and anteriorly by air in tracheal lumen

– Abnormal appearance

• > 5.5 mm

• Persistently thickened on serial radiographs

Trachea

• Posterior tracheal stripe

– Outlined posteriorly by air in right lung or esophageal

lumen and anteriorly by air in tracheal lumen

– Abnormal appearance

• > 5.5 mm

• Persistently thickened on serial radiographs

Retrotracheal space

• Retrotracheal space (“Raider triangle”)

– Boundaries

• Anterior posterior tracheal wall-right lung

• Posterior thoracic vertebral bodies

• Superior thoracic inlet

• Inferior aortic arch-left lung

– Size varies with age, body habitus, and lung inflation

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Retrotracheal space Retrotracheal space

Retrotracheal space

• Retrotracheal space (“Raider triangle”)

– Boundaries

– Contents

Esophagus

Left recurrent laryngeal nerve

Thoracic duct

Lymph nodes

Lungs

Retrotracheal space

• Retrotracheal space (“Raider triangle”)

– Boundaries

– Contents

– Pathology

Congenital vascular lesions

Acquired vascular lesions

Esophageal abnormalities

Mediastinal masses

Infections

Retrotracheal space

i d l l i

esophageal abnormalities

Zenker diverticulum

achalasia

esophageal atresia

duplication cyst

esophageal leiomyoma

congenital vascular lesions

left aortic arch with aberrant right subclavian artery

right aortic arch with aberrant left subclavian artery

double aortic arch

Franquet et al. Radiographics 2002; 22:S231-246

acquired vascular lesions

aneurysm of aberrant subclavian artery

aortic aneurysm

esop agea y

esophageal carcinoma

mediastinal masses

intrathoracic goiter

schwannoma /neurofibroma

hemangioma

lymphatic malformation

hematoma

infections

tuberculous/pyogenic mediastinitis

abscess

Retrotracheal Space

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Large airways

McComb. J Thorac Imaging 2002; 17:58-69

Large airways

Large airways

Courtesy of Robert Suh, M.D.

Large airways

• Right upper lobe bronchus (RUL)

– Projects between aortic arch and left pulmonary

artery

Large airways

• Right upper lobe bronchus (RUL)

– Anterior margin closely related to RUL artery

– Superior margin closely related to azygous vein

Large airways

• Right upper lobe bronchus (RUL)

– Inconsistently visualized

– Increasing conspicuity contiguous pathology

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Large airways

• Left main-upper lobe continuum (LULC)

– Consistently visualized distinct landmark

– Projects below left pulmonary artery

Large airways

• Left main-upper lobe continuum (LULC)

– Projects below left pulmonary artery (LPA)

• LPA (superior and posterior)

• Left superior pulmonary vein (inferior and anterior)

Large airways

• Left main-upper lobe continuum (LULC)

– Continuum along left mainstem into LUL bronchus

• Variable in size and shape

• Occasionally, round lucency within round lucency

Large airways

• Left main-upper lobe continuum (LULC)

– Continuum along left mainstem into LUL bronchus

• Variable in size and shape

• Occasionally, round lucency within round lucency

Large airways

• Left main-upper lobe continuum (LULC)

– Continuum along left mainstem into LUL bronchus

• Variable in size and shape

• Occasionally, round lucency within round lucency

Large airways

• Posterior wall of bronchus intermedius

– Intermediate stem line

– Continuous with right mainstem bronchus, terminating

at origin of RLL superior segmental bronchus

– Approximated posteriorly by azygoesophageal recess

– Typically projects over LULC

• Foretells rotation

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Large airways

• Posterior wall of bronchus intermedius

– Intermediate stem line

– Continuous with right mainstem bronchus, terminating

at origin of RLL superior segmental bronchus

– Approximated posteriorly by azygoesophageal recess

– Typically projects over LULC

• Foretells rotation

Large airways

• Posterior wall of bronchus intermedius

– Intermediate stem line

– Continuous with right mainstem bronchus, terminating

at origin of RLL superior segmental bronchus

– Approximated posteriorly by azygoesophageal recess

– Typically projects over LULC

• Foretells rotation

Large airways

• Posterior wall of bronchus intermedius

– Intermediate stem line

– Continuous with right mainstem bronchus, terminating

at origin of RLL superior segmental bronchus

– Approximated posteriorly by azygoesophageal recess

Large airways

• Posterior wall of bronchus intermedius

– Abnormal > 3 mm

Large airways

• Posterior wall of bronchus intermedius

– Abnormal > 3 mm

Large airways

• Posterior wall of bronchus intermedius

– Abnormal > 3 mm

99

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Large airways

• Posterior wall of bronchus intermedius

– Abnormal > 3 mm

Arteries and veins

• Left pulmonary artery (LPA)

– Short posterosuperior and lateral mediastinal course

– When outlined superiorly by air, resembles “miniature

aortic arch”

Arteries and veins

• Left pulmonary artery (LPA)

– Short posterosuperior and lateral mediastinal course

– When outlined superiorly by air, resembles “miniature

aortic arch”

Arteries and veins

• Left pulmonary artery (LPA)

– Obscured superior border

• AP window lymphadenopathy

– Lobulated posterior border

• Hilar lymphadenopathy

Arteries and veins

• Left pulmonary artery (LPA)

– Obscured superior border

• AP window lymphadenopathy

– Lobulated posterior border

• Hilar lymphadenopathy

Arteries and veins

• Left pulmonary artery (LPA)

– Obscured superior border

• AP window lymphadenopathy

– Lobulated posterior border

• Hilar lymphadenopathy

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Arteries and veins

• Right pulmonary artery (RPA)

– In actuality, “right hilar vascular opacity”

– Conglomerate of pulmonary arteries and veins

Arteries and veins

• Right pulmonary artery (RPA)

– Longer lateral mediastinal course than LPA

– Divides at the edge of the mediastinum

– RPA = upper aspect of right hilar vascular opacity

– Interlobar artery = lower aspect of rt hilar vasc opacity

– Poorly marginated secondary to branching and lack of

adjacent lung

Arteries and veins

• Right pulmonary artery (RPA)

– Longer lateral mediastinal course than LPA

– Divides at the edge of the mediastinum

– RPA = upper aspect of right hilar vascular opacity

– Interlobar artery = lower aspect of rt hilar vasc opacity

– Poorly marginated secondary to branching and lack of

adjacent lung

Arteries and veins

• Right pulmonary artery (RPA)

– Longer lateral mediastinal course than LPA

– Divides at the edge of the mediastinum

– RPA = upper aspect of right hilar vascular opacity

– Interlobar artery = lower aspect of rt hilar vasc opacity

– Poorly marginated secondary to branching and lack of

adjacent lung

Arteries and veins

• Right pulmonary artery (RPA)

– Enlargement of right hilar vascular opacity with

lobulated contour

• Hilar lymphadenopathy

Arteries and veins

• Right ventricular outflow tract

• Ascending thoracic aorta

• Variable visibility• Variable visibility

– Approximation of lung and fat to anterior borders

– Alignment with path of x-ray beam

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Arteries and veins

• Right ventricular outflow tract

• Ascending thoracic aorta

Arteries and veins

• Right ventricular outflow tract

• Ascending thoracic aorta

Arteries and veins

• Inferior vena cava (IVC)

– Occasionally, anterior wall also outlined by lung

Arteries and veins

• Inferior vena cava (IVC)

– Occasionally, anterior wall also outlined by lung

Arteries and veins

• Left brachiocephalic vein

– Retromanubrial opacity

McComb. J Thorac Imaging 2002; 17:58-69

Arteries and veins

• Superior vena cava

• Right brachiocephalic vein

• Innominate artery

• Right subclavian artery• Right subclavian artery

• Composite S-shaped opacity on lateral

radiograph

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Arteries and veins

• Superior vena cava

• Right brachiocephalic vein

• Innominate artery

• Right subclavian artery• Right subclavian artery

McComb. J Thorac Imaging 2002; 17:58-69

Three clear spaces

• “Spine sign”

– Increasing lucency as progress

down thoracic vertebral bodies

• Less soft tissue attenuation in

l h t ll d tlower chest wall compared to

upper chest wall/shoulders

Three clear spaces

• “Spine sign”

– Two types of abnormalities

• Localized opacity with discrete edge

– Lung mass or consolidation

– Mediastinal mass

• Increased density without edge

– Pleural thickening/disease

– Lower lobe collapse

Three clear spaces

• “Spine sign”

– Two types of abnormalities

• Localized opacity with discrete edge

– Lung mass or consolidation

– Mediastinal mass

• Increased density without edge

– Pleural thickening/disease

– Lower lobe collapse

Three clear spaces

• “Spine sign”

– Two types of abnormalities

• Localized opacity with discrete edge

– Lung mass or consolidation

– Mediastinal mass

• Increased density without edge

– Pleural thickening/disease

– Lower lobe collapse

Three clear spaces

• Anterior clear space

– Increasing lucency as progress superiorly from the

densest portion of the heart

• Decreasing width of anterior mediastinum,

b i i t PA/ di t l l tbeginning at PA/ascending aorta level to

SVC/brachocephalic veins

– Variable degree of lucency

• Amount of lung protruding behind manubrium

• Women have decreased retrosternal lucency

103

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Three clear spaces

• Anterior clear space

– Increasing lucency as progress superiorly from the

densest portion of the heart

• Decreasing width of anterior mediastinum,

b i i t PA/ di t l l tbeginning at PA/ascending aorta level to

SVC/brachocephalic veins

– Variable degree of lucency

• Amount of lung protruding behind manubrium

• Women have decreased retrosternal lucency

Three clear spaces

• Anterior clear space

– Increasing lucency as progress superiorly from the

densest portion of the heart

• Decreasing width of anterior mediastinum,

b i i t PA/ di t l l tbeginning at PA/ascending aorta level to

SVC/brachocephalic veins

– Variable degree of lucency

• Amount of lung protruding behind manubrium

• Women have decreased retrosternal lucency

Three clear spaces

• Anterior clear space

– Opacification with our without discrete edge

• Anterior mediastinal mass

• Lung mass or consolidation

Three clear spaces

• Retrocardiac clear space

– Increasing lucency as progress inferiorly from

between the posterior border of heart and anterior

vertebral bodies (infrahilar)

D i idth f di ti• Decreasing width of mediastinum

– Esophagus and azygous vein

– Air-filled right lower lobe (azygoesophageal

recess)

Three clear spaces

• Retrocardiac clear space

– Increasing lucency as progress inferiorly from

between the posterior border of heart and anterior

vertebral bodies (infrahilar)

D i idth f di ti• Decreasing width of mediastinum

– Esophagus and azygous vein

– Air-filled right lower lobe (azygoesophageal

recess)

Three clear spaces

• Retrocardiac clear space

– Opacification with or without discrete edge

• Lung or mediastinal mass (m. common hiatal hernia)

• Lung consolidation (edge represents major fissure)

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Inferior hilar window

• Sub-area of retrocardiac clear space

– Avascular area along anteroinferior hilar composite

– Boundaries

• Right middle lobe bronchus

• Left lower lobe bronchus

– Devoid of nodular opacities > 1 cm

Inferior hilar window

• Sub-area of retrocardiac clear space

– Avascular area along anteroinferior hilar composite

Inferior hilar window Inferior hilar window

Inferior hilar window Inferior hilar window

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Inferior hilar window

Courtesy of Robert Suh, M.D.

Inferior hilar window

Courtesy of Robert Suh, M.D.

Inferior hilar window

Courtesy of Robert Suh, M.D.

Conclusions

• The lateral chest radiograph provides a

perspective that significantly enhances the

evaluation for thoracic disease

• Awareness of routinely visualized anatomic

structures and spaces should facilitate improved

interpretation of conventional chest radiographs

Posttest question

• On a properly positioned (i.e. non-rotated) lateral

radiograph, the posterior wall of the bronchus

intermedius projects over which structure?

a) Right upper lobe bronchus

b) Right hilar vascular opacity

c) Left main-upper lobe continuum

d) Left pulmonary artery

References

1) Franquet T, Erasmus JJ, Gimenez A, et al. The retrotracheal space: normal

anatomic and pathologic appearances. Radiographics 2002; 22:S231-S246.

2) McComb BL. The chest in profile. J Thorac Imaging 2002; 17:58-69.

3) Park CK, Webb WR, Klein JS. Inferior hilar window. Radiology 1991;

178:163-168.

4) Feigin D. Lateral chest radiograph: a systematic approach. Acad Radiol) g g p y pp

2010; 17:1560-1566.

5) Landay MJ. Anterior clear space: how clear? How often? How come?

Radiology 1994; 192:165-169.