Imaging in Thoracic Trauma

IMAGING IN
THORACIC TRAUMA
WAN NAJWA ZAINI WAN MOHAMED
RADIOLOGIST, HOSPITAL QUEEN ELIZABETH II
1st Sabah Thoracic Surgical Update, 5 – 6 Oct 2018

CONTENTS
• INTRODUCTION
• ANATOMY OVERVIEW
• IMAGING TOOLS
• RADIOLOGICAL SIGNS/ FEATURES

INTRODUCTION
• Trauma is a leading cause of death in developing countries | 4th in first-world
countries
• Loss of productive years of life – because most occur in young individuals
• Traffic accidents, falls, recreational, violence
• Rapid diagnosis important to avoid morbidity and mortality

INTRODUCTION
• Thoracic injuries
10-15% of all trauma, 25% of trauma fatalities
• Mechanism of trauma
Direct Injury – Blunt, Penetrating, Baro Trauma, Radiation Trauma
Indirect Injury – Complication Of Remote Injury/ Treatment
• Blunt Chest Injury
Causes – MVA (75%), fall, blow, blast, violent action
30% require hospital admission

INTRODUCTION
• Penetrating Injury
Causes: Fracture of rib, gunshot, stab
Permanent cavity inside the tissue, crushed, expansion
Projectile passes through – tract
• Blunt (70-80%) > penetrating
– Compression  thoracic wall injuries
– High velocity injury  visceral injuries
• Rx mostly conservative. Thoracotomy rate <10% in blunt, 15-30% in penetrating
thoracic trauma

CHEST ANATOMY OVERVIEW
• Thoracic cage:
 anterior: sternum
 posterior: thoracic spine, scapula
 lateral: ribs, clavicle
• Content:
 mediastinum – superior, anterior, middle and posterior
 Lung parenchyma
 Pleura – negative pressure

• Gross anatomy
air spaces, bronchial tree, interstitium,
vascular system, lymph nodes /
lymphatic system, pleural reflection,
thoracic cage
• Radiographic anatomy
opaque – interstitium, lymph nodes,
vascular system, thoracic cage
lucent – air spaces, bronchial tree

RIGHT LUNG : LOBAR AND SEGMENTAL BRONCHUS
• Main bronchus – steeper,
shorter, wider
• 3 lobar, 10 segmental
bronchus – upper (3),
middle (2), lower (5)
• Bronchioles – 6-20 division
of segmental bronchus
• Upper lobe bronchus – 2.5
cm after bifurcation

LEFT LUNG : LOBAR AND SEGMENTAL BRONCHUS
• Main bronchus – less
steeper, longer
• 2 lobes, 9 segmental –
upper (5), lower (4) medial
basal
• Upper lobe bronchus – 5 cm
after bifurcation

PLEURA
• Parietal pleura – lining the thoracic cavity
• Visceral pleura – investing the lung
• Fissure: 2 layers of visceral pleura –
oblique (both sides) and transverse (right
only)
• Accessory lobe: azygous, posterior
accessory (left), inferior accessory (right),
middle lobe (left) – 4 layers of pleura
• Costophrenic angles: most dependent
space – 50 ml obliterate posterior, 100-
150 ml obliterate lateral

IMAGING TOOLS
1. Chest Radiograph
Portable
2. Ultrasound (as a part of extended FAST)
Bedside
3. CT Scan
most accurate
Initial survey /
“screening tool”

Chest Radiograph
• Views
Preferably AP erect
CXR in expiration – detect small pneumothorax
AP supine at the end of inspiration
Decubitus - suspected side up
• Supine radiograph is most difficult to analyse, under reporting is common

Chest Radiograph
• Indications
Tube and line malposition – most critical
Thoracic cage injury, Flail chest
Pneumothorax, Hemothorax
Pneumomediastinum, pneumopericardium
Lung contusion/ laceration
Mediastinal widening
Diaphragm injury
Others –spine fractures

2. Ultrasound (eFAST Scan)
• Extended FAST (eFAST) very useful for quick pericardial and pleural spaces
evaluation in chest trauma
• Can detect 15 - 20 ml of fluid
• Studies have shown excellent sensitivities and specificities approaching 100%
• Able to decrease time to operative intervention, patient length of stay, cost,
rates of complications, CTs, and DPLs performed
• Limitations : operator’s experience, patient’s body habitus, presence of
subcutaneous emphysema, pneumoperitoneum or pneumomediastinum

2. Ultrasound (eFAST Scan)
PERICARDIAL EVALUATION
• Curvilinear probe
• Technique
B-mode (grey scale)
Subcostal/ subxiphisternum –
transverse plane, liver as window
• Indications
Haemopericardium
Cardiac Tamponade
PLEURAL EVALUATION
• Curvilinear/ linear probe Technique
B mode, M mode if B mode
equivocal
Anterior thoracic - longitudinal
plane along midclavicular line at 3rd
– 4th intercostal space
• Indications
Pneumothorax
Haemothorax

3. CT Scan
• Most accurate for diagnosis of several thoracic trauma
• Yield of CT is higher when done after an abnormal initial CXR or performed
selectively based on clinical criteria
• Patient preparation
Hemodynamic – must be stable
IV contrast – a must
Renal function test – risk/benefit ratio
Pregnancy test – yes if status unknown/ in doubt
• CT Technique
Helical mode

3. CT Scan
No plain scan
Thinnest collimation possible and 2 – 2.5mm multiplanar reformation
Late arterial phase + delays for vascular injuries
• Indications
Injuries of pleural space
Injuries of lungs, airways
Injuries of heart, oesophagus
Injuries of aorta and great vessels
Injuries of diaphragm
Injuries of chest wall

RADIOLOGICAL
SIGNS &
ASSESSMENT

RADIOLOGICAL SIGNS &
ASSESSMENT
• Isolated sign not common. Usually in combination
• E.g. Fractured ribs might cause major injury to the lung parenchyma
(contusion, laceration and hemorrhage) and other complications
• Recap:
Table 1: Attenuation of the X-Ray beam
Tissue absorption Effect on the radiograph
Least Air or gas
Fat
Soft tissue
Most Bone or
calcium
Black image
Dark grey image
Grey image
White image

RADIOLOGICAL SIGNS &
ASSESSMENT
1. Tubes/ Lines - malposition
2. Soft tissue – subcutaneous emphysema, foreign bodies
3. Thoracic Cage – fracture, flail chest
4. Pleura – pneumothorax, tension pneumothorax, haemothorax,
pneumohaemothorax
5. Lung – contusion, laceration, fat embolism, aspiration pneumonia, foreign body,
pulmonary oedema, adult respiratory distress syndrome
6. Trachea & Bronchi – laceration, fracture
7. Mediastinum – aortic Injury, mediastinal hematoma, pneumomediastinum,
pneumopericardium, haemopericardium, oesophageal rupture
8. Diaphragm – rupture
9. Others – spine fracture, cord injury, nerve root injury

1. Tubes/ Lines
Tubes/ Lines Malposition
• Ideal position of ETT tip = 5 ± 2 cm
above carina @ T2 to T4 level
• Tip position changes depending on
neck position and rotation
may change by up to 2 cm
neck flexion  tip downwards
neck extension  tip upwards
• In children, optimum position is 1.5
cm above carina
Right mainstem bronchial intubation

1. Tubes/ Lines
Left chest tube – chest wall placement NG tube – looped around carina
Case courtesy of A.Prof Frank Gaillard, Radiopaedia.org, rID: 32358

2. Soft Tissue
Subcutaneous emphysema
• Most common cause: trauma
• Presence of air locules in the
subcutaneous tissue or muscle
plane. May track to the neck and
abdominal wall.
• Hyperlucencies in the subcutaneous
tissue or along muscle plane
“Gingko leaf sign”

3. Thoracic Cage
Rib fracture
• Most frequent 4-10
• If 8-12, should suspect associated
abdominal injuries
• 1st to 3rd rib fractures considered
high energy trauma, often
associated with major intrathoracic
or cranial injuries

3. Thoracic Cage
Flail Chest
• Most significant chest wall injuries
• Associated with high impact
• When 3 or more contiguous
segmental ribs fractured in 2 or
more places
• Affected wall sunken in during
inspiration
• Patients often require mechanical
ventilation for prolonged periods

3. Thoracic Cage
Clavicle fracture
• most common chest wall injuries
• 80% occur in middle third
Scapular fracture
• Uncommon
Sternal fracture
• Usually associated with high energy
trauma
• Commonly at body, manubrium
Sternoclavicular dislocation
• Anterior – more common, benign
course
• Posterior – more serious, assoc. with
major intrathoracic injuries

4. Pleura
Pneumothorax
• Air in the pleural space
• Causes:
Fractured rib penetrates the lung
parenchyma
Rapid acceleration-deceleration
Barotrauma – IPPV
Cardiopulmonary resuscitation
• Signs in upright CXR:
Visible visceral pleural edge as a thin
sharp white line
No lung markings peripheral to line
• Signs in supine CXR:
Hyperexpanded hemithorax
Increased lucency
Increased sharpness of heart border
Deep sulcus sign – when air collects
laterally and deepens the lateral
costophrenic angle
Double diaphragm sign – when air
outlines anterior portions of
hemidiaphragm, anterior costophrenic
sulcus visualized

4. Pleura
• eFAST Normal lung:
B mode – Lung sliding “marching
ants sign”
M Mode – “Seashore” appearance
• eFAST Pneumothorax:
B mode – Loss of lung sliding “dead
ants sign”
M mode – Stratosphere “Barcode”
B & M modes – lung point, most
specific sign

4. Pleura
Tension Pneumothorax
• Air leak from lung parenchymal injury, increasing pressure within
• Mediastinal displaced away
decreased venous return
compressing opposite lung
• Hemodynamically unstable, can progress to complete cardiovascular collapse
• Immediate decompression needed

Postmortem CXR. Image from trauma.org

4. Pleura
Haemothorax
• Blood in pleural space
• Source: chest wall, lung parenchyma, heart or great vessels
• In 25-50% of patients with blunt chest trauma and 60-80% of patients with
penetrating wounds
• Radiographic features similar to pleural effusion
• Massive hemothorax when >1,500 mL of blood or > 1/3 of blood volume
• Tension haemothorax – massive intrathoracic bleeding causing ipsilateral
lung compression and mediastinal displacement

4. Pleura
• eFAST very high sensitivity (92%), and specificity (100%)
• CT useful to evaluate nature of pleural fluid in the setting of trauma by
assessing the attenuation value. Blood attenuation 35-70 HU
Case courtesy of Dr Andrew Dixon,
Radiopaedia.org, rID: 31555

4. Pleura
Haemopneumothorax
• When there is concurrent presence
of a haemothorax and
a pneumothorax
• Concurrently occur in 5% of patients
with pneumothorax

5. Lung
Contusion
• Interstitial and/or alveolar lung injury
without any frank laceration
• Usually occurs secondary to non-
penetrating trauma
• CXR:
Not sensitive
Faint patchy consolidative regions
following history of blunt trauma
Usually shows rapid improvement with
time in days

5. Lung
• CT :
Typically seen as focal non
segmental (typically crescentic)
areas of parenchymal opacification
Can have sub-pleural sparing
with smaller contusions which
can be a distinguishing feature
Commoner posteriorly and in
lower lobe

5. Lung
Laceration
• Results from frank laceration of lung parenchyma secondary to trauma, there is
almost always concurrent contusion
• Classification :
Type I : compression rupture
Type II : compression shear
Type III : direct puncture / rib penetration
Type IV : adhesion tears
• CXR:
Linear tear that becomes round or ovoid (pneumatocele) with time
Can be similar to contusion. Gaseous lucencies may be seen in or adjacent to the
areas of consolidation

5. Lung
 May be difficult to appreciate, often obscured by surrounding lung contusion,
consolidation and hemothorax.

5. Lung
• CT:
Regions of pulmonary contusion
and blebs (pneumatocoeles) with
air fluid levels
Due to normal pulmonary elastic
recoil, lung tissues surrounding a
laceration often pull back from the
laceration itself, manifesting as a
round or oval cavity
Pneumatocoeles appear as 'holes'
in the lung parenchyma “Swiss
cheese sign”
Case courtesy of Dr Domenico Nicoletti, Radiopaedia.org, rID: 38519

5. Lung
Fat Embolism
• Lipid emboli from bone marrow enter
pulmonary and systemic circulation
• Usually occurs in the context of a long
bone fracture
• 1 to 2 days post-trauma, resolves in 1-4
weeks
• CXR:
Can resemble ARDS
Widespread homogeneous &
heterogeneous opacities

5. Lung
• CT:
Areas of consolidation
Ground-glass opacities with
geographic distribution and/or
interlobular septal thickening
Small (<1cm) nodular opacities
Fatty filling defects in pulmonary
arteries – rare

6. Trachea & Bronchi
Tracheobronchial Injury
• 1.5% of major thoracic trauma, 30%
missed
• 80% within 2.5 cm of carina (blunt
trauma)
• Can be identified in 70% of CT
• Bronchoscopy gold standard
• CXR:
Subcutaneous emphysema
Pneumothorax
Pneumomediastinum
Bronchial injury – pulmonary alveolar
rupture “Macklin effect”
Case courtesy of Dr Bruno Di Muzio, Radiopaedia.org, rID: 59456

7. Mediastinum
Aortic Injury
• Critical life threatening condition
• 16% MVA fatalities, more with blunt
trauma
• 85-90% mortality prior to reaching
hospital
• 90% of aortic ruptures occur just
distal to the origin of the left
subclavian artery

7. Mediastinum
• CXR (related to signs of mediastinal
haematoma):
Widening of the mediastinum > 8 cm
at aortic arch level
Tracheal or NG tube deviation to the
right
Widening of right paraspinal or
paratracheal stripe
Loss of aortopulmonary window
indistinct aorta definition
Left apical cap sign
Normal in 10-15%
Case courtesy of Dr Andrew Dixon, Radiopaedia.org, rID: 45368

7. Mediastinum
• CT may show indirect signs:
Mediastinal hematoma
Periaortic fat stranding
Other chest injuries
• CTA :
Signs of mediastinal hematoma
Abnormal soft tissue density
around the mediastinal structures
Location is important, periaortic
hematoma much more suggestive
than isolated mediastinal
hematoma remote from aorta
Signs of aortic injury :
Intraluminal filling defect (intimal
flap or clot)
Abnormal aortic contour (mural
hematoma)
Pseudoaneurysm
Extravasation of contrast

Case courtesy of Dr Sophie O'Dowd, Radiopaedia.org, rID: 47799

TEVAR Procedure

7. Mediastinum
Pneumomediastinum
• Presence of extraluminal gas within the mediastinum.
• Gas may originate from lungs, trachea, bronchi, oesophagus, peritoneal
cavity and track from mediastinum to neck or abdomen
• CXR:
Small amounts of gas appear as linear or curvilinear lucencies outlining
mediastinal contours:
Anterior to the pericardium - pneumopericardium
Around the pulmonary artery or its major branches ‘ring around artery sign’

7. Mediastinum
Around the aorta or its major branches ‘tubular artery sign’
Around the bronchial tree ‘double bronchial wall sign’
Trapped posterior to pericardium ‘continuous diaphragm sign
Subcutaneous emphysema
Pediatric – elevated thymus ‘spinnaker sail sign’

Case courtesy of Radswiki, Radiopaedia.org, rID: 11791

7. Mediastinum
Pneumopericardium
• Gas does not extend beyond aortic root
or main pulmonary artery
• Occasionally difficult to differentiate
with pneumomediastinum
Pneumo Gas extension Air distribution
Mediastinum Outline aortic
knuckle
Little or no change on
positioning
Pericardium Aortic root,
MPA
Alter with positioning

7. Mediastinum
Haemopericardium
• Accumulation of blood in the pericardium
• Source: Great vessels, heart, pericardial vessels
• CXR:
>250 mL is necessary to be detectable
Subpericardial fat stripe measures >10 mm
Symmetrical enlargement of cardiac silhouette (water-bottle sign)
• eFAST:
Fluid (anechoeic) around the heart
Cardiac Tamponade – collapsed right heart chambers (RV specific), distended
IVC

7. Mediastinum
Oesophageal Rupture
• A rare but serious medical emergency
with a very high mortality rate
• CXR:
Non-specific
Usually show wide mediastinum,
pneumomediastinum, left pleural
effusion, hydropneumothorax
• Contrast Enhanced Esophography :
Extravasation of contrast material into
the mediastinum

7. Mediastinum
• CT :
• Focal esophageal wall thickening
• Periesophageal fluid collections
• Free mediastinal air
• Contrast extravasation into the
mediastinum and pleural space

8. Diaphragm
Diaphragmatic rupture
• In 3-7% of patients with blunt and 6-46% of patients with penetrating
thoraco-abdominal trauma
• 90% of tears occur on the left side
• CXR:
Loss of the normal hemidiaphragm contour
Herniated stomach or bowel above the diaphragm with or without focal
constriction of the viscus at the site of the tear ‘collar sign’
Left hemidiaphragm much higher than the right

8. Diaphragm
• CT:
Direct CT Signs
Segmental Diaphragmatic Defect – focal and abrupt loss of continuity in the
diaphragm
Dangling Diaphragm – the free edge of the torn diaphragm which curls inward
from its normal course toward the center of the body forming a comma shaped
or curvilinear structure
Absent Diaphragm – absence of part or all of the hemidiaphragm without
demonstration of a tear

8. Diaphragm
Indirect CT Signs :
Herniation through a Defect
Collar Sign
Hump and Band Signs
Dependent Viscera Sign
Sinus Cut-off Sign
Abdominal Content Peripheral to
the Diaphragm or Lung Sign
Elevated Abdominal Organs Sign

9. Others
Spine fracture
• Multiple in 10%
• Thoracic spine injuries have a much higher incidence of neurological deficit than
cervical or lumbar spine injuries
Cord trauma
• 25% spine fractures
• 90% neurologic injury
• Most common site = T9-11
Nerve root trauma
• Especially to the brachial plexus

Imaging in Thoracic Trauma

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