2. Outline
• Introduction
• Normal CXR- technical aspects
• Normal Anatomy
• Approach to Interpretation
• Patterns of Abnormality
3. Introduction
• The CXR is the most commonly performed
imaging procedure in general Radiology
departments
• Comprises 30 – 50% of studies
• One of the most difficult films to interpret
– For Radiologists
– For you… on-call… at night… on your own!
5. The Normal CXR
• Standard CXR is taken:
– PA – minimal magnification of the heart
– Patient standing
– Full inspiration
• In ill patients, the CXR is usually taken:
– AP – magnifies cardiac shadow
– Often supine – diaphragms higher, lung volumes
lower, pathology often obscured
8. The Lateral CXR
• Purpose:
– To pinpoint location of a lesion seen on PA
– To identify lesions hidden behind the heart on PA
• Left lateral = left side of patient is against
digital plate = standard lateral projection
• Right lateral = performed to assess a lesion in
the right lung (decreases magnification of
lesion)
9. The Lateral CXR
• In practice, lateral radiographs are not routinely
performed any more so you will rarely have to
interpret one
• We occasionally request one ourselves when
reporting a PA chest radiograph, to clarify an
apparent abnormality rather than going straight
to CT
• When there is a definite abnormality on a PA
radiograph that requires further investigation, we
tend to go directly to CT nowadays
10. Additional CXR Views
• Lordotic
– Direction of x-ray beam relative to patient is angled
upwards at 45 degrees
– This projects clavicles above lung apices
– Useful if suspect an apical mass but is obscured by
clavicle
– Also useful if suspect an apparent apical lesion is
actually in a rib or clavicle
• Decubitus
– To confirm the presence of fluid suspected on upright
film (e.g. subpulmonic effusion)
11. Subpulmonic effusion on decubitus film
• The PA film shows an apparently elevated right diaphragm
• On the decubitus view, the effusion flows up along the side of the lung
12. Expiratory CXR
• Makes a pneumothorax appear relatively larger
than on an inspiratory film
• PTx may only visible on expiration film
• When you see the word ‘expiration’ on a CXR you
are almost certainly looking for a pneumothorax
(especially in an exam!)
• Expiratory film is also useful in kids when looking
for air trapping due to an obstructing foreign
body – lung on obstructed side remains expanded
54. Before you start…
1. Check patient label – name, DOB, gender
2. Orientation
– R or L marker (?dextrocardia)
– PA or AP (if not labeled, assume PA)
– Inspiratory or expiratory (if not labeled = insp)
– Erect or supine (again, if not labeled assume
erect)
– Rotated? (clavicles relative to spinous process!)
55. Rotated ED film
One lung field appears whiter,
Difficult to assess cardiac silhouette
Same patient,
better centred CXR
Traumatic diaphragmatic hernia
57. Same image shown the correct way around –
Patient had Kartagener’s Syndrome with situs inversus
58. Before you start…
3. Adequate exposure?
– Should just about be able to see thoracic
vertebrae through heart
• Can’t see them at all? – underexposed, everything too
white
• Vertebrae and disk spaces very clear? – overexposed,
everything too dark
• In over- and under-exposed CXRs, lung pathology is
easily obscured
• This is less of a problem now that we have digital
radiography and automatic exposure control
59. Before you start…
4. Adequate inspiration?
– Count ribs – choose one of these methods
• 9 or 10 ribs posteriorly
• 6 ribs anteriorly (I prefer this one)
– If inspiration is suboptimal, basal lung pathology
may be obscured
63. Airway
• Trachea
– Central?
• Can be pulled by
– lobar collapse
– fibrosis (e.g. old TB)
– lobectomy
• Can be pushed by
– mediastinal mass
– tension pneumothorax
– large pleural effusion
64. Airway
• Trachea
– Narrowed?
• Retrosternal goitre, other mediastinal masses
• Carina
– Splayed?
• Normal carinal angle is ~60 degrees (range 40-75)
• Angle increased by subcarinal lymphadenopathy, left
atrial enlargement
72. Bones
• Destructive lesions – metastases
• Erosion by adjacent tumour, e.g. Pancoast
• Rib fractures
– Sensitivity of CXR is less than 20%
– However, when you see one look carefully for
pneumothorax, haemothorax, lung contusion
• Shoulder dislocation
77. Cardiovascular system
• Heart size <50% of cardiothoracic ration on PA
film
• Generalize cardiomegaly or specific chamber?
• Valve replacement?
• Sternotomy wires?
• Pacemaker? – check for complications if
recently inserted (pneumothorax)
83. Cardiovascular
• Pulmonary vasculature
– Generalized increase in vascular markings
• Left to right shunt
– Focal or unilateral decrease in lung markings
• Westermark’s sign (PE)
– Large central pulmonary arteries with sudden
tapering
• Pulmonary hypertension, e.g. chronic lung disease, PPH
84. Cardiovascular
• Pulmonary vasculature
– Increased size of upper lobe pulmonary veins in
CCF – subtle early CXR sign
• Finally, look BEHIND the heart
– Lung nodule/mass
– Hiatus hernia
– Oesophageal dilatation (tumour, achalasia)
85. Upper lobe venous diversion
- patient with mitral stenosis
Left atrial enlargement
Kerley B lines
88. Diaphragms
• Right higher than left by no more than 2.5 cm
• Larger difference, or L higher than R
– Phrenic nerve palsy e.g. tumour, surgery
– Volume loss in lung e.g. lobar collapse, lobectomy,
pneumonectomy
– Diaphragmatic hernia
– Subpulmonic effusion
89. Diaphragms
• Depressed, flattened diaphragms
– Hyperinflation (asthma, COPD, cystic fibrosis)
• GAS BELOW DIAPHRAGM (erect film)
– Need to be sitting up for at least 20 minutes
• NO gas below diaphragm (no gastric air
bubble)
– Sign of achalasia
• Costophrenic angles - blunted?
– pleural effusion
94. Examine the Lungs
• Are the lungs equal in density?
• One lung too white
– Solitary breast
– Pleural effusion
– Pleural mass (mesothelioma, mets)
– Lobar collapse
– Consolidation
– Pulmonary mass
97. Examine the Lungs
• Are the lungs equal in density?
• Both lungs too dark
– Overexposed film – check if vertebral bodies too
clearly seen
– COPD
• Count ribs (8 or more anteriorly)
• Flattened diaphragms
• Bullae
99. Examine the Lungs
• Are the lungs equal in density?
• Both lungs too white
– Underexposed film
– Pulmonary oedema
– Pulmonary fibrosis (what zones??)
– Miliary shadowing – TB, mets
101. Examine the Lungs
• Are the hemithoraces equal in volume?
– Increased volume
• Tension pneumothorax
• Large effusion
• Expanded lobe (e.g. Klebsiella pneumonia)
102. Examine the Lungs
• Are the hemithoraces equal in volume?
– Decreased volume
• Lobar collapse
• Lobectomy, pneumonectomy
• Fibrothorax (restrictive, thickened pleura secondary to
old TB or empyema)
• Diaphragmatic paralysis or rupture
104. Soft Tissues
• Surgical emphysema – neck and chest
– Trauma
– Surgery
– Chest drain
– Asthma
• When you see surgical emphysema, search
very carefully for a pneumothorax and/or
pneumomediastinum
107. CXR Patterns
• Having identified that the lungs are abnormal,
you now need to decide what the problem is
• Which of the following patterns does the
abnormality fit into?
– Alveolar consolidation
– Interstitial lung disease
– Atelectasis (collapse)
– Nodules and masses
– Cavities and cysts
– Calcification/ossification
108. Alveolar Consolidation
• Signs
– May be localized or diffuse
– Homogeneous, amorphous increased density
– Ill-defined margins
– Air bronchograms
– No volume loss
111. Alveolar Consolidation
• Which lobe is involved?
• Look for absent silhouette:
– Right hemidiaphragm = RLL
– Right heart border = RML
– Left hemidiaphragm = LLL
– Left heart border = lingula (of LUL)
– None – could be upper lobes or apical segments
of lower lobes
112. RUL (above horizontal fissure) and
lingular (obscuring left heart border) pneumonia
Horizontal fissure
120. Atelectasis
• Signs
– Opacification of a lobe
– Volume loss
• Displacement of fissures
• Elevated hemidiaphragm
• Mediastinal displacement
• Tracheal displacement
• Compensatory hyperinflation of opposite lung
121. Atelectasis
• Right upper lobe atelectasis
– Collapses superiorly and medially
– Wedge shaped opacity in right upper zone
– Horizontal fissure displaced upwards
– Oblique fissure displaced anteriorly on lateral CXR
122. Atelectasis
• Left upper lobe atelectasis
– ‘veil’-like opacity in left hemithorax
– Often obliterates left heart border silhouette (as
lingula is in LUL)
– Elevated left hilum
– Oblique fissure displaced anteriorly
123. LUL collapse -
trachea displaced to left
left hilum elevated
left hemidiaphragm elevated
124. Atelectasis
• Right middle lobe atelectasis
– Collapses medially obliterating right heart border
– On lateral, see wedge-shaped opacity anteriorly
– Pulls horizontal fissure downwards
126. Atelectasis
• Lower lobe atelectasis
– Similar appearance on both sides
– Obliterates normal silhouette of hemidiaphragm
– On lateral CXR, see triangular density posteriorly
with increasing opacity of lower thoracic
vertebrae
129. Nodules and Masses
• Nodule is <3cm, mass is >/= 3cm
• Solitary or multiple?
• Solitary – long differential diagnosis e.g.
– Bronchogenic ca, granuloma, hamartoma, met
• Multiple – also long ddx
– Mets, granulomas, rheumatoid nodules,
sarcoidosis
132. Cavities and Cysts
• Cyst = thin wall (< 3mm)
– Fluid or air-filled, or both (air/fluid level)
• Cavity = thicker wall (> 3mm)
– Always contain air +/- air/fluid level
– Usually in an area of consolidation, a mass or a
nodule
137. Final Comments
• Before diving into a CXR, take a step back and
look at the age/gender, any labels on the
image (L/R, erect, AP, expiration), technical
quality
• If you remember your ABCDEs you’re unlikely
to miss any findings
