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Principles of Chest X-Ray Interpretation
Dr Rod Taylor Consultant Respiratory Physician
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Different from us….
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Only Two Choices Hmmn! There are far too many white bits!
That’s funny - this one’s got too many black bits!
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= important radiological
Chest X-ray P = important radiological principle
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Vertebral spines equidistant
The Normal CXR Vertebral spines equidistant Horizontal fissure Left hilum Cardiophrenic angle Descending aorta Right diaphragm Costophrenic angle
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It’s All Relative… 1 P Stupid humans…
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P Why Does It Show Up? Because there is something
of a different radiological density next to it. Four main densities: P
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Étienne de Silhouette The silhouette sign If a structure shows up,
there must be adjacent to it something of a different radiological density. If a structure does not show up, there must be adjacent to it something of a similar Controller-General of Finances during the Seven Years War (1754 – 63)
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Silhouetted Hills This one doesn’t This hill shows up
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Rotation PA
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The Lobes Front Back
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Lateral View (Right) Upper Lobe Middle Lobe Lower Lobe Heart Oblique
fissure Upper Lobe Apical segment of lower lobe Middle Lobe Lower Lobe Horizontal fissure Heart Vertebral bodies appear to darken
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Lateral View (Left) Upper Lobe Lingula Lower Lobe Heart No fissure
(normally) Upper Lobe Oblique fissure Lingula Lower Lobe Heart
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Naming of Segments Apical Medial Anterior Posterior Lateral
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Don’t Forget…. The bones Gas under the diaphragm
Has this patient had a chest x-ray? Oh, good, then I can start! Gas under the diaphragm
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P It’s All Relative… 2 Look for collateral evidence Normal CXR Too
White? Too Black? Normal CXR P Look for collateral evidence
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P What Do You See? The most obvious abnormality is
likely to be the primary event. Other, more subtle, changes are likely to be secondary to this. P
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The Man in the Street Dryclough Lane
Er, there’s a white bit on the right… at the top… um… which comes… ooh, about halfway down… with a sharp, um, line, at the bottom…
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Right Upper Lobe Consolidation
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The ‘Pair of Scissors Sign’
If you could cut along a line seen on a CXR with a pair of scissors - think of a pleural boundary or fissure.
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Interlobar Effusion
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Right Upper Lobe Collapse
Horizontal fissure is pulled up, producing a sharply-defined RUZ opacity. Trachea is pulled to the right. Right hilum is pulled upwards. Right hemidiaphragm may be pulled up.
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Fissure extends medial to hilum
Vertebrae get whiter Diaphragm indistinct Diaphragm disappears
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Right Lower Lobe
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Right Lower Lobe Collapse
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Horizontal fissure Oblique fissure
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Horizontal fissure
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Middle Lobe Collapse
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Right M & LL Collapse Oblique fissure Horizontal fissure
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Displaced oblique fissure
Overinflated lower lobe Tongue of collapsed upper lobe Elevated left diaphragm
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Left Upper Lobe Collapse
Overinflated left lower lobe
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Collapse Consolidation
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What is it?
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“Radiological Homeostasis”
If a structure is displaced on a CXR, then something else will happen to compensate for that displacement. Example: collapse of one lobe overinflation of another P
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If a Structure is Displaced
Pulled out of place Look for collateral evidence Pushed out of place
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Left heart border indistinct
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Left heart border visible
Oblique fissure Left heart border visible Diaphragm indistinct
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Descending aorta indistinct
Triangular opacity Diaphragm indistinct
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Collapsed Left Lower Lobe
Descending aorta Diaphragm visible
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Left Lower Lobe Collapse
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Collapsed left lower lobe
Collapsed right lower lobe
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Left main bronchus ends
abruptly
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Total Lung Collapse
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Pleural Effusion Davis, Gardner & Qvist 1963, BMJ
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Basic Principles
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INTERLUDE
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Bronchial Tree
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Bronchial Tree RUL LUL ML Upper division Lingula Basal lower Basal
Apical lower Apical lower
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Anaesthetist’s Eye View
Lingula Middle lobe Basal lower Basal lower L trachea R Right upper Left upper division Apical lower Apical lower
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Use Your Imagination!
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Aspiration and Gravity
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Apical Segment Apical segment Anterior Posterior Apical segment
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P Air Bronchogram Two requirements: 1. The bronchus must contain air.
Contrast bronchogram Air bronchogram Two requirements: 1. The bronchus must contain air. 2. The surrounding lung must not. P
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Resolution Nodules Fibrosis Ground glass
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Ground Glass Shadowing
Can still see the vessels and airways
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Consolidation Obscures the vessels and airways Consolidation
Ground glass shadowing
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Pixels and Voxels Pixel Voxel
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Volume Averaging When a pixel contains more than
one type of tissue, it shows the average density of the voxel. 1. One big object, only partially within the voxel 2. Lots of small objects, all within the voxel
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Partial Voluming
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Partial Voluming Aortic arch
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Partial Voluming (1)
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Partial Voluming
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Partial Voluming (2) Ground glass shadowing
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Individual ingredients
Volume-averaged mixture Individual ingredients
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Ground Glass ‘Micro-fibrosis’
Normal Bronchiectatic
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Traction Bronchiectasis
Dilated bronchus Fibrosis
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Pulmonary Fibrosis
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Plugging and thickening
Tree in Bud Sign Plugging and thickening of bronchioles
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Basic Principles
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If only everything was as simple as interpreting chest x-rays…
(Sigh) If only everything was as simple as interpreting chest x-rays…
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