2. Gamal Rabie Agmy, MD, FCCP
Professor of Chest Diseases, Assiut University

3. Air Bronchogram
• In a normal chest x-ray, the tracheobronchial tree is not
visible beyond the 4th order. As the bronchial tree
branches, the cartilaginous rings become thinner, and
eventually disappear in respiratory bronchioles. The
lumen of the bronchus contains air and the surrounding
alveoli contain air. Thus, there is no contrast to visualize
the bronchi.
• The air column in the bronchi beyond the 4th order
becomes recognizable if the surrounding alveoli is filled,
providing a contrast or if the bronchi get thickened
• The term air bronchogram is used for the former state
and signifies alveolar disease.

4. The sign implies:
•patency of proximal airways
•evacuation of alveolar air by absorption
(atelectasis), replacement (pneumonia) or
combination of both
•Consolidation, Bronchoalveolar carcinoma,
lymphoma

7. Silhouette Sign
Adjacent Lobe/SegmentSilhouette
RLL/Basal segmentsRight diaphragm
RML/Medial segmentRight heart margin
RUL/Anterior segmentAscending aorta
LUL/Posterior segmentAortic knob
Lingula/Inferior segmentLeft heart margin
LLL/Superior and basal segmentsDescending aorta
LLL/Basal segmentsLeft diaphragm
Cardiac margins are clearly seen because there is contrast between the fluid
density of the heart and the adjacent air filled alveoli. Both being of fluid density,
you cannot visualize the partition of the right and left ventricle because there is no
contrast between them. If the adjacent lung is devoid of air, the clarity of the
silhouette will be lost. The silhouette sign is extremely useful in localizing lung
lesions.

8. Atelectasis Right Lung
Homogenous density right hemithorax
Mediastinal shift to right
Right hemithorax smaller
Right heart and diaphragmatic silhouette are not identifiable

9. Atelectasis Left Lung
Homogenous density left hemithorax
Mediastinal shift to left
Left hemithorax smaller
Diaphragm and heart silhouette are not identifiable

10. Lateral
Movement of oblique and transverse
fissures
Atelectasis Right Upper Lobe
Homogenous density right upper lung
field
Mediastinal shift to right
Loss of silhouette of ascending aorta

11. Atelectasis Left Upper
Lobe
Hazy density over left
upper lung field
Loss of left heart
silhouette
Tracheal shift to left
Lateral
A: Forward movement of
oblique fissure
B: Herniated right lung
C: Atelectatic LUL

12. Consolidation Right
Upper Lobe /
Density in right upper lung
field
Lobar density
Loss of ascending aorta
silhouette
No shift of mediastinum
Transverse fissure not
significantly shifted
Air bronchogram

13. S Curve of Golden
When there is a mass
adjacent to a fissure, the
fissure takes the shape
of an "S". The proximal
convexity is due to a mass,
and the distal concavity is
due to atelectasis. Note the
shape of the transverse
fissure.
This example represents a
RUL mass with atelectasis

14. Cut Off Sign
• When you see an abrupt ending of visualized
bronchus, it is called a "cut off sign". It indicates
an intrabronchial lesion. This is useful to identify
the etiology of atelectasis . Be careful as the
tracheobronchial tree is three dimensional and
the finding need to be confirmed with tomogram.
In the modern era, a CT scan will take care of
this.

15. Pulmonary Artery Overlay
Sign
This is the same concept as
a silhouette sign. If you can
recognize the interlobar
pulmonary artery, it means
that the mass seen is either
in front of or behind it.
This is an example of a
dissecting aneurysm.

16. AV Fistula
Osler-Weber-Rendu
Syndrome
"Pulmonary nodule"
Multiple lesions
Feeding vessel
Cardiomegaly
Patient presented with
severe congestive heart
failure and severe iron
deficiency anemia. Had
multiple telangiectasia of
tongue, lips and
conjunctivae.

17. AV Fistula
Osler-Weber-Rendu
Syndrome
"Pulmonary nodule"
Multiple lesions
Feeding vessel
Cardiomegaly
Patient presented with
severe congestive heart
failure and severe iron
deficiency anemia. Had
multiple telangiectasia of
tongue, lips and
conjunctivae.

19. Radiographic Signs of Pneumomediastinum
Subcutaneous emphysema
Thymic sail sign
Pneumoprecardium
Ring around the artery sign
Tubular artery sign
Double bronchial wall sign
Continuous diaphragm sign
Extrapleural sign
Air in the pulmonary ligament

32. Potential Sources of Mediastinal Air
Intrathoracic
Trachea and major bronchi
Esophagus
Lung
Pleural space
Extrathoracic
Head and neck
Intraperitoneum and retroperitoneum

33. Air Crescent Sign
Can be visualized in X-rays and CT
•Crescentic collection of air within
consolidation or nodular opacity
•Seen in pulmonary cavitary process
•Usually announces recovery
•It is a result of increased granulocyte activity

35. Characteristic of invasive pulmonary
aspergillosis
•Tumor, hematoma, Wegener
granulomatosis, hydatid cyst, TB,
nocardiosis, bacterial abscess
•Not confused with Monod’s sign
•air surrounding fungus ball or mycetoma
in preexisting cavity
Air Crescent Sign

37. Continuous Diaphragm Sign
•Described by Levin in 1973
•Normally central part of diaphragm is
lost due to apposition of heart
•Air interposed between the heart and
diaphragm results in gas-tissue
interface
•Seen on chest radiographs
•Characteristic of pneumomediastinum

40. Bulging Fissure Sign
Consolidation spreading rapidly, causing lobar expansion and
bulging of the adjacent fissure inferiorly .
Historically Klebsiella pneumoniae involving the right upper lobe .
Friedlander pneumonia.

41. Deep Sulcus Sign
•Seen on radiographs in supine position
•Characteristic of pneumothorax
•30% pneumothoraces are undetected
•Lucency in lateral costophrenic angle
•Air collects anteriorly and basally
•Useful in neonates and ill patients
•Include lateral costophrenic angles

43. CT angiogram Sign
Identification of vessels within an
airless portion of lung on contrast-
enhanced CT .
The vessels are prominently seen
against a background of low-
attenuation material .
Associatedwith:
bronchoalveolar cell carcinoma
lymphoma
infectious pneumonias.

44. Fallen Lung Sign
This sign refers to the appearance
of the collapsed lung occurring
with a fractured bronchus .
The bronchial fracture results in
the lung to fall away from the
hilum, either inferiorly and laterally
in an upright patient or posteriorly,
as seen on CT in a supine patient.
DD:
Pneumothorax causes a lung to
collapse inward toward the hilum.

45. Ring Around Artery Sign
•Visualized on lateral chest radiographs
•Lucency along or surrounding RPA
•Characteristic of pneumomediastinum
•Usually is accompanied by other ancillary signs:
•continuous diaphragm sign
•Naclerio’s V sign
•thymic sail sign

47. Thymic Sail Sign Naclerio’s V Sign

48. Flat waist Sign
This sign refers to flattening of the contours of the aortic knob and adjacent
main pulmonary artery .
It is seen in severe collapse of the left lower lobe and is caused by leftward
displacement and rotation of the heart

50. Finger in Glove Sign
Visible on chest radiographs or CT
•Indicates mucoid impaction within an obstructed bronchus
•Characterized by branching tubular or fingerlike opacities

51. Finger in Glove Sign
Originate from the hilum and are directed
peripherally
•Also seen in cases of dilated bronchi with
secretions
•Distal lung remains aerated by collateral
drift through interalveolar pores (pores of
Kohn) and Lambert canal

53. Hampton Hump Sign
Pulmonary infarction secondary to pulmonary embolism produces
an abnormal area of opacification on the chest radiograph, which
is always in contact with the pleural surface.

54. Luftsichel Sign
•German for sickle of air (luft: air sichel:
crescent)
•Paramediastinal lucency due to
interposition of lower lobe apex between
mediastinum and shrunken upper lobe
•Occurs more commonly on the left than in
the right

57. Halo Sign
CT shows nodular consolidation associated with a halo of ground-glass opacity
(GGO) in both apices resulting from invasive pulmonary aspergillosis.
This halo represents hemorrhage.
When seen in leukemic patients, is highly suggestive of the diagnosis of
invasive pulmonary aspergillosis.

58. Double Density Sign
•Indicates left atrial enlargement
•Occurs when right side of the left atrium
pushes into adjacent lung
•Splaying of the carina
•Superior displacement of left main stem
bronchus on frontal view

59. Double Density Sign
•Posterior displacement of left main stem
bronchus on lateral view
•Posterior displacement of esophagus on
barium study

60. Walking Man Sign

61. Juxtaphrenic Peak Sign
This sign refers to a small triangular shadow that obscures the dome of
the diaphragm secondaryto upper lobe atelectasis . The shadow is
caused by traction on the lower end of the major fissure, the inferior
accessory fissure, or the inferior pulmonaryligament.

62. Luftsischel Sign
In left upper lobe collapse, the superior segment of the left lower lobe, which is
positioned between the aortic arch and the collapsed left upper lobe, is
hyperinflated. This aerated segment of left lower lobe is hyperlucent and
shaped like a sickle, where it outlines the aortic arch on the frontal chest
radiograph.
This peri-aortic lucency has been termed the luftsichel sign, derived from the
German words luft (air) and sichel (sickle).

63. Doughnut Sign
•Detect mediastinal adenomegaly
•Lateral chest radiograph
•Subcarinal lymphadenopathy
•Mass posterior to bronchus intermedius
and inferior hilar window
•CT primary modality for detecting
mediastinal lymphadenopathy

64. Pulmonary
hypertension
Normal
Lymphadenopathy

65. Cervicothoracic Sign
•Used to determine location of mediastinal
lesion in the upper chest
•Based on principle that an intrathoracic
lesion in direct contact with soft tissues of
the neck will not outlined by air
•Uppermost border of the anterior
mediastinum ends at level of clavicles

66. Cervicothoracic Sign
• Middle and posterior mediastinum extends
above the clavicles
•Mediastinal mass projected superior the
level of clavicles must be located either
within middle or posterior mediastinum
•More cephalad the mass extends the most
posterior the location

69. Thoracoabdominal Sign
•Posterior costophrenic sulcus extends
more caudally than anterior basilar lung
•Lesion extends below the dome of
diaphragm must be in posterior chest
whereas lesion terminates at dome must be
anterior
•Cervicothoracic and thoracoabdominal
signs were described by Felson

71. Tapered Margins Sign
•A lesion in the chest wall, pleura or
mediastinum have smooth tapered
borders and obtuse angles
•While parenchymal lesions usually form
acute angles

74. Water Bottle Sign

75. Westermark Sign
•Described by Neils Westermark in 1938
•Chest radiograph and CT show
increased lucency or hypoattenuation
•Typically signifies either occlusion of a
larger lobar/segmental artery or
widespread small vessel occlusion

77. Fleischner Sign
•Described by Felix Fleischner
•Enlargement proximal pulmonary
arteries on plain film or angiography
•PA enlargement due to embolus
•Commonly in the setting of massive PE
•It has relatively low sensitivity
•Abrupt tapering of an occluded vessel
distally (knuckle sign)

79. Hilum Overlay Sign
•Described by B. Felson
•If hilar vessels are sharply delineated it
can be assumed that the overlying mass
is anterior or posterior
•If mass inseparable pulmonary arteries
structures are adjacent to one another

82. Hilum Convergence Sign
•Described by B. Felson
•Used to distinguish between a prominent
hilum and an enlarged pulmonary artery
•If branches of PA converge toward central
mass is an enlarged PA
•If branches of PA converge toward heart
rather than mass is a mediastinal tumor

84. CT Halo Sign

85. CT Halo Sign
•Ground glass attenuation surrounding a
pulmonary nodule/mass on CT images
•Described by Kuhlman in 1985 in patients
with invasive aspergillosis
•Associated w hemorrhagic nodules and
may be caused neo or inflammatory
•Disease pathologically active with tumor
spread, hemorrhage or inflammation

87. Reverse Halo Sign
•Central ground-glass opacity surrounded
by denser consolidation of crescentic or
ring shape, at least 2 mm thick
•First described by Voloudaki in 1996
•Kim in 2003 used the term reverse halo
•Found to be relatively specific for crypto-
genic organizing pneumonia (COP)

88. Reverse Halo Sign
•Seen in other conditions:
•Wegener’s granulomatosis
•lymphomatoid granulomatosis
•paracoccidiodomycosis
•neoplastic (metastasis)
•invasive aspergillosis
•lipoid pneumonia

90. Split Pleura Sign
•Seen on contrast enhanced CT of
chest
•Thickened visceral and parietal pleura
with separation by a collection
•Empyema or exudative effusion
•Exudative: bacterial pneumonia,
cancer, viral infection, PE

92. Tree-in-Bud Sign
•Commonly seen at thin-section CT
•Initially described in endobronchial spread
of Tuberculosis
•Recognized in diverse entities
•Small centrilobular nodules soft-tissue
attenuation connected to multiple branching
structures

93. Tree-in-Bud Sign
•

95. Crazy Paving Sign
•Scattered or diffuse GG attenuation w
superimposed intralobular and interlobular
septa thickening
•Commonly seen at thin-section CT
•Initially described in PAP
•Recognized in diverse entities

96. Crazy Paving Sign

98. Comet Tail Sign
•Seen on CT of the chest
•Consists of curvilinear opacity extending
from subpleural mass toward hilum
•Produced by the distortion vessels and
bronchi that lead to adjacent rounded
atelectasis

100. Signet Ring Sign
•Seen on CT/HRCT scans of chest
•CT finding in patient with bronchiectasis
•Ring shadow representing dilated thick-
walled bronchus associated a nodular opacity
representing pulmonary artery
•Distinguish from cystic lung lesions

101. Pearl ring sign