Radiology of mediastinum

1. Radiological mapping of
mediastinum
Dr Bayyaram Rambhoopal Redddy
DM 1st Year Resident
SCBMCH, Cuttack

3. DIVISIONSOF
MEDIASTINUM
It is divided by a horizontal plane
extending from sternal angle to lower
border of 4th thoracic vertebra into:
1. Superior mediastinum: above the
plane
2. Inferior mediastinum: below the
plane, it is subdivided into:
Anterior mediastinum: in front of
pericardium
Middle mediastinum: contains heart &
pericardium
Posterior mediastinum: behind
pericardium

4. The Felson method of division is based on findings at
lateral chest radiography

5. CONTENTSOF INFERIORMEDIA
TINUM

6. Cluesto locate mediastinal mass

8. Lung mass Mediastinal mass

9. INTERFACE LINES AND STRIPES
• The air in the lungs abuts various mediastinal structures.
Where the interface is long and vertical it results in a longitudinal or slightly angled line on
the CXR.
• Mediastinal lines:
are thin (<1mm in width) linear opacities that result from contact between two aerated
structures outlining thin intervening tissue on both sides, such as the anterior and posterior
junction lines, azygoesophageal line.
• Mediastinal stripes:
are bands that result from air outlining thicker intervening mediastinal structure, include
the right and left paratracheal stripes.

10. Anterior Junction Line
• The line is formed by the anterior apposition of the
lungs and consists of the four layers of pleura
separating the lungs behind the upper two-thirds of
the sternum.
• The line runs obliquely from upper right to lower left
and does not extend above the manubriosternal
junction.
• Contains variable amount of fat.
• Obliteration or abnormal convexity of line suggest
anterior mediastinal disease.

12. Posterior Junction Line
• Seen above the level of the azygos vein and aorta
and that is formed by the apposition of the lungs
posterior to the esophagus.
• usually extend from third to fifth thoracic vertebrae.
• posterior junction line can be seen above the
suprasternal notch and lies almost vertical, whereas
the anterior junction line deviates to the left.

13. Collimated posteroanterior chest radiograph shows the posterior
junction line (arrow) projecting through the tracheal air column.

14. CT scan shows the posterior junction line (arrow), which is formed by
the interface between the lungs posterior to the mediastinum and
consists of four pleural layers.

16. • The thickness of this stripe
should not exceed 4 mm.

17. Posteroanterior chest radiograph shows the right paratracheal stripe (arrow).
The azygos vein is seen at the inferior margin of the stripe at the
tracheobronchial angle.

18. CT scan shows the
right wall of the
trachea with medial
and lateral air–soft
tissue interfaces
caused by air within
the tracheal lumen
and right lung.

19. • The right paratracheal stripe can be widened
due to abnormality of any of its
components, from the tracheal mucosa to the
pleural space.

20. Left Paratracheal Stripe

21. • Left Paratracheal Stripe
Visible on 21%–31% of
PA chest radiographs
• Seen less frequently
than right.

22. Paraspinal Lines
• The paraspinal lines are created by the interface
between lung and the pleural reflections over the
vertebral bodies.
• The left paraspinal line is much more commonly
seen than the right. The descending aorta holds
the pleural reflection off the vertebral
body, allowing the lung–soft tissue interface to be
more tangential to the x-ray beam.
• The left paraspinal line runs parallel to the lateral
margin of the vertebral bodies and can lie
anywhere medial to the lateral wall of the
descending aorta

23. Right paraspinal line:
The right paraspinal line appears straight and typically extends from T8 – T12.
Its presence on 23% of posteroanterior radiographs.

25. Left paraspinal line
• Reported on 41% of PAradiographs
• The left paraspinal line is seen more frequently than the right paraspinal line due to the
presence of the descending thoracic aorta on the left

26. Normal left paravertebral stripe. This is the interface
between the lung and the paravertebral soft tissues.
Note that a right paravertebral stripe is not evident.

27. CT scan shows the left paraspinal line. The descending aorta holds the pleural
reflection (arrow) away from the vertebral body, which allows the lung–soft
tissue interface to be more tangential to the x-ray beam and therefore
visualized as a line

28. CT scan shows a paraspinal abscess (arrow) effacing the paraspinal lines.
The air–soft tissue interface between the lung and aorta remains intact
(arrowhead), thereby preserving the normal radiographic appearance of
the lateral aortic wal

29. An abnormal contour of the left paraspinal line

30. Azygoesophageal recess
• The azygoesophageal recess is the interface between the right lung and
the mediastinal reflection, with the esophagus lying anteriorly and the
azygos vein posteriorly within the mediastinum.
• On X-ray,it appears as a line –
• - in its upper 1/3rd , it deviates to the right at the level of the carina to
accommodate the azygos vein arching forward.
• middle 1/3rd , the line has a variable appearance: It is usually straight.
• lower 1/3rd , usually straight. ( air in esophagus)

32. CT scan shows the
azygoesophageal recess
(white arrow) formed
by the esophagus
anteriorly (black arrow)
and the azygos vein
posteriorly
(arrowhead).

33. • The azygoesophageal recess reflection is a pre-
vertebral structure and is, therefore, disrupted
by prevertebral disease.
• It has an interface with the middle
mediastinum; thus, the resulting line seen at
radiography can be interrupted by
abnormalities in both the middle and posterior
compartments.

34. Posteroanterior chest radiograph demonstrates a subcarinal abnormality with
increased opacity (*), splaying of the carina, and abnormal convexity of the
upper and middle thirds of the azygoesophageal line (arrowheads)

35. Corresponding CT scan helps confirm a subcarinal mass
(arrow), which proved to be a bronchogenic cyst.

36. Cervico thoracic sign
• The anterior mediastinum ends at the level of the clavicles.
• The posterior mediastinum extends much higher.
• Posterior masses above the level of the clavicles have an interface
with lung and therefore typically have sharp, well-defined margins;
in contrast, anterior masses above the level of the clavicles do not have
an interface with lung, so that their margins are not usually sharp.

38. Thoraco abdominal sign
• A sharply marginated mediastinal mass seen through the diaphragm
must lie entirely within the chest.
• The posterior costophrenic sulcus extends far more caudally than the
anterior aspect of the lung
• Therefore Any mass that extends below the dome of the diaphragm
and remains sharply outlined must be in the posterior compartments
and surrounded by lung, and Any mass that terminates at dome of
diaphragm must be anterior

39. Negative thoraco abdominal sign
• Convergence of the lower lateral margin of the mass towards the
spine - mass is probably entirely intrathoracic
•

40. Hilum overlay sign
• When a mass arises from the hilum, the pulmonary vessels are in
contact with the mass & as such their silhouette is obliterated.
• The ability to see the edges of the vessels through the mass implies
that the mass is not contacting the hilum, & is therefore either
anterior or posterior to it.

41. Hilum convergence sign
• Distinguishes enlarged hilum due to enlarged pulmonary arteries or
due to mass
• If vessels directly converge onto hilar shadow - Then the enlargement
is vascular.
• If the vessels appear to converge medial to the lateral aspect of the
hilar shadow then the enlargement is due to mass.

44. • Anterior mediastinal masses
prevascular - Thymic masses
- Retrosternal thyroid
- Teratoma
- Lymph nodal mass
- Epicardial fat pad
- Morgagni ‘ s hernia
- pleuropericardial cyst
precardiac
- Anterior mediastinal masses in the prevascular
region can obliterate the anterior junction line.

45. Radiological charecteristics
• Silhouette with right cardiac border, ascending aorta, aortic knuckle
• obliteration of the anterior junction line
• obliteration of cardiophrenic angle and retrosternal space
• mass effect on the trachea
• preservation of posterior mediastinal lines
• hilum overlay sign

46. Middle Mediastinal Masses
• Lymphadenopathy
• Aortic aneuyrsm
• Enlarged pulmonary artery
• Foregut duplication cyst
• Tracheal lesions

47. posteroanterior
chest
radiograph, the right
paratracheal stripe is
not seen, having
been obliterated by
a right paratracheal
mass.

49. • TheAP window is bounded by the aortic arch
superiorly and the pulmonary artery
inferiorly, with its lateral aspect seen as the
aortic-pulmonary window reflection due to the
interface between the left lung and the
mediastinum.
• A convex border between the AP window and
the lung is considered abnormal. Most
commonly - lymphadenopathy

50. On a posteroanterior
chest radiograph, the AP
window reflection
(arrowhead) extends
from the aortic knob to
the left pulmonary
artery and has a normal
concave appearance.
The aortic-pulmonary
reflection (arrow) is a
more anterior line and
extends from the aortic
arch to the level of the
left main bronchus.

51. Chest
radiograph
shows the AP
window with
an abnormal
convex border
(arrow)

52. CT scan demonstrates lymphadenopathy (arrow), which accounts for
the distortion of the AP window

53. Posteroanterior chest radiograph demonstrates the AP
window with a convex border (arrow)

54. pitfalls
• A right-sided aortic arch, seen in 0.5% of the
general population, may mimic paratracheal
lymphadenopathy because it obliterates the
right paratracheal stripe.
• Absence of the aortic knuckle on the left
should help correctly identify this variant.
• Left sided SVC.

55. Posteroanterior chest radiograph demonstrates an abnormality in the
right paratracheal region (arrow) with loss of the paratracheal stripe.
Note, however, the absence of the aortic knuckle on the left.

56. CT scan shows a right-sided aortic arch

57. Posterior Mediastinal Masses
• Esophageal lesions, hiatal hernia
• Foregut duplication cyst
• Descending aorta aneuyrsm
• Neurogenic tumour
• Paraspinal abscess
• Lateral meningocele
• Extramedullary haematopoiesis

58. Radiological charecteristics
• obliteration of posterior junction line
• obliteration of paraspinal lines
• right side convexity of azygoesophageal recess
• cervico-thoracic sign
• thoraco-abdominal sign

59. 1 – Supra-clavicular, sternal notch nodes
2 – upper paratracheal
4 – lower paratracheal
5 – sub-aortic
6 – para-aortic
inferior mediastinal node
7 – sub-carinal
8 – paraoesophageal
9– pulmonary ligament
10 – hilar nodes
Lymph node location

60. • 1. Supraclavicular zone nodes
These include low cervical,
supraclavicular and sternal notch
nodes
• Upper border: lower margin of
cricoid.
• Lower border: clavicles and upper
border of manubrium.
• The midline of the trachea serves
as border between 1R and 1L

61. • 2R RT UPPER PARATRACHEAL
• Extends up to left lateral border of
trachea
• Upper border: upper border of
manubrium
• Lower border: lower border of left
brachiocephalic vein
• 2L LEFT UPPER PARATRACHEAL
• Upper border: upper border of
manubrium
• Lower border: upper border of arch of
aorta

62. • 3A PREVASCULAR
• Below the apex
• Above the carina
• Rt side anterior to the SVC
• Lt side anterior to Lt common
carotid artery

63. • 3P RETROTRACHEAL
• Below apex
• Above carina
• Station 3 LN not accessible
through mediastinoscopy
• 3P nodes can be accessible with
endoscopic ultrasound (EUS).

64. • 4R. RIGHT LOWER
PARATRACHEAL
• Upper border: lower border of
left brachiocephalic vein
• Lower border: lower border of
azygos vein.
• 4R nodes extend to theleft
lateral border of the trachea.

65. • 4L LOWERPARATRACHEAL NODES
• are located to the left of the left
tracheal border, between a horizontal
line drawn tangentially to the upper
margin of the aortic arch and a line
extending across the left main
bronchus at the level of the upper
margin of the left upper lobe
bronchus.
• These include paratracheal nodes that
are located medially to the
ligamentum arteriosum.
• 4L nodes are between the pulmonary
trunk and the aorta, but are not
located in the AP-window

66. • 5 SUBAORTIC NODES
• Subaortic or aorto-pulmonary window
nodes are lateral to the ligamentum
arteriosum or the aorta or left
pulmonary artery and proximal to the
first branch of the left pulmonary
artery and lie within the mediastinal
pleural envelope.
• 6 PARA-AORTIC NODES
• Para-aortic (ascending aorta or
phrenic) nodes are located anteriorly
and laterally to the ascending aorta
and the aortic arch from the upper
margin to the lower margin of the
aortic arch.

67. • 7. SUBCARINAL NODES
• These nodes are located caudally to
the carina of the trachea, but are not
associated with the lower lobe
bronchi or arteries within the lung.
• On the right they extend caudally to
the lower border of the bronchus
intermedius.
• On the left they extend caudally to the
upper border of the lower lobe
bronchus.
• On the left a station 7 subcarinal node
to the right of the esophagus.

68. • 8 PARAESOPHAGEAL NODES
• These nodes are below the
carinal nodes and extend
caudally to the diaphragm.
• On the leftan image below the
carina. To the right of the
esophagus a station 8 node.

69. • 9. PULMONARY LIGAMENT
NODES
• Pulmonary ligament nodes are
lying within the pulmonary
ligament, including those in the
posterior wall and lower part of
the inferior pulmonary vein.
• The pulmonary ligament is the
inferior extension mediastinal
pleural reflections that surround
the hila.

70. • 10 HILAR LYMPHNODES
• Hilar nodes are proximal lobar
nodes, distal to the mediastinal
pleural reflection and nodes
adjacent to the intermediate
bronchus on the right
• Below azygous vein on right
• Below top of left pulm artery on
left
• Above interlobar region bilaterally
• Nodes in station 10 -14 are all
N1-nodes, since they are not
located in the mediastinum.

71. AtT3 Level

72. AT T4 LEVEL

73. AT T5 LEVEL

74. AT T6 LEVEL

75. Mediastinum
Level I Aortic branches level
Level II Aortic arch level
Level III Aorto pulmonary window level
Level IVLeft pulmonary artery level
Level V Right pulmonary artery level
Level VI Cardiac level

76. Level I Aortic branches level
Rt.Brachiocephalic vein
Brachiocephalic Artery
Left common carotid
Left subclavian artery

77. Level II: Aortic arch level
SVC
Aortic arch

78. Level III Aorto pulmonary window level
Ascending aorta
Descending aorta
SVC
Pul.Artery

79. Level IV Left pulmonary artery level
Truncus arteriosis
Left Pul.Artery
Left Pul.Vein

80. V Rt Pulmonary artery level

81. Level VI-Cardiac level(4 chamber level)
Right atrium Right Ventricle
Left atrium
Left Ventricle
Aortic valve

82. Level VI-Cardiac level(3 chamber level)
Left Atrium
Right Ventricle
IVC
esophagus
Left ventricle

83. I Aortic Branches II Aortic Arch III Aorto pulmonary window
IV Lt. Pulm. artery V Rt. Pulm. artery VI Cardiac level