mediastinum anatomy and imaging

1. Radiological imaging of
mediastinal masses.
Dr. Arun Kumar Singh

2. Introduction
 The mediastinum is the region in the chest
between the pleural cavities that contain the
heart and other thoracic viscera except the lungs
Boundaries
Anterior - sternum
Posterior - vertebral column and paravertebral
fascia
Superior -thoracic inlet
 Inferior - diaphragm
 Lateral - parietal pleura

3. Boundaries of mediastinum
Thoracic inlet
Sternal Angle
sternum
Thoracic vertebra
Thoracic oulet

4. TS: Mediastinum
4
CS: Mediastinum

5. Divisions of mediastinum
MEDIASTINUM
Superior
mediastinum
Inferior
mediastinum
Anterior
mediastinum
Middle
mediastinum
Posterior
mediastinum

6. Mediastinum divisions
Superior
Mediastinum
Posterior
Mediastinum
Sternal
Angle
Anterior
Mediastinum
Middle
Mediastinum
T4
T5
divided into superior mediastinum and inferior mediastinum by an imaginary line

7. Superior Mediastinum
Boundaries
 Ant: Manubrium sterni
 Post: T-1 to T-4
 Sides: Mediastinal pleura
 Sup: Plane of thoracic inlet
at T1
 Inf: Imaginary line joining
sternal angle and lower
border T-4
7

8. Superior Mediastinum
 It contains:
 Trachea
 Esophagus
 Blood vessels (large veins &
arteries) (listed later)
 Nerves (listed later)
 Thoracic duct
 Thymus
 Lymph nodes: (listed later)

9. Superior mediastinum contents
Blood Vessels
Veins:
SVC
Lt & Rt brachiocephalic
veins,
Arteries:
Arch of Aorta
Brachiocepalic artery
Lt Common carotid
Lt subclavian artery

10. Superior Mediastinum
Nerves
1. Vagus nerve
2. Left Recurrent
Laryngeal nerve.
3. Phrenic nerve.

11. Superior Mediastinum
Lymph nodes:
 Highest mediastinal
 Paratracheal
 Prevascular
 retrotracheal

12. Anterior Mediastinum
 Lies ant. to pericardium
Boundaries:
Anterior: body of sternum
Posterior: pericardium
superior: imaginary line
separating sup. &
inf.mediastinum
Infreior: diaphragm
Lateral: mediastinal pleura

13. Anterior mediastinum
contains:
Thymus
Lymph nodes
fat

14. Thymus
Located in anterior
mediastinum.
Develops from endoderm
of 3rd pharyngeal pouch
Present in childhood,
involutes in adults
Blood supply
Arterial :i nt. Mammary arteries
Venous: internal thoracic veins
Lymphatic drainage: lower
cervical, int. Mammary and hilar
nodes

15. Middle Mediastinum
Boundaries:
Anterior: posterior surface of
sternum
Posterior: oesophagus, desc.
thoracic aorta, azygous vein
Superior: plane seperating sup.&
inf mediastinum
Inferior: diaphragm
Lateral: mediastinal pleura

16. Middle Mediastinum
Contents:
Heart enclosed in
pericardium
Arteries: Ascending Aorta,
Pulmonary trunk with its Lt
& Rt branches
Veins: SVC,Pulmonary
veins
Nerves: Phrenic,
vagus nerve
Bifurcation of Trachea with
two principal bronchi
Tracheobronchial lymph
nodes
16

17. Posterior Mediastinum
Boundaries:
Ant. Pericardium, Bifurcation of trachea
Post. T5 to T12
sup. Transverse thoracic plane
Inf. diaphragm
Sides: Mediastinal pleura
17

18. Posterior Mediastinum
Contents:
Oesophagus
Arteries
Descending Aorta with its
branches
Veins
Azygos
Hemizygos
Accessory hemizygos
Nerves:
Vagus
Splanchnic nerves
Thoracic duct
lymph nodes
Posterior mediastinal
18

21. anatomical Acc. To felson

22. Above the acrh of aorta,
through the sternoclavicular
joints

23. Aortic arch level. The superior vena cava (S) and aortic arch (ARCH) lie
anterior to the trachea (T) and esophagus (E). The thymus, which has undergone
fatty infiltration, is anterior to the arch.

24. Aortopulmonary window level. The aortopulmonary
window is between the ascending (A) and descending (D) aorta
and the superior vena cava (S).

25. left pulmonary artery level.
the left of the left pulmonary artery (LPA) lie the left superior pulmonary veins.
The truncus anterior (TA), or right upper lobe pulmonary artery, is anterior to
the right upper lobe bronchus. The azygoesophageal recess (AZE) is a
concavity anterior to the spine. The superior pericardial recess (SPR) is an
extension of the pericardium.

26. At the level of left pulmonary artery

27. right pulmonary artery level. The main pulmonary artery (PA) divides
into the left (LPA) and right (RPA) pulmonary arteries. The right pulmonary
artery passes anterior to the right main bronchus, and the left pulmonary
artery passes over the left main bronchus.

28. right pulmonary artery level.
The right superior pulmonary vein is to the right of and lateral to the
intrapulmonary portion of the right pulmonary artery. Anterior to the left main
and upper lobe bronchi is the left superior pulmonary vein, and posterior to
the left upper lobe bronchus is the left lower lobe pulmonary artery .

29. Left and right atrial level: The left atrium (LA) is the most superior and posterior
chamber of the heart. Superior pulmonary veins enter the anterosuperior portion of
the left atrium. The left atrial appendage (LAP) is situated anterior and to the left of
the left atrium, adjacent to the main pulmonary artery (P). The right atrial appendage
(RAP) is anterior to the superior vena cava (S) and adjacent to the ascending aorta
(A). D, descending aorta; LPA, left pulmonary artery; RPA, right pulmonary artery.

30. Left and right
ventricles

33. LEFT: A lung mass abutts the mediastinal surface and creates acute angles
with the lung.
RIGHT: A mediastinal mass will sit under the surface of the mediastinum,
creating obtuse angles with the lung

34. Posteroanterior
chest radiograph
shows loss of the
cardiac
silhouette at the
border of the right
side of the heart
and an epicardial
fat pad with
relatively low
density

35. CT scan shows
the fat pad
(arrow) as an
area of
homogeneous
fat attenuation
adjacent to the
right border of
the heart.

37. See sharp
margin
above clavicle
Mass is in posterior mediastinum. because it remains sharply outlined in apex
of thorax, indicating that it is surrounded by lung.
This particular example is a ganglioneuroma

41. .
1- Retro-sternal goiter.
2- Tortuous innominate artery.
3- Fat deposition.
4- Enlarged lymph nodes.
5- Ascending aortic aneurysm.
6- Thymoma.
7- Germ cell tumour.
8- Pleuro-pericardial cyst.
9- Morgagni hernia.
10- Para-thyroid adenoma.

42. 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.

43. Posteroanterior chest radiograph demonstrates the anterior
junction line

44. CT scan shows the four layers of pleura that
constitute the anterior junction line

45. Chest CT scan
demonstrates an
anterior
mediastinal
mass. The
anterior junction
line is obliterated,
whereas the lung
interfaces with
the hilar vessels
(arrow) and aorta
(arrowhead) are
preserved.

46. Anterior mediastinal masses
Prevascular - Thymic masses
- Retrosternal thyroid
- Teratoma
- Lymph nodal mass
- Parathyroid masses
Cardiophrenic angle mass - Epicardial fat pad
- Morgagni’s hernia
- pericardial cyst
‘Anterior mediastinal masses in the prevascular region can
obliterate the anterior junction line.’

48. Hilum can
be seen
through
mass
this must be an anterior mediastinal mass because it overlaps rather than “pushes
out” the main pulmonary arteries This particular example is a thymoma

49. Right Paratracheal Stripe
The right paratracheal stripe is seen projecting through
the SVC. It is formed by the trachea, mediastinal
connective tissue, and paratracheal pleura and is
visible due to the air–soft tissue interfaces on either
side.
paratracheal stripe should be uniform in width with a
normal width ranging from 1 to 4 mm.
The azygos vein lies at the inferior margin of the right
paratracheal stripe at the tracheobronchial angle.

50. 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.
posteroanterior chest radiograph, the
right paratracheal stripe is not seen,
having been obliterated by a right
paratracheal mass.

51. 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.

52. 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)

53. Posteroanterior chest radiograph shows the azygoesophageal line

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

55. 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.

56. 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)

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

58. 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.

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

60. 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.

61. Posteroanterior chest radiograph shows a mass (arrow)
obliterating the posterior junction line. Note that the mass
extends above the level of the clavicle and has a well-demarcated
outline due to the interface with adjacent lung
(arrowhead).

62. CT scan helps confirm the posterior location of the mass
(arrow), which proved to be a bronchogenic cyst.

63. 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

64. 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

65. On a collimated
posteroanterior
chest
radiograph, the
left paraspinal
line (arrow) is
seen separate
and distinct
from the
vertebral body
(black
arrowhead) and
the descending
thoracic aorta

66. The paraspinal lines are disrupted by
paravertebral disease—which commonly includes
diseases originating in the intervertebral disks
and vertebrae—and by neurogenic tumors.

67. Posteroanterior chest radiograph shows a mass (arrow) effacing the left
paraspinal line. The lateral wall of the descending aorta is seen as a
separate entity (arrowhead).

68. 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

70. Thymic
carcinoma.

78. The causes of calcification in a mediastinal
mass
Anterior mediastinum
Aneurysm of aortic arch
Aneurysm of ascending aorta
Bronchogenic cyst
Retrosternal goitre
Thymoma
Posterior mediastinum
Germ cell tumour
Aneurysm of descending aorta
Lymphoma after radiotherapy
Neurogenic tumour
Haemangioma
Neurobtastoma
Neurofibrosarcoma
Middle mediastinum
Ganglioneuroma
Lymph node enlargement
Neurenteric cyst,Tubercutosis ,Abscess
Histoplasmosis ,Haematoma,Lymphoma after radiotherapy
Leiomyoma of oesophagus,Sarcoidosis,Silicosis
Amyloidosis,Mucin-secreting adenocarcinoma

80. Morgagni
hernia.

81. Middle mediastinal
Thme maidsdslee mse(d2ia5s%tina)l. masses widened the para-tracheal
stripes, displaced the azygo-oesophageal
recess on right side.
1- Lymph nodes enlargement.
2- Aortic arch aneurysm.
3- Enlarged pulmonary artery.
4- Dilated superior vena cava.
5- Bronchogenic cyst.
6- Tracheal lesions.
7- Cardiac tumours.

84. Bronchogenic
cyst.

89. Aneurysmal dilatation of the main pulmonary artery
and the right pulmonary artery with peripheral
pruning due to PH

92. Posterior mediastinal
masses(25%). • Neurogenic tumours.
•Pharyngio-esophygeal pouch.
•Descending thoracic aortic aneurysm.
• Esophageal lesions
•Para-vertebral masses.
•Neuroenteric cysts.
•Bochdalek hernia.
•Pancreatic pseudocyst.
•Abscess.
•Fibrosis.
• Extra-medullary hematopoiesis.
•Lateral meningocele.

94. Posterior mediastinal
schwannoma.

95. Schwannoma
.

100. Bochdalek's
hernia.

101. BOCHDALEK’S
HERNIA

102. Descending thoracic aortic
aneurysm.

103. Posterior mediastinal mass with para-vertebral
abscess.

104. Thank
You.