Radiological imaging of mediastinal masses.

Dr. Arun Kumar Singh

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 - sternumPosterior - vertebral column and paravertebral

fasciaSuperior -thoracic inletInferior - diaphragmLateral - parietal pleura

Sternal Angle

Thoracic inlet

Thoracic oulet

Boundaries of mediastinum

sternum

Thoracic vertebra

TS: Mediastinum

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CS: Mediastinum

Divisions of mediastinum

MEDIASTINUM

Superiormediastinum

Inferior mediastinum

Anterior mediastin

um

Middle mediastin

um

Posterior mediastin

um

Superior Mediastinum

Posterior Mediastinum

Anterior Mediastinum

Middle Mediastinum

Sternal Angle

T4

T5

divided into superior mediastinum and inferior mediastinum by an imaginary line passing through sternal angle anteriorly lower border of 4th thoracic vertebra posteriorly

Mediastinum divisions

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

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Superior Mediastinum

It contains: Trachea Esophagus Blood vessels (large

veins & arteries) (listed later)

Nerves (listed later) Thoracic duct Thymus Lymph nodes: (listed

later)

Superior mediastinum contents

Blood Vessels

Veins: SVCLt & Rt brachiocephalic veins,

Arteries:Arch of Aorta Brachiocepalic arteryLt Common carotid Lt subclavian artery

Superior Mediastinum

Nerves1. Vagus nerve2. Left Recurrent

Laryngeal nerve.

3. Phrenic nerve.

Superior Mediastinum

Lymph nodes:

Highest mediastinal Paratracheal Prevascular retrotracheal

Anterior Mediastinum

Lies ant. to pericardiumBoundaries:

Anterior: body of sternumPosterior: pericardiumsuperior: imaginary line separating sup. & inf.mediastinumInfreior: diaphragmLateral: mediastinal pleura

Anterior mediastinum contains:

ThymusLymph nodes fat

Thymus

Located in anterior mediastinum.

Develops from endoderm of 3rd pharyngeal pouch

Present in childhood, involutes in adults

Blood supplyArterial :i nt. Mammary arteries

Venous: internal thoracic veins

Lymphatic drainage: lower cervical, int. Mammary and hilar nodes

Middle Mediastinum

Boundaries:

Anterior: posterior surface of sternum

Posterior: oesophagus, desc. thoracic aorta, azygous vein

Superior: plane seperating sup.& inf mediastinum

Inferior: diaphragmLateral: mediastinal pleura

Middle MediastinumContents:

Heart enclosed in pericardium

Arteries: Ascending Aorta, Pulmonary trunk with its Lt &

Rt branches

Veins: SVC,Pulmonaryveins

Nerves: Phrenic, vagus nerve

Bifurcation of Trachea with two principal bronchi

Tracheobronchial lymph nodes16

Posterior Mediastinum Boundaries:

Ant. Pericardium, Bifurcation of tracheaPost. T5 to T12

sup. Transverse thoracic plane

Inf. diaphragm

Sides: Mediastinal pleura

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Posterior MediastinumContents: Oesophagus Arteries Descending Aorta with its

branches

Veins Azygos Hemizygos Accessory hemizygos

Nerves: Vagus Splanchnic nerves

Thoracic ductlymph nodes Posterior mediastinal

anatomical Acc. To felson

Above the acrh of aorta, through the sternoclavicular joints

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.

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

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.

At the level of left pulmonary artery

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.

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 .

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.

Left and right ventricles

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

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

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

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

.

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.

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.

Posteroanterior chest radiograph demonstrates the anterior junction line

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

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.

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.’

Hilum can be seen through mass

this must be an anterior mediastinal mass because it overlaps rather than “pushes out” the main pulmonary arteriesThis particular example is a thymoma

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.

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.

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.

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)

Posteroanterior chest radiograph shows the azygoesophageal line

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

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.

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)

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

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.

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

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.

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).

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

Paraspinal LinesThe 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

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

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

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

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).

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

Thymic carcinoma.

The causes of calcification in a mediastinal mass Anterior mediastinum Aneurysm of aortic archAneurysm of ascending aorta Bronchogenic cystRetrosternal goitreThymoma Posterior mediastinumGerm cell tumour Aneurysm of descending aortaLymphoma after radiotherapy Neurogenic tumourHaemangioma NeurobtastomaNeurofibrosarcomaMiddle mediastinum GanglioneuromaLymph node enlargement Neurenteric cyst,Tubercutosis ,AbscessHistoplasmosis ,Haematoma,Lymphoma after radiotherapy Leiomyoma of oesophagus,Sarcoidosis,SilicosisAmyloidosis,Mucin-secreting adenocarcinoma

Morgagni hernia.

Middle mediastinal masses(25%). The middle mediastinal 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.

Bronchogenic cyst.

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

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.

Posterior mediastinal schwannoma.

Schwannoma.

Bochdalek's hernia.

BOCHDALEK’S HERNIA

Descending thoracic aortic aneurysm.

Posterior mediastinal mass with para-vertebral abscess.

Thank You.