normal mediastinum radiograph

Johan Rey P. MonPost-Graduate

InternMEDIASTINUM

NORMAL RADIOGRAPH

Narrow, vertically oriented structure that resides between the medial parietal pleural layers of the lungs

Extends from the sternum to the bodies of the vertebrae; and from the superior thoracic aperture to the diaphragm

Contains the thymus gland, the pericardial sac, the heart, the trachea and the major arteries and veins

MEDIASTINUM

BOUNDARIES

Boundaries Anterior – sternum and

costal cartilages

Posterior – 12 thoracic vertebrae

Superior – thoracic inlet

Inferior – diaphragm

Lateral – mediastinal pleura

BOUNDARIES OF THE MEDIASTINUM

DIVISIONS

Superior mediastinum*

Inferior mediastinum Anterior

- anterior to the pericardial sac and posterior to the body of the sternum

Middle- contains the pericardial sac and its contents

Posterior- posterior to the pericardial sac and the diaphragm and anterior to the bodies of the vertebrae

DIVISIONS OF THE MEDIASTINUM

Boundaries ContentsAnterior Mediastinum (Prevascular)

Superiorly - by the thoracic inlet, Laterally - by the pleura, Anteriorly - by the sternum, and Posteriorly - by the pericardium and great vessels

Internal mammary vesselsInternal mammary ad prevascular lymph nodesThymus

Middle Mediastinum (Vascular)

Anteriorly - by the anterior mediastinum Posteriorly - by the posterior mediastinum.

Heart and pericardiumAscending and transverse aortaMain and proximal right and left pulmonary arteriesConfluence of pulmonary veinsSuperior and inferior vena cavaTraches and main bronchiLymph nodes and fat within mediastinal spaces

Posterior Mediastinum (Post-vascular)

Lies behind the heart and pericardium and extends from the level of the thoracic inlet to the 12th thoracic vertebra.

Descending aortaEsophagusAzygos and hemiazygos veinsThoracic ductSympathetic ganglia and intercostal nervesLymph nodes

MEDIASTINAL CONTOUR

Right paratracheal stripe seen in two thirds of normal films  made up of right brachiocephalic

vein and SVC

Arch of the azygous vein

Ascending aorta

Superior vena cava (SVC)

Right atrium

Inferior vena cava (IVC)

RIGHT CARDIOMEDIASTINAL CONTOUR

Left paratracheal stripe made up of left common carotid

artery, left subclavian artery and the left jugular vein

Aortic arch +/- aortic nipple (left superior intercostal vein)

Pulmonary artery

Auricle of left atrium

Left ventricle

LEFT CARDIOMEDIASTINAL CONTOUR

Superior mediastinum Great vessels Thymus

Ascending aorta

Right ventricular outflow track

Right ventricle

ANTERIOR CARDIOMEDIASTINAL CONTOUR

Left atrium and pulmonary veins

Right atrium

Inferior vena cava

POSTERIOR CARDIOMEDIASTINAL CONTOUR

Consists of potential spaces used to describe the location of disease processes

Important diseases change the appearance of the aortic knuckle, the aorto-pulmonary window and the right para-tracheal stripe

MEDIASTINAL CONTOURS

The aortic knuckle (red line) represents the left lateral edge of the aorta as it arches backwards over the left main bronchus, and pulmonary vessels.

The contour of the descending thoracic aorta (yellow line) can be seen in continuation from the aortic knuckle.

NORMAL AORTIC KNUCKLE

The aorto-pulmonary window lies between the arch of the aorta and the pulmonary arteries.

Between the Aortic Knuckle (AK) and the Left Pulmonary Artery (LPA)

The descending aorta (DA) marks its posterior boundary.

AORTO-PULMONARY WINDOW

From the level of the clavicles to the azygos vein the right edge of the trachea is seen as a thin white stripe.

Normal: <3 mmThickened: may represent

paratracheal mass or enlarged lymph node

RIGHT PARA-TRACHEAL STRIPE

MEDIASTINAL MASSES

ANTERIOR MEDIASTINAL MASSES

MIDDLE MEDIASTINAL MASSES

MIDDLE MEDIASTINAL MASSES

POSTERIOR MEDIASTINAL MASSES

POSTERIOR MEDIASTINAL MASSES

HILUM

• Junction of the lung with the mediastinum and is composed of upper lobe pulmonary veins and branches of the pulmonary artery and corresponding bronchi

• On chest radiographs, the term hilum represents the composite shadow of the bronchi, pulmonary arteries and veins, and lymph nodes on the medial aspect of each lung.

• Left hilar shadow is higher in the right in 90% of individuals

HILUM

On a true lateral radiograph, the right and left hilar shadows are not completely superimposed and comprise a combination of the right and left pulmonary arteries and the superior pulmonary veins

Inferior hilar window- An avascular aspect of the composite hilar shadow, inferior to the shadow of the right pulmonary artery and veins and anterior to the descending left pulmonary artery and left superior vein

LEFT LATERAL VIEW OF THE HILUM

HILAR MASS

RUL bronchus is seen in approximately 50% of individuals as an end-on, round lucency at the upper margin of the composite hilar shadow

Recognition of this bronchus, when not visible on prior radiographs, should suggest a mass or lymph node enlargement about the bronchus

LEFT LATERAL VIEW OF THE HILUM

HEART

• It lies primarily in the anterior left hemithorax, with the LV lying on the left hemidiaphragm

• The RA extends to the right of midline as it receives systemic blood from the SVC, IVC, and coronary sinus

• The RA and RV lie primarily anterior to the planes of the LA and LV

• The RV is the most anterior chamber and abuts the sternum

• The LA is subcarinal and midline in the thorax

HEART

HEART

CARDIOMEDIASTINAL ANATOMY(PA VIEW)

1. Superior vena cava2. Right atrium3. Inferior vena cava4. Aortic arch5. Main pulmonary artery6. Left atrial appendage7. Left ventricle

CARDIOMEDIASTINAL ANATOMY

(LATERAL VIEW)

1. Left atrium2. Left ventricle3. Inferior vena cava4. Right ventricle5. Right pulmonary artery6. Left pulmonary artery7. Aorta

Refer to the bulges of the cardiomediastinal contour on frontal chest radiographs.*

Right cardiomediastinal border: the right atrium is the only

normal bulge

MOGULS OF THE HEART

Left cardiomediastinal border: 1st mogul- uppermost, located paratracheally

above the carina, and formed by the aortic arch (aortic knuckle or knob)

2nd mogul- located just above the left main bronchus and represents the main pulmonary artery segment

3rd mogul- NEVER NORMAL if present, it lies below the left main

bronchus and is usually formed by prominent left atrial appendage, which is commonly seen in rheumatic heart disease

MOGULS OF THE HEART

4th mogul- bulge just above the diaphragm formed by the left ventricular margin or cardiac apex

5th mogul- bulge at the cardiophrenic angle- may be caused by prominent pericardial fat pad, pericardial cyst, or adenopathy

MOGULS OF THE HEART

Right cardiac borders:1. Superior vena cava2. Inferior vena cava3. Right atrium

CARDIAC BORDERS

Left cardiac borders:1. Aortic knob2. Main pulmonary trunk3. Left ventricle

CARDIAC BORDERS

RA LVRV

LALV

HEART CHAMBERS

Heart size is assessed as the cardiothoracic ratio (CTR)

Determines the relation of the heart to the width of the chest at its widest part near the level of the diaphragm

Cardiac size is measured by dropping parallel lines down both sides of the heart, at the most lateral points on each side, and measuring between them.

Thoracic width is measured by dropping parallel lines down the inner aspect of the widest points of the rib cage, and measuring between these.

CARDIOTHORACIC RATIO

AdultPA view = 0.50AP view = 0.55

PediaAge (wks) Range0-3 0.60-0.504-7 0.64-0.528-15 0.62-0.5116-23 0.62-0.5124-31 0.61-0.5032-39 0.61-0.5140-47 0.60-0.4948-55 0.57-0.49

Age (yrs) Range0-1 0.65-0.391-2 0.60-0.392-3 0.50-0.393-4 0.52-0.404-5 0.52-0.405-6 0.50-0.407 0.49-0.438 0.49-0.429 0.49-0.4110 0.49-0.4311 0.49-0.4312 0.46-0.40

CARDIOTHORACIC RATIO NORMAL VALUES

THANK YOU!!!