Anatomy of Chest

Dr. Muhammad Bin ZulfiqarPGR-1 FCPS SHL

Structures to identify

• Heart• Lungs• Mediastinum• Pleural space• Chest wall

• …Everything else!– Bones, soft-tissues

IMAGING MODALITIES

1. Plain chest Radiograph2. Fluoroscopy 3. Computerized tomography4. Radionuclide lung scan 5. MRI6. Ultrasound7. Pulmonary angiography

Plain chest radiograph

• Diagnostic in 80% cases• Standard views

1. Postero-anterior(P/A)2. Lateral (right/left)

• Additional views1. Oblique view(ribs)2. Apical lordotic view3. Expiration view4. Decubitus view

CXR InterpretationNormal structures visible

1. Tracheal air column. 2. Carina. 3. First rib.4. Peripheral lung fields have no markings except: 5. The minor fissure. 6. Top of the R diaphragm is usually between the

anterior 6th & 7th ribs, and overlying the posterior 10th & 11th ribs.

7. Left diaphragm is lower (in 90-95%) by roughly half an interspace.

8. Inferior margins of the posterior ribs.9. Anterior mediastinal line.10. Superior vena cava.11. Azygos vein.12. Right descending pulmonary artery. 13. Pulmonary arteries and veins. 14. Right atrium. 15. Inferior vena cava. 16. Aortic arch. 17. Left pulmonary artery. 18. Border of the left ventricle. 19. Descending aorta. 20. Fat density lines in the intermuscular fascial

layers

Chest radiograph with superimposed mediastinal stripes.

Yellow: right paratracheal stripe. Light blue: right and

left paraspinal stripes. Red: azygoesophageal

stripe. Brown: pleuroesophageal

stripe. Purple: anterior junction line

complex. Pink: left subclavian artery

border. Light green: posterior-superior junction line. Dark green: para-aortic

line.

Lobes and Fissures

RULLUL

RLL

RML

LLL

Left Lateral View Right Lateral View

LUL

LLL

RUL

RML

RLL

http://www.wikiradiography.com/page/Chest+Radiographic+Anatomy

AORTIC ARCH

LT. HEMI DIAPHRAGM

NORMAL CHEST ANATOMYLATERAL CHEST XRAY

COLON GAS

TRACHEA

OBLIQUE FISSURE

HORIZONTAL FISSURE

RT. HEMI DIAPHRAGM

10

1. A line is drawn from anterior surface of the body of 6th thoracic vertebrae passing through the apex of the heart up to anterior lower most part of diaphragm.

2. Another straight line is drawn from anterior surface of the body of T-6 vertebrae to the sternum.

. Segmental Anatomy of Lung

Segmental Anatomy of

Lung

Lateral viewOn a normal lateral view the contours of the heart are visible and the IVC is seen entering

the right atrium.The retrosternal space should be radiolucent,

since it only contains air. Any radiopacity in this area is suspecctive of a process in the

anterior mediastinum or upper lobes of the lung.

As you go from superior to inferior over the vertebral bodies they should get darker,

because usually there will be less soft tissue and more radiolucent lung tissue (red arrow).

If this is not the case, look carefully for pathology in the lower lobes.

The contours of the left and right diaphragm should be visible.

The right diaphragm should be visible all the way to the anterior chest wall

(red arrow).Actually we see the interface between the air in the lungs and the soft tissue

structures in the abdomen.The left diaphragm can only be seen to

a point where it borders the heart (blue arrow).

Here the interface is lost, since the heart has the same density as the structures below the diaphragm.

The left main pulmonary artery (in purple) passes over the left main bronchus and is higher than the right pulmonary artery (in blue) which

passes in front of the right main bronchus.

Pectus excavatumIn patients with a pectus excavatum the right heart border can be ill-defined, but this is normal.

It produces a silhouette sign and thus simulating a consolidation or atelectasis of the right middle lobe.

The lateral view is helpful in such cases.Pectus excavatum is a congenital deformity of the ribs and the sternum producing a concave

appearance of the anterior chest wall.

Vena azygos lobeA common normal variant is the azygos lobe.

The azygos lobe is created when a laterally displaced azygos vein makes a deep fissure in the upper part of the lung.

On a chest film it is seen as a fine line that crosses the apex of the right lung.

Here another patient with an azygos lobe.

The azygos vein is seen as a thick structure within the azygos fissure.

In some patients an extra joint is seen in the anterior part of the first rib at the point where the bone meets the calcified

cartilaginous part (arrow).This may simulate a lung mass.

Cervical Rib

Computed Tomography

• Role of CT– Main further investigation

for most CXR abnormality (eg nodule/mass) or to exclude disease with normal CXR

– Main investigation for certain scenarios (PE, dissection, trauma)

Computed Tomography

• Numerous protocols/techniques depending on clinical history

• Helical/spiral versus high resolution

• Contrast– Renal failure– Allergy

Secondary lobule The secondary lobule is the basic anatomic unit of pulmonary structure and function. It is the

smallest lung unit that is surrounded by connective tissue septa. The secondary lobule is supplied by a small bronchiole (terminal bronchiole) in the center, that is paralleled by the

centrilobular artery. Pulmonary veins and lymphatics run in the periphery of the lobule within the interlobular septa.

Centrilobular area is the central part of the secondary lobule.

Perilymphatic area is the peripheral part of the secondary lobule.

CT angiogram. Frontal or

coronal view of chest-3D slab

image showing pulmonary

vessels.

MRI

• Multiple planes• No radiation• Common Indication

– Pancoast tumour– Brachial plexus– Cardiac– Vascular (aorta)

• Usually targeted examination (unlike CT)

Coronal

Indications for MRI

•A chest MRI provides detailed pictures of tissues within the chest area.•A chest MRI may be done for the following reasons:•As an alternative to angiography, or to avoid repeated exposure to radiation•Clarify findings from previous x-rays or CT scans•Diagnose abnormal growths in the chest•Evaluate blood flow•Show lymph nodes and blood vessels•Show the structures of the chest from multiple angles•See if cancer in the chest has spread to other areas of the body - this is called staging; staging helps guide future treatment and follow-up and gives you some idea of what to expect in the future•Tell the difference between tumors and normal tissue

Normal 32-year-old female. MR angiography

derived maximum intensity projection

reconstruction shows normal pulmonary artery

anatomy: pulmonary artery main stem (black arrow), right pulmonary artery (white arrow) and

left pulmonary artery (asterisk).

the 3D reconstruction of the MRA image (1) allows the visualization of the entire pulmonary vasculature identifying the subsegmental pulmonary arteries.

Dynamic contrast-enhanced MRA image in the oblique axial plane (2, 3, 4) allow the evaluation of pulmonary circulation, including perfusion of the lung fields,

which is homogeneous and symmetric.

1: Right lung 2:Left lung 3:Cardiac silhouette 4.Mediastinum

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