Chest X-Ray: Basics

Interpreting the CXR
General format:
Check the technical aspects
-Name, date, projection, rotation, penetration, inspiration
Cardiac shadow
-Size, shape, calcification
Mediastinum
-Position, width, outline, density, tracheobronchial tree
Hila
-Position, size, density, concave
Lungs
-Size, transradiancy, fissures, focal or generalised pulmonary infiltration
Pleural spaces
-Effusions, soft tissue masses, calcification, pneumothorax
Bones
-Fractures, lytic or sclerotic lesions
Soft tissues
-Masses, calcification

Technical Aspects
Check the side markers
Have you got L and R the right way around?

Assessment of rotation
Distance between medial ends of the clavicles and the spinous processes

Penetration
• Intervertebral disc spaces just visible through mid-cardiac shadow
• Pulmonary structures visible with clarity
• Few vessels in outer third

Inspiration
Full inspiration:
• 6-7 anterior ribs
• 10-11 posterior ribs

Cardiac shadow
Heart Size
• Cardiac Transverse Diameter (CTD) = a+b
< 15.5cm (males)
< 15.0cm (females)

• Cardio-Thoracic Ratio (CTR) =a+b÷c+d
< 0.5

Cardiac configuration
• Dilated left ventricle:
-Ischaemic/dilated cardiomyopathy
-Aortic reflux
-Mitral reflux
-VSD, PDA
-Anaemia, hyperthyroid, Paget’s, AVF

• Failing left ventricle:
-AS, HTN, Coarctation

• Cardiomegaly (CTR > 0.5)

• Large third “mogul”

• Double density right heart border

• Displaced descending aorta

• Dilated left atrium:
-Mitral stenosis or myxoma
-Mitral reflux, VSD, PDA,
-ASD (late)

The mediastinum
• Mediastinal position
• Ratio:
- 1/3 to the Rt of midline
- 2/3 to the Lt of midline

Left heart border
• Aortic arch
•Main (left) PA
•Left atrial appendage
•Left ventricle
Right heart border
•Brachiocephalic vein
•SVC
•Right atrium
•IVC
- blurred or obscured and 'indistinct' right heart border

Hila
•Position of hilar point:
-Right = 6th rib in mid-axillary line
-Left = 0–2.5cm higher

•Outline:
- "V" shaped

Lungs
•Size
•Transradiancy
•Fissures
•Focal or generalised pulmonary infiltration

Horizontal fissure
6th rib in mid-axillary line

Azygos fissure
4-layers of pleura, containing azygos vein

Plural Spaces
•Effusions
•Soft tissue masses
•Calcification
•Pneumothorax

Bones
•Fractures
•Lytic or sclerotic lesions

Soft Tissues
•Masses
•Calcification