2.2 CXR Heart and Mediastinum Anatomy

Question 1

What are the 3 imaging techniques in CXR which can vastly affect image quality?

Answer 1

1. Inspiration
2. Penetration
3. Rotation

Question 2

Describe the differences between a CXR with good inspiratory effort versus a poor inspiratory effort.

Answer 2

1. Ribs
   
   • 8-9 posterior ribs should be visible
2. Lung markings
   
   • Crowded lung markings if poor inspiratory effort

A poor inspiratory effort on a film means that lung fields are hazy and also smaller lung volumes are visible. This makes detection of an abnormality difficult.

Question 3

Understand how to count anterior and posterior ribs in a CXR.

Answer 3

Question 4

Describe the effect of wrong penetration on a film.

Answer 4

1. Overpenetration
   
   • Everything looks more dark, including lung fields, can mimic pneumothorax
2. Underpenetration
   
   • Everything looks hazy and white, difficult to see what is going on

Question 5

Describe the effect of rotation on a CXR.

How do you see if a film is rotated?

Answer 5

If a patient is rotated, the mediastinum and hilum towards the side of a rotation will appear larger, mimicking a mass.

‘Side of a rotation’, i.e. if a person is rotating to the R, their L shoulder is coming forward towards the film.

Z-axis refers to the axis upon which the patient hypothetically rotates.

Question 6

Memorise and recite an algorithm for looking at a CXR.

Answer 6

This is one suggested method by Dr Hetal Verma.

Question 7

Point out the key mediastinal structures in this PA view of the chest.

Answer 7

1. Trachea - midline
2. Shadow of the SVC
3. R and L hila - they are key regions for lymphadenopathies or masses
4. R atrium - represented by the entire R heart border
5. Aorta - you can see both ascending and descending aorta in the upper chest and also the rest of the descending aorta in the lower chest
6. L ventricle - represented by the entire L heart border

Question 8

Point out the key mediastinal structures in this lateral view of the chest.

Answer 8

1. Retrosternal clear space - should always be anterior to heart and mediastinal structures
2. R ventricle - represented by the anterior border of heart on lateral view
3. R hemidiaphragm is denser and higher than the L hemidiaphragm due to the underlying liver
4. Aorta - arches to the right
5. Only 1 hilum present due to the R and L hila overlapping
6. Posterior heart border on lateral view has 2 parts - the superior part represents the RA, whereas the inferior part represents the LA.