Chest X-ray Interpretation

Chest X-ray Interpretation

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Learning Outcomes

1. Describe the overall systematic approach to chest X-ray interpretation i.e. patient details, projection, technical quality.
2. Explain how a technically inadequate chest x-ray could lead to misdiagnosis.

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1# Check patient details

2# Check projection

AP

PA

Lateral

Title 1

Title 2

Title 2

The effect of projection on magnification of the heart on chest X-rays

The divergent nature of the X-ray beam has been exaggerated to highlight this point.

(A) In an AP view, the heart is further from the X-ray detector plate. There is a significant magnification of the heart (dashed arrow) due to the divergent nature of the X-ray beam.

(B) In a PA view there is very little magnification of the heart as it is located closer to the X-ray detector plate.

Text button

Text button

Cardiothoracic ratio CTR

The heart should be 50% or less than the width of the thorax on a PA chest x-ray CTR=(C/T)×100%

3# Assess Technical Adequacy

Field

Does the film cover the entire region of interest?

Hover on the image opposite to find 3 important regions that shouldn't be missed when checking the adequacy of the field of a chest-X-ray

RIP 🪦

R → Rotation I → Inspiration P → Penetration

Rotation

• This is a supine chest x-ray therefore the projection is AP.

• It is anonymous so there are no patient details.

• The heads of the clavicles are not equidistant from the the spinous processess (SP) therefore it is rotated.

• Patient rotation can erroneously give the impression that the mediastinum is shifted or that there is lung pathology

Inspiration

• Count down to the lowest rib crossing the diaphragm

• 8-10 posterior ribs or 5-7 anterior ribs should be visible in the midclavicular line

• More ribs with flattened diaphragms indicate hyperinflation → COPD

• Less ribs indicates poor inspiration or expiration. Less air in the lungs makes the lungs hyperdense. A raised diaphragm can falsely enlarge the size of the heart and obscure the hemidiaphragms

10 posterior ribs → good inspiration

Poor Inspiration

Click on the image to reveal the answer

Adequate Inspiration

click on the image to reveal the answer

(same patient)

Penetration

• An adequately penetrated chest X-ray is one where the vertebrae are just visible behind the heart.

• (A reminder to check behind the heart).

• The left hemidiaphragm should be visible to the edge of the spine.

• Loss of the hemidiaphragm contour or of the paravertebral tissue lines may be due to lung or mediastinal pathology.

Which chest X-ray is adequately penetrated?

Click to reveal the correct answer

Techincal Adequacy

Make three comments regarding the technical adequacy of this PA chest x-ray. (Hover over the image for the answers)