Chest X-ray Interpretation

Chest X-ray Interpretation

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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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Learning Outcomes

1# Check patient details

Lateral

AP

Title 2

Title 2

PA

2# Check projection

Title 1

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

(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.

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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.

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

Cardiothoracic ratio CTR

3# Assess Technical Adequacy

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

Does the film cover the entire region of interest?

Field

R → Rotation I → Inspiration P → Penetration

RIP 🪦

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

10 posterior ribs → good 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

Inspiration

Click on the image to reveal the answer

Poor Inspiration

click on the image to reveal the answer

(same patient)

Adequate Inspiration

• 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.

Penetration

Click to reveal the correct answer

Which chest X-ray is adequately penetrated?

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

Techincal Adequacy