Overview
Before interpreting findings on a chest x-ray, it is important to assess the x-ray's quality.
Look For
- Exposure - underpenetrated or overpenetrated
- Inspiratory film - the x-ray should be taken in deep inspiration
- Rotation - look at the medial ends of the clavicles, and the vertebrae
Exposure
The ideal x-ray allows the right amount of penetration through the chest, so that the x-ray may be properly interpreted.
In order to assess penetration, check that the vertebrae are just visible behind the heart.
Underpenetration occurs when not enough x-rays pass through the body. This results in an overly dense x-ray, with no structures visible behind the cardiac silhouette.
Overpenetration results in an x-ray that is too radiolucent, where the fine details of the lung fields are unable to be properly visualised.
Inspiration
If there is adequate inspiration, the diaphragm should be at the level of the posterior 10th rib.
An expiratory film may resemble a pneumothorax.
Rotation
Look at the medial ends of the clavicle and posterior spinous process - the side to which the patient is rotated normally becomes more translucent.
Example
- A rotated film with the patient's head obscuring the apices.
![A rotated film with the patient's head obscuring the apices.]()
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