Assessment of chest x-ray technical adequacy (approach)
Described below are some points on an approach to the assessment of the chest x-ray technical adequacy. Rarely, a technically inadequate chest x-ray will prohibit diagnostic interpretation but knowledge of the limitations will impact on diagnostic confidence.
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Exposure/penetration
- assessed by looking at the lower thoracic vertebral bodies, whose outline should just be visible on a PA projection
- the spine should be seen through the heart 1
- poor penetration: pulmonary vessels and interstitial markings appear more prominent, loss of detail at the lung bases and vertebrae, results in increased density
Inspiratory effort
- anterior aspect of at least six ribs must be noted above the dome of the right diaphragm
- alternatively, posterior aspects of at least eight to nine ribs should be visualized 1
- poor effort: the cardiac shadow may appear spuriously enlarged, crowding of vessels at lung bases
Rotation
- thoracic spinous processes are equidistant from the medial end of each clavicle on a frontal image
- rotation to the right may cause: pseudo-mediastinal mass, hyperlucency of the right lung
- rotation to the left may cause: aortic arch may appear spuriously enlarged, hyperlucency of the left lung
Magnification
- films on anteroposterior views slightly magnify the heart 1
Angulation
- medial ends of the clavicles should be projected over the posterior third or fourth ribs 1
- clavicles will have a S shape 1