Compared to a patient with pneumonia, an emphysema patient will require exposure that is:

• A. 50% more
• B. The same
• C. Less
• D. 100% more

Answer: (C)

Exposure settings in radiography are chosen based on how much the body tissues attenuate the X-ray beam. Emphysema makes the lungs more radiolucent because of increased air content and hyperinflation, so fewer photons are absorbed. That means you can achieve an adequately exposed image with less exposure overall to avoid making the lungs look too dark or washed out. Pneumonia, on the other hand, adds solid-appearing tissue (consolidation) that increases attenuation, so more exposure is needed to penetrate and to preserve visibility of the lung markings and detail. Because of these density differences, an emphysema patient generally requires less exposure than a patient with pneumonia.