Which projection typically results in less magnification of the heart in chest radiographs?

• A. AP projection
• B. PA projection
• C. Lateral projection
• D. Oblique projection

Answer: (B)

Heart size on a radiograph is influenced by geometry: the farther an object is from the image receptor, the more magnified its image becomes because X-ray beams diverge as they travel from the source to the detector. In a PA chest view, the patient stands facing the detector with the chest pressed against it, so the heart sits close to the image receptor and farther from the X-ray tube. This arrangement minimizes the magnification of the heart’s silhouette. In an AP view, the heart is closer to the tube and farther from the detector, which increases magnification. Lateral and oblique views alter the silhouette but do not reduce magnification as effectively as the PA projection. So, the PA projection typically results in less magnification of the heart.