Which projection requires the patient to suspend respiration to obtain a clear sacrum image?

• A. AP axial projection of the sacrum
• B. AP axial projection of the coccyx
• C. Lateral sacrum
• D. Lateral coccyx

Answer: (A)

Minimizing motion is essential when imaging the sacrum with an axial projection because the beam passes through the sacrum at a sharp angle and any movement during the exposure can blur the sacral outline. The AP axial sacrum (often done with a cephalad angle) sits near the abdominal organs and diaphragmatic motion; stopping respiration reduces diaphragmatic excursion and abdominal movement, yielding a crisper, more accurate image of the sacrum. End-expiration or a brief breath-hold helps stabilize the area during the exposure so the angled beam can capture the sacrum without blur. The other views involve different angles or regions, and while breath-holding can be used, the need for a respiration pause is not as critical for them as it is for the AP axial sacrum to achieve a sharp image.