What is the correct central ray angulation for an AP projection of the sacrum?

What is the correct central ray angulation for an AP projection of the sacrum?

• A. 15 degrees caudad
• B. 0 degrees
• C. 15 degrees cephalad
• D. 30 degrees cephalad

Answer: (C)

An AP axial view of the sacrum is best obtained with the central ray angled toward the head to align with the sacral anatomy. Angling the ray 15 degrees cephalad compensates for the sacrum’s anterior inclination inside the pelvis, allowing the sacral body and foramina to be seen clearly without excessive superimposition from the lumbar spine or pelvis. A zero-degree angle would not provide the axial projection needed and would cause foreshortening, while a larger angle like 30 degrees would overdo the tilt and distort the anatomy. Therefore, 15 degrees cephalad is the appropriate angulation.

An AP axial view of the sacrum is best obtained with the central ray angled toward the head to align with the sacral anatomy. Angling the ray 15 degrees cephalad compensates for the sacrum’s anterior inclination inside the pelvis, allowing the sacral body and foramina to be seen clearly without excessive superimposition from the lumbar spine or pelvis. A zero-degree angle would not provide the axial projection needed and would cause foreshortening, while a larger angle like 30 degrees would overdo the tilt and distort the anatomy. Therefore, 15 degrees cephalad is the appropriate angulation.