Which pair correctly matches angulation for sacrum and coccyx AP axial?

• A. Sacrum 15 degrees cephalad; Coccyx 10 degrees caudad
• B. Sacrum 15 degrees caudad; Coccyx 10 degrees cephalad
• C. Sacrum 0 degrees; Coccyx 0 degrees
• D. Sacrum 10 degrees cephalad; Coccyx 15 degrees caudad

Answer: (A)

AP axial views of the sacrum and coccyx use a small angled CR to align the beam with these structures and reduce overlapping with surrounding pelvic anatomy. The sacrum sits in a position that benefits from a cephalad (toward the head) tilt of about 15 degrees; this cephalad angulation helps project the sacral body, reduces superimposition by the lumbar spine, and minimizes foreshortening so the sacral canal and foramina are better seen. The coccyx, being more distal and often obscured by the pelvis, is best demonstrated with a caudad (toward the feet) angle of about 10 degrees, which moves the coccyx away from the pubic symphysis and pelvic bones, decreasing overlap and magnification of the distal coccyx. Using zero degrees would typically yield more overlap and poorer visualization, and reversing the angles would misproject the structures.