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

In obtaining an anteroposterior (AP) projection of the sacrum, the central ray is angled 15 degrees cephalad. This specific angulation is crucial because it helps to project the sacrum in a plane that minimizes the distortion caused by its natural curvature and the anatomical position of the pelvis. By angling centrally toward the head, the radiograph captures a clearer image of the sacral anatomy, allowing for better visualization of structures and alignment.

This cephalad angulation helps to align the sacrum parallel to the film or imaging receptor, which is essential for obtaining diagnostic-quality images, as it enhances the fidelity of the anatomical structures being examined. This technique reduces superimposition of surrounding anatomical structures on the radiograph, ensuring that the sacral region is clearly represented.

Understanding the correct angulation is vital for radiographic positioning and can significantly impact the diagnostic utility of the images obtained.