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

The appropriate central ray angulation for an AP axial projection of the coccyx is 10 degrees caudad. This angulation is crucial for optimizing the visualization of the coccyx by aligning the x-ray beam with the natural curvature of the sacrum and coccyx. By angling the beam caudally, the projection helps to reduce the overlap of the coccyx with the pubic symphysis, which can obscure the area of interest. This technique ensures a clearer and more diagnostic image of the coccyx, highlighting any possible fractures or abnormalities.

In this case, other angulations may not effectively highlight the coccyx. For example, a 5-degree cephalad or 0-degree angle might not align well with the anatomy, risking potential obscuration of the area due to anatomical overlap. Additionally, a 15-degree caudad angulation could potentially project the coccyx too far down, leading to distortion or an inadequate view. Thus, using a 10-degree caudad angle optimally balances the need for a clear image while considering the anatomical orientation.