CAMRT Radiography Practice Exam

What angle is used for the central ray in an AP axial coccyx projection?

1. 10 degrees cephalad

2. 10 degrees caudad

3. 15 degrees cephalad

4. 15 degrees caudad

The correct answer is: 10 degrees caudad

In the AP axial coccyx projection, the central ray is directed 10 degrees caudad. This angle is important for properly visualizing the coccyx, which is located at the distal end of the vertebral column. The caudad angle helps to alleviate any superimposition of the coccyx on the pubic symphysis and allows for a clearer view of the coccyx against the background of the surrounding anatomy. By angling the tube 10 degrees toward the feet, practitioners can obtain a radiograph that shows the coccyx projected free from the pelvic structures, thus ensuring accurate assessment and diagnosis. In this context, employing a cephalad angle would not provide the desired visualization because it would push the coccyx further into the pelvic cavity, complicating its view. Therefore, using a 10-degree caudad angle facilitates the optimal positioning required for this specific imaging procedure.