CAMRT Radiography Practice Exam

What is the central ray angle for an AP sacrum projection?

1. 10 degrees caudad

2. 15 degrees cephalad

3. 20 degrees cephalad

4. 30 degrees caudad

The correct answer is: 15 degrees cephalad

For an anteroposterior (AP) projection of the sacrum, the central ray is angled 15 degrees cephalad. This specific angling is essential because it helps in projecting the sacrum within the field of the image receptor while minimizing the effects of the natural curvature of the sacrum. The 15-degree cephalad angle aligns the central ray with the sacral curvature, which helps in producing a clearer and more diagnostic image. The cephalad angling also assists in avoiding superimposition of the sacrum over the pubic symphysis, ensuring better visualization. Proper positioning and angling are critical for accurate image acquisition in radiographic practice, especially in the pelvis region where anatomical structures are closely situated. Understanding the correct angle is vital for radiologic technologists in order to optimize image quality and to provide the right information to the healthcare providers interpreting the images.