Final answer:
For a PA Axial Mandible projection, the CR should be centered at the lips, and the tube should be angled 20 to 25 degrees cephalad for an adult. Adjustments may be necessary based on individual anatomy.
Step-by-step explanation:
The center of the Central Ray (CR) for a PA Axial Mandible radiographic projection is directed to exit through the midpoint of the mandible, which is generally the lips. This is typically done with the patient's forehead and nose touching the image receptor. For the tube angle, you would angle the CR approximately 20 to 25 degrees cephalad (upward toward the head) for an adult. This angle may need to be adjusted based on the individual's anatomy to properly visualize the mandibular rami, angles, and lower borders. Remember, maintaining good communication with the patient is crucial to ensure correct positioning and optimal image quality.