Final answer:
The CR should be directed perpendicular to the central point of the clavicle when examining it in the PA position, in order to obtain an axial projection and visualize fractures that may not be visible otherwise.
Step-by-step explanation:
When examining the clavicle in the PA position, the CR (central ray) should be directed perpendicular to the central point of the clavicle. This means that the CR should be aimed directly at the center of the clavicle, which is located between the sternoclavicular joint and the acromioclavicular joint. By directing the CR in this way, an axial projection of the clavicle can be obtained, helping to visualize fractures that may not be visible using a perpendicular CR.