How should collimation be adjusted for a lateral elbow projection?

When performing a lateral elbow projection, proper collimation is crucial for achieving optimal image quality while minimizing radiation exposure. Adjusting the collimation to include the elbow joint with the distal humerus and proximal ulna/radius ensures that all relevant anatomical structures are captured in the image. This focus allows for a comprehensive assessment of the joint, including the integrity of the bones and any potential pathologies.

In this context, including the entire arm would be excessive and could lead to unnecessary exposure to surrounding tissues. Similarly, focusing solely on the forearm would omit critical details of the elbow joint itself, which is the primary area of interest in this projection. Centering on the wrist joint would not be appropriate either, as it lies distal to the elbow and is not relevant for a lateral elbow examination. Thus, option B is the correct choice for optimal collimation in this situation.