Final answer:
The central ray for an AP projection of the sternum should be directed perpendicular to the sternum, aligning with its anatomy which includes the manubrium, body, and xiphoid process.
Step-by-step explanation:
For an AP projection of the sternum, the central ray should be directed perpendicular to the sternum. Depending on the habitus of the patient, generally speaking, the central ray should be angled neither up nor down but should be directed straight at the sternum. The sternum itself consists of three parts: the manubrium, the body, and the xiphoid process. The sternal angle, an important anatomic landmark, is located between the manubrium and the body of the sternum. This is also the site for the attachment of the second rib to the sternum. The proper identification of the sternum's anatomy is crucial for accurate radiographic imaging.