Where should the central ray enter for an AP projection during an operative cholangiogram?

In an AP projection during an operative cholangiogram, the central ray should ideally enter at the location indicated by the surgeon. This is because the operative cholangiogram is performed during surgery, typically to visualize the bile ducts and assess for any obstructions or stones. The surgeon's indication takes into account the specific anatomy and positioning of the patient during the procedure, ensuring that the image accurately captures the area of interest.

Furthermore, the surgeon's guidance ensures that the radiologic technologist targets the correct area, which might not align with standard landmarks such as the midpoint of the abdomen or the xiphoid process due to the unique surgical field involved in each case. Thus, the location specified by the surgeon is essential for obtaining optimal images that will assist in surgical decision-making and patient care during the procedure.