Final answer:
The CR for a lateral projection of a barium-filled stomach should enter the midpoint of the patient's body at the level of the iliac crest.
Step-by-step explanation:
The CR (central ray) for a lateral projection of a barium-filled stomach should enter the midpoint of the patient's body. This is typically at the level of the iliac crest, or the top of the hip bone.
By aligning the CR with the midpoint of the patient's body, the X-ray image will provide a clear and accurate view of the entire stomach without distortion.
For example, if the patient's stomach is filled with barium and they are lying on their side for the lateral projection, the CR should enter the midpoint of the patient's body from the side.