What is a safer way to obtain images of a child's stomach function? x-rays or gamma camera?

My 7 year old son is going to ingest a small amount of radioactive material in a nuclear breakfast before the hospital images his stomach digesting the meal. They can either do x-rays every 15 minutes for 3 to 4 hours or they can position him under a gamma camera and view the stomach as it digests the meal. Which one is safer and gives him less radiation and less risk? thank for helping