This document discusses sources of radiation and the average radiation exposure from various medical treatments. It lists common medical procedures like chest X-rays, abdominal X-rays, dental X-rays, and thyroid scans along with the average radiation exposure in millirem that each procedure delivers to patients. Procedures involving radioactive iodine or radium implants can expose patients to much higher levels of radiation, from 3,000 to 20,000 millirem.