Compare radiation exposure from common imaging procedures.
Average background radiation is ~3 mSv/year (~0.0082 mSv/day). A chest X-ray delivers ~0.02 mSv, while a CT abdomen gives ~10 mSv. The dose-risk relationship is linear for cancer risk estimation. Annual occupational limit is 20 mSv. There is no safe threshold, so imaging should follow ALARA principles.