Typical Patient Exposures

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Compare Exposure Measurements

  • The national average of natural, unavoidable (often referred to as background) radiation dose to each of us is about 620 millirem per year (228 of that is estimated to come from radon exposure).
  • 300 millirem is the average received from all medical exposures. 300 mrem represents a six fold increase in average medical exposures over the past 25 years. Half of the average background medical exposure (147 mrem) is from computed tomography (CT) exams, a relatively new technology that has significantly improved diagnostic imaging.
  • The occupational dose limit to a radiation worker, such as a dental hygienist or assistant, medical X-ray technologist, radiologist, or therapy technologist is 5000 millirem per year.
  • The established dose limit to a member of the public from non-medical or dental X-ray sources (such as airport X-ray machines) is 100 millirem per year.
  • There is NO LIMIT for exposure to properly prescribed diagnostic and therapeutic sources for a patient. These exposures can be whatever is necessary based on the patient's medical and dental needs.
  • The maximum exposure from a security scan using the full body scans is 0.025 millirem per scan. This very low exposure level is equal to five minutes of radiation exposure one receives during a cross country flight (exposure is based on altitude) or the exposure one receives during a Seattle to Portland flight. For more information go to the FDA Products for Security Screening of People.

Typical Exams and Exposures

Below is a list of representative patient exams and the skin entrance exposures associated with them.

  • Dental bitewing (3 inch diameter area)
    • 300 millirem -- film
    • 90 millirem -- digital radiography (DR)
    • 140 millirem -- computed radiography (CR)
  • Chest X-ray 20 millirem (14 x 17 inch area)
  • Abdominal film 300 millirem (14 x 17)
  • Lumbar spine 350 millirem (14 x 17)
  • Extremity X-ray 30 millirem (8 x 10)
  • Skull X-ray 100 millirem (8 x 10)
  • Breast (mammogram) 175 millirads (glandular tissue dose)

Nationwide Evaluation of X-Ray Trends

The Nationwide Evaluation of X-Ray Trends (NEXT) (PDF) program is a partnership of agencies which perform studies to characterize the radiation doses patients receive during diagnostic X-ray examinations.