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Radiation: Ionizing Radiation and Diagnostic Exams

What's the Problem?

Radiation, a form of energy, is all around us, produced by the earth and even by our own bodies. It exists in both natural and man-made forms and has many beneficial uses, including x-rays and many other diagnostic exams (like CT scans). Many diagnostic exams or tests involve exposure to ionizing radiation.

Tests involving exposure to ionizing radiation include:

  • X-rays (including dental x-rays, chest x-rays, and spine x-rays)
  • CT/CAT (computed tomography) Scans
  • PET (positron emission tomography) Scans
  • Fluoroscopy

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Repeated exposure to ionizing radiation from many diagnostic exams may be harmful. Exposure to large amounts of radiation can cause cancer as well as other adverse health effects, including mental retardation in children who were exposed in the womb.

Who's at Risk?

Individuals who are administered a large number of diagnostic examinations using ionizing radiation could be at risk.  Exposures to ionizing radiation should only be as long as is necessary to perform the test. Accumulated dose of radiation increases as a person undergoes more exams.  
Receiving x-rays at a younger age is riskier than at an older age because children are more sensitive than adults. Because children are growing more rapidly, there are more cells dividing and a greater opportunity for radiation to disrupt the process. Fetuses are also more sensitive to radiation from diagnostic tests. However, the period during which they may be exposed and be harmed is short.
Women are at a somewhat higher lifetime risk than men for developing cancer from radiation after receiving the same exposures at the same ages.

What Could Happen?

All medical tests have risk and benefits and usually the benefits of a medical test outweigh its risks.  X-rays and other tests involving ionizing radiation could result in a small increase in the chance of developing cancer later in life. Cataracts and skin burns may develop following exposure to very high levels of radiation.

Can Health Effects from the Radiation in Diagnostic Exams Be Prevented?

For the most part, the risk of harm is small, but exposure to ionizing radiation from some diagnostic exams can be limited by monitoring the number of medical x-rays, CT/CAT scans, PET scans, and fluoroscopy exams per year. Doctors and radiation experts can help reduce your exposure to and risk of harm from diagnostic ionizing radiation by:

  • Checking to see if you have had a similar test done recently that can provide them with the background information they need.
  • Checking to see if a test that does not use ionizing radiation can provide similar information.
  • Estimating in advance the typical radiation dose for the test.
  • Estimating your exposure to radiation from the test.
  • Making certain the least possible amount of radiation is used for your procedure.

The Bottom Line

  • Monitor the number of scans with ionizing radiation (x-rays, CT scans, PET scans, fluoroscopy).
  • Accumulated dose of radiation increases as a person undergoes more exams.
  • Exposure to large amounts of radiation, especially over a short period of time, can result in serious health effects.
  • Children may be more susceptible than adults to the effects of radiation.
  • Fetuses are extremely sensitive to radiation.

Case Examples

Medical Imaging

James is a 10 year old football player.  During a recent football game, James suffered a suspected concussion.  James’ parents are worried because this is the second time he has had a possible concussion and with each, James has to have a CT scan.  Knowing that each diagnostic scan uses ionizing radiation, James’ parents are worried. After talking to a pediatrician, James’ parents are aware that the risk of radiation exposure from a medically necessary imaging exam is quite small when compared to the benefit of correct diagnosis and intervention.

Medical Imaging and Pregnancy

Lauren is pregnant and recently began feeling abdominal pains.  Her doctor suggested she receive a CT scan to diagnose the problem. Lauren wonders if her fetus will be exposed and in danger.  In addition, she is worried about future pregnancies and the health of her reproductive system.  The doctor informs Lauren that the risk to her and her fetus is small and that the benefit of finding out her medical condition is far greater. She agrees to go ahead with the test.

  • Page last reviewed: June 24, 2014
  • Page last updated: June 24, 2014
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