Understanding X-rays

• Are X-rays Safe?
• Radiation Versus Radioactive
• Diagnostic X-rays Do Not Increase the Risk of Cancer
• Recommendations
• Synonyms and Keywords
• References
• Authors and Editors

Are X-rays Safe?

Diagnostic x-rays are safe. But who hasn't wondered about them when undergoing a chest x-ray, mammogram, routine dental x-rays, or an x-ray for a broken bone?

No scientific data indicate any danger. In fact, there is evidence that low doses may actually reduce the chance of cancer. The question about the amount of radiation you receive is difficult for x-ray technicians and doctors to answer because very few x-ray units have an instrument to measure the radiation to the patient.

You may have heard that even the smallest amount of radiation may cause cancer. Based on this unscientific assumption, the risk of causing a fatal cancer from a chest x-ray is 10 times greater than the risk of dying in a commercial airline flight. Or a CT scan of the kidneys has a greater risk of inducing a fatal cancer than a cigarette smoker has of dying from any cancer. These statements produce unnecessary worry. There is no data to show any risk from diagnostic x-rays.

• A radiologist is the doctor trained to read your x-ray. A medical physicist is the best-trained person to explain your dose risk. But most people having x-rays never get to see the medical physicist or the radiologist. Questions about radiation are often asked of the radiographer. This is the trained technician who positions you for an x-ray and makes the exposure. This person is usually not able to respond to your questions about radiation.
  
  
• If you ask, and are told a dose, you may not understand what a dose of 1 millisievert (mSv) might mean. But if this effective dose is converted into the amount of time it would take you to accumulate the same effective dose from background radiation, you could make a comparison. For example, the average background rate of radiation you get just living in the United States is about 3 mSv per year. So a mammogram of 1 mSv would translate into the amount of radiation you would get by just living in the US about 4 months.
  
  
• This method of explaining radiation is called Background Equivalent Radiation Time or BERT. The idea is to convert the effective dose from the exposure to the time in days, weeks, months, or years to obtain the same effective dose from background. This method has also been recommended by the US National Council for Radiation Protection and Measurement (NCRP).
  
  
• To calculate BERT, one good way is to use the average background in the US including contributions to the lung from radon progeny. This is assumed to be 3 mSv/y (300 mrem/y). The background in different parts of the US varies about half of this value, either more or less. This uncertainty is unimportant for understanding radiation exposure. The effective dose from common diagnostic x-ray procedures is typically less than the amount of radiation you receive from nature in 2 years.