Radiation Exposure: What is the Lifetime Limit?


Medical Imaging Radiation ExposureDose management has been an ongoing conversation within the medical enterprise imaging arena with debate centering on life time radiation exposure. Recently, The New York Times opined about the consequences of radiation from medical imaging. Their attention-grabbing premise that “we are giving ourselves cancer” has been refuted by Mohan Doss, a medical physicist residing in Philadelphia, Penn., in a line-by-line critique.

The enterprise radiology community has discussed the need for devising a blueprint for radiology standardization. We’ve written about their ongoing efforts.

And legislation regarding radiation safety has been passed in both California and Texas, mandating strict procedures and reporting requirements for CT scanners and radiation therapy procedures, as well as reporting radiation overdoses to the state Department of Public Health. So, it’s safe to say that both the health care sector and public health officials are making strides toward identifying radiation limits that serve patient safety and population health.

In fact, the National Institute of Health (NIH) has studied the biological effects and adaptive response to CT scans and found that radiation treatment actually reduces DNA damage in animals.

MIT Weighs In On Radiation Exposure         

What many consumers may not know is that there are sources of naturally occurring radiation from radioactive elements and minerals in the body plus cosmic radiation and radon. Interestingly, radiation exposure is slightly higher at higher elevations, so the Mile High City, Denver, measures 400 millerems per year vs. 300 millerems at sea level. (Source: MIT)

Environmental sources of radiation include air flight at a 35,000 altitude, eating a diet heavy in potassium-rich foods, such as bananas and Brazil nuts, and watching four or more hours of television per day.

In addition, therapeutic radiation treatment represents a high concentration of radiation only to the target organ, for example, the thyroid. The radiation exposure for other parts of the body is not distributed in equal measure. Variables, such as a person’s weight, can also affect radiation levels throughout the whole body.

What Are Permissible Levels of Radiation Exposure?

The average exposure in the United States from natural sources of radiation is 300 millerems per year at sea level. Federal standards were established in 1994 for limits in addition to natural occurring radiation and medical imaging scans:

  • Adult: 5,000 Millerems
  • Minor: 500 Millirems
  • Fetus: 500 Millerems
  • Occupational limit: 5,000 Millerems (per year for adult radiation workers including soldiers exposed to radiation)
  • Astronauts: 25,000 Millerems per Space Shuttle mission

There are a number of professional associations pushing for greater levels of awareness to lower dose radiation in children, such as the Image Gently alliance, as well as adults, such as the Image Wisely campaign sponsored by the ACR-RSNA.

When you read the research, you can make an informed decision about the risks vs. benefits of radiation exposure and determine the efficacy of undergoing diagnostic or therapeutic medical imaging. As medical imaging technology continues to advance, personalized dose management is becoming more common.

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