Answer to Question #15128 Submitted to "Ask the Experts"

My one-month-old baby had a series of five skull x rays with estimated total dose of 0.1 millisievert (mSv). Is this a cause for concern? Is it more dangerous if all five x rays were taken back-to-back as opposed to spread out over a week or two? How does risk work in terms of multiple x rays? Does each x ray act as its own risk or is the risk cumulative? With x rays, do you either get cancer or you don't for each occurrence?

It is understandable that you are concerned about the diagnostic radiation your child was exposed to. That being said, I can assure you that the dose you mentioned (0.1 mSv) is very low and should not be a concern for you. By way of comparison, the average radiation dose received each year by a person living in the United States from natural sources such as cosmic radiation and radiation from the earth, is 3 mSv. So, your child's dose of 0.1 mSv is equal to about two weeks of natural radiation exposure. With an exposure this low, the cancer risk to your child is so small that it is virtually the same as it would be under normal circumstances. 

In addition to 0.1 mSv being a very low dose of diagnostic radiation, you should consider the medical benefit gained by the health care team having the information obtained from the x rays in terms of the care of your child. Parents are often concerned with the risks involved with getting x rays, but the benefits of those tests most often outweigh any small risk. An x ray may show where the problem is in a way that may be missed without the exposure. X rays may help to show a medical problem that can then be treated.

I hope your concerns have been alleviated, but I will also briefly address your other questions. First, it's important to understand that cancer risks from radiation are extrapolated (or estimated) based on cancers that are known to be caused by very high doses of radiation, at least 1,000 times higher than the dose your child received. There has never been a documented case of cancer arising from an exposure of 0.1 mSv. Generally speaking, younger people are considered more at risk from radiation exposure because they have a longer time to develop cancer. But cancers from radiation take decades to develop. Therefore, if a person receives a radiation exposure when they are 65 years old, it's less likely that they will live long enough to develop a cancer, whereas a person who is much younger, with a longer life expectancy, has a higher risk. In terms of multiple exposures over a short period of time, again because the cumulative dose in this case is so low, it doesn't matter. But you may be aware that patients with cancer, who receive very high doses of therapeutic radiation, have many "fractions" of radiation as part of their treatment plan. This is because, at very high therapeutic doses, the body does need time to repair itself between fractions. But with the very low doses from skull x rays, timing is not important.

I hope this information is helpful to you. The dose your child received was very low. Diagnostic x rays are very safe but it's always wise to ask the doctor what tests are being done and why.

Linda Kroger, MS