ct scan

CT scans can increase the risk of cancer in children

In the past twenty years, there has been a huge increase in the number of CT and the newer PET scans performed. A recent report in the Journal of the American Medical Association found that between 1996 and 2010, the number of CT scans in the U.S. increased by a factor of three, and the number of MRI scans increased four times.

An important point is that CT scans function by exposing the patient to direct ionizing radiation, and to get the beautifully detailed images that result from these scans, multiple x-rays are performed (multiple “slices”), then reassembled by the device software to produce the final result. Because of the multiple slices, CT scans expose the patient to much more radiation than standard x-rays.

While these more advanced imaging techniques often make diagnoses that are impossible to make by standard x-rays, there has been concern that they are being performed in excess, and that based on long-term cancer studies following the atomic bomb in Japan, a small increase in cancer incidence would be expected secondary to the medical radiation exposure.

Based on this information, the British medical journal The Lancet, published this month a study that examined the medical records of almost 180,000 British children who underwent CT scans between 1985 and 2002. The researchers looked at the rates of leukemia and brain cancer over this long period, and found that children under age 15 with a history of two or three head scans suffered a three-times increased risk of later brain cancer compared to unexposed children, and that 5 to 10 scans tripled the risk of leukemia.

These cancers are rare in children, x-ray exposure or not, but still, it is estimated that of the 600,000 head and abdominal scans performed yearly in children under 15 in the U.S., about 500 of them might ultimately die of a cancer caused by the radiation from the multiple scans. It is estimated that up to 2% of future cancers may be due to medical radiation exposure.

Is the message that CT and combination CT/PET scans should be avoided, especially in children? The message is: avoid unnecessary scans, and always inquire about alternative non-radiation tests. Dr. David Bremmer, a professor of radiation research at Columbia University (New York) estimates that about 1/3 of CT scans could be avoided, or replaced by some other diagnostic technique.

Undergoing one CT scan is rarely a problem; the issue compounds if someone, especially a child, undergoes multiple scans, as the risk of cancer seems to go up with the number of scans performed.

So if your doctor requests a CT or PET scan, ask some questions such as: is it necessary to do a scan that involves radiation exposure? Could the diagnosis be made by ultrasound or MRI (neither of which exposes the patient to radiation) instead? If it is indeed necessary to perform a CT or CT/PET scan, you can ask the radiation facility what measures they take to decrease the radiation exposure. Radiation centers are aware of the issue, and some have begun using newer equipment and techniques that lower the radiation exposure.

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