Paper points to association between medical scans and thyroid cancer rate

In a recent study, researchers at the National Cancer Institute's Division of Cancer Epidemiology and Genetics explored the connection between radiological scans and the increased rate of thyroid cancer.

A discussion published in the journal Clinical Oncology pointed to computed tomography (CT) scans, as well as medical and dental X-rays, as being the sources of a significant portion of the average American's exposure to radiation.

The authors estimated that 20 percent of the radiation a person receives in an entire year comes from diagnostic medical scans, which include dental X-rays and CT scans.

They noted that the latter accounts for a disproportional amount of the collective irradiative dose. According to researchers, CT scans contribute to 47 percent of the average per capita exposure to radiation, even though they only comprise 8 percent of the total medical scans performed in a year.

Since many CT scans often involve the head, neck and upper abdomen, the group theorized that repeated exposure to such imaging techniques may deliver a significant dose of radiation.

Particularly during childhood, the thyroid may be sensitive to radiation exposure. A 1995 study published in the journal Radiation Research (RR) estimated that a child under the age of 15 will be more than seven times more likely to experience abnormal thyroid growth for each gray of exposure, a unit that measures radiation absorption.

For comparison, the authors of the RR study said that cancer therapies typically involve at least 10 grays of absorption.

In the most recent paper, researchers came to the conclusion that using CT scans and radiation therapy is often necessary for treating thyroid cancer, but should be carefully considered when used on children under the age of 15.

Thyroid cancer affects nearly 45,000 Americans every year. Close to 2 percent of people diagnosed with thyroid carcinomas are under the age of 20, according to the National Cancer Institute.
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