More CT scans mean higher radiation exposure

NEW YORK (Reuters Health) - US researchers argue that the growth in the number of CT scans performed over the years has increased the likelihood of higher radiation exposures, which may result in a significant public health problem.

In the article, in this week's New England Journal of Medicine, Drs. David J. Brenner and Eric J. Hall, from Columbia University Medical Center in New York, discuss the radiation dose in CT scans -- which use x-rays -- the biologic effect of low doses of ionizing radiation, and the risks of CT use.

The authors raise the possibility that the risks of cancer from CT scans may have been underestimated or overlooked in the past. This is concerning because many of the scans performed in the US are probably not medically necessary, they add.

According to the article, more than 62 million CT scans are now performed annually in the US. That compares to only 3 million scans in 1980.

This increase in CT usage is largely responsible for the near doubling of the average personal radiation exposure that occurred during the same period.

Brenner and Hall note that the low doses of radiation received from CT scanning were initially thought to be harmless. However, evidence from atomic bomb survivors exposed to a similar level of radiation suggests that, in the long-term, it does translate into an elevated cancer risk.

The researchers estimate that in the future up to 2 percent of all malignancies in the US could be due to radiation from CT scans.

They offer three suggestions for lowering the radiation risks of CT scans: reduce the dose of CT-related radiation; replace CT scans with non-radiation imaging methods, such as MRI and ultrasound, when feasible; and reduce the total number of CT scans performed.

SOURCE: New England Journal of Medicine, November 29, 2007.