A Possible Antidote for Radiation Exposure from CT Scans?

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Francesco Ruggeri

With traces of radioactive material from Fukushima appearing in rainwater as far away as Boston, concerns about radiation exposure are at an all-time high. But even if you’re not anxious about contamination from Japan, you may be wondering about the health risks associated with everyday sources of radiation — from the sun to airport scanners and routine medical procedures like mammograms and CT scans.

But if scientists from University of Toronto are right, you may not have to worry as much about the damage from X-rays in coming years. Reporting at the annual meeting of the Society of Interventional Radiology, Dr. Kieran Murphy, a radiologist at the university, said that a cocktail of antioxidants he and his team have developed could cut the damage done to DNA by radiation from CT scans by as much as 50%, if taken before the scan.

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Murphy’s concoction works by blocking the effect of free radicals, or unstable compounds made when radioactive waves collide with water, generated by radiation. Free radicals can damage DNA and are responsible for the premature aging and death of cells. Murphy’s idea was to flood the body with antioxidants that neutralize free radicals prior to medical procedures such as CT scans, which use X-rays to image the body; the antioxidants would counter the damage from radiation.

To test the theory, Murphy tagged a protein that repairs DNA with a fluorescent marker in blood samples from the study participants; the tag makes DNA visible under a special microscope. Murphy then showed that patients who took the antioxidant mixture had a lower concentration of the labeled repair protein than those who did not take the liquid. Having fewer repair proteins, he says, means that less DNA was damaged.

It’s an elegantly simple idea that was inspired, Murphy says, by the list of things his mother-in-law was not allowed to take, such as vitamin A, C, and D, when she was undergoing breast cancer treatment. She was told the antioxidants would interfere with the radiation’s ability to damage the breast cancer cells. Looking at the list, Murphy wondered if it didn’t make sense to combine the compounds into a cocktail that would protect against radiation damage.

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So far, Murphy has tested the compound only on his own blood samples and those of his two colleagues. They took blood samples before taking the antioxidants, then again afterward, and irradiated both batches of blood. The post-treatment samples showed 30% to 50% less DNA damage, which was enough to get approval for a larger trial of 30 volunteers. The participants will be heart patients who need cardiac CT scans; half will take the antioxidant solution, while the other half will not and Murphy’s team will analyze their blood for differences in DNA damage.

He stresses that while any CT scan causes some damage to DNA, for the most part the body’s own repair mechanisms are able to overcome such low-level changes. “We have to balance the risks with the benefits,” he says. “By far the majority of the time, the risk is far, far worth the benefit. We’re just trying to say that if we can reduce that risk a little more, it’s a good thing. Then we might be able to allow more screening. If we can increase the number of women who feel safe having a mammogram or the number of people who feel comfortable having a colorectal CT to detect colon cancer, or the number of people who get a coronary calcium screen to pick up signs of future heart trouble, then that would be a good thing.”

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It will be a while before the formula will be ready for that, but if the planned trial proves that it’s possible to protect people from the effects of low-dose radiation, it will go a long way toward easing people’s concerns about radiation exposure.