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By A. Pawlowski

CT scans have become a vital tool in medicine, using X-rays to create virtual “slices” of your body that help doctors diagnose everything from cancer to internal injury.

But about a third of CT scans are not necessary and needlessly expose patients to radiation, according to Health magazine, which recently took a closer look at the rewards and risks of medical imaging.

The main worry is how all that exposure adds up over time, said Dr. Roshini Raj, contributing medical editor at Health.

“When you’re exposed to radiation, it can penetrate into the tissues of your body and actually cause DNA damage to your cells,” Raj told TODAY’s Natalie Morales and Willie Geist.

“We do have mechanisms to repair that damage but with repeated exposure, those mechanisms are overwhelmed, those mutations tend to accumulate and eventually could cause cancer.”

Raj recommended asking your doctor these three questions if he or she orders a CT scan for you:

1. Is this scan really going to change how we treat my issue?

If the answer is no, the test may not be necessary, Raj said. So if no matter what the result is, doctors are still going to give you a certain medication, then there’s no point in doing the scan.

2. Is there an alternative that doesn’t have a radiation risk?

Ultrasounds and MRIs are great ways to diagnose certain conditions, Raj said.

3. What dose of radiation will I receive?

Comparison of radiation exposure for a chest CT and smoking a pack a day for a year. A millisievert (mSv) is the measure of radiation absorbed by the body.Today

“Unfortunately, a chest CT scan done at one hospital may give you a very different dose of radiation than one done at another hospital,” Raj said. Obviously, you want the lowest dose possible.

You’re exposed to small amounts of radiation every day by just living on Earth, Raj pointed out. Travelers get an extra dose when they pass through airport scanners, but it’s very minimal and “not a big deal at all,” she added.

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Then, there are dental X-rays. Raj’s philosophy is that you may need them, but not every time you go to the dentist. Be extra careful with children.

“They’re much more susceptible to radiation injury because they’re growing. Their cells are dividing more rapidly. They’re more prone to those mutations,” she cautioned. “So certainly ask about dosage whenever an X-ray or a CT scan is ordered for a child.”

Bottom line: One CT scan is not the end of the world, but you never know when you may need another one. So limit your exposure as much as possible and look for alternatives if they are available, Raj said.

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