Radiation exposure: What to know

Some cancer patients may have concerns about the safety of various diagnostic scans, especially those that expose them to ionizing radiation on a regular basis.

Here, MD Anderson experts Dianna Cody, Ph.D., Kyle Jones, Ph.D., and Joseph Steele, M.D., weigh in to dispel some myths about diagnostic imaging.

Taking pictures in the dark

Before we had X-rays, MRIs and PET scans, doctors had to perform exploratory surgery to find out what was going on inside the human body. For patients, that meant a frightening procedure and a painful recovery, sometimes with no real benefit. Now, diagnostic imaging allows doctors to peek inside patients without ever touching a scalpel.

“If you think about the alternative,” Jones says, “I would say a scan is much more appealing.”

Not all diagnostic imaging involves ionizing radiation. (Ultrasound and MRI are two exceptions.) But for those that do, MD Anderson doctors use the lowest doses possible to get the answers they need.

“The quality of the images is directly tied to exposure level. If there’s not enough ionizing radiation, the image quality is terrible, and we may miss subtle findings that could be important,” Cody says. “It’s like taking a picture in the dark. If you don’t have enough light, you can’t really see anything.”

Quality control: the right test for the right question

The risks of radiation exposure through medical testing are actually very small — and still theoretical. But MD Anderson minimizes even those risks by tailoring the amount of radiation to the size of each patient, as well as to the purpose of each scan.

“We use only the amount of radiation necessary to answer the question,” Jones says. “And contrary to what you may have heard, these tests cannot result in people becoming sterile, passing on DNA problems to children or experiencing radiation sickness. None of those are even remotely possible with diagnostic imaging.”

Lower doses of radiation are generally sufficient for screening exams, such as X-rays for lung cancer and mammograms for breast cancer. But when staging a newly diagnosed cancer, higher doses of radiation are sometimes needed to detect small tumors in the liver or tiny lesions on the walls of the colon.

“We generally follow a radiation protocol called ‘ALARA,’ or ‘as low as reasonably achievable,’” Steele says. “But it’s critically important for us to know if someone has metastatic disease because proper staging helps us determine the most effective treatment.”

Changing technologies and protocols reduce exposure

MD Anderson uses some of the most advanced equipment available to perform scans. And as technology evolves, our doctors are able to reduce the amount of radiation used in diagnostic imaging even more.

“If you look at our data for the past six years in interventional radiology, we have consistently decreased radiation exposure by 30-40% on average,” Jones says.

Changes in the way some conditions are treated have also resulted in fewer scans using ionizing radiation. Over the past 10 years, for instance, doctors have increasingly used ultrasounds rather than CT scans to diagnose appendicitis.

In addition, each diagnostic scan ordered by an MD Anderson physician is reviewed by another doctor or specialist to ensure it’s appropriate and necessary before it even takes place. That means patients at MD Anderson can rest assured that whatever test they undergo, it will be the right one for them, at the right dose, to answer the right question at the right time.

“We owe it to patients to always make sure that that’s the case,” Jones says.

Asking questions and letting go

Still, if patients have any concerns, they should not hesitate to ask questions.

“When a physician orders an exam, it is totally within a patient’s rights to ask why,” Cody says. “And when they ask what we’re looking for, their doctor should have a very specific answer.”

Once patients have had their concerns addressed, though, it’s important to try to relax.

“The risk is actually very small compared to the information you’re about to get,” Cody says. “So take a deep breath and let it go.”