Experts weigh risks of CT scans

• They give doctors more information%2C cut need for exploratory surgery
• Biggest worry is for children because radiation exposure accumulates over lifetime
• Scanners manufactured in past 10 years are calibrated for kids

GREENVILLE, S.C. — CT scans have transformed medicine.

They can provide stunningly detailed images of the inside of the brain.

They can pinpoint the precise location of a potentially fatal blood clot in the lungs.

And they can show pictures of a beating heart so clear that a cardiothoracic surgeon knows what he will encounter before he has made the first incision.

That's all improved diagnosis and treatment for countless millions.

But these scans aren't without risk.

They deliver much more radiation than X-rays. And some fear that these tests can cause cancer later in life, particularly in children.

CT, or computerized tomography, scans use a series of X-rays taken from many angles to provide cross-sectional images of the inside of the body, according to the National Institutes of Health.

They can be used to diagnose illnesses and internal injuries as well as to monitor cancer and other diseases.

About 68 million CT scans are performed in the USA each year, about 10% of them in children, according to the American College of Radiology, which holds that medical imaging is linked to greater life expectancy, lower mortality rates and reduced hospitalizations.

But National Cancer Institute researchers reported in the The Lancet last year that children and young adults who had had multiple CTs have a small increased risk of leukemia and brain tumors in the decade after their first scan.

After looking at more than 175,000 children and young adults, the researchers estimated that "for every 10,000 head CT scans performed on children 10 years of age or younger, one case of leukemia and one brain tumor would occur in the decade following the first CT beyond what would have been expected had no CT scans been performed."

CT scans deliver ionizing radiation to the area being scanned and to nearby tissues, potentially damaging DNA, the researchers said.

And children are more vulnerable to that radiation than adults — two to 10 times more — according to Dr. Michael Thomason, medical director of pediatric radiology at Greenville Health System here.

But another study in last month's journal Radiology concluded that the conditions for which young adults had CTs posed a greater risk than radiation from the scans.

The researchers looked at 22,000 patients 18 to 35 who most commonly had a CT scan for trauma, abdominal pain and cancer.

After an average of 5.5 years, 7.1% of those who had had a chest CT scan and 3.9% of those who had abdominal CT scan had died, much higher than the expected 0.1% risk of death from radiation-induced cancer. And even when the cancer patients were culled from the statistics, the risk of death ranged from 2.5% to 5%, well above the risk in the general population.

Still other research also shows that a quarter to a third of all CT scans are unnecessary.

A Columbia, S.C., health care consultant, Lynn Bailey, said another problem is that radiation exposures aren't tracked over a patient's life.

"Chest X-rays and dental X-rays are cumulative," she said.

Simply the best

Since the technology was introduced about three decades ago, CT scan use has ballooned, according to National Cancer Institute researchers.

Part of the growth has come with increasing emergency room use, according to Dr. Jim Haswell, a radiologist with Upstate Carolina Radiology who works at Bon Secours St. Francis Health System here. In that setting, patients are more likely to get a scan than if they go to their primary care doctor, he said.

A growing population of older people with health-care problems is another reason more scans are ordered, he said. But the main reason the scans are done so often is because they are the best imaging tool available.

"MRIs give you similar information," he said. "But they cost quite a bit more, take longer to do, and there are more patient criteria about who can have an MRI." Magnetic resonance imaging doesn't use radiation but instead uses a magnetic field and pulses of radio waves to make pictures of organs, bones and blood vessels.

CT scans offer tremendous benefits in diagnosis, said Dr. Jeff Hanna, medical director of radiology services at Greenville Memorial Hospital.

"CT gives you dramatically more information and faster," he said. "You can do a CT scan in 5 to 7 seconds."

They've replaced other tests that often carry more risk, he said. For instance, CT angiography has replaced catheter angiography to look for aneurysms and blockages, reducing the risk of stroke from 1% to 3% to nearly zero.

They also identify problems that other studies can't show, said Chris Gilmer, manager of CT and interventional radiology at the hospital. "They've not only replaced one test but in a lot of cases a series of tests to find the answer," adding that a chest X-ray can look normal while a CT reveals a serious problem.

CT scans also have supplanted exploratory surgery, Thomason said.

"When my father was a general surgeon, they took so many patients to surgery (because) they had no idea what they had wrong with them," he said. "In 2013, that's pretty unusual. CT is so exquisite, you get the right answer the overwhelming majority of the time. So the good part is it keeps kids from going to surgery."

Plus, other tests often require anesthesia, particularly in children, Thomason said. So using CT scans avoid the risks associated with that.

Questioning the risk

Nonetheless, one chest CT scan typically delivers about 70 times the radiation of one chest X-ray, according to the American College of Radiology. Other research reports that CT scans can deliver hundreds of times the radiation of X-rays.

While the scans account for 10% of all radiology imaging, they are responsible for about 50% of all medical radiation, Thomason said. And though medical use accounted for 15% of all ionizing radiation in the 1980s, it's up to half today.

Before 2000, few people thought about the radiation from diagnostic tests. But gradually, researchers began to question the risk of CT scans, especially for children, sparking anxiety among parents and prompting change in the medical community.

"There has been a dramatic evolution with CT technology that's resulted in increased clinical usefulness, increased scans and increased radiation dose," he said. "We were asleep at the switch with regard to CT dose."

And even though the dose of radiation is much lower today than in earlier scanners, doctors should make sure that a CT scan really is needed before ordering one, especially in children, Haswell said.

"It's our job to child-size the exposure," Thomason said.

Today programs around the country are designed to reduce the amount of radiation in children, to make sure tests are done only when warranted, and to ensure that proper techniques are used, like the Image Gently Campaign.

First, a physician should ask himself if the patient needs imaging, Thomason said. If the answer is yes, the doctor should determine whether another test, such as an ultrasound or MRI, both of which don't use radiation, can be substituted.

So for instance, Thomason said a CT scan shouldn't be the default test for routine abdominal pain or suspected appendicitis. Ultrasound should be used first.

And while CT scans are indicated for adults in certain situations, such as fluid around the lungs, that's not the case with children. The scans also should be avoided in young patients who are going to have multiple exams and pregnant women, he said.

"We try to be as careful as possible," Haswell said. "When we see a patient coming back for a CT scan who's had a bunch recently, we talk to the referring doctor to make sure they know what's going on."

If a CT is necessary, the technologist should make sure the lowest dose is used, that only the affected area is scanned, and that multiple scans are avoided, according to the campaign. Finally, a record of the child's radiation history should be kept.

Monitoring equipment

CT scanners are calibrated in terms of output, but the amount of radiation a person absorbs depends on gender, size and weight, Hanna said.

No scanners have been created just for children, but all can be adjusted to emit radiation appropriate for children, said Gilmer, adding that all scanners manufactured in the past decade have pediatric protocols in place.

Safeguards also prevent scanners from emitting too much radiation without anyone's knowledge, he said.

That happened at the Los Angeles-based Cedars-Sinai Medical Center in 2009, when officials confirmed that more than 200 patients had gotten up to eight times the normal dose over a year and a half, according to the Los Angeles Times.

New machines are put through rigorous testing and inspection and the American College of Radiology must accredit them, Gilmer said.

But some research suggests that up to a third of all CT scans are unnecessary.

That includes cases where the tests were ordered for inappropriate or debatable indications and exams repeated because of failed communications between physicians, Thomason said.

Defensive medicine, or fear of lawsuits, also plays some role, he said.

Hanna added that more tests are done in general because of defensive medicine.

And because imaging tests are so lucrative, some have questioned profit motives at centers where physicians have a financial interest, Thomason said.

Those kinds of issues should be less of a concern as reimbursement shifts to getting the right diagnosis with the fewest tests at the lowest cost, he said.

Better technology

While the doctors said they weren't aware of any other tests on the horizon that might replace CT scans, they added that the technology is improving all the time.

Another recent study in the journal JAMA Internal Medicine showed that only 35% of 271 patients surveyed at the Denver Veterans Affairs Medical Center had discussed the potential risks of a CT scan with their doctor before having the test.

The American Association of Physicists in Medicine supports national legislation requiring accreditation of all facilities that perform imaging tests to ensure minimum standards, such as having qualified individuals conduct the tests. It also advocates requiring that those who do imaging tests graduate from an approved program and pass a national certification exam.

While some parents ask about radiation dose, that's not as much of a concern as what's ailing their child, Gilmer said.

"We're not saying be complacent about the radiation risk from CT," said Dr. Susanna Lee, chief of women's imaging at Massachusetts General Hospital and assistant professor of radiology at Harvard Medical School who was lead researcher on the Radiology research.

"But these people being imaged might have been in a motor-vehicle accident, or have a perforated appendix or life-threatening cancer, and we're trying to gain information from scans that can help them," she said. "That's the part that gets lost in the debate."