CT Scans Raises Concerns About Radiation Exposure

CT ScanIllustration by Kai Ti Hsu for The Washington Post

There seems to be a growing concern about over use of diagnostic imaging, which in the past two decades has exploded into a $100 billion-a-year business. While imaging aids in diagnosis and has helped many patients avoid exploratory surgery, it has also spawned concerns about ballooning costs, including from duplicate procedures, potential harm from the tests themselves and the overtreatment of harmless conditions found during scans.

These “incidentalomas” — so named because they are found unexpectedly — include benign lung and thyroid nodules and other common conditions that can lead to unnecessary and expensive workups as well as treatment that can cause complications.

Much of the attention has focused on computed tomography, or CT, scans, which use hundreds of X-rays to create detailed three-dimensional images that enable doctors to see things previously visible only through a biopsy or surgery.

CT scans, like X-rays and PET scans, use ionizing radiation which can damage DNA and cause cancer. There are two other imaging technologies, MRI scans and ultrasound, which do not use radiation. CTs are used for a plethora of reasons, among them finding kidney stones, evaluating chest pain and detecting tumors or other abnormalities.

Widely hailed as one of the most important medical advances of the past century, CT scans were developed in the 1970s. Their use in the United States grew from 3 million in 1980 to more than 85 million in 2011. Although CT scans are an essential diagnostic tool, the Food and Drug Administration reports that an estimated 30 to 50 percent of imaging tests are believed to be medically unnecessary.

Increased Cancer Risks from Scans

Like X-rays, CT scans represent a potentially significant health problem, one that experts say may not show up for years: cancer caused by radiation. In most cases, it is impossible to definitively attribute cancer to radiation exposure that occurred years or even decades earlier. And overall, the risk from a single scan is small: The National Cancer Institute (NCI) estimates that the additional risk of developing a fatal cancer from a scan is 1 in 2,000, while the lifetime risk of dying of cancer is 1 in 5.

The question of risk remains a matter of fierce debate among radiologists: Some say that the amount of radiation used in diagnostic studies is safe and that the benefits far outweigh the small chance that a person will develop cancer. But others say that while patients should never avoid scans that are medically necessary, excessive radiation doses and indiscriminate use of imaging pose a clear and demonstrable danger.

Studies published in 2007 and 2009 by teams from Columbia University and the NCI predicted that up to 2 percent of future cancers — about 29,000 cases and 15,000 deaths annually — might be caused by CT scans. A 2011 report by the Institute of Medicine found that the two environmental factors most strongly associated with breast cancer were radiation exposure and the use of post-menopausal hormones.

Multiple Scans present more danger

While a single scan would rarely be concerning, many Americans undergo multiple tests. A 2009 study by researchers at Brigham and Women’s Hospital in Boston found that among 31,000 patients who had a diagnostic CT scan in 2007, 33 percent had more than five during their lifetime, 5 percent received 22 or more, and 1 percent underwent more than 38 scans.

Some hospitals tend to perform double scans — one with a contrast agent and a second without it. Doctors sometimes refuse to accept or are unable to access radiology studies done elsewhere and send patients for duplicate tests at a facility in which they have an ownership interest. Doctors who have a financial stake in radiology clinics or who own scanners use imaging substantially more often than those who don’t, studies have found. And increasingly, specialists are requiring that patients get a scan before they first see a patient.

According to the FDA, which has launched an initiative to reduce unnecessary exposure to medical radiation, the effective doses from diagnostic CTs are “not much less than the lowest doses of 5 to 20 mSv received by some of the Japanese survivors of the atomic bombs” dropped over Hiroshima and Nagasaki in 1945. Some of these survivors have “demonstrated a small but increased radiation-related excess relative risk for cancer mortality.”

Radiation exposure is cumulative, and children, who undergo between 5 million and 9 million CT scans annually, are much more vulnerable to its effects. Studies performed in the United Kingdom in 2012 and Australia in 2013 found an increase in cases of leukemia and malignant brain tumors among children and young adults who had undergone CT scans. One concern, said Hernanz-Schulman, a past president of the Society for Pediatric Radiology, is that many children undergo CT scans in adult facilities and may receive excessive doses because scanners are not adjusted between patients.

Concerns about overuse and potential harm have prompted actions by federal health officials as well as consumer and physician groups. These include the Image Wisely and Image Gently campaigns, as well as the national Choosing Wisely effort, which seeks to educate patients and doctors about unnecessary tests such as CT scans for headaches or back pain.

A “decision support” system that creates a set of standards for doctors to follow, pioneered at Massachusetts General Hospital in Boston, reduced the rate of inappropriate imaging tests from 6 percent in 2006 to 1.5 percent in 2014, said James Brink, the hospital’s radiologist-in-chief. A similar statewide program in Minnesota cut the growth rate from 7 percent per year to about 1 percent annually.

New Medicare rules will require doctors to consider appropriateness criteria developed by the American College of Radiology when ordering imaging. Beginning this year, Medicare will reduce by 5 percent reimbursement for CT scans performed on machines that fail to meet modern standards, including the ability to automatically adjust radiation doses.

Reducing the number of unnecessary CT scans may be an uphill battle

A recent study found that doctors who order a lot of tests — a practice known as defensive medicine — get sued less often.

Some radiologists say they spend their days reading scans that trigger a cascade of follow-up tests and procedures for conditions that nearly always turn out to be benign.

To determine whether a CT is necessary patients should ask why the scan is being done, how the results might affect treatment and whether an alternative such as ultrasound or an MRI could be used instead.

From Kaiser Health Network, the story also ran in The Washington Post.

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