Americans are receiving more testing and imaging that makes use of ionizing radiation than ever before. The healthcare profession knows that excessive radiation can be a contributing factor to many forms of cancer such as leukemia (blood cancer) breast cancer, and thyroid cancer just name a few.
Ionizing radiation is high-frequency radiation that has enough energy to remove an electron from (ionize) an atom or molecule. Ionizing radiation has enough energy to damage the DNA or the genetic makeup inside cells, which in turn may lead to cancer.
Ionizing radiation is a proven human carcinogen (cancer causing agent). The evidence for this comes from many different sources, including studies of atomic bomb survivors in Japan, people exposed during the Chernobyl nuclear accident, people treated with high doses of radiation for cancer and other conditions, and people exposed to high levels of radiation at work, such as uranium miners.
Even though great strides have been made in cancer prevention and treatment, cancer rates remain high and may soon surpass heart disease as the leading cause of death in the United States. One of the important culprits may come from your doctor who is prescribing excessive imaging studies that make use of ionizing radiation. The use of medical imaging with high-dose radiation — CT scans in particular — has soared in the last 20 years. Our resulting exposure to medical radiation has increased more than six fold between the 1980s and 2006. The radiation dose of CT scans (a series of X-ray images from multiple angles) is 100 to 1,000 times higher than conventional X-rays such as a chest X-ray.
The risks have been demonstrated directly in two large clinical studies in Britain and Australia. In the British study, children exposed to multiple CT scans were found to be three times more likely to develop leukemia and brain cancer. In a 2011 report sponsored by Susan G. Komen, concluded that radiation from medical imaging, and hormone therapy, the use of which has substantially declined in the last decade, were the leading environmental causes of breast cancer, and advised that women reduce their exposure to unnecessary CT scans.
One in 10 Americans undergo a CT scan every year, and many of them get more than one CT scan every year. While it is difficult to know how many cancers will result from medical imaging, a 2009 study from the National Cancer Institute estimates that CT scans conducted in 2007 will cause a projected 29,000 excess cancer cases and 14,500 excess deaths over the lifetime of those exposed. Given the many scans performed over the last several years, a reasonable estimate of excess lifetime cancers would be in the hundreds of thousands. Unless we change our current practices or overusing CT scans, 3 percent to 5 percent of all future cancers may result from exposure to medical imaging.
We know that these tests are overused. But even when they are appropriately used, they are not always done in the safest ways possible. The rule is that doses for medical imaging should be as low as reasonably achievable. But there are no specific guidelines for the imaging centers to use to identify what optimum low doses are, and thus there is considerable variation within and between institutions. The dose at one hospital can be as much as 50 times stronger than at another.
A recent study at one New York hospital found that nearly a third of its patients undergoing multiple cardiac imaging tests were getting a cumulative effective dose equivalent to 5,000 chest X-rays. And last year, a survey of nuclear cardiologists found that only 7 percent of stress tests were done using a “stress first” protocol (examining an image of the heart after exercise before deciding whether it was necessary to take one of it at rest), which can decrease radiation exposure by up to 75 percent.
But we still have a long way to go. Fortunately, we can reduce the rate of medical imaging by simply avoiding unnecessary scans and minimizing the radiation from appropriate ones. For example, emergency room physicians routinely order multiple CT scans even before examining a patient. For example a patient with possible diagnosis of a kidney stone can often be diagnosed with a history, a physical exam, a urine test, and very simple x-ray called a KUB which has minimal radiation exposure compared to a spiral CT scan that is so frequently ordered.
Better monitoring and guidelines would also help. The Food and Drug Administration oversees the approval of scanners, but does not have regulatory oversight for how they are used. We need clear standards, published by professional radiology societies or organizations like the Joint Commission or the F.D.A. In order to be accredited for CT scans, hospitals and imaging clinics should be required to track the doses they use and ensure that they are truly as low as possible by comparing them to published guidelines.
Patients have a part to play as well. Consumers can go to the website, http://www.choosingwisely.org, to learn about the most commonly overused tests. Before agreeing to a CT scan, they should ask: Will it lead to a better treatment and outcome? Would they get that therapy without the test? Are there alternatives that don’t involve radiation, like ultrasound or MRI? Even when we go to the dentist to have our teeth cleaned, we need to question the dentist about the routine use of dental x-rays and if you do get dental x-rays, it is important to wear a neck shield that protects your thyroid gland.
Bottom Line: We are probably receiving more radiation through medical tests and is important to question your doctor about the necessity of using so many imaging tests that increase our exposure to ionizing radiation.
A version of this op-ed appears in print in the New York Times on January 31, 2014.