“Lets just do a CT scan to be sure…” the doctor says. These days, having a CT scan seems routine, like having a strep test when you have a sore throat. In 2007, about 70 million CT scans were performed in the U.S. — triple the number done in 1993.1 About two-thirds of CT scans are done on women.1
Although CT (pronounced “cat”) scans may sound warm and fuzzy, these three-dimensional X-rays expose people to very high doses of radiation. A chest CT exposes patients to more than 400 times the radiation dose than a regular chest X-ray. Over the last 15 years, radiation exposure has skyrocketed, not because of radiation treatment, but because of the use of CT scans for diagnosis.2 In the U.S, radiation exposure from medical imaging has increased 600-fold over the past 20 years.3
Recently, a large, national study of beneficiaries of six integrated health systems found that the increased use of CT scans from 1996 to 2010 doubled the average annual dose of radiation from 1.2 millisieverts (abbreviated as “mSv,” a measure of radiation) to 2.3 mSv. Further, it has more than doubled the number of people who had “high” levels of annual radiation exposure (more than 20-50mSv) or “very high” levels of exposure (more than 50 mSv); the numbers rose from 0.6 percent of beneficiaries to 1.4 percent. More than one in ten of these patients received high or very high annual exposure.4
This is bad because radiation exposure causes cancer and other health problems. Any X-ray exposure increases cancer risk. A study of 120,000 survivors of the atomic bombings in Japan found that even survivors who received low radiation doses (10mSv) had a significantly increased risk of developing cancer.3
In fact, it’s thought that up to two percent of U.S. cancer diagnoses may be due to CT scans.2 The problem of radiation exposure is one we thought we’d stopped long ago. Until the 1960s, X-rays were used to treat acne, ringworm, tonsillitis, and other problems.3 Later, many of the patients treated with these X-rays developed cancers of the skin, breast, thyroid, or brain. That cancer epidemic put a stop to using X-rays to treat minor health problems, although radiation is still used to treat cancer. Cancer patients treated with radiation (especially children), are at high risk of developing a second cancer from the radiation; among survivors of Hodgkin’s lymphoma, secondary cancers are a leading cause of death.3
Don’t get us wrong — CT scans have saved many lives by diagnosing bleeding in the brain or tiny cancers that can’t be detected with regular X-rays. CT technology provides astonishingly detailed images, revealing abnormalities as small as a grain of rice. CT scans can also decrease surgeries; CT scans for patients with abdominal pain reduced the number of unnecessary appendectomies in women aged 45 and younger from 42.9 percent in 1998 to 7.1 percent in 2007.1
Unfortunately, the more detailed the image, the higher the radiation dose. And often, the scans provide more detail than needed. Evidence shows that radiation doses from CT scans could be halved without affecting diagnostic accuracy.2 CT scan’s cancer risks are not trivial. For every 1,000 20-year-old women who have a multiphasic abdominal and pelvic CT, about 4 will develop cancer directly due to the test.3
Astoundingly, patients are not routinely informed of increased cancer risks when undergoing CT scans. And, most radiologists and radiology technicians have little idea what doses of radiation patients may receive. Actual doses may be even higher than radiologists think. One researcher found that radiation doses vary tremendously among different facilities and machines. For the same test, radiation doses can vary as much as 20 times between patients.3 Although CT scanners are extremely sophisticated, they do not routinely have warning systems that indicate when a patient is getting a higher than usual radiation dose.
Radiation’s cancer risks may be worth the risk in treating cancer, but radiation risks from diagnostics change the equation, especially if a diagnosis can be made by a non-cancer-causing imaging technique, or through the almost-lost art of the physical exam.
The U.S. has no clear dose guidelines for CTs, and no medical or governmental organizations collect and report radiation data. Why do physicians order so many CT scans? Some may fear malpractice suits if they fail to discover a rare condition or injury. Others profit from the procedure. In 2006, cardiologists earned about 36 percent of their Medicare revenues from CT scanners and other imaging devices.1
We recommend: If a physician orders a CT study for you, ask whether it’s absolutely necessary. Could you wait and have another, or follow-up, physical exam rather than the CT? Could you have an MRI, ultrasound, or plain-film X-ray instead? (MRIs and ultrasound are not harmful, and plain-film X-rays expose one to much less radiation than CT scans).
Let your health providers know you’re concerned about radiation exposure, and make sure the lowest radiation dose is used. Request a radiation shield for your breasts, thyroid (neck), and pelvis. If you’re pregnant, do not have a CT scan unless it is a matter of life and death. Obtain a digital version of your scan, so the test won’t have to be repeated elsewhere. And, record the dose of radiation you received, and show it to your health care providers.1 Remember, radiation exposure is cumulative, and the more exposure you’ve had, the higher your risk of developing radiation-induced cancer.
Special thanks to Evans Whitaker, MD Medical Librarian at Dominican Hospital, Santa Cruz, CA, for assistance with this article.
This article was written by: Charlea Massion and Adriane Fugh-Berman
1. Berrington de González A, Mahesh M, Kim KP et al., “Projected cancer risks from computed tomographic scans performed in the United States in 2007.” Arch Intern Med. 2009; 14;169(22):2071-7.
2. Smith-Bindman R., Miglioretti DL, Johnson E, et al., “Use of Diagnostic Imaging Studies and Associated Radiation Exposure for Patients Enrolled in Large Integrated Health Systems,” 1996-2010,” JAMA 2012;307(22): 2400-2409.
3. Miglioretti DL, Smith-Bindman R, “Overuse of Computed Tomography and Associated Risks,” Am Fam Physician 2011; 83(11):1252-1254. Available online at http://0-www.aafp.org.library.lausys.georgetown.edu/afp/2011/0601/p1252.html.
4. Smith-Bindman R, “Diagnostic Imaging and Radiation: What’s the Risk?” Presentation at the UCSF ‘Controversies in Women’s Health Conference’, December 8, 2012.