With More Scans, More Radiation
Dec. 01, 2010 - When emergency physicians need to make a speedy diagnosis in the ER, one tool that’s become standard is the CT scanner.
CT scan use in ERs rose by nearly sixfold between 1995 and 2007, according to a study published this week in the journal Radiology. If that trend continues, one in five ER visits will involve a CT scan by next year.
But the growing number of CT scans raises concerns about the potential health risks posed by the ionizing radiation that the scanners emit, the researchers say.
Ionizing radiation can cause cancer because it can damage cells in the body, and federal experts warn that one way to protect yourself is to avoid unnecessary medical X-rays. In fact, the study points out, CT scans represent the largest source of medically related exposure to ionizing radiation in the U.S.
Doctors’ increasing use of the CT scanner isn’t surprising, says study author David B. Larson, M.D., at Cincinnati Children’s Hospital Medical Center. It is, he says, “an extremely valuable tool.”
CT scanners, around since the 1970s, are an improvement over conventional X-rays because they show cross-sectional pictures of bone, soft tissue, and blood vessels. In an ER, they can help pinpoint internal injuries and bleeding.
Hospital ERs have shifted their use of CT scans shifted over time. In 1995, the first year that data was collected for the National Hospital Ambulatory Medical Care Survey, most scans were of patients complaining of headaches. By 2007, the last year of the survey, more patients were being scanned to help diagnose abdominal or chest pain.
That finding is noteworthy because abdominal scans typically expose people to higher levels of radiation than CT exams focused on a headache diagnosis. The estimated population radiation dose associated with these ER visits has jumped from 2,259 sieverts in 1995 to 50,937 sieverts in 2007. That’s a 23-fold increase.
Ionizing radiation – the type emitted by CT scans – poses a health risk because the excessive exposure to radiation can damage or kill cells in the body. Damaged cells may become abnormal and turn cancerous, the EPA says. The amount of radiation you’re exposed to builds up over your lifetime.
Dr. Larson suggests that CT scan use should be discussed on a case-by-case basis. "Often the decision is not straightforward," he says, "and, when in doubt, it may be easier just to get the scan. … In order to make sure that CT is used appropriately, we need to develop better methods of tailoring the evidence to each patient situation. This will be a challenge, but it is not insurmountable."
Robert Zimmerman, M.D., at Weill Cornell Medical Center in New York City, agrees. “We need to … reduce the amount of radiation associated with these scanning exams to make sure they're safe and people have confidence they are safe," he says.
But, he adds, "every situation is different. And patients have to keep in mind if they've had scans in the past, or know if they're repeating something that's already been done. Patients have to bring that to the table and discuss it with their attending physicians. But certainly, when appropriate, this kind of care needs to be done."
Diagnosing with Radiation
A number of medical procedures use low levels of ionizing radiation to help in diagnosing diseases and conditions. Here’s a look at the most common ones:
• X-ray. A type of radiation called an X-ray passes through your body and is recorded on a special plate that produces a picture of bones, muscle, and other tissue.
• CT scan. A device that combines X-rays and computer technology to produce horizontal and vertical cross-sectional images of your body.
• Fluoroscopy. A continuous X-ray beam is passed through your body so that the radiologist can see body parts in motion, similar to an X-ray “movie.”
• Nuclear medicine. A small amount of radioactive material is absorbed by body tissue, and a special camera then detects the radiation given off by an organ or other tissue.
In the X-ray, CT scan, and fluoroscopy procedures, the radiation passes through your body. In nuclear medicine procedures, the radioactive material – called a tracer – leaves your body within a few hours to a few days.
MRI scans and ultrasound scans do not use ionizing radiation.
Always talk with your doctor to find out more information.