Medical imaging exams have long been used to detect diseases at an early stage, and so are often credited with increasing life expectancy and reducing cancer mortality rates. But there are concerns that widespread use, and possibly even overuse, of such scans has resulted in increased radiation exposure for Americans. Eastern Maine Medical Center is taking steps to decrease potential risks to patients.

CT scanning -- sometimes called CAT scanning -- is a medical test that combines special x-ray equipment with computers to produce detailed images of internal organs, bones, soft tissue and blood vessels.

"CT Scan is a test that uses radiation to look inside the body in a very elegant and specific way such that we can see every organ of the body from the brain to the toes," says Dr. Paul Templeton, Chief of Radiology at Eastern Maine Medical Center. "It is essential in medical practice these days, often in the detection and treatment of cancer, but also in nonmalignant diseases, such as evaluation of serious trauma cases to see if there's been organ injury, brain injury. Also in cases of infection, for instance, determining whether a child or adult has appendicitis."

But while CT scans are useful and necessary tools, Templeton says, they do expose patients to radiation, and that comes with a risk. "There's been a recognition that the radiation delivered during a CT scan has a small, but probably real, risk of causing cancer in a small number of people," he says. "It should be recognized very clearly that this risk is relatively low and that this risk has not been exactly defined."

The uncertainty can be unsettling to patients, and CT scans should only be performed when a clear medical benefit outweighs any associated risk, Templeton says. That's why each patient who is referred to Eastern Maine Medical Center for a CT scan is reviewed by a radiologist to determine if a similar CT scan has been done at another location.

The hospital also decides whether there's an acceptable substitute test for CT. "We are taking, I think, extraordinary steps to reduce the amount of radiation that we're delivering here," Templeton says. "Recognizing that CT is essential and that CT requires radiation, there are a number of things that can be done to lower the amount of radiation and therefore to reduce the risk."

Eastern Maine Medical Center makes a special effort to perform the evaluation on children and adults under 40 years of age, who have a higher risk of developing radiation-related cancer, Templeton says. The hospital has reduced the number of CT scans on children by nearly five percent, and the number of CT scans on adults under 40 by two percent.

The hospital has also reduced the dosage of radiation used during CT scans by 20 to 30 percent in the last two years. But Templeton says that doesn't make the scans any less effective. "If you lower the radiation too much the images become grainy and have less diagnostic capability -- it would be the same as a photograph that becomes too pixel-y. So what we've done here is lowered the radiation to as low as reasonably possible while maintaining the high diagnostic accuracy of the test."

Some in the medical community question the issues being raised about the safety of CT scans. "There are, at present, no clinical studies that show that radiation from medical imaging exams cause cancer," says Shawn Farley, a spokesman for the American College of Radiology. "The ones that have been in the news lately have all made assumptions based on research done on survivors of the atomic blast in Hiroshima, Japan, which is a different scenario."

Studies published recently have suggested that patients have been unnecessarily exposed to radiation from CT scans, and two new studies reported in the Archives of Internal Medicine are the first to quantify the extent of exposure and the risks.

Researchers from the University of California, San Francisco, found that the same imaging procedure performed at different institutions -- or even on different machines at the same hospital -- can result in wide variations in radiation doses, some 13 times higher than others. The risk may be small for any single patient, but the number of CT scans could cause a sharp increase in radiation-related cancer nationwide, according to the study.

Farley says the American College of Radiology recommends people ask a number of questions before getting a CT scan. "How will having this imaging exam improve my healthcare or improve my health? Are there alternatives to this exam that do not use radiation? They should ask whether the imaging dose will be 'child-sized' for their child, because the amount of radiation absorbed and/or released by the body for a 225-pound man is different than, say, a 35-pound three-year-old."

The American College of Radiology offers a list of criteria to help physicians prescribe the most appropriate imaging exam for more than 200 clinical conditions. And it recommends patients visit the Website www.imagegently.com for information on radiation exposure from medical imaging exams.