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Abdominal CT Dose Can Be Cut in Half for "Thinner" Patients, A New Study Indicates

LEESBURG, VA -- November 18, 2002 -- Radiologists might be able to reduce radiation dose by 50 percent for abdominal CT examinations and still get "good" quality images as long as the patient weighs less than 180 pounds and has a waistline measuring no more than 42 inches, a new study indicates.

Thirty-nine abdominal CT image sets produced by using a standard radiation dose (240-300 mA) were compared to the same number of images produced using half that dose, says Sanjay Saini, MD, of Massachusetts General Hospital and Harvard Medical School, and an author of the study. Two radiologists specially trained in abdominal CT "scored" the CT images based on anatomic details of the liver, spleen, adrenal glands, kidneys, pancreas, and abdominal wall, says Dr. Saini. Although the reviewers preferred the images that resulted from the higher dose examinations the lower dose images were considered "acceptable" in thinner patients, he says. Dr. Saini notes that the reviewers were looking at normal structures; this study did not "test" for the diagnostic information in the images.

"It used to be, with conventional plain film examinations, that the radiation dose was adjusted depending on the patient's size to avoid overexposing or underexposing the film," says Dr. Saini. The exposure problem doesn't happen with CT so doses gradually increased because higher doses meant a less grainy image, he says. However, "with the dramatic increase in the use of CT, we've become more concerned about dose levels," he says.

Dr. Saini adds that reducing dose levels is a cooperative effort between radiologists and the medical industry. "This research was funded, in part, by GE Medical Systems," says Dr. Saini. Manufacturers will soon introduce CT scanners, in which the radiation dose dynamically changes depending on the density of the body part being imaged, Dr. Saini predicts.

The study, one of the first to look at abdominal CT and dose, appears in the November issue of the American Journal of Roentgenology.

SOURCE: American Roentgen Ray Society

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