Text size:

Potential overuse of CT scans questioned

BY DELTHIA RICKS | delthia.ricks@newsday.com

8:55 PM EST, November 28, 2007

Doctors may be overusing CT scans, the popular diagnostic tool that exposes patients to far more radiation than conventional X-rays, scientists in Manhattan report Thursday.

The analysis by investigators at Columbia University Medical Center comes on the heels of another released this week by researchers at Brown University, who found pregnant women are being exposed to twice the amount of radiation through CT scans as they were in 1997.

Even though the amount of radiation absorbed by pregnant women is still small, a doubling of the radiation dosage in only a decade is cause for concern, experts say, because imaging procedures expose the developing fetus to gene-altering X-rays. Between 1997 and 2006, investigators found the number of imaging studies of all types performed on pregnant women increased by 121 percent. The greatest increases were in the number of CT exams.

In the latest research, reported in today's New England Journal of Medicine, Columbia's David Brenner and Eric Hall found the number of CT scans have dramatically increased for everyone over the past 27 years. In 1980, there were only 3 million scans ordered annually in the United States. Now, an estimated 62 million CT exams are performed. The result, scientists say, is a marked increase in the average personal exposure, which has doubled since 1980.

Hall, a scientist at Columbia's Center for Radiological Research, said the analysis was driven by a key fact: "We know that radiation causes cancer," he said of ionizing radiation's capacity to damage DNA, which can lead to mutations.

Brenner, also a scientist at the center, added that even though a doubling of radiation exposure has occurred for individuals, that amount of exposure currently does not reach a level of alarm.

His concern centers on medicine's increasing reliance on CT scans, which he theorizes could ultimately lead to a public health crisis if usage continues to rise at the current rate.

CT scans, also known as CAT scans, for computerized axial tomography, produce three-dimensional X-ray images of structures in the body that are quickly taken in multiples and displayed on a screen. The technology can reveal abnormalities that are too small or too obscured to be revealed by conventional X-rays. As a tool, it has been vital in diagnosing trauma patients and those with cancer.

"The radiation dose from a CT scan is far larger than from a conventional X-ray," Brenner said. "It's 50 times to 100 times larger." But he conceded Wednesday it has become a indispensable tool for oncology and other specialized areas of medicine.

He raises questions over so-called "defensive medicine."

"One of the most common examples of defensive medicine is when people come to an emergency room and are given a CT scan even without a diagnosis by a physician," he said.

Brenner also cited what he called controversial usages of CT scanning: whole-body scanning, virtual colonoscopy and CT scanning as a lung cancer screening technique.

Dr. Shahriyour Andaz, director of thoracic oncology at South Nassau Communities Hospital in Oceanside, strongly defends CT scanning for lung cancer screening. He said the technique is a low-dose method of searching for early tumors and benefits of the scan outweigh the risks. The technique, not widely used, is still in clinical trials.

"With lung cancer, the mortality is 100 percent. We have never had a patient die from a CT scan," Andaz said.