Regulators at the Food and Drug Administration (FDA) are concerned that the growing popularity of high-tech computerized body imaging for health screening could be exposing the public to risky levels of radiation.

Recent advances in computerized tomography (CT) technology have increased the efficiency and lowered the price of the scans. The changes have helped spawn a new nationwide industry of unregulated boutique clinics where patients pay $300 to $500 of their own money to get CT scans not for diagnosis, but for regular health screening.

The agency is worried that easily available screening with CT has the potential of exposing patients to unhealthy repeat doses of the X-ray radiation the machines use to form images. While FDA evaluates the safety and effectiveness of CT scanners and other medical devices for regular use, it has no power to regulate how those machines are used once they reach doctors offices.

Whole-body scans require higher doses of the X-ray radiation CT scanners use to make images. As more and more people visit clinics to be screened for lung cancer, heart disease and other ailments, they could be absorbing more radiation more often than the FDA originally intended.

It's an open free-for-all in many communities. There is a perception by the public that CT scanning is a benign thing.

The average whole-body CT scan delivers 0.2 to 2.0 rads of radiation, depending on the size of the patient's body. Studies of Japanese survivors of the US atomic attacks on Hiroshima and Nagasaki in WWII linked an increased risk of cancer to lifetime cumulative exposures of 5 to 20 rads.

At 2 rads per exam, we're not far from potentially dangerous radiation doses.

Most doctors who work with CT scanners know to monitor the cumulative radiation doses patients receive. Professional societies also put out guidelines designed to promote the safe and effective use of the machines. But the self-pay nature of many CT boutiques allows patients to visit several different clinics as often as they like.