In the 1970s, computed axial tomography (CAT), or CT, scans revolutionized diagnosis, offering pictures  ith up to 20 times the detail of ordinary x-rays, particularly of bones, blood vessels and soft tissues of the body. It has made it possible to scan for diseases of the abdomen, lungs, heart, liver and pancreas, and even for early osteoporosis.

Adapted from an image-processing system developed for the Apollo moon landings, CT scans take a 360-degree series of crosssectional x-ray images from multiple angles—up to 30 shots—by passing a pencil-thin beam through a particular portion of the body, usually with the use of a contrast agent. An X-ray tube on a moveable ring revolves around your body, taking individual slices of images; this  nformation is then passed through a computer, which reconstructs the slices into a three-dimensional  mage on a video screen.

The problem is, now that your doctor has such a computerized diagnostic toy at his disposal, he’s more  ikely to want to play with it. Indeed, the CT scan is now the special province of the ‘worried well’—perfectly healthy people who are convinced that an annual scan will catch something dreaded like cancer before it strikes.  Although Japan leads the world in per capita CT-scan use, some 62 million CT scans are now carried out every year in the US—a 20-fold increase in just 25 years. Even in the UK, the number of CT scans has doubled in the last decade, and is set for a massive increase with the purchase of £20 million’s worth of new equipment.

While no doubt CT scanning represents the height of 20th-century technology, it also poses far more  isks than most other tests, blasting you with far higher doses of radiation than ordinary x-rays.

This month’s issue of WDDTY exposes just how much more. The latest estimates are that one standard course of CT scans exposes you to more radiation than the citizens of Hiroshima or Nagasaki received when the atomic bomb was dropped on their cities.

Shockingly, the carnage from these hyper-x-rays can only be estimated, as a large-scale study into their safety has never been carried out. Nevertheless, David Brenner, a leading radiologist from Columbia University in New York, has finally gone public to admit that they are likely to account for some 29,000 new cases of cancer every year in the US. Worse, CT scans could be causing 100,000 new cases of cancer per year across the globe.

But this might be worth it if CT scans are accurate and could in any way prevent future illness. However, the latest evidence is that CT scans can be wrong up to 75 per cent of the time in trauma injuries, and almost one-third of the time in early-stage diagnoses.

The bottom line is that the diagnostic revolution promised by this state-of-the-art gadgetry has failed to materialize. Although all the early evidence showed that CT scans would reduce diagnostic time, reassure doctors of their diagnosis or treatment plans and preclude the need for other tests, very few studies have proven that this knowledge has in any way reduced illness, shortened hospital stays or prevented death. And it now appears that CT is simply killing perfectly healthy people.

There is virtually no disagreement in medical circles that ionizing radiation is damaging. “Medical irradiation is by far the largest man-made contribution to the radiation burden of the population of developed countries,” once wrote Richard Wootton, professor and director of medical physics at Hammersmith Hospital in London, in a textbook on the subject. The only thing that has changed is the degree—every CT scan magnifies that risk 500 times.