Bet you didn't know this invention was by a South African

You'll never believe how many inventions have come from South Africans
You'll never believe how many inventions have come from South Africans

#Trending has come to the end of the run of its popular general knowledge excerpts from the book Know Your Nation. But don’t despair, we have a brand new series of excerpts in store.

What a Great Idea! by Mike Bruton published by Jacana Media is a stunning, full-colour book that documents South Africans’ amazing inventions and innovations. It’s a way of making us realise how much South Africans have contributed to the world. Our first extract is about the CAT scanner.

The accidental discovery of X-rays by German scientist Wilhelm Röntgen in 1895, while passing electricity through gas-filled bottles, revolutionised medical science. Röntgen had no idea what he had discovered when he found that the rays had the miraculous ability to penetrate dense objects, so he called them “X” rays.

In one of the most famous images in science, he exposed his wife’s hand to the X-rays and produced a perfect image of her bones (and wedding ring). X-rays were quickly adopted by the medical profession. For the first time, we could look inside a patient’s body without surgery, determining the basic structure of organs at the flick of a button. The next challenge was to take three-dimensional X-rays of the body. This challenge was addressed by South Africa’s first nuclear physicist, Allan MacLeod Cormack, and a British electrical engineer Godfrey Hounsfield, who were jointly awarded the Nobel Prize for medicine and physiology in 1979 for their co-invention of the CAT scanner. In a CAT scanner, the X-ray source and detector can be rotated around the patient’s body so that views are obtained from all angles. A computer uses this information to create a 3D picture of a slice through the body, showing whether it is diseased or damaged.

Cormack had difficulty raising interest in his invention, partly because computers that could make the necessary calculations quickly enough did not exist then. Godfrey Hounsfield at EMI in England came to the rescue when he used Cormack’s and other algorithms to develop a method for computerising 3D X-rays. In 1972, he made the first practical CAT scanner, which provided doctors with a 3D glimpse inside the body and opened up a whole new field of medical research and diagnostics. CAT scanners are now used in every major hospital worldwide.

It is widely considered that the CAT scanner ushered medicine into the “space age”. Its invention transformed medical operations from painful and sometimes dangerous invasive procedures to precisely targeted, noninvasive techniques. As with all great inventions, the CAT scanner was initially developed for a narrow application but was later used more widely. They are now also used for testing manufactured objects and studying internal structures and processes in industrial, biological, environmental, space science and astronomy contexts.

Out of 100, science writer Tim Philbin rated the CAT scanner as the 53rd greatest invention. It is the only invention from the southern hemisphere to feature on the top 100 list.

  • What a Great Idea! is published by Jacana Media and can be purchased at major bookstores at a recommended selling price of R295
  • If you’d still like to purchase Know Your Nation, email Tim Mostert at
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