I recently had a CAT scan as part of a medical check-up. As I slid through its intricate workings and it beamed its rays through my body, I wondered who had invented this wondrous machine and what impact it has had on medical practice.
I recently had a CAT scan as part of a medical check-up. As I slid through its intricate workings and it beamed its rays through my body, I wondered who had invented this wondrous machine and what impact it has had on medical practice.
Scientists call something ‘X’ when they don’t know what it is. The German physicist, Wilhelm Röntgen, accidentally discovered X-rays on 8 November 1895 while doing humdrum research on vacuum tubes.
He had no idea what he had discovered when he found that rays streaming out of gas bottles, through which he had passed electric discharges, had the miraculous ability to penetrate dense objects. In one of the most famous images in science, Röntgen exposed his wife’s hand to the X-rays and produced a perfect image of the bones in her hand (and her wedding ring) on a photographic plate.
After Röntgen published his work, X-rays were quickly adopted by the medical profession. For the first time medical doctors could look inside a patient’s body without surgery. The structure of hard organs, especially bones, could be determined at the flick of a button.
The next challenge, to create a 3D image using X-rays, was addressed by a South African nuclear physicist, Allan Cormack, and British electrical engineer Godfrey Hounsfield. Cormack studied the problem of measuring and interpreting the absorption of X-rays passing through the body from different directions.
In 1957, while working at Groote Schuur Hospital in Cape Town, he built a simple, prototype CAT scanner and developed mathematical formulae that used data from X-ray ‘slices’ of a patient’s body to create a 3D image of the whole body. These reconstructions were the first computerised tomograms, or three-dimensional diagrams, ever made, although his ‘computer’ was a simple desktop calculator.
But Cormack had difficulty raising interest in his invention partly because computers were not then readily available that could make the necessary calculations quickly enough.
That was when British scientist Godfrey Hounsfield came to the rescue. He used Cormack’s calculations and developed a method of his own for computerised tomography. In 1972 he made the first practical CAT scanner for examination of the head, and provided medical doctors with their first detailed 3D glimpse inside the human body. A whole new field of medical research and diagnostics had been initiated.
In 1979 Hounsfield and Cormack received the Nobel Prize in Medicine for their co-invention of the CAT scanner.
An interesting aside is that the research laboratory in which Hounsfield worked (the EMI Central Research Laboratory in London) was funded by EMI, the company that held the rights to the music of the Beatles. EMI made a huge profit from the Beatles and ploughed some of this revenue back into medical research. So the success of the Beatles contributed indirectly to the invention of the CAT scanner!
Perhaps the titles of some of their songs – ‘Do you want to know a secret’, ‘We can work it out’, ‘With a little help from my friends’, ‘The inner light’ and ‘Watching rainbows’ were prophetic!
The CAT scanner lead to many major advances in medicine and transformed our way of looking inside the body, from painful and sometimes dangerous surgery to precisely targeted techniques that don’t involve any cutting or slicing. It is widely considered that the CAT scanner ushered medicine into the space age.
It is the trademark of a great invention that it is initially developed for one narrow application but later finds far wider application in other fields. The CAT scanner is a classic example of this trend as it is now used, not only in medicine, but also for testing and examining manufactured products in the industrial, biological, environmental and astronomical fields.
