The famous X-ray photograph Wilhem Röntgen took of his wife’s hand showed both the potential and the limitations of using X-ray images in medicine. The bones of Röntgen’s wife’s hand can be clearly seen, as can her wedding ring, but soft tissues, blood vessels and nerves are all invisible. Over 70 years later, computed tomography, commonly known as CT or CAT scans, has taken X-ray imaging to another level by integrating X-rays with digital technology to generate three-dimensional views of inner organs and soft tissues.

Allan Cormack devised a mathematical method for measuring different tissue densities within the body, and he predicted that these calculations could be used to create X-ray images of cross-sectional slices of organs like the brain. Godfrey Hounsfield brought Cormack’s predictions to fruition, by developing a method of his own that collects a series of X-ray exposures taken around an area of the body to construct an image of a ‘slice’ of that area, and by constructing the first clinically usable machine that could create these images.

Like Röntgen’s X-ray images, Hounsfield’s first published computed tomography images in 1972 stunned the world. Up until that time, X-ray images of the head clearly showed the skull bones, but the brain looked like a grey, undifferentiated fog. With computed tomography, the fog suddenly cleared. Doctors could now see clear images of cross-sections of the brain, with the grey and white matter and liquid-filled cavities clearly visible.

Computed tomography received such immediate acceptance and met with such unreserved enthusiasm that it soon became an established method for the examination of all organ systems of the body. For opening up this new avenue in medical diagnostics, Cormack and Hounsfield received the Nobel Prize in Physiology or Medicine in 1979.