Conrad Rontgen (1845-1923) was the first person to take X-ray photographs of a person, winning the first Nobel Prize in Physics in 1901. X-ray films are sometimes referred to as Rontgenograms in his honor. For the first time, surgeons could see shrapnel and bullets contained within the body. However, X-rays were two-dimensional. In order to see how deep an object was, a second X-ray picture, usually perpendicular to the first , had to be taken. X-rays also fail to image the body's soft tissues very well.
Many techniques had been tried to improve the images produced by X-rays, but it was not until computer-assisted tomography (CAT) was developed that these problems were solved. Godfrey Hounsfield (1919-2004) devised the CAT scan in 1968, and by 1971 a prototype scanner was installed at Atkinson Morley's Hospital, Wimbledon, England, for use in clinical trials. In computer-assisted tomography, the X-ray tube is moved so that many images are taken from different angles, allowing depth to be viewed. The X-ray film is replaced by sensitive detectors, and a computer reconstructs the images. Because the detectors are over a hundred times more sensitive than film, subtle variations in tissue density can be elicited.
The first use of the new technology was to distinguish normal brain from diseased tissue. By 1975, larger scanners that could image the entire body were being marketed. In the 1960s, Allan Cormack (1924- 1998) had' independently begun work with the mathematical technique necessary to reconstruct the images. Cormack and Hounsfield shared the 1979 Nobel Prize in Medicine or Physiology.
