classic inventions

CAT Scan

The computed axial tomography scan, or CAT scan, was developed by South African physicist Allan Cormack and Godfrey Hounsfield of EMI Laboratories. Their achievement secured them the 1979 Nobel Prize in Physiology or Medicine. Cormack's interest in the problem of X-ray imaging of soft tissues or layers of tissue of differing densities was first aroused when he took up the part-time position of physicist for a hospital radiology department. The two-dimensional representations of conventional X-ray plates were often unable to distinguish between such tissues. More information could be gained if X-rays of the body were taken from several different directions, but conventional X-ray techniques made this procedure problematic. In the early 1960s, Cormack showed how details of a flat section of soft tissues could be calculated from measurements of the attenuation of X-rays passing through it from many different angles. He thus provided the mathematical technique for the CAT scan, in which an X-ray source and electronic detectors are rotated about the body and the resulting data is analysed by a computer to produce a sharp map of the tissues within a cross-section of the body.