Professor Allan Cormack

Professor Allan MacLeod Cor-mack, who was immensely proud of his roots in the Scottish Highlands, died in Massachusetts, US, where he had spent most of his career.

He was awarded the 1979 Nobel Prize for Physiology or Medicine jointly with Englishman Godfrey Hounsfield, for their invention of the X-ray diagnostic technique, com-puter assisted tomography, now known across the world either as CAT, or computer tomography (CT).

Born in Johannesburg, South Africa, to an electrical engineer father who had emigrated from Caithness, Allan won a scholarship to the University of Cape Town, where he graduated in physics, going on to specialise in chrystallography for his masters' degree there in nuclear physics.

He then won a fellowship which took him to Cambridge University, where he was a post-graduate research student for two years.

After six years lecturing at his alma mater in South Africa, the brilliant young scientist then spent two years as a research fellow at Harvard University in the mid-1950s. The rest of his career was spent in New England as a professor at Tufts University, although he had several visiting professorships to other institutions of academic excellence, including the Univer-sity of California. His portrait later featured on a South African postage stamp honouring that country's Nobel laureates.

At the time of his death, Professor Cormack had been planning a visit to Caithness this summer, to further a personal quest for his ancestral roots. His family had worked Stemster Farm, at John O'Groats, on the very tip of Scotland's mainland.

In his address at the 1979 awards ceremony, Professor Cormack told how his experiences in Cape Town in the mid-1950s had set him on the road to the research which brought him the supreme prize. He did many practical experiments to check the measurements of the behaviour of X-ray beams passing through the various materials which make up the tissues of the human body.

Concluding that there were often difficulties in interpreting the two dimensional images then available, Cormack spent years calculating and developing the equations necessary for image reconstruction.

He concluded that by using a specialised computer he could combine a number of X-ray projections taken at various angles to reconstruct the image three-dimensionally.

Fellow laureate Godfrey Houns-field was working independently on the problem at EMI laboratories in England. He developed the first clinically usable equipment, called the EMI scanner, which was able to examine inside the human head. With Cormack's calculations, the equipment was then extended to cover the other parts of the body.

At the Nobel Prize awards ceremony, Hounsfield and Cormack were praised for their ''ingenious new thinking'', which had made a tremendous impact on everyday medicine and also opened up new areas of research. Now even quite small hospitals throughout the world use CAT or CT scanners routinely.

In 1980 the University of Cape Town presented its highest honour, the Gold Medal, to the Scots emigrant's son.

Stemster Farm was one of three made available in 1496 to the three de Groot brothers, from Holland, as part of their royal commission by King James IV to establish the first daily ferry service to Orkney. Allan Cormack's research has shown that he was a descendant of the Groat family, with John O'Groats being named after the oldest brother, John.