Allan M. Cormack
After graduating from the University of Cape Town in 1944 Cormack
pursued advanced studies there and at the University of Cambridge. He
was a lecturer at Cape Town from 1950 to 1956 and then, after a year’s
research fellowship at Harvard University, became assistant professor
of physics at Tufts University. His main research at Tufts centered on
the interaction of subatomic particles. He advanced to full professor in
1964, was chairman of the department from 1968 to 1976, and retired
in 1980. He became a U.S. citizen in 1966.
A part-time position as physicist for a hospital radiology department first
aroused Cormack’s interest in the problem of X-ray imaging of soft
tissues or layers of tissue of differing densities. 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 analyzed by a computer to produce a sharp map of the tissues within
a cross section of the body. Cormack became a member of the
American Academy of Arts and Sciences in 1980.