Robert S. Ledley | CT scanner pioneer, 86

Robert S. Ledley, 86, a dentist turned biomedical researcher and computing trailblazer who invented the first CT scanner capable of producing cross-sectional images of any part of the human body, died Tuesday in Kensington, Md.

The cause was Alzheimer's disease, his son Fred said.

Nearly every field of medicine has been affected by the whole-body CT scanner, short for computerized tomography.

Robert Steven Ledley was born on June 28, 1926, in the Queens borough of New York City. After receiving his D.D.S. from New York University in 1948, he enrolled as a graduate student at Columbia to study physics. He received his master's degree in physics in 1950. His professors included the Nobel Prize winners Enrico Fermi, Hans Bethe, and I.I. Rabi.

The year before, he had married Terry Wachtell, a music major at Queens College. At his urging, she switched to math, earned a master's degree in the subject and became a mathematics teacher.

In 1951, during the Korean War, Dr. Ledley was in the Army Dental Corps, assigned to a research unit at Walter Reed Army Medical Center in Washington, where he worked on improving prosthetic dental devices.

After his discharge from the Army, he went to work in Washington at the National Bureau of Standards' Dental Materials Section, where he helped his wife get a job, as a programmer on the Standards Eastern Automatic Computer, or SEAC. It was she who introduced him to computers.

Dr. Ledley began his work on CT scanning in 1973.

He was inducted into the National Inventors Hall of Fame in 1990 and awarded the National Medal of Technology and Innovation by President Bill Clinton in 1997. The original prototype of the ACTA scanner is at the Smithsonian Institution.

In addition to his wife and his son Fred, Dr. Ledley is survived by another son, Gary; and four grandchildren. - N.Y. Times News Service