Lemelson-MIT Program
Who We Are Awards Outreach News
Invention Dimension Search Site Map Contact Us
Inventor of the Week

Inventor of the Week Archive

Browse for a different Invention or Inventor


Robert S. Ledley, inventor of the full-body Computer Tomography (CT) scanner, was born in 1926 in New York City. He studied dentistry, receiving a D.D.S. from the New York College of Dentistry in 1948, and went on to earn an M.A. degree in theoretical physics from Columbia University in 1950.

He first worked for Washington D.C.'s National Bureau of Standards (now the National Institute of Standards and Technology) and later moved on to Johns Hopkins University where he was a physicist and research analyst. From 1968 to 1970, he was professor of Electrical Engineering in the School of Engineering and Applied Science at the George Washington University.

In 1970 Ledley joined the School of Medicine, Georgetown University Medical Center, as a professor in the Department of Physiology and Biophysics. It was there, in 1973, that he developed the Automatic Computerized Transverse Axial (ACTA) x-ray scanner, known as the first whole-body CT machine.

The machine had a revolutionary impact on diagnostic medicine; it was able to generate visual models of internal organs not possible for conventional x-ray machines to produce. The three-dimensional reconstructions, created by transmitting X-ray beams through transverse axial slices of the body, allowed physicians to view soft tissue in the body with detail unlike any they had been able to see before, improving diagnosis of cancers, heart disease, bone disease and other irregularities. The technology was also used in radiation therapy planning.

In 1974 Ledley became a professor in the Medical Center's Department of Radiology. In 1975 he was appointed Director of the Medical Computing and Biophysics Division, a role he maintains as of this writing (March 2003).

Ledley has contributed to a number of areas within the field of diagnostic medicine and in other scientific areas as well. He patented the image processor (originally called the Texture Analysis Computer or TEXAC). He also wrote the first comprehensive textbook for engineers on digital computer engineering.

He developed computer systems for organizing the often very large volume of medical data required for precise diagnosis. He co-produced the first large-scale biotechnology databases, Protein Information Resources (PIR), to organize all known protein and DNA sequences. He also invented the instrumentation and computer algorithms used for automated chromosome analysis for prenatal diagnosis of birth defects.

Over the course of his near-50-year career, Ledley earned more than 60 patents and numerous awards and honors, including induction into the National Inventor's Hall of Fame in 1990. In 1997, he received the National Medal of Technology, awarded by President Clinton. He is editor-in-chief of four scientific journals and has been the president and research director of the National Biomedical Research Foundation since 1960.

[March 2003]

Invention Dimension
Inventor of the Week Inventor of the Week
Inventor's Handbook Inventor's Handbook
Games & Trivia Games & Trivia
Links & Resources Links & Resources