Professor Who Revolutionized Radiology Dies At 86

Posted in GUMC Stories

Emeritus professor who created the first whole-body CT scanner that revolutionized the practice of radiology passed away on July 24.

Robert S. Ledley, who pioneered the use of electronic digital computers in biology and medicine, had been a faculty member in the departments of radiology, physiology and biophysics at Georgetown University Medical Center (GUMC) for nearly 40 years.

A recipient of the National Medal of Technology in 1997 from President Bill Clinton, he died in Kensington, Md., at the age of 86.


“He was great innovator, scholar, scientist and educator,” said Dr. Howard Federoff, GUMC’s executive vice president for health sciences and executive dean.

Ledley also received several patents on applications to medical instrumentation. The prototype for the CT scanner he created is displayed at the Smithsonian Institution.

The recipient of a doctorate in dental surgery from New York University and a master’s degree in mathematical physics from Columbia University, he founded the National Biomedical Research Foundation and moved it to GUMC in 1970.

It was there that he supported and created most of his computer systems and inventions.


In addition to pioneering the use of computers to aid physicians and treat patients, he also began developing genetic databases. In the 1960s, he and colleague Margaret Dayhoff compiled an atlas of all known protein sequences.

Later, when it was put in electronic form, it became the Protein Information Resource (PIR), one of the premier protein sequence databases in the world. It is used by almost everyone in the field of molecular biology.

In addition to the National Medal of Technology, Ledley received the 1998 Morris F. Collen Award for lifetime achievements from the American Medical Informatics Association and American College of Medical Informatics.

In 1990, he was inducted into the National Inventors Hall of Fame.


In a 1998 Georgetown Magazine article, Ledley explained that he began rendering mechanical drawings at the age of 6. He told the magazine that soon after he started creating toys such as trick locks and marionettes out of wood.

The article noted that while he was working on the prototype for the CT scanner, the engineer he was working with wanted specficisabout the signal the scanner would emit.

“I’ve never done it before, I didn’t have the foggiest idea,” Ledley recalled in the article. “So he says, ‘Well, how can I make [it work] if I don’t know what the signal is going to be?’ ”

Stumped, Ledley said “You want a number? I’ll give you a number: 10. Ten of whatever it is. … And he made it for 10, then adapted it for the actual value.”

The professor often started with a pie-in-the-sky idea and ended up with an invention that furthered the medical profession


Ledley is survived by his wife, Terry, and two sons, Fred (M’78), and Gary (M’82), both graduates of Georgetown’s School of Medicine.

“My father loved science, and he was privileged in his career to have an opportunity to go into worlds that were so unknown at time,” Fred Ledley said in an article on the GUMC website. “He was one of the first people who had the pleasure of thinking about how computers could be applied to healing.”

Fred Ledley, a professor of natural and applied sciences at Bentley University, has treated children’s genetic diseases with gene therapy at Howard Hughes Medical Institute and is the author of a novel, Sputnik’s Child. His brother is a cardiologist at Drexel University College of Medicine.

(Published August 1, 2012)