November 25: The CAT-scan

Medical inventor Robert S. Ledley (Levy) was granted patent #3,922,522 for “diagnostic X-ray systems” known as the CAT-scan on this date in 1975. The equipment, which uses computer-processed x-rays to allow doctors to see inside tissue surgery, was a great advance on the diagnostic capacity of simple x-rays. Ledley (1926-2012) was a professor of physiology, biophysics, and radiology at Georgetown University School of Medicine who worked to inspire the adoption of computer technology by medical researchers and doctors. In 1960 he established the National Biomedical Research Foundation (NBRF), where he helped to automate the analysis of chromosomes and develop body-scanner technology. Ledley was inducted into the National Inventors Hall of Fame in 1990 and received the National Medal of Technology in 1997. At his parents’ insistence, Ledley had trained to be a dentist while studying physics at Columbia University, where I.I. Rabi noted that Ledley had become the world’s only physicist who could pull teeth. His numerous inventions did include some advanced prosthetic dental devices. He also made advances in optical pattern recognition and computer design, and founded or headed several significant science journals. “It’s hard to explain to people what the significance of an invention is, so it’s hard to get funding. The first thing they say is that it can’t be done. Then they say, ‘You didn’t do it right.’ Then, when you’ve done it, they finally say, ‘Well, it was obvious anyway.’” —Robert Ledley