Ledley wanted to study physics, but his family insisted on a career that had a better job potential. “His family said he could study physics as long as he also became a licensed dentist, so he could always make a living doing dentistry,” said Prof. Joseph November of the University of South Carolina, who is writing Ledley’s biography. Once he got his DDS degree in 1948, Dr. Ledley went on to study physics at Columbia, and got his Master’s in 1950. One of his professors, Nobel Prize winner Isidor Rabi, “joked that Ledley was the only physicist who could pull a man’s tooth,” November says. And it’s in that field, not dentistry, that Ledley made his mark: he invented the Automatic Computerized Transverse Axial scanner, the first computerized x-ray scanner which could create cross-sectional images of any part of the human body.
It’s now known as the Computerized Axial Tomography (or CAT) scanner, which revolutionized medical imaging and, thus, diagnosis and treatment. Ledley was an early proponent of using computers in medicine, after he was introduced to the machines by his wife, who worked for the U.S. National Bureau of Standards: his 1959 journal papers “Reasoning Foundations of Medical Diagnosis” and “Digital Electronic Computers in Biomedical Science” were groundbreaking. “The idea that computers could assist physicians in diagnosis and choice of therapy was a totally new understanding of the process of medical diagnosis,” said Dr. Alan N. Schechter of the National Institutes of Health. Ledly was awarded the National Medal of Technology and Innovation in 1997, and the first ACTA scanner is in the Smithsonian Institution’s collection. Dr. Ledley died July 24, from Alzheimer’s disease. He was 86.