Dr. Robert S. Ledley Developer of Full-Body CT Scanner, Dead at 86

The developer of the first computed tomography (CT) scanner capable of generating full body, cross-sectional images of the human body, Dr. Robert S. Ledley died July 24, 2012, in Kensington (MD, USA). He was 86 years old.

Dr. Ledley, a Georgetown University (Washington DC, USA) physicist and biotech researcher, first trained as a dentist and in the late 1950s, and he became an advocate for using data processors to help diagnose disease. In 1973, Dr. Ledley introduced one of the most significant diagnostic advancements that he called the automatic computed transverse axial scanner (ACTA). It was the first machine capable of generating cross-sectional images of any area of the body.

Dr. Ledley’s prototype did not include the contemporary unit’s tunnel--in his original prototype, the patient passed through a thinner ring-like scanner--but most CT scanners currently rely on his basic concept. CT technology, originally developed several years earlier by Nobel Prize-winning scientists Godfrey Hounsfield and Allan M. Cormack, changed the way medical imaging was practiced. Before the arrival of CT scans, doctors relied on X-ray images, which revealed only hard tissue such as bone.

Dr. Ledley’s machine began to become widely available in the mid-1970s and he was inducted into the US National Inventors Hall of Fame in 1990, and in 1997 received the National Medal of Technology. Dr. Ledley developed and built his original scanner in a basement laboratory at Georgetown University, with help from a local machinist and a final paint job by a nearby Cadillac car dealership. The machine was first used on a patient at the Georgetown University hospital, where a toddler was taken after falling off his bicycle and hitting his head. With the CT scanner, clinicians scanned his brain and found a blood clot that, unnoticed, might have killed the child.

In 1956, Dr. Ledley was hired as an assistant professor of electrical engineering at the Georgetown University. In 1974, Dr. Ledley formed the Digital Information Science Corp. (DISCO), selling the machines for USD 300,000 each.

Robert Steven Ledley was born June 28, 1926, in Flushing, Queens, NY, USA. Dr. Ledley received a DDS degree from New York University (New York, NY, USA) in 1948, while also studying physics at Columbia University (also in New York), where he received a Master’s degree in 1949. He worked and taught over the years at the US National Institute of Standards and Technology (NIST; Gaithersburg, MD, USA), where he used one of the early modern computers, as well as at Johns Hopkins University (Baltimore, MD, USA) and George Washington University (Washington DC, USA. He joined Georgetown in 1970 and retired in 2005.

Dr. Ledley had more than 20 patents and wrote one of the first comprehensive textbook for engineers on digital computer engineering. He also developed skid-resistant crutches. Moreover, Dr. Ledley was an early advocate of computer-based medical diagnostics, 50 years before medical residents began utilizing computers to type their patients’ symptoms into online programs.

The original prototype of the ACTA scanner is housed in the Smithsonian Institution (Washington DC, USA).

Related Links:
Smithsonian Institution