Robert Steven Ledley (June 28, 1926 – July 24, 2012), professor of physiology and biophysics and professor of radiology at Georgetown University School of Medicine, pioneered the use of electronic digital computers in biology and medicine. In 1959, he wrote two influential articles in Science: "Reasoning Foundations of Medical Diagnosis" (with Lee B. Lusted) and "Digital Electronic Computers in Biomedical Science". Both articles encouraged biomedical researchers and physicians to adopt computer technology.
In 1960 he established the National Biomedical Research Foundation (NBRF), a non-profit research organization dedicated to promoting the use of computers and electronic equipment in biomedical research. At the NBRF Ledley pursued several major projects: the early 1960s development of the Film Input to Digital Automatic Computer (FIDAC), which automated the analysis of chromosomes; the invention of the Automatic Computerized Transverse Axial (ACTA) whole-body CT scanner in the mid-1970s; managing the Atlas of Protein Sequence and Structure (created in 1965 by Margaret O. Dayhoff); and the establishment of the Protein Information Resource in 1984. Ledley also served as editor of several major peer-reviewed biomedical journals.
In 1990, Ledley was inducted into the National Inventors Hall of Fame. He was awarded the National Medal of Technology in 1997. He retired as president and research director of the NBRF in 2010.
Family and education
Robert Ledley was born on June 28, 1926, in Flushing Meadows, Queens, New York City."Lemelson Center for the Study of Innovation & Innovation", Smithsonian-Lemelson: Robert Ledley Papers 1972-1981, Retrieved Apr 14, 2012. His father, Joseph Levy, was an accountant and his mother, Kate Levy, was a schoolteacher before becoming a homemaker. Robert had a sister, Marion, and a half-brother, Ralph. All three siblings were surnamed Ledley.
Among Ledley's childhood friends in Flushing was Margaret Oakley Dayhoff, who would later spend most of her career working at the National Biomedical Research Foundation and who would become a founder of the field of bioinformatics. Ledley attended the Horace Mann School, from which he graduated in 1943."Robert S. Ledley, DDS '43" , Horace Mann School: 2000 Award for Distinguished Achievement Recipients, Retrieved Apr 14, 2012.
As an undergraduate student at Columbia University Ledley excelled in physics, taking undergraduate and graduate courses within his first two years as a student. When, however, he informed his parents of his desire to become a physicist, they objected on the grounds that a career in physics would not be feasible for him given the scarcity of steady jobs in that field. Instead, they urged him to make his living as a dentist. Ledley attempted to follow both paths at once; he enrolled in the New York University College of Dentistry while continuing to pursue his education in physics at Columbia.Ledley, Robert. (1990) "Medical Informatics: A Personal View of Sowing the Seeds." p. 89. During the day, Ledley would take dentistry training courses at NYU, then he would take the subway to Columbia to take evening courses in physics. After receiving his DDS from NYU in 1948, Ledley became a full-time physics graduate student at Columbia, where he took courses from many noted physicists including I.I. Rabi (who joked that Ledley was the only physicist who could pull a man's tooth), Enrico Fermi, Hans Bethe, and J.A. Wheeler. Ledley received a MS in physics from Columbia in 1950.Ledley, Robert. (1990) "Medical Informatics: A Personal View of Sowing the Seeds." p. 90.
In 1949, Ledley married Terry Wachtell (born 1926), a mathematics teacher at Queens College, and sister of Herbert Wachtell."TERRY WACHTELL WED; Queens College Teacher Is Bride of Dr. Robert S. Ledley", New York Times (Aug. 1949), Retrieved Apr 14, 2012. The couple had two sons, Fred (born 1954) and Gary (born 1957). When the couple moved to the DC area in the early 1950s, Terry was employed as a computer programmer until leaving work to raise their sons. Both sons graduated from Georgetown University School of Medicine. Fred Ledley is Professor of Natural and Applied Sciences at Bentley University and is the author of numerous scientific papers as well as the novel, Sputnik's Child (2011)."Faculty Profile: Fred D. Ledley", Bentley University, accessed Apr. 14, 2012. Gary Ledley is a practicing cardiologist associated with Drexel University."Gary Ledley, M.D.", Drexel University College of Medicine, Retrieved Apr 14, 2012.
Robert Ledley died of Alzheimer's disease in Kensington, Maryland, USA on July 24, 2012.
Early research career
U.S. Army dental research
In 1950, shortly after the outbreak of the Korean War, Ledley was contacted by a U.S. Army recruitment officer, who offered him a choice: he could volunteer to join the U.S. Army Dental Corps as a first lieutenant or be conscripted into the infantry as a private. Ledley promptly volunteered, and was sent to the U.S. Army Medical Field Service School for training. Because Ledley was also trained in physics, he was assigned to a dental research unit at Walter Reed General Hospital, in Washington, D.C.
During his time in the army, Ledley was responsible for improving prosthetic dental devices (such as dentures) then widely used by Army personnel. Notably, Ledley drew on his training in dentistry and physics to develop a system that optimized the process of fitting dentures by allowing dentists to determine the "angle of chew," or the mean slope of each tooth relative to the surface of an object (e.g. a piece of food) being bitten. Ledley presented this work to the American Physical Society in 1952, and it generated nationwide attention via an Associated Press newspaper story titled "Mathematics Used to Keep False Teeth in Place." Ledley formally published his research in
Work with Standards Eastern Automatic Computer
Ledley's work on dental prosthetics brought him into collaboration with researchers based at the National Bureau of Standards Dental Materials Research Section, where he was offered a research job in 1952 following his discharge from the Army. There he encountered the Standards Eastern Automatic Computer, one of the earliest stored-program electronic digital computers. Ledley's first interaction with SEAC came via his wife, Terry, who worked as one of the machine's programmers – Robert taught himself to program by examining programs (on perforated paper tape) and manuals Terry brought home. Ledley started to use SEAC himself for his dental research, but after proving an adept programmer and troubleshooter, he found himself working with SEAC (and later DYSEAC) full-time on a wide variety of projects, including a remote-controlled aircraft guidance system. pp. 46-47
For Ledley, working with SEAC produced an epiphany, concerning both his career and the potential importance of computers to biomedical research. He recalled: "I had previously realized that although, conceptually, physics equations could be written to describe any biomedical phenomenon, such equations would be so complex that they could not feasibly be solved in closed form. Thus SEAC would be my panacea, because the equations would become tractable to numerical methods of solutions. Or so I truly believed at the time. That was to be my field, application of computers to biomedical problems."
Operations research and the RNA Tie Club
Though Ledley had envisioned a career of employing computers to solve biomedical problems as early as the early 1950s, it would be several years before he would pursue that career full-time. At the National Bureau of Standards, Ledley's work was primarily related to solving military problems using the techniques of operations research. For instance, he published an article in the journal Operations Research showing how one could use Boolean algebra to reduce complex military decision-making problems to the point where they could be resolved using a collection of truth tables and yes-or-no questions.November, Joseph (2012). Biomedical Computing: Digitizing Life in the United States. p. 48.
When Ledley lost his job at the NBS in 1954 due to budget cuts, he turned down an offer to work for IBM (which hired Ledley's colleagues en masse). Instead, he found employment as an "Operations Research Analyst" at the Operations Research Office at Johns Hopkins University. There, his work remained mostly focused on military problems, but his expertise in biology, physics, mathematics, and computing caught the attention of one of his new ORO colleagues, George Gamow. Gamow, who was renowned for his contributions to the Big Bang cosmological model, had taken an interest in molecular biology immediately after James D. Watson and Francis Crick elucidated the double helix structure of DNA in 1953. Gamow believed Ledley's skills could be instrumental in helping to crack the genetic code, that is, by solving the problem of how a DNA sequence translates into proteins. In 1954, Gamow invited Ledley to join the elite RNA Tie Club; some other members of the club were Watson, Crick, Richard Feynman, Max Delbrück, Edward Teller, and Sydney Brenner.November, Joseph (2012). Biomedical Computing: Digitizing Life in the United States. pp. 42-43.
Ledley's main work for the RNA Tie Club was an effort to generate a set of contingency tables for the purpose of writing a computer program that would determine the correspondence between any three-letter sequence (triplet) of nucleotide bases and any amino acid (the building blocks of proteins). Sponsored by Gamow, Ledley published his work in 1955 in the Proceedings of the National Academy of Sciences.November, Joseph (2012). Biomedical Computing: Digitizing Life in the United States. p. 49. See: Ledley, R.S. "Digital Computational Methods in Symbolic Logic, with Examples in Biochemistry," Proceedings of the National Academy of Sciences 41 (July 1955): 498–511. Though Ledley had produced a combinatorial table that could theoretically be used to determine which three-letter sequence of DNA bases corresponded to which amino acid, the problem required several thousand years of computation time on the world's fastest computers (circa 1955) to produce a solution.
Having established that computers could not be used reasonably quickly to decode DNA, Ledley drifted away from the RNA Tie Club. Ultimately the code was broken in the 1961 Nirenberg and Matthaei experiment, which did not use computers and which was not carried out by RNA Tie Club members.November, Joseph (2012). Biomedical Computing: Digitizing Life in the United States. p. 52.
Electrical engineering
In 1956, Ledley was hired as an assistant professor of electrical engineering at the George Washington University School of Engineering and Applied Science. There, he taught some of the earliest courses on computer programming and wrote his first book, Digital Computer and Control Engineering (1960). At GWU, Ledley acquired the Florida Automatic Computer I and II, two descendants of SEAC that had been discarded by the U.S. Air Force as surplus, for the purpose of establishing a "computation center" that would use the computers to automate Frederick Sanger's process of determining the amino acid sequence of proteins. The center was never built, however, because the National Institutes of Health rejected Ledley's request for a grant to fund it, and because the university balked at the prospect of installing and supporting the two enormous computers.
Collaboration with Lee B. Lusted