The ACTA (Automatic Computerized Transverse Axial) scanner was developed in 1973. The introduction of this first full-body CAT (Computer Assisted Tomography)--or CT (Computerized Tomography)--scanner lead to advancement in medical imaging and diagnostic medicine, especially for non-invasive viewing of soft tissue inside the body. The machine revolutionized diagnosis in cancer, heart disease, and soft tissue irregularities by transmitting X-ray beams through transverse axial slices of the body, resulting in computerized cross-sectional images of the body part scanned. Robert S. Ledley, of Georgetown University Medical Center, designed the ACTA scanner, and it was first used in clinical operation there in 1973.
Robert Ledley received a D.D.S. degree from New York College of Dentistry in 1948 and a M.A. degree in theoretical physics from Columbia University in 1950. Shortly thereafter he worked for both the National Bureau of Standards (now the National Institute of Standards and Technology) and the Johns Hopkins University as a physicist and research analyst. From 1968 to 1970, he was professor of Electrical Engineering in the School of Engineering and Applied Science at the George Washington University. In 1960 he founded and became president of the National Biomedical Research Foundation (NBRF). He joined the School of Medicine, Georgetown University Medical Center in 1970 as a professor in the Department of Physiology and Biophysics. In 1974 he became a professor in the Medical Center's Department of Radiology and in 1975 was appointed director of the Medical Computing and Biophysics Division.
Homer Twigg graduated from the University of Maryland Medical School in 1951 and entered the United States Public Health Service where he received training in radiology. In 1957, he joined the Radiology Department of the Georgetown University Medical Center and was one of the first radiologists to work with Dr. Ledley in applying the ACTA scanner to clinical situations.
Robert Zeman received his M.D. from Northwestern University in 1976. In 1977 he began his residency at Yale New Haven Hospital, in New Haven, Connecticut, and was appointed assistant professor of Diagnostic Radiology at Yale University in 1981. The following year he joined Georgetown University School of Medicine as an assistant professor of Radiology and held numerous other positions there until his appointment as Clinical Director of the Department of Diagnostic Radiology in 1986.
David Griego, Georgetown University Medical Center CAT scanning supervisor and radiology specialist, and Seong Ki Mun, director of the Division of Imaging Physics were interviewed for their knowledge of current trends in the field of medical imaging.