Smithsonian Videohistory Collection

Background

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.

Participants

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.

Video Sessions

This collection consists of five interview sessions, totalling approximately 8:26 hours of recordings, and 154 pages of transcript. There are three generations of tape for each session: originals, dubbing masters, and reference copies. In total, this collection is comprised of 24 original videotapes (23 Beta videotapes, and 1 U-Matic videotape), 10 dubbing master videotapes (10 U-Matic videotapes), and 7 reference copy videotapes (7 VHS videotapes). Also included is one audio interview, totalling approximately 4:30 hours of audiotape, and 96 pages of transcript.

Session One (c. 1978), a documentary film, "The ACTA Scanner," explains the operating principles of the ACTA scanner, c. 1978, including:

• techniques used to convert X-ray information into images;
• demonstration of scanner operation with attention to gantry rotation and image manipulation.

Documentary is not transcribed. The original master, dubbing master, and reference copy information listed below corresponds to the film-to-videotape transfer from original 16mm color film. The original film was deposited in the Division of Medical Sciences, NMAH

Original Master: 1 Beta videotape
Dubbing Master: 1 U-Matic videotape
Reference Copy: 1 VHS videotape
Transcript: no transcription
6 minutes

Session 2 (April 6, 1989), in the Medical Imaging exhibit, NMAH, featured Ledley discussing the development of the ACTA scanner, c. 1960-1975, including:

• research in medical imaging prior to the introduction of X-ray CT imaging;
• work of other researchers in the X-ray CT field;
• principles of X-ray CT imaging;
• activities at NBRF and decision to develop scanner;
• division of labor within scanner development team;
• functions of various scanner parts.

• original ACTA scanner with close-ups of its various components;
• wood prototype of scanner;
• Ledley's original engineering notes and mechanical drawings.

• creation and history of NBRF;
• tour of office and development areas;
• demonstration of the simultaneous Hi-lo power microscope;
• demonstration of the Metachrome (automated chromosome analysis) machine;
• tour of the design areas, electronic shop, and computer facilities;
• demonstration of the V-Scan (automated chromosome analysis) machine;
• demonstration of the AGA (automated genetic analyzer) machine;
• tour of the protein database facilities;
• narration with transparencies covering the commercial production of the ACTA scanner.

• publications of NBRF;
• V-Scan machine;
• AGA machine;
• transparencies/slides of equipment.

• introduction and impact of Ledley's ACTA scanner;
• capabilities and applications of current X-ray CT scanners;
• discussion of comparative costs of various imaging modalities;
• applications of other imaging modalities at the Center's Imaging Physics Division; discussion of ethical issues affecting medical imaging;
• tour of the Center's X-ray CT facilities and procedures areas;
• demonstration of the Image Management and Communication System.

Visual documentation included:

• slides of early and contemporary CT scans;
• a complete CT scanning session with a patient.

Original Masters: 8 Beta videotapes
Dubbing Masters: 3 U-Matic videotape
Reference Copies: 2 VHS videotapes
Transcript: 61 pages
3 hours

• childhood and family life;
• interest in physics;
• dentistry training;
• work at the National Bureau of Standards;
• research and publications;
• founding of the National Biomedical Research Foundation;
• development of the ACTA scanner.