Robert S. Ledley

Robert S. Ledley invented the whole-body CT (computerized tomographic) diagnostic X-ray scanner. Born in New York City, Ledley earned a D.D.S. from New York University in 1948 and an M.A. from Columbia University in 1949. Eventually, he became professor of physiology, biophysics, and radiology at the Georgetown University Medical Center.

Ledley is best known for the ACTA (Automatic Computerized Transverse Axial) diagnostic X-ray scanner, the first whole-body computerized tomography (CT) machine. The ACTA Scanner set the basic design for modern CT scanners, including the first use of the convolution method for CT-image reconstruction, the first high-resolution digital TV display for medical imaging, and the tilting gantry. Ledley also revolutionized diagnostic medicine by doing medical imaging and three-dimensional reconstructions using CT in radiation therapy planning and in the diagnosis of bone diseases.

In addition to the ACTA scanner, Ledley patented the image processor and wrote the first comprehensive textbook for engineers on digital computer engineering. He also developed the computational methods in Boolean algebra, used in digital circuit design. In 1960, he founded the National Biomedical Research Foundation, and he has also served as editor of several peer-reviewed scientific journals.