X-ray computed tomography: an engineering synthesis of multiscientific principles.

The discovery of X-rays in 1895 heralded a new era in the practice of medicine-visualization into the body without painful and often life-threatening surgery. The discovery was almost immediately recognized and accepted for its potential as a new medical diagnostic technique, a methodology which has been characterized by many evolutional improvements during the intervening 85 years. These advances have been perpetuated by development of more sophisticated and powerful instruments which have broadened and refined the utilization of X-rays for medical imaging. However, not until the early 1970s did any new implementation of X-ray imaging have revolutionary impact on the practice of medicine. In 1971 an X-ray scanner was developed which produced cross-sectional images of the brain by employing several different scientific concepts, some known for over 50 years. The reduction of these concepts to practice was a significant scientific achievement, and was based on a precisely engineered instrument which transmitted X-rays through the body and recorded their attenuation around 180 degrees, providing the data for computation and display of cross-sectional images of the body. Although the decade of the 1970s has seen this new technology-called X-ray computed tomography (CT)-develop and expand into several areas of application, the foremost of these remains in medical imaging whereas phenomenal evolution in capabilities of CT scanners has occured. However, the trend toward faster scanners with concomitant improvements in imaging accuracy holds promise for significant applications in basic biomedical and physiological research as well, with capabilities for quantitative analysis of anatomic-physiologic relationships and for noninvasive diagnostic body tissue examination and determination of tissue characteristics which have heretofore been possible only by surgical procedures, histological techniques, and/or pathological dissection at autopsy. This review chronicles the relatively short history of X-ray computed tomography and attempts to put in perspective the fundamental reason for its remarkable success, namely that it derives from an ingenious engineering synthesis of several well-founded principles in the basic and applied sciences.