TABLE OF CONTENTS The first major development in medical electronics was the discovery of X-rays by the German physicist, Wilhelm Roentgen, in 1895. He was experimenting with a rather crude cathode-ray tube when he discovered that mysterious rays had penetrated soft materials and left shadow profiles of the bones of his hand on a fluorescent screen. He called them X-rays because, at that time, they were not known to be short-wave electromagnetic radiation. This discovery made possible, for the first time, the nonintrusive examination of the internal organs of living persons, so it had far-reaching implications for scientific and medical research.
Subsequent developments in X-ray machines improved the resolution of X-ray radiograms while minimizing patient exposure to the dangerous rays. More recently closed-circuit television, multicolor CRTs, and computers have made it possible to enhance the basic radiogram with digital signal processors and software algorithms that produce video "slices" or section views of living organs. The technique, known as computed tomography or CT scanning, provides color-coded images to highlight specific internal body functions.
The images are formed from data taken from a circular array of sensors surrounding a rotating X-ray scanner. Further data processing can yield three-dimensional views of human organs such as the brain or heart for further study or analysis.
Another noteworthy advance in medical instrumentation was made when it was found that atoms in living tissue will emit resonant RF signals in the presence of strong magnetic fields and radio waves. This led to the invention of
