The history of real time ultrasound

Abstract This paper deals with real time two-dimensional ultrasonic imaging. In the early 1960s, one of the most important applications of ultrasound was to the brain. With the A-scan, the main aim was to detect any midline shift, in order to determine some space occupying object. Any other echo was usually difficult to recognize. Manual or mechanical scanning turned out to be inadequate for producing meaningful pictures of the brain. In this situation, it seemed quite logical that a viable two-dimensional scanning system for the brain had to answer at least the two principal requirements that made the A-scan successful: the real time feature and the small probe size. A possible solution appeared to be the concept of electronic sector scanning, later also called phased array technique. The first prototype that we developed, Electroscan I, was demonstrated in 1967 (Erlangen and Stockholm) by means of a film which showed simultaneously a moving metal bar in water and its instantaneous echoes. Later, in 1969 (Vienna), real time images of the brain through the intact skull were shown. Nowadays, in cardiology, phased array sector scanners are used almost exclusively. The latest developments in real time scanners concern three-dimensional (3-D) imaging. Thanks to the incredible progress in digital and chip technology, such systems are now already commercially available. The first linear array systems appeared in 1971.