50 years real-time electronic sector scanning

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In the early sixties many pioneers investigated the possibilities of ultrasound pulse-echo techniques for diagnostic purposes. The main areas were neurology, gynaecology & obstetrics, radiology and ophtalmology. The Institute of Medical Physics where I was employed had close connections with some neurologists pioneering in ultrasound for brain diagnostics. The experts often were relatively successful as far as it concerned A-scan. In contrast to this, attempts to obtain useful results with B-scan were very disappointing. I was convinced that the relative success of A-scan, in spite of its one-dimensional character, was due to the fact that A-scan is a true real-time system. That makes searching for the best picture possible by moving the probe slightly while observing the result simultaneously. The trials with all kinds of mechanical B-scan systems, in order to obtain two-dimensional pictures, suffered from the fact that one sees the result only after the scan is completed. The results were extremely disappointing for brain imaging, mainly due to irregularly shaped skull bone and its high absorption. I was absolutely convinced that two-dimensional scanning at a high repetition rate and with an essentially stationary probe would provide superior results. Observing moving objects, like the heart, would probably become possible. Both for brain and heart a probe with a small “footprint” is essential, as was the case already with A-scan equipment. In 1964 we decided to explore if such a new system is feasible. We would then have a fast B-scan system comparable with A-scan but with the vital difference that it is two-dimensional and real-time. We started to develop such a system of which the first prototype, the Electroscan, became operational in the beginning of 1969. It was able to produce real time ultrasound images in the form of a sector of 90 degrees, divided in 32 different directions, and with a scanning rate of 30 frames per second. This system was published at the 1st World Congress of the WFUMB in Vienna, 1969. This obviously explains the title of this lecture. We can say now that the success of electronic sector scanning has been enormous. It is applied in numerous medical areas. In echo-cardiography, for instance, the use of “phased array” has become almost exclusive. The Electroscan was developed in a period in which the computer and chip technology were relatively at a poor level. The fact that nowadays even 3-dimensional real-time scanners exist shows clearly how much ‘good ideas’ are dependant on technical developments.