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World's First High-Resolution Electronic Scanning Type Ultrasound Diagnostic Equipment

Toshiba's development of an original electronic linear scanning system for the abdominal region and an electronic sector scanning system for the heart provided greatly improved resolution compared with conventional products.

World's First High-Resolution Electronic Scanning Type Ultrasound Diagnostic Equipment

Ultrasound diagnostic equipment uses an ultrasound beam to scan the interior of the human body by means of a probe applied to the body surface, and displays cross-sectional images of the internal organs. From the brief lapse of time required for the ultrasound beam emitted by the probe to be reflected from each layer of an internal organ, distances are calculated and processed as image data. In 1971, the Electronic Device Research Laboratory of the Research and Development Center (currently the Corporate Research & Development Center) started conducting research on how to represent the moving internal organs of the body as image data.

The first prototype electronic linear scanning system for gallbladder examinations was completed in 1975, with the simple target of visualizing gallstones. However, although the system obtained clear images of a hollow experimental sponge, problems were encountered when visualizing a gallbladder. There were large variations in the sensor transmission and receiving properties and in the characteristics of the probe circuit components, and the design of the system for increasing the resolution was also found to be insufficient. These experiences revealed that it would be difficult to commercialize a product, but when another company started to sell electronic scanning type diagnostic equipment at around the same time, the urgent need to achieve commercialization became apparent. As the mission of the Research and Development Center was to connect original research to business opportunities, it was decided that full-scale efforts would be devoted to commercializing an original system.

The images produced by the product already released by the other company were not clear enough to be used for medical diagnosis, so we decided to develop an electronic linear scanning system for the abdominal region with high resolution that no other company possessed. Various technologies were incorporated into the system including subdicing, which reduced image-degrading sidelobes to 1/100 their former level; electron convergence, which converged the ultrasound beam within the surface of the region being scanned; the use of a small-angle sector, which doubled the scanning line density; and an integrated cutting method, which made it possible to uniformly manufacture the array oscillators with their electrodes. Also, with commercialization in mind, the properties of the components and circuits were thoroughly investigated to ensure the consistent performance of all channels at all times.

In 1976, the second prototype was completed and tested in a joint research project with the Kanto Central Hospital. The newly developed system successfully accomplished visualization including gallstones moving in a gallbladder and a fetus moving in the body of an expectant mother. Vivid images were obtained that had never been seen before, and one of the participating doctors reported that he was so moved by the experience that he started shaking. In August the same year, the first product (SAL-10A) attracted considerable attention when it was exhibited at the World Congress on Ultrasound in Medicine and Biology in San Francisco. It was then demonstrated at various hospitals in the U.S., where it received high evaluations for its remarkable image quality. After that, that SAL-20A model was developed as a much more compact version and sold throughout the world. The SAL-20A was widely acclaimed for its superior features, and was also exhibited at the U.S. Smithsonian Institution.

In addition to linear scanning of the abdominal region, there is another ultrasound beam scanning method called sector scanning. This performs scanning as though looking through a gap in the body at the heart surrounded by the lungs and ribs. In 1976, when our company developed the electronic linear scanning system for the abdominal region, another company commercialized an electronic sector scanning system for the heart. However, some of the components of that product had to be adjusted at the time of operation and it was not yet sufficiently useful as a finished product. We decided to create our own sector scanning type ultrasound diagnostic equipment that would be simple and require no adjustments as a basic policy, and started the development work. The key technology in this case was a variable delay circuit, which was necessary for sector scanning. Trial manufacturing was carried out with cooperation from a components group, but the circuitry was complicated and commercialization was abandoned for some time. Later, however, the concept of a read-only memory (ROM)-controlled delay line with high accuracy and a simple configuration was born, and the equipment was completed in May 1977.

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