Application of semiconductor strain gauge for continuous measurement of intracranial pressure.

In order to record intracranial pressure continuously, we have recently developed a microminiature pressure transducer using semiconductor strain gauges. The pressure cell has a small disk-shaped structure, and it can be directly inserted into the intracranial cavity through a small burr hole. Previous investigations of the semiconductor strain gauge have dealt almost exclusively with the field of technology. In 1954, the first piezoresistive measurements for semiconductors were made in connection with a basic research for the transistor technology. Shortly after the original measurements, efforts were made toward applications. One of us, Igarashi, studied the piezoresistive semiconductor strain gauges of Germanium and Silicon in 1956 6l 7J , and devised a miniature pressure cell in 1965 for the purpose of measuring the pressure in the technological field 1l . The semicondutctor strain gauge is generally small in size. Although it has about 70 times higher sensitive gauge factor than that of the wire strain gauge, the former is affected by temperature about 10 times more than that of the latter. It might be, therefore, adopted into the living body as a device for measuring intracranial pressure, if only the compensation for temperature effects is ascertained. In this paper , a newly devised microminiature pressure cell is introduced and its clinical as well as experimental use is demonstrated.