Hudson Arthur C, Trollope Brian J: Echoencephalograph. Canadian Patents and Development, Rymek Edward, March 25, 1975: US3872858 (20 worldwide citation)

This echoencephalograph applies an ultrasonic pulse to the patient's head, the pulse travels to a predetermined structure and is partially reflected as an echo pulse. The travel time is determined and a digital display indicates the distance from the outside of the patient's head to the predetermine ...