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The ultrasonic diagnostic devices available at present can only represent one section of the fetus. We have developed a system for three-dimensional reconstruction of the ultrasonic fetal image in order to facilitate the understanding of the 3-D structure of the fetus and also to make 3-D recordings of this image. Either a real-time linear array probe or a convex array probe of the ultrasonic scanner was mounted on a position sensing arm of a manual compound scanner in order to detect the position of the probe. A microcomputer was used to convert the positional information to a recording of a visual image of videotape. This image was superimposed onto the ultrasonic tomographic image simultaneously using a superimposer and was recorded on the video tape, thereafter, being recalled by the image processing minicomputer. The minicomputer VAX11/780 (DEC) system was used for 3-D reconstruction and 3-D display. In the memory system the image of the anterior uterine wall was identified and subsequently excluded in order to visualise the fetus more clearly. The threshold of brightness was set to a high level so that the fetus could be separated from the amniotic fluid. The fetus was displayed three-dimensionally using computer graphics. Using this system, we have made it possible to observe the whole image of the fetus in utero non-invasively. This system offers a method for easier understanding of the 3-D structure of the fetus in utero and also makes 3-D recording possible. In the future, we confidently expect that this system will be used for screening for fetal anomalies and abnormalities of fetal growth.
Baba et al. (Sun,) studied this question.