Development of an ultrasonic system for three-dimensional reconstruction of the fetus.

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.