A coded cephalometer for interactive multiple measurements of biparietal diameter

A coded cephalometer is described which allows multiple interactive independent measurements of the fetal biparietal diameter at one examination and comparative multiple measurement trials on the same patient using different equipments. The principles of the system are described, and in particular the methods of coding the displayed values and randomising the marker positions. The cephalometer may be used with either a real time scanner or a conventional B scanner for both the assessment of performance and the training of operators.