MEASUREMENT OF FETAL MOVEMENTS USING MULTICHANNEL ULTRASOUND PULSED DOPPLER - AUTORECOGNITION OF FETAL MOVEMENTS BY MAXIMUM-ENTROPY METHOD

Changes in fetal movements indicate biophysical conditions and functio nal development The precise evaluation of fetal movements in clinical medicine requires the development of a continuous automated monitoring technique. A basic study of the measurement of fetal movements was ca rried out by modifying the Doppler ultrasound module of a cardiotocogr aph to produce low-frequency Doppler signals and five simultaneous out puts at various depths. These outputs represent displacement inside ti ssue at the various depths. Signal processing was executed on a 32-bit computer with a high-accuracy displacement estimation technique using the arc-tangent method. Results showed successful tracking of minute movements, such as fetal breathing movements (FBM), while rejecting ot her movements derived from maternal breathing etc. Using spectral anal ysis by the maximum entropy method (MEM), fetal movements were classif ied in three groups (FBM, fetal gross movements (FGM) and fetal heart movements (FHM)), based on the character of their special peak frequen cies. The order of movement recognition was first FGM, then FBM and la stly FHM. FBM were more successfully recognised by MEM than by convent ional B-mode observation methods. Small body movements were difficult to recognise as FGM by MEM in some cases. Although further studies are required for clinical application, it appears that automated assessme nts of fetal movements should be possible with this technique.