DISTANCE OF FETAL MOVEMENT MEASURED USING THE ANALYTICAL SIGNAL DERIVED FROM NON-DIRECTIONAL DOPPLER SOUND

Foetal Heart Rate (FHR) monitoring using the Doppler shift resulting f rom the movements of the foetal heart is a standard examination in mos t obstetrical wards. Other movements also give rise to a low frequency Doppler shift. These signals are incompletely understood. Their chara cteristics may offer a way for diagnostic exploitation through complem enting or replacing time consuming ultrasound observation of foetal mo vements. It is shown that a wealth of information is contained in thes e signals which can easily be extracted on line by a standard PC compu ter using straightforward methods of signal processing. In its amplitu de an ultrasonic Doppler signal contains information concerning the si ze of the reflector in movement and speed as frequency. The displaceme nt of the reflector can also be derived from the phase evolution of a complex Doppler signal. Examples of signals generated by various types of foetal activity are shown and analyzed. (C) 1998 IPEM. Published b y Elsevier Science Ltd. All rights reserved.