1Gunma University, Faculty of Engineering, 2Faculty of Medicine, Tokyo University
Fetal movement, Doppler, Measurement
It is well known that fetal movement is one of the most useful parameters in the diagnosis of fetal well-being. Several methods have been proposed to observe the fetal movements. For example, movements were measured from the change of intensity at the proper position on the M-mode image. Another method used variation of the Doppler detection signals to detect fetal movements. However, it is difficult to measure the fetal movements quantitatively using these methods. In this paper, aimed at measuring the fetal movements with high accuracy, a new method is proposed. In this method, based on the use of the ultrasonic pulsed Doppler technique, the fetal movements are calculated from the phase variation of the received ultrasonic waves. This system has the following features. 1) It uses a new method which can reduce effectively the estimation error due to the random structures of the scatterers. 2) The displacements of the fetal movements can be measured at multiple points. This may allow simultaneously monitoring of both fetal movements and fetal heart rate. 3) It uses a circular type small ultrasonic transducer which can be attached easily to the mother's abdomen. In this paper, the signal processing methods used in the system are discussed and the construction of the system is presented. The basic experimental results which were obtained using the constructed system are shown.