On processing of Doppler returns from the foetal heart: An electronic processing method for extraction of valvular timing information

An electronic processing scheme intended for use in conjunction with a multicrystal ultrasonic array to measure cardiac intervals in the human foetus is described. This new processing method possesses sufficient signal extraction capability to allow the time of opening of the aortic valve to be determined and tracked. Application of this method to a pulsed Doppler and continuous wave Doppler system is discussed. Features include amplitude independent detection, rapid response time and excellent frequency selectivity. Laboratory and clinical test results are presented that demonstrate the viability of an instrument based on this principle.