Amplitude and phase estimator for real-time biomedical spectral Doppler applications

In a typical echo-Doppler investigation the moving blood is periodically insonated by the transmitting bursts of ultrasound energy. The echoes, shifted in frequency according to the Doppler effect, are received, coherently demodulated and processed through a spectral estimator. The detected frequency shift can be exploited for blood velocity assessment. The spectral analysis is typically performed by the conventional Fast Fourier Transform (FFT), but, recently, the application of the Amplitude and Phase EStimator (APES) was proved to produce a good quality sonogram based on a reduced number of transmissions. Unfortunately, the much higher calculation effort needed by APES hampers its use in real-time applications. In this work, a fixed point DSP implementation of APES is presented. A spectral estimate - based on 32 transmissions - occurs in less than 120μs. Results obtained on echo-Doppler investigations on a volunteer are presented.