Novel intelligent wavelet filtering of embolic signals from TCD ultrasound

Transcranial Doppler ultrasound can be used to detect emboli in blood flow for predicting stroke. Embolic signals (ES) have characteristic transient chirps suitable for wavelet analysis. We have implemented and evaluated the first on-line intelligent wavelet filter to amplify embolic signals building on our previous work in detection. Our intelligent wavelet amplifier uses the matching filter properties of the Daubechies 8/sup th/ order wavelet to amplify ES. Even the smallest ES is enhanced without affecting the signal due to the blood flow. We show an increase of over 2 db (on average) in ES strength and a significant improvement in detection accuracy.