Novel intelligent wavelet filtering of embolic signals from TCD ultrasound

Abstract

Transcranial Doppler ultrasound can be used to detect emboli in blood flow for predicting stroke. Embolic signals 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 8th order wavelet to amplify embolic signals. Even the smallest embolic signal is enhanced without affecting the background blood flow signal. We show an increase of over 2db (on average) in embolic signal strength and an improvement in detection of 10-20%.