Ivo B. Gonçalves, Ana Leiria and M. M. M. Moura
Short-time Fourier transform (STFT) and different configurations of continuous wavelet transform (CWT) were tested for detection and localization embolic events. Simulated Doppler ultrasound blood flow signals of middle cerebral artery added with embolic signals and four different locations of emboli in the cardiac cycle were tested. Compared with mother wavelets for CWT analysis were Morlet, Mexican hat, Meyer, Gaussian (order 4) and Daubechies (orders 4 and 8), and the thresholds for detection (equated in terms of false positive, false negative and sensitivity) were 2 and 3.5 dB for the CWT and STFT, respectively. The results indicate that although the STFT allows accurately detecting emboli, better time localization can be achieved with the CWT. Among the CWT, the current best overall results were obtained with Mexican hat mother wavelet, with optimal results for sensitivity (100% detection rate) for nearly all emboli power values studied.