The Application of Wavelet Transforms to Blood Flow Velocimetry
This chapter presents a technique for blood flow velocimetry using wavelet transforms and wideband signals. Ultrasonic signals with high fractional bandwidths and large time-bandwidth products are processed with wideband/wavelet transform methods. This approach removes many of the narrowband assumptions typically invoked when measuring blood flow. The received signals are assumed to be reflected from particles moving in the blood stream. Instead of measuring the Doppler shift associated with the reflection, the time-scaling of the signal is obtained along with the round trip travel time of the signal. This time-scaling more accurately reflects the effects of motion on the signals than does a Doppler shift since a Doppler shift is an approximation to time-scaling. The continuous wavelet transform is then used to obtain the axial velocity of scatterers.