Lora G. Weiss
Appl. Res. Lab., Penn State Univ., State College, PA 16804
The goal of blood flow velocimetry is to obtain an accurate measurement of the velocity of the blood as it flows through a blood vessel. If the measurement technique underestimates the blood flow velocity, then the measurement may appear normal and an occlusion may go undetected. To prevent an incorrect diagnosis, new methods for blood flow velocimetry are needed. This paper presents a technique for blood flow velocimetry using wavelet transforms, and it compares this technique to the conventional narrow-band Doppler methods often applied. Ultrasonic signals with high fractional bandwidths and/or large time-bandwidth products are processed with wavelet transforms. By applying wavelet transforms, many narrow-band assumptions typically invoked when measuring blood flow may be removed. With the wavelet method presented, instead of measuring the Doppler shift associated with the reflection of a signal, the time-scaling of the signal is obtained along with the round trip travel time. 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.