Estimation of Blood Flow Parameters Using Pulse Doppler Ultrasound with Corrections for Spectral Broadening.

Significant errors in quantitative measurement of blood flow using pulse Doppler ultrasound may occur if the effects of frequency dependent attenuation of ultrasound in tissue and scattering of ultrasound in blood are neglected. These effects cause distortion of an ultrasonic pulse as it propagates through tissue and is back scattered by moving blood. Therefore, estimates of blood flow parameters based upon ultrasonic echoes which have been affected by these frequency dependent mechanisms will be in error. Based upon a theoretical model of the interactions of ultrasound with tissue and blood, the estimation of blood flow parameters by pulse Doppler ultrasound is formulated here as a non-random parameter estimation problem. A maximum likelihood estimation scheme which compensates for frequency dependent attenuation and scattering of ultrasound in tissue and blood has been developed. This estimator has been implemented using a prototype digital pulse Doppler system designed and constructed for this purpose. Experimental results obtained using this system are presented along with theoretical aspects of the estimation problem and transmit waveform design.