Flow quantification in valvular heart disease based on the integral of backscattered acoustic power using Doppler ultrasound

The noninvasive quantification of pathologic backflow referred to as regurg itant flow, associated with valvular heart disease has been an elusive medi cal goal. To dare, techniques based on ultrasound have been unsatisfactory due to weak assumptions and indirect estimations. Here, instead, we propose to estimate regurgitant flow directly front the Doppler spectrum of the ba ckscattered ultrasound. Since backscattered spectral power is proportional to the sonified blood volume and spectral frequency is directly related to velocity, power times velocity should be proportional to flow. To date, how ever; investigators have assumed this held only for laminar flow, not for r egurgitant jets in which turbulence augments backscatter. We demonstrate th at this challenge can be overcome by analyzing the Doppler spectrum at the origin of the regurgitant jet, where flow is laminar since turbulence has n ot vet developed. We present in vitro and in vivo data that demonstrate tha t there is a linear proportionality between regurgitant flow and the integr al of Doppler power rimes velocity (PVI). Power measurements were also cali brated by applying a dual-beam technique, providing absolute values of flow rate and volume in vivo. In our work we demonstrate that in patients with valvular heart disease, th is new PVI technique allows for the measurement of regurgitant pow directly and noninvasively for the first time, overcoming the limitations of curren t techniques.