DETERMINATION OF PRESTENOTIC FLOW-VOLUME USING AN AUTOMATED-METHOD BASED ON COLOR DOPPLER IMAGING FOR EVALUATING ORIFICE AREA BY THE CONTINUITY EQUATION - VALIDATION IN A PULSATILE FLOW MODEL

Objective-To evaluate, in a pulsatile flow model simulating flow condi tions in valvar stenoses, whether accurate determination of orifice ar ea can be achieved by the continuity equation using automated determin ation of flow volumes based on spatiotemporal integration of digital c olour Doppler flow velocities. Methods-A method for automated determin ation of flow volumes which takes into account the velocity distributi on across a region of interest was examined using flow through a tube and various restrictive outlet orifices with areas ranging between 0.2 and 3.1 cm(2). the sampling rectangle of the Doppler method was posit ioned proximal to the obstructions within the flow convergence zone fo r evaluating prestenotic flow volume. Stenotic jet velocities were rec orded by continuous wave Doppler to obtain the integral under the velo city curve. Prestenotic flow volume was then divided by the velocity i ntegral to calculate functional orifice area according to the continui ty equation. Results-The presence of parabolically shaped velocity pro files across the prestenotic region was demonstrated by the Doppler me thod. Excellent agreement was found between prestenotic flow volumes a ctual values (r = 0.99, SEE = 1.35 ml, y = 0.99x-0.24). Use of the con tinuity equation led to a close correlation, with a orifice sizes. Cor rection of Doppler data for flow contraction yielded an excellent agre ement with actual orifice areas. Conclusions-The study validated the a ccuracy of a Doppler method for automated determination of flow volume s for quantifying orifice area by the continuity equation. Prestenotic flow volume and functional orifice area could be evaluated reliably i n the presence of non-flat velocity profiles. Thus the method contribu tes to the non-invasive assessment or valvar stenoses.