DOPPLER VELOCITY RATIO MEASUREMENTS EVALUATED IN A PHANTOM MODEL OF MULTIPLE ARTERIAL-DISEASE

The objective of this study was to evaluate in vitro the accuracy of t he Doppler velocity ratio (VR) (intrastenotic velocity/prestenotic or poststenotic velocity) under different geometric conditions simulating the presence of multiple stenoses. A steady flow loop model was used to test the influence of the presence of a concentric obstruction of 8 4% area reduction positioned at a distance of 10, 20 and 30 tube diame ters, either proximal or distal to the stenosis under study. The steno sis under evaluation was either concentric or eccentric and had a perc entage of area reduction ranging from 20% to 91%. An ultrasound color Doppler system was used to perform both pulsed-wave (PW) Doppler and c olor-flow velocity measurements. VRs were computed by dividing the max imum velocity of the jet by the velocity at 6 and 10 diameters both pr oximal and distal to the stenosis under study. A strong correlation wa s obtained between VR computed using color flow and PW Doppler velocit ies (r = 0.99). Results indicated that using the prestenotic velocity as a reference velocity generally provided a more sensitive VR index t o grade arterial stenosis than using the poststenotic velocity. From a curve fit model, the measured percentages of stenosis were calculated from the VR data and compared to the true percentages. The correlatio n coefficient, r, was 0.95. When the proximal and distal stenoses were at 10 diameters of the stenosis investigated, r was 0.91, while it in creased to 0.98 when the distance was 20 diameters or more. Although V R is theoretically not influenced by hemodynamic factors, we demonstra ted that, in practice, the presence of multiple stenoses reduced its s ensitivity. Volumetric flow measurements are suggested to obviate this limitation.