In vitro validation of volumetric blood flow measurement using Doppler flow wire

Determination of any volumetric blood flow requires assessment of mean bloo d flow velocity and vessel cross-sectional area. For evaluation of coronary blood flow and flow reserve, however, assessment of average peak velocity alone is widely used, but changes in velocity profile and vessel area are n ot taken into account. We studied the feasibility of a new method for calcu lation of volumetric blood flow by Doppler power using a Doppler flow wire. An in vitro model with serially connected silicone tubes of known lumen di ameters (1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mm) and pulsatile blood flow rangi ng from 10 to 200 mL/min was used. A Doppler flow wire was connected to a c ommercially available Doppler system (FloMap(R), Cardiometrics) for online calculation of the zeroth (M-0) and the first (M-1) Doppler moment, as well as mean flow velocity (V-m). Two different groups of sample volumes (at di fferent gate depths) were used: 1. two proximal sample volumes lying comple tely within the vessel were required to evaluate the effect of scattering a nd attenuation on Doppler power, and 2. distal sample volumes intersecting completely the vessel lumen to assess the vessel cross-sectional area. Area (using M-0) and V-m (using M-1/M-0) obtained from the distal gates were co rrected for scattering and attenuation by the data obtained from the proxim al gates, allowing calculation of absolute volumetric how. These results we re compared to the respective time collected flow. Correlation between time collected and Doppler-derived flow measurements was 0.98 (p < 0.0001), wit h a regression line close to the line of equality indicating an excellent a greement of the two measurements in each individual tube. The mean paired f low difference between the two techniques was 1.5 +/- 9.0 mL/min (ns). Dire ct volumetric blood flow measurement from received Doppler power using a Do ppler flow wire system is feasible. This technique may potentially be of gr eat clinical value because it allows an accurate assessment of coronary flo w and flow reserve with a commercially available how wire system. (C) 2000 World Federation for Ultrasound in Medicine & Biology.