Volumetric flow measured in a laminar jet phantom using a two-dimensional speckle tracking system

A two-dimensional speckle tracking system was used to measure volumetric flow rates in a free laminar jet in vitro. The system utilized the Sum-Absolute-Difference (SAD) pattern matching algorithm to track small speckle regions between successive pulse-echo acquisitions in order to determine 2D velocities. Velocity profiles were measured across the jet diameter at a transducer angle of 90° at six flow rates from 2-12 cm/s. The profiles were then integrated, assuming a circular cross-section, to compute the volumetric flow rates. Experimental volumetric flow rates exhibited excellent agreement with actual rates (best fit line: y=1.04x-0.043, R²>0.99), with a mean error of 3.5%. Results indicate that accurate volume flow estimates can he obtained at 90°, where current uni-dimensional Doppler instruments fail, in circular free laminar jets