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Aims: To validate Echo Particle Image Velocimetry (PIV)Methods: String and rotating phantoms with different speed patterns were imaged with high-end ultrasound systems at varying insonation angles and frame rates. Images were analyzed for velocity and direction and for complex motion patterns of blood flow with dedicated software. Post-processing was done with MATLAB-based tools (Dflow, JUV, University Leuven).Results: Velocity estimation was accurate (r=0.99, p<0.001, mean difference 0.4±2 cm/s). Maximally detectable velocity was dependent on frame rate and insonation angle and reached 42 cm/s under optimal conditions. At higher velocities estimates became random. Direction estimates did not depend on velocity and were accurate in 80-90%. Motion patterns were correctly identified with three ultrasound systems.Conclusion: Echo-PIV appears feasible. Velocity estimates are accurate, but the maximal detectable velocity depends on imaging settings. Direction estimation works sufficiently, even at high velocities. Echo-PIV may be used in different ultrasound systems for flow assessment, particularly if the patterns of flow are investigated.