1J-2 Development of a Customized Echo Particle Image Velocimetry System for Real Time Multi-component Hemodynamics Measurements: System Characterization and Initial Experiments

The measurement of multi-component temporal blood velocity and shear stress distributions in the cardiovascular system is important in hemodynamic evaluation of patients with various cardiovascular diseases since changes in local flow patterns may reflect development and progression of pathology. Here, we report on a custom designed echo particle image velocimetry (Echo PIV) system, with improved dynamic velocity range and spatial resolution over prior systems, to perform real time non-invasive measurement of multi-dimensional velocity and shear stress components in arteries and hearts by identifying and tracking flow tracers (ultrasound contrast microbubbles) within the flow fields. The customized Echo PIV system was developed with a novel linear ultrasound array transducer (128 elements, 7.5 MHz center frequency, 73% bandwidth), a custom-controllable signal processing system and custom PIV analysis. The maximum achievable frame rate of the system is 1786 fps, which allows maximum velocities up to 2.14 m/s to be measured. Initial in vitro measurements were made on pipe flows, simulating flow in blood vessels and in vitro models simulating abdominal aortic aneurysms (AAA). Ultrasound Doppler measurements of peak velocity were also taken in the pipe flow studies for comparison. Echo PIV measured velocities agreed well with Doppler measurements with a maximum deviation of 3.6%. The Echo PIV system also captured successfully the vortex rings in AAA models and the corresponding shear stress distributions in these flow fields. Such multi-component velocity measurements are clinically unfeasible using conventional ultrasound Doppler flow imaging