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Session: Poster session II
Session starts: Thursday 24 January, 16:00

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Jason Voorneveld (Biomedical Engineering, Thorax Center, Erasmus MC)
Hicham Saaid ()
Christiaan Schinkel ()
Antonius van der Steen ()
Frank Gijsen ()
Nico de Jong ()
Tom Claessens ()
Sasa Kenjeres ()
Johan Bosch ()

Abstract:
Left ventricular (LV) blood flow is a promising early stage biomarker of ventricular dysfunction. However, blood flow in the LV is a 3D phenomenon and current clinical measurement techniques are limited to 1D /2D. Echo-particle image velocimetry (echo-PIV) can be used to measure 3D blood flow patterns but requires high frame rates to effectively track the fast flows expected in the LV. We use a prototype transesophageal (TEE) matrix probe, capable of 3D high volume rate (4 kHz) imaging and test the capabilities of 4D echo-PIV in a realistic and dynamic LV phantom. A compliant, optically and acoustically transparent silicone LV chamber, encased in an acrylic box, was fitted with bio-prosthetic mitral and aortic valves (Edwards), connecting to atrial and compliance chambers. The system uses a piston pump (ViVitro) to impose pressure and volume changes in the acrylic box, causing realistic flow patterns to circulate inside the LV. The ‘ground truth’ flow patterns in the LV are captured using tomographic PIV, a 3D optical velocimetry technique with very high spatial (12.4 pixel/mm) and temporal (2000 fps) resolution. Using the TEE matrix probe (Oldelft, 5 MHz), connected to a Verasonics Vantage 256, single diverging waves were transmitted to insonify a field of view of 24 x 24° up to a depth of 10 cm. Nine overlapping beams were acquired in a gated sequence with the pump cycle to obtain the full field of view of the LV without reducing frame rate. Ultrasound contrast agent (SonoVue, 20µl/l) was added for visualizing LV flow. Echo-PIV was then performed in the spherical domain using normalized cross correlation with a kernel size of 5.7mm x 12° x 12° and an overlap of 50% x 75% x 75%, resulting in a vector map resolution of 2.5mm x 3° x 3°. The vector maps obtained with echo-PIV were then qualitatively compared to the tomographic PIV results. The high velocity trans-mitral jet velocities of ~1 m/s could be captured by 4D-echo-PIV although there was still some underestimation present, especially in the lateral directions. This phantom is a useful tool for further optimization of echo-PIV.