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research-article

Optimized Time-Resolved Echo PIV-PTV Measurements Elucidate Blood Flow in Patients with Left Ventricular Thrombus

[+] Author and Article Information
Kaushik Sampath

Department of Mechanical Engineering, Johns Hopkins University, 3400 N Charles St, Latrobe 223, Baltimore, MD 21218
kaushik@jhu.edu

Thura T Harfi

Division of Cardiology, Department of Medicine, Johns Hopkins University, 600 N Wolfe St, Baltimore, MD 21287, USA
thura.harfi@gmail.com

Ricard/T George

Division of Cardiology, Department of Medicine, Johns Hopkins University, 600 N Wolfe St, Baltimore, MD 21287, USA
rtgeorge3@gmail.com

Joseph Katz

Department of Mechanical Engineering, Johns Hopkins University, 3400 N Charles St, Latrobe 122, Baltimore, MD 21218
katz@jhu.edu

1Corresponding author.

ASME doi:10.1115/1.4038886 History: Received May 15, 2017; Revised December 19, 2017

Abstract

Contrast ultrasound is a widely used clinical tool to obtain real-time qualitative blood flow assessments in the heart, liver, etc. Echocardiographic particle image velocimetry (echo-PIV) is a technique for obtaining quantitative velocity maps from contrast ultrasound images. However, unlike optical PIV, routine echo images are prone to non-uniform spatiotemporal variations in tracer distribution, making analysis difficult for standard PIV algorithms. This study introduces optimized procedures that integrate image enhancement, PIV and particle tracking velocimetry (PTV) to obtain reliable time-resolved 2D velocity distributions. During initial PIV analysis, multiple results are obtained by varying processing parameters. Optimization involving outlier removal and smoothing is used to select the correct vector. These results are used in a multi-parameter PTV procedure. To demonstrate their clinical value, the procedures are implemented to obtain velocity and vorticity distributions over multiple cardiac cycles using images acquired from four left ventricular thrombus (LVT) patients. Phase averaged data elucidate flow structure evolution over the cycle and are used to calculate penetration depth and strength of LV vortices, as well as apical velocity induced by them. Present data are consistent with existing[1] time-averaged minimum vortex penetration associated with LVT occurrence. However, due to decay and fragmentation of LV vortices, as they migrate away from the mitral annulus, in two cases with high penetration, there is still poor washing near the resolved clot throughout the cycle. Hence, direct examination of entire flow evolution may be useful for assessing risk of LVT relapse before prescribing anticoagulants.

Copyright (c) 2017 by ASME
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