Seungik Baek

The Withrow Distinguished Scholar Award

2013

NSF CAREER Award

2012

MSU Intramural Research Grants Program (IRGP) Award

2007

Texas A&M University

PhD

Mechanical Engineering

2003

Seoul National University

BS

Biosystem Engineering

1996

The Impact of Prestretch Induced Surface Anisotropy on Axon Regeneration

Chun Liu, Ryan Pyne, Jungsil Kim, Neil Thomas Wright, Seungik Baek, and Christina Chan

2016

Nerve regeneration after spinal cord injury requires proper axon alignment to bridge the lesion site and myelination to achieve functional recovery. Significant effort has been invested in developing engineering approaches to induce axon alignment with less focus on myelination. Topological features, such as aligned fibers and channels, have been shown to induce axon alignment, but do not enhance axon thickness. We previously demonstrated that surface anisotropy generated through mechanical prestretch induced mesenchymal stem cells to align in the direction of prestretch. In this study, we demonstrate that static prestretch-induced anisotropy promotes dorsal root ganglion (DRG) neurons to extend thicker axon aggregates along the stretched direction and form aligned fascicular-like axon tracts. Moreover, Schwann cells, when cocultured with DRG neurons on the prestretched surface colocalized with the aligned axons and expressed P0 protein, are indicative of myelination of the aligned axons, thereby demonstrating that prestretch-induced surface anisotropy is beneficial in enhancing axon alignment, growth, and myelination.

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Association of Intraluminal Thrombus, Hemodynamic Forces, and Abdominal Aortic Aneurysm Expansion Using Longitudinal CT Images

Byron A. Zambrano, Hamidreza Gharahi, ChaeYoung Lim, Farhad A. Jaberi, Jongeun Choi, Whal Lee, Seungik Baek

2015

While hemodynamic forces and intraluminal thrombus (ILT) are believed to play important roles on abdominal aortic aneurysm (AAA), it has been suggested that hemodynamic forces and ILT also interact with each other, making it a complex problem. There is, however, a pressing need to understand relationships among three factors: hemodynamics, ILT accumulation, and AAA expansion for AAA prognosis. Hence this study used longitudinal computer tomography scans from 14 patients and analyzed the relationship between them. Hemodynamic forces, represented by wall shear stress (WSS), were obtained from computational fluid dynamics; ILT accumulation was described by ILT thickness distribution changes between consecutives scans, and ILT accumulation and AAA expansion rates were estimated from changes in ILT and AAA volume. Results showed that, while low WSS was observed at regions where ILT accumulated, the rate at which ILT accumulated occurred at the same rate as the aneurysm expansion. Comparison between AAAs with and without thrombus showed that aneurysm with ILT recorded lower values of WSS and higher values of AAA expansion than those without thrombus. Findings suggest that low WSS may promote ILT accumulation and submit the idea that by increasing WSS levels ILT accumulation may be prevented.

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Computational fluid dynamic simulation of human carotid artery bifurcation based on anatomy and volumetric blood flow rate measured with magnetic resonance imaging

Hamidreza Gharahi, Byron A. Zambrano, David C. Zhu, J. Kevin DeMarco, Seungik Baek

2016

Blood flow patterns and local hemodynamic parameters have been widely associated with the onset and progression of atherosclerosis in the carotid artery. Assessment of these parameters can be performed noninvasively using cine phase-contrast (PC) magnetic resonance imaging (MRI). In addition, in the last two decades, computational fluid dynamics (CFD) simulation in three dimensional models derived from anatomic medical images has been employed to investigate the blood flow in the carotid artery. This study developed a workflow of a subject-specific CFD analysis using MRI to enhance estimating hemodynamics of the carotid artery. Time-of-flight MRI scans were used to construct three-dimensional computational models. PC-MRI measurements were utilized to impose the boundary condition at the inlet and a 0-dimensional lumped parameter model was employed for the outflow boundary condition. The choice of different viscosity models of blood flow as a source of uncertainty was studied, by means of the axial velocity, wall shear stress, and oscillatory shear index. The sequence of workflow in CFD analysis was optimized for a healthy subject using PC-MRI. Then, a patient with carotid artery stenosis and its hemodynamic parameters were examined. The simulations indicated that the lumped parameter model used at the outlet gives physiologically reasonable values of hemodynamic parameters. Moreover, the dependence of hemodynamics parameters on the viscosity models was observed to vary for different geometries. Other factors, however, may be required for a more accurate CFD analysis, such as the segmentation and smoothness of the geometrical model, mechanical properties of the artery’s wall, and the prescribed velocity profile at the inlet.

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