Retta El Sayed^1,2, Alireza Sharifi², Charlie Park², Diogo Haussen³, Jason Allen^1,2,3, and John N Oshinski^1,2
1Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, GA, United States, ²Department of Radiology & Imaging Sciences, Emory University, Atlanta, GA, United States, ³Department of Neurology, Emory University, Atlanta, GA, United States

Carotid webs (CaWs) have been linked to cryptogenic strokes and therefore quantifying different hemodynamic parameters is essential to understand the mechanism of clot formation in patients. Computational fluid dynamics (CFD) based on patient-specific geometry and PCMR inlet flow conditions was conducted on five subjects with CaWs, five subjects with mild atherosclerosis (with a similar degree of luminal narrowing), and three healthy control subjects. The total area within the carotid bifurcation that contained low shear rate values associated with clot formation is significantly larger in CaW subjects compared to subjects with atherosclerotic lesions or healthy subjects. 

Alasdair Graeme Morgan¹, Michael Graeme Thrippleton¹, Ning Jin², Joanna Wardlaw¹, and Ian Marshall^1
1Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom, ²Siemens Medical Solutions USA, Inc., Cleveland, OH, United States

We examined the test-retest repeatability and intraobserver reliability of 4D flow MRI while assessing the pulsatility and flow rates of a variety of cerebral arteries and veins in healthy volunteers. A subset of these vessels were also measured using 2D phase-contrast MRI, a more established method, to assess the level to which the lower-resolution (but higher-coverage) 4D method could compare to its 2D counterpart. Flow pulsatility appears to play a role in the development of cerebral small vessel disease and so testing the capabilities of 4D flow in this context is an important step before applying it to clinical studies.

Ansgar Adler¹, Philip Schaten², Yong Wang³, and Martin Uecker^4
1Insitut of Medical Engineering Graz, Graz, Austria, ²Institut Diagnostic and Interventional Radiologie, Göttingen, Germany, ³Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany, ⁴Institut of Medical Engineering, Graz, Austria

The lattice Boltzmann method (LBM) is a powerful technique to simulate complex fluid dynamical systems. The extension of the LBM to flow with a spin degree of freedom in external magnetic fields has shown promising results in 2D. Here, we describe first 3D numerical results utilizing extended kinetic-theory based boundary conditions. The simulation of a laminar pipe flow is verified on the Pouiseuille flow and shown to be able to predict signal changes caused by in-flow effects as expected from previous flow experiments.

Chiara Trenti^1,2, Magnus Ziegler^1,2, Niclas Bjarnegård¹, Tino Ebbers^1,2, Marcus Lindenberger^1,3, and Petter Dyverfeldt^1,2
1Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden, ²Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden, ³Department of Cardiology, Linköping University Hospital, Linköping, Sweden

Current guidelines for risk stratification of abdominal aortic aneurysm are based on vessel diameter and are not sufficient to prevent catastrophic events. Wall shear stress based parameters (WSS, OSI and RRT) are potential markers for AAA altered hemodynamics. Here, WSS vectors were computed from 4D flow MRI in the whole aorta of patients with AAA, age-matched elderly controls, and young normal controls. The aorta was divided in five segments and average values were computed in each segment. AAA had lower WSS and higher RRT in the IAA compared to proximal segments and to the age-matched controls, but not higher OSI.

Renske Merton¹, Eric M. Schrauben¹, Gustav J. Strijkers², Aart J. Nederveen¹, and Pim van Ooij^1,3
1Radiology and Nuclear Medicine, Amsterdam University Medical Centers, Amsterdam, Netherlands, ²Department of Medical Engineering & Physics, Amsterdam University Medical Centers, Amsterdam, Netherlands, ³University Medical Center Utrecht, Utrecht, Netherlands

Capturing 3D aortic motion over the heart cycle may give insight into a new biomarker for aortic disease and potentially improve the measurement of aortic hemodynamic parameters. An isotropic, free-breathing, respiratory-corrected 3D CINE balanced steady-state free precession imaging technique of the thoracic aorta was developed to investigate scan-rescan reproducibility of aortic diameter and displacement measures in nine healthy volunteers. Scan-rescan diameter was highly reproducible (CV<10% , ICC=0.85-0.86 and Pearson’s ρ=0.87) while displacement was more variable (CV=34-42%, ICC=0.34-0.50, ρ=0.59-0.72). These results are encouraging for future studies investigating aortic motion in health and aortopathy. 

Katja Degenhardt¹, Christoph Stefan Aigner¹, Simon Schmidt^2,3, Fabian J. Kratzer³, Max Müller⁴, Armin M. Nagel^3,4, Jeanette Schulz-Menger^5,6, and Sebastian Schmitter^1,2,3
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ³Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ⁴Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany, ⁵Department of Cardiology and Nephrology, Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max-Delbrueck Center for Molecular Medicine and HELIOS Hospital Berlin Buch, Berlin, Germany, ⁶DZHK (German Center for Cardiovascular Research), partner site Berlin, Berlin, Germany

The aim of this work is to develop and investigate an accurate sequence for MR flow quantification. We utilized a 3D ultra-short echo time (UTE) flow sequence to minimize the displacement artifact that frequently occurs in MR flow imaging. In UTE acquisitions, the position is encoded at the beginning of the readout. Thus, the time difference between velocity encoding and spatial position encoding is minimized. This leads to an improved accuracy of the velocity quantification. The sequence was tested and validated against a reference sequence and a conventional 4D flow sequence in a flow experiment in vitro at 3T.

Alessandro M Scotti¹, Qingfei Luo¹, Zheng Zhong², Noreen T Nazir³, Karen L Xie⁴, and Xiaohong Joe Zhou^1,4,5,6
1Center for MR Research, University of Illinois at Chicago, Chicago, IL, United States, ²Department of Radiology, Stanford University, Stanford, CA, United States, ³Division of Cardiology, Department of Medicine, University of Illinois at Chicago, Chicago, IL, United States, ⁴Department of Radiology, University of Illinois at Chicago, Chicago, IL, United States, ⁵Department of Neurosurgery, University of Illinois at Chicago, Chicago, IL, United States, ⁶Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, United States

The aortic valve dynamics is traditionally examined using ultrasound echocardiography in clinical practice. Recently, a novel MRI technique capable of sub-millisecond temporal resolution, coined get-SPEEDI MRI, was successfully applied to visualize the aortic valve dynamics. We have evaluated both get-SPEEDI and echocardiography on healthy human subjects and found a substantial agreement between both techniques in the characterization of the aortic valve opening and closing phases. The sub-millisecond temporal resolution of get-SPEEDI allows for the measurement of steep AVA variations and the visualization of detailed features that may reflect the cardiac function and physiology.