Leonardo A Rivera-Rivera¹, Steven Kecskemeti¹, Mu-Lan Jen¹, Zach Miller¹, Sterling C Johnson¹, Laura Eisenmenger¹, and Kevin M Johnson^1
1University of Wisconsin, Madison, Madison, WI, United States

Accurate and precise assessment of neurovascular flow in the brain requires high image fidelity which can be difficult to obtain in populations with high tendencies to move, such as geriatrics and pediatrics. This study presents a 3D radial sampling and multi-scale low rank image reconstruction for self navigated motion correction of 4D-Flow with validations in phantom and invivo studies.

Mariana B. L. Falcão¹, Adèle L.C. Mackowiak¹, Simone Rumac¹, Mario Bacher^1,2, Giulia Rossi¹, Milan Prša³, Estelle Tenisch¹, Tobias Rutz⁴, Jessica Bastiaansen^1,5,6, Ruud Van Heeswijk¹, Peter Speier², Michael Markl^7,8, Matthias Stuber^1,9, and Christopher W. Roy^1
1Department of Diagnostic and Interventional Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, ²Siemens Healthcare GmbH, Erlangen, Germany, ³Woman- Mother- Child Department, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, ⁴Service of Cardiology, Centre de Resonance Magnétique Cardiaque (CRMC), University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, ⁵Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), University hospital Bern (Inselspital), Bern, Switzerland, ⁶Translational Imaging Center, sitem-insel, Bern, Switzerland, ⁷Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, ⁸Department of Biomedical Engineering, Northwestern University, Chicago, IL, United States, ⁹Center for Biomedical Imaging (CIBM), Lausanne, Switzerland

We introduce a novel method for combining multiple free-running MRI acquisitions together, through the use of cardiac and respiratory signal extraction with Pilot Tone navigation called Synchronization of Neighboring Acquisitions by Physiological Signals (SyNAPS). We demonstrate the initial feasibility and utility of SyNAPS on a setup for joint reconstruction of back-to-back dynamic anatomical and flow MRI acquisitions, here named 4D flow SyNAPS. Overall, 4D flow SyNAPS enabled an improved structural visualization, when compared to the magnitude images from free-running 4D flow datasets alone, and the resulting flow measurements showed better agreement with reference 2D flow acquisitions.

Justin Baraboo¹, Elizabeth Weiss¹, Maurice Pradella¹, Liliana Ma¹, Julia Hwang¹, Suvai Gunasekaran¹, Mariana Falcão², Christopher W Roy², Matthias Stuber², Rod Passman¹, Daniel Kim¹, and Michael Markl^1
1Northwestern University, Chicago, IL, United States, ²University of Lausanne, Lausanne, Switzerland

RR-resolved 5D flow is a novel MRI technique that can acquire time-resolved 3D hemodynamics for varying RR-interval durations during atrial fibrillation (AF) (5D = 3D+cardiac time+RR-interval duration). The purpose of this study was to apply RR-resolved 5D flow MRI in a cohort of AF patients with and without a prior history of stroke. We saw significantly lowered left atrial peak velocities and trends toward higher atrial blood stasis in AF patients with previous stroke history vs no previous stroke history who underwent arrhythmia during MRI acquisition. RR-resolved 5D flow may be a promising approach for cardiovascular imaging in arrhythmic patients.

Judith Zimmermann^1,2, Kathrin Bäumler¹, Tyler E Cork^1,3, Michael Loecher^1,4, Alison L Marsden^3,5, Dominik Fleischmann¹, and Daniel B Ennis^1,4
1Department of Radiology, Stanford University, Stanford, CA, United States, ²Department of Computer Science, Technical University of Munich, Garching, Germany, ³Department of Bioengineering, Stanford University, Stanford, CA, United States, ⁴Division of Radiology, Veterans Affairs Health Care System, Palo Alto, CA, United States, ⁵Department of Pediatrics, Stanford University, Stanford, CA, United States

Understanding flow dynamics in type-B aortic dissection (TBAD) is of high clinical interest to predict complications and individualize treatment. Here, we sought to evaluate 4D-flow MRI at high and low spatial image resolution, in comparison to high resolution, high signal-to-noise 2D phase contrast MRI. Further, we compare TBAD hemodynamics and flow alterations owing to changes in tear size. We leverage novel 3D printing technology to manufacture three compliant TBAD models with altered tear morphology and perform pressure- and flow-controlled MRI with an advanced in vitro flow setup. 

Pietro Dirix¹, Stefano Buoso¹, Eva Peper¹, and Sebastian Kozerke^1
1Institute for Biomedical Engineering, University and ETH Zürich, Zürich, Switzerland

We present a pipeline to synthesize patient-specific pulsatile turbulent 4D flow MRI datasets of the aorta. Aortic motion and inflow are extracted from in-vivo 2D cine and time-resolved 2D phase-contrast data. Computational fluid dynamics is used to obtain 4D velocity and turbulence fields to simulate MR signals using multipoint 4D flow tensor MRI protocols, which are reconstructed into velocity and turbulence maps with a Bayesian approach. As a result, realistic paired data of ground truth and their projection into MR images enable assessing accuracy and precision of encoding and inference, training of inference machines and, ultimately, deriving optimal experimental designs.

Tomas Vikner¹, Nina Karalija^1,2, Anders Eklund^1,2, Jan Malm³, Lars Nyberg^1,2,4, and Anders Wåhlin^1,2,5
1Department of Radiation Sciences, Umeå University, Umeå, Sweden, ²Umeå Center for Functional Brain Imaging (UFBI), Umeå University, Umeå, Sweden, ³Department of Clinical Science, Neurosciences, Umeå University, Umeå, Sweden, ⁴Department of Integrative Medical Biology (IMB), Umeå University, Umeå, Sweden, ⁵Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden

Small vessel disease (SVD) is associated with elevated vascular stiffness and pulsatility, but longitudinal studies are lacking. Using a 4D flow MRI approach sensitive to age-differences in pulsatility in large and small cerebral arteries, we evaluated 5-year changes in pulsatility in relation to changes in white matter lesions (WML) and perivascular spaces (PVS), radiological markers of SVD. Pulsatility change correlated with WML and PVS volume change, but pulsatility at baseline did not predict WML and PVS progression. However, WML and PVS volumes at baseline predicted 5-year pulsatility change, suggesting that microvascular dysfunction associated with SVD accelerates pulsatility increases. 

Ioannis Koktzoglou^1,2, Rong Huang¹, and Robert R Edelman^1,3
1Radiology, NorthShore University HealthSystem, Evanston, IL, United States, ²Radiology, Pritzker School of Medicine, University of Chicago, Chicago, IL, United States, ³Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States

Quantitative time of flight (qTOF) is a recently described 3D magnetic resonance angiography (MRA) technique for simultaneous luminal and hemodynamic evaluation of the intracranial arteries, that provides higher contrast-to-noise ratio efficiency than 3D phase contrast (PC) MRA and reduces in-plane flow displacement artifacts visible on standard 3D TOF MRA. We hypothesized that the use of a quiescent interval slice-selective-based data acquisition strategy (qQISS) that boosts arterial-to-background contrast might improve the quantitation of intracranial arterial flow velocity. Compared to qTOF MRA, we found that qQISS MRA improved agreement with PC MRA for measuring intracranial blood velocity.