Lena Schmitzer¹, Alexander Seiler², Nico Sollmann¹, Christine Preibisch^1,3, Kilian Weiss⁴, Claus Zimmer¹, Fahmeed Hyder⁵, Jens Göttler^1,5, and Stephan Kaczmarz^1,5
1School of Medicine, Department of Neuroradiology, Technical University of Munich, Munich, Germany, ²Department of Neurology, Goethe University Frankfurt, Frankfurt, Germany, ³School of Medicine, Clinic of Neurology, Technical University of Munich, Munich, Germany, ⁴Philips Healthcare, Hamburg, Germany, ⁵MRRC, Yale University, New Haven, CT, United States

Internal carotid artery stenosis (ICAS) is a well-known risk factor for stroke. While collaterals play a pivotal role in ischemic stroke, their effects in ICAS are not entirely understood. We assessed primary collaterals, i.e., configuration of the Circle of Willis by MR-Angiography, and high Coefficients of Variance in Dynamic Susceptibility Contrast MRI as surrogate of secondary collaterals. Moreover, individual watershed areas (iWSA) were determined in a group of ICAS patients and healthy volunteers. Our results demonstrate post-interventional shifts of iWSA, mainly influenced by primary collateral flow. No secondary collateral flow was found in patients similar to age-matched healthy participants.

Qingle Kong^1,2, Yue Wu¹, Dehe Weng³, Jing An³, Yan Zhuo^1,4, and Zihao Zhang^1,4
1Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, ²MR Collaboration, Siemens Healthcare Ltd, Beijing, China, ³Siemens Shenzhen Magnetic Resonance Ltd, Shenzhen, China, ⁴The Innovation Center of Excellence on Brain Science, Chinese Academy of Sciences, Beijing, China

The impairment of microvessels can lead to neurologic diseases such as stroke and vascular dementia. The imaging of lumen and vessel wall of perforating arteries requires an extremely high resolution due to their small caliber size. In this study, we developed a 3D inner-volume (IV) TSE (SPACE) sequence with optimized spatially selective excitation (SSE) RF pulses. High resolution of isotropic 0.30mm within ten minutes was achieved for the black- blood images of lenticulostriate artery (LSA) for the first time. The IV-SPACE images showed clearer delineation of vessel wall and lumen of LSA than conventional SPACE images.

Stephan Kaczmarz^1,2, Lena Schmitzer¹, Jens Göttler^1,2, Kilian Weiss³, Christian Sorg¹, Claus Zimmer¹, Fahmeed Hyder², Christine Preibisch¹, and Alexander Seiler^4
1School of Medicine, Department of Neuroradiology, Technical University of Munich (TUM), Munich, Germany, ²MRRC, Yale University, New Haven, CT, United States, ³Philips Healthcare, Hamburg, Germany, ⁴Department of Neurology, Goethe University Frankfurt, Frankfurt, Germany

Detection of leptomeningeal collateral blood flow has high clinical relevance, but clinically applicable imaging methods are lacking. While a novel approach based on coefficient of variance (CoV) analysis of dynamic susceptibility contrast (DSC) MRI was recently proposed, relations to hemodynamic alterations remained unknown. Moreover, the role of leptomeningeal collaterals in internal carotid artery stenosis (ICAS) is under debate. We present multi-parametric hemodynamic evaluation within high CoV-voxels from 29 asymptomatic ICAS-patients and 30 age-matched healthy controls. Our results suggest no enhanced leptomeningeal collateral recruitment in asymptomatic ICAS. However, hemodynamic characteristics imply detection of voxels that are prone to future leptomeningeal recruitment.

Li Feng¹ and Lirong Yan^2
1Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²USC Stevens Neuroimaging and Informatics Institute, University of Southern California, Los Angeles, CA, United States

Non-contrast enhanced 4D MRA has emerged as a promising approach in charactering flow dynamics. The major challenge of conventional 4D MRA is relatively long scan time. Recently developed 4D MRA combining golden-angle stack-of-stars acquisition and compressed sensing reconstruction can significantly shorten scan time. However, this method only exploits spatial sparsity based on individual frames. The current study aims to test the feasibility of a newly developed low-rank and sparsity-based image reconstruction method to highly accelerate 4D MRA. Our initial results suggest that higher acceleration rates can be achieved using GraspMRA without compromising image quality and temporal fidelity.

David Marlevi¹, Jonas Schollenberger², Maria Aristova³, Edward Ferdian⁴, Alistair A Young^4,5, Elazer R Edelman¹, Susanne Schnell^3,6, C. Alberto Figueroa², and David Nordsletten^2,5
1Massachusetts Institute of Technology, Cambridge, MA, United States, ²University of Michigan, Ann Arbor, MI, United States, ³Northwestern University, Chicago, IL, United States, ⁴University of Auckland, Auckland, New Zealand, ⁵King's College London, London, United Kingdom, ⁶University of Greifswald, Greifswald, Germany

4D Flow MRI images cerebrovascular blood flow in-vivo, however, estimation of relative pressure is difficult due to the unique flow and anatomies found in the brain. We evaluated the performance of three different techniques (reduced Bernoulli (RB); unsteady Bernoulli (UB); virtual Work-Energy Relative Pressure (vWERP)) for cerebrovascular assessment. Using patient-specific in-silico models, we show that accurate estimations are dependent on sufficient spatial resolution (dx < 0.75 mm³) and used approach (vWERP achieving accurate estimates; RB/UB showing systematic underestimation bias). With similar dependencies indicated in-vivo, these results underline both potentials and challenges of mapping cerebrovascular relative pressure by 4D Flow MRI. 

Hendrik Mattern¹, Stefanie Schreiber^2,3,4, and Oliver Speck^1,3,4,5
1Biomedical Magnetic Resonance, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany, ²Department of Neurology, Otto-von-Guericke-University, Magdeburg, Magdeburg, Germany, ³German Center for Neurodegenerative Disease, Magdeburg, Germany, ⁴Center for Behavioral Brain Sciences, Magdeburg, Germany, ⁵Leibniz Institute for Neurobiology, Magdeburg, Germany

Vessel distance mapping (VDM) is proposed as a novel tool to enable quantitative and qualitative assessment of vascular patterns in deep gray matter structures. At 7T, ToF angiography and QSM were used to depict the arterial and venous vasculature in six subjects. Based on vessel segmentations, vessel distance maps were generated by computing the Euclidean distance of each non-vessel voxel to its closest vessel. Compared to state-of-the-art methods, VDM interpolates the sparse vessel data to enable new ways to analyze vascular patterns with respect to the surrounding structure.

Chen Cao^1,2, Jing Lei², Yan Gong³, Song Jin², Jinxia Zhu⁴, Ming Wei⁵, and Shuang Xia^6
1Department of Radiology, First Central Clinical College, Tianjin Medical University, Tianjin, China, ²Department of Radiology, Tianjin Huanhu Hospital, Tianjin, China, ³Department of Radiology, Tianjin Medical University Nankai Hospital, Tianjin, China, ⁴MR Collaboration, Siemens Healthcare Ltd., Beijing, China, ⁵Department of Neurosurgery, Tianjin Huanhu Hospital, Tianjin, China, ⁶Department of Radiology, Tianjin First Central Hospital, School of Medicine, Nankai University, Tianjin, China

Pre-operative recanalization assessment for acute intracranial large-vessel occlusion (LVO) can help optimize endovascular therapy and shorten procedural times. We prospectively examined 46 patients with acute intracranial LVO who underwent high-resolution magnetic resonance imaging (HRMRI) before endovascular therapy. HRMRI had good agreement with angiographic assessment of the causes of occlusion (κ=0.89, 95% CI, 0.69–1.00) and length of occlusion (concordance correlation coefficient=0.75, 95% CI, 0.59–0.86). Intraluminal enhancement was associated with procedural complexity (r=0.81, P< .001) and procedural times (r=0.64, P< .001). HRMRI before recanalization can help define the vascular status and assist with endovascular therapy of acute intracranial LVOs.

Xiao Gao¹, Xiaowei Wang², Kai Qiao¹, Cassandre Labelle-Dumais², Douglas Gould², and Myriam M. Chaumeil^1
1Department of Radiology, University of California, San Francisco, San Francisco, CA, United States, ²Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, United States

Cerebral small vessel diseases (cSVDs) are a group of conditions that account for up to 30% of strokes. Clinical manifestations associated with cSVD include blood–brain barrier (BBB) leakage, microbleeds, and white matter lesions. Here, we use multimodal MRI at 14.1Tesla to characterize radiological findings observed in innovative mouse models of cSVD caused by mutations in Collagen type IV alpha 1 (Col4a1). By leveraging several image processing toolboxes, we established a workflow that could successfully differentiate between disease subtypes based on the spatial distribution and volume of lesions. 

Shannon Helsper^1,2, Xuegang Yuan^1,2, and Samuel Colles Grant^1,2
1National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, United States, ²Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, United States

This study evaluates therapeutic efficacy of human mesenchymal stem cell (hMSC) derived treatments applied to an ischemic stroke rat model. The goal is to determine if the presence of hMSC or hMSC derivatives in an ischemic region is required or if delivery of cell secretions alone can improve outcomes, either locally at the lesion or by recruiting regenerative neural progenitor cells. Biochemical markers of tissue recovery measured longitudinally using sodium chemical shift imaging and relaxation-enhanced MR spectroscopy at 21.1 T enables increased sensitivity, enabling insight into ionic and metabolic regulation while enabling to determine therapy efficacy.

Frederick A Bagdasarian^1,2, Xuegang Yuan^1,2, and Samuel Colles Grant^1,2
1National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, United States, ²Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, United States

DTI, NODDI and DKI techniques were applied to diffusion data acquired at 21.1 T to identify microtissue changes in ischemic brain tissue following adult human mesenchymal stem cell (hMSC) or control treatment. Scanning was conducted 1-21 d post-MCAO and treatment. 2D hMSC significantly reduced cell swelling (ICVF) at nearly every time-point in white matter while preserving orientation integrity (ODI), normal levels of DTI metrics, and early phase kurtosis. In grey matter, 2D hMSC restored DTI metrics to naïve levels quicker than control treatments, as did ICVF and ODI. Kurtosis had high variability, with minor trends evident.