Stroke: MRA & Vessel Wall Imaging

Wednesday 14 May 2014

Thomas W Okell¹, George WJ Harston², Michael A Chappell³, Fintan Sheerin⁴, Martino Cellerini⁴, Stephen J Payne³, James Kennedy⁵, and Peter Jezzard^1
1FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, United Kingdom, ²Nuffield Department of Medicine, University of Oxford, Oxford, Oxfordshire, United Kingdom, ³IBME, Department of Engineering Sciences, University of Oxford, Oxford, Oxfordshire, United Kingdom, ⁴Department of Neuroradiology, Oxford University Hospitals NHS Trust, Oxford, Oxfordshire, United Kingdom, ⁵Radcliffe Department of Medicine, University of Oxford, Oxford, Oxfordshire, United Kingdom

Multi-postlabeling delay vessel-encoded arterial spin labeling is capable of generating artery specific quantitative maps of cerebral blood flow and bolus arrival time non-invasively and without contrast agent. This method was applied to serially study hyper-acute stroke patients. Changes in the vascular territories over time were observed, with collateral flow appearing to spare tissue from infarction. Significant delays to blood arrival were measured in regions around the perfusion deficit compared to the contralateral side. This technique shows promise for diagnosis, prognosis and understanding the pathophysiology of acute stroke.

Michael Loecher¹, Kevin Johnson¹, Patrick Turski², and Oliver Wieben^1,2
1Medical Physics, University of Wisconsin Madison, Madison, Wisconsin, United States, ²Radiology, University of Wisconsin Madison, Madison, Wisconsin, United States

A novel algorithm is presented for tracking blood flow through the whole brain neurovasculature using 4D flow imaging data. The method incorporates probabilistic streamlines, displacement corrections, and additional fluid constraints. The algorithm was tested in 5 patients with aneurysms or arteriovenous malformations (AVMs). Good agreement is seen when compared to pseudo-continuous arterial spin labeling (PCASL). The technique also allows for retrospective seed placement to selectively measure downstream vessels, or evaluate AVM feeding and draining.

Can Wu¹, Timothy Carroll^1,2, Sameer Ansari^2,3, Amir Honarmand^2,3, Parmede Vakil², Michael Hurley^2,3, Bernard Bendok^2,3, James Carr², and Michael Markl^1,2
1Biomedical Engineering, Northwestern University, Chicago, IL, United States, ²Radiology, Northwestern University, Chicago, IL, United States,³Neurological Surgery, Northwestern University, Chicago, IL, United States

4D flow and perfusion MRI were combined to quantitatively evaluate macro- and microvascular hemodynamics in cerebral arteriovenous malformations (AVMs), investigate the influence of Spetzler-Martin grade on AVM hemodynamics, and identify potential relationships between changes in macro- and microvascular flow and perfusion. The results demonstrated the influence of Spetzler-Martin grade on AVM hemodynamics in the feeding arteries, draining veins, and the straight sinus. In addition, we could identify significant relationships between large vessel flow and perfusion ratios. These findings demonstrate the potential of our imaging protocol for the comprehensive characterization of the impact of AVMs on macro- and microvascular hemodynamics.

Parmede Vakil¹, Michael C Hurley², Shyam Prabhakaran², Bernard Bendok², H. Hunt. Batjer³, Timothy J Carroll², and Sameer A Ansari^2
1Northwestern University, Chicago, IL, United States, ²Northwestern University, IL, United States, ³UT Southwestern, Texas, United States

Applications of dynamic contrast enhanced MRI in neurovascular diseases such as intracranial aneurysms, intracranial atherosclerotic disease, and vasculitis have not been previously explored. We demonstrate the utility of DCE-MRI in a study of patients with various neurovacular pathologies.

Can Wu¹, Shyam Prabhakaran², Timothy Carroll^1,3, Parmede Vakil³, Neil Chatterjee^1,3, Amir Honarmand^3,4, Sameer Ansari^3,4, James Carr³, and Michael Markl^1,3
1Biomedical Engineering, Northwestern University, Chicago, IL, United States, ²Neurology, Northwestern University, Chicago, IL, United States,³Radiology, Northwestern University, Chicago, IL, United States, ⁴Neurological Surgery, Northwestern University, Chicago, IL, United States

The purpose of this study was to evaluate the feasibility of 4D flow MR imaging for the comprehensive evaluation of intracranial hemodynamics in 20 patients with intracranial atherosclerotic disease (ICAD) including quantitative analysis of peak velocity and mean blood flow in the large intracranial vessels. The results demonstrated significant impact of regional stenotic lesions on the hemodynamics in systemic vascular territories. Combined evaluation of the qualitative visualization of the blood flow patterns and distribution of blood flow velocities and quantitative hemodynamic markers may provide additional insight into the pathophysiology and risk stratification for ICAD patients.

Aofei Liu¹, Xihai Zhao², Huijun Chen², Zhensen Chen², William Kerwin³, Chun Yuan^2,3, Bin Du¹, and Wei-Jian Jiang^1
1New Era Stroke Care and Research Institute, The Second Artillery General Hospital PLA, Beijing, China, ²Center for Biomedical Imaging Research & Department of Biomedical Engineering, Tsinghua University, Beijing, China, ³Department of Radiology, University of Washington, Seattle, WA, United States

We sought to compare DSA and MR vessel wall imaging in evaluating the degree of stenosis and plaque distribution in BA. Of 31 subjects, the stenotic degree measured by DSA and MRI was 32.9% and 42.9% respectively. Excellent agreement was found between DSA and MRI in stenosis measurement (r=0.898, P<0.001). DSA underestimated the degree of luminal stenosis, which may be due to its limitation in viewing eccentrically stenotic lesion. The incidence of plaque affecting each quadrant on MRI is greater than that of DSA, suggesting MR vessel wall imaging may be a better imaging modality to evaluate lesion distribution in BA.

Jinnan Wang¹, Michael Helle², Zechen Zhou³, Peter Börnert², and Chun Yuan^4
1Philips Research North America, Seattle, WA, United States, ²Philips Research Europe, Hamburg, Hamburg, Germany, ³Tsinghua University, Beijing, Beijing, China, ⁴University of Washington, Seattle, WA, United States

Intracranial artery atherosclerosis is a key contributor of stroke. MR evaluation of the vessel wall has been technically challenging because of the difficulty of suppressing blood and CSF at the same time. In this study, a simultaneous blood and CSF suppression was developed and tested in vivo. This technique essentially provides an effective way to achieve multi-contrast intracranial atherosclerosis imaging, creating a unique solution to study the clinical impact of intracranial artery disease.

Yuan Huang¹, Zhongzhao Teng^1,2, Umar Sadat³, and Jonathan H Gillard^1
1University Department of Radiology, University of Cambridge, Cambridge, Cambridge, United Kingdom, ²Department of Engineering, University of Cambridge, Cambridge, United Kingdom, ³Department of Surgery, Cambridge University Hospitals NHS Foundation Trust, Cambridge, Cambridge, United Kingdom

Plaque composition detected by imaging alone cannot accurately predict future cerebrovascular risk, and additional analyses or biomarkers are required. Under physiological conditions, carotid plaques are subjected to mechanical loading from pulsatile blood pressure. FC rupture may occur when this loading exceeds its material strength. Different computational strategies, including 2D structure-only, 3D structure-only, 3D one-way and fully coupled fluid-structure interaction (FSI), have been employed to examine plaque stress. This study indicated that 2D simulations yielded a poor performance in predicting stress and 3D structural-only models showed good qualitative and quantitative agreement with the 3D fully coupled FSI.

Alexandra A.J. de Rotte¹, Wouter Koning², Anne G. den Hartog³, Sandra M. Bovens⁴, Aryan Vink⁵, Shahrzad Sepehrkhouy⁵, Jaco J.M. Zwanenburg⁶, Dennis W.J. Klomp⁶, Gerard Pasterkamp⁷, Frans L. Moll³, Peter L. Luijten⁶, Gert Jan de Borst³, and Jeroen Hendrikse^6
1Radiology, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, ²University Medical Center Utrecht, Utrecht, Netherlands, ³Vascular Surgery, University Medical Center Utrecht, Utrecht, Netherlands, ⁴Bioengineering, Imperial College London, London, United Kingdom, ⁵Pathology, University Medical Center Utrecht, Utrecht, Netherlands, ⁶Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ⁷Experimental Cardiology, University Medical Center Utrecht, Utrecht, Netherlands

First, the use ultra-high field 7T MR imaging to visualize the total burden of cerebral infarcts (both macro- and microinfarcts) was evaluated. Second, the presence of micro- and macroinfarcts was correlated with histopathology of carotid artery plaque. This study shows that a histopathological thinner fibrous cap is associated with more infarcts (both micro and macroinfarcts) in the hemisphere ipsilateral to a >70% symptomatic carotid artery stenosis. Other histopathological plaque characteristics were not related to infarcts (micro and macro). Microinfarcts are common in this patient group with symptomatic carotid artery stenosis but are most often find in combination with macroinfarcts.

Farhang F Jalilian^1,2, David E Crane¹, FuQiang Gao¹, Sandra E Black^1,3, and Bradley J MacIntosh^1,2
1Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, Sunnybrook Research Institute, Toronto, ON, Canada, ²Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Division of Neurology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada

Cerebral Small Vessel Disease (SVD) is the most prevalent disease that affects the brain. We investigate the use of susceptibility-weighted imaging (SWI) in visualizing medullary veins and assessing the SVD. The study involves automatic segmentation of: 1) venous vasculature and 2) white matter lesions. Our results show there is a higher vein fraction in white matter lesions compared to normal white matter, and a positive correlation between periventricular vein fraction and SVD lesion burden. Our findings showcase the utility of SWI and highlight the importance of investigating the venous vasculature for its involvement in the etiology of the SVD.