Stroke & Vascular Malformations
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Friday 11 May 2012
Room 219-220  10:30 - 12:30 Moderators: Kei Yamada, Satoru Takahashi

10:30 0756.   Fully automated DWI-PWI mismatch quantification in acute stroke
Kartheeban Nargenthiraja1, Lars Riisgaard Ribe1, Kristina Dupont Hougaard1,2, Josef Alawneh3, Tae-Hee Cho4, Susanne Siemonsen5, Josep Puig Alcantara6, Niels Hjort1, Salvador Pedraza6, Jens Fiehler5, Norbert Nighoghossian4, Jean-Claude Baron3, Leif Østergaard1, and Kim Mouridsen1
1Center of Functionally Integrative Neuroscience, Aarhus University, Aarhus, Denmark, 2Department of Neurology, Aarhus University Hospital, Aarhus C, Denmark,3Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom, 4Hopital Neurologique Pierre Wertheimer Creatis, Insa/UCBL, CNRS UMR5220 - INSERM U1044, Lyon I, France, 5Department of Neuroradiology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany, 6Department of Radiology-IDI, University Hospital Dr Josep Trueta of Girona, Spain

The identification of perfusion-diffusion (PWI-DWI) mismatch tissue in acute stroke is highly subjective. We present an algorithm which performs automatic mismatch segmentation based on PWI and DWI images, and compare the mismatch masks to manually outlined masks performed by four experts in 168 patients. PWI lesion outlining was performed on fitted TTP maps by subsequent morphological grayscale reconstruction, normalization, thresholding, connected component analysis, and level-set smoothing. DWI lesion outlining was performed on B=1000 images by morphological grayscale reconstruction, and level-set smoothing. Volumes of automatic masks show good agreement with volumes of masks where three or more experts agreed (R2=0.93)

10:42 0757.   Automated Stroke Disability Prediction and Mismatch Analysis by Employing Lesion Topography and Statistical Models
Roland Bammer1, Matus Straka1, and Gregory W Albers2,3
1Center for Quantitative Neuroimaging, Department of Radiology, Stanford University, Stanford, CA, United States, 2Stanford Stroke Center, Department of Neurology, Stanford University, Stanford, CA, United States, 3on behalf of the DEFUSE investigators

— DWI/PWI have been demonstrated to be reliable surrogate imaging markers for infarct core and at-risk tissue in acute stroke. Thus far, imaging-based prediction of clinical outcome has been primarily relied on overall lesion size and/or volumetric mismatch between stroke core and at-risk tissue. Here, we use a novel approach that employs importance-weighting to the mismatch analysis, where brain voxels contribute more or less to the scoring metric, based on their location and relative contribution to disability-based population statistics. Using a statistical model (i.e. stroke atlas), weights were derived from an acute stroke patient population and it could been shown that this topographic method predicts stroke disability extremely well.

10:54 0758.   MRI as witness for acute stroke patients with unknown onsets
Ona Wu1, Lawrence L Latour2, Shlee S Song3, Karen L Furie4, Steven Warach2, and Lee H. Schwamm4
1Athinoula A Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, 2National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD, United States, 3Department of Neurology, Cedar Sinai Medical Center, Los Angeles, CA, United States, 4Department of Neurology, Massachusetts General Hospital, Boston, MA, United States

MR WITNESS is a multi-center clinical trial of thrombolysis in acute stroke patients with unwitnessed onset. Enrolled subjects must exhibit MRI patterns consistent with early stage stroke: FLAIR negative or exhibit FLAIR signal intensity increase less than 15% compared to normal tissue. We investigated the inter-rater and inter-site reproducibility of this algorithm among 15 readers from two sites. We compared the performance to a simpler qualitative assessment of FLAIR positive or negative. We found that combining FLAIR+signal intensity had Fleiss’ lower case Greek kappa=0.89 compared to lower case Greek kappa=0.74 using simple FLAIR assessments. MR WITNESS algorithm is a robust, and reproducible approach.

11:06 0759.   MRI observation of intraplaque hemorrhage and atherosclerotic plaque severity in patients
James Qiupeng Zhan1, Alan Moody1, and Cristina Nasui2
1Sunnybrook Hospital, Toronto, Ontario, Canada, 2Medical Imaging, University of Toronto, Toronto, Ontario, Canada

This is a first time use of the MRIPH to measure vessel wall and to define IPH at the same time. 16 patients with MRIPH positive were scans and obtain 3D MRIPH and TOF .Images were reformatted into axial images and segmentation were used to delineate lumen contour and outer wall contour. Multivariate ANOVA is used to compare lumen area, outer wall area, vessel wall area, and maximum vessel wall thickness with IPH positive slices and IPH negative slices at each patient. This study shows that IPH occurs at the more severe atherosclerotic cases having the following characteristics: a thicker outer wall, smaller vessel lumen, bigger vessel wall and bigger maximum vessel wall thickness.

11:18 0760.   
Collateral supply patterns in patients with internal carotid stenosis and occlusion investigated with territorial and reactivity arterial spin labeling
Nolan S. Hartkamp1, Jeroen Hendrikse1, Reinoud P.H. Bokkers1, Matthias J.P. van Osch2, and Esben T. Petersen1
1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2C.J. Gorter Center, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands

Collateral circulation plays a vital role in patients with steno-occlusive disease, in particular for predicting outcome. By combining territorial ASL which measurement collateral flow with ASL before and after an acetazolamide challenge, we have classified the supply patterns and their respective auto regulative capacity in ICA stenosis and occlusion patients. In particular, we categorize the collateral perfusion either as primary, i.e. via the circle-of-willis or secondary as collateral flow via the ophthalmic artery or leptomeningeal collaterals. Secondary collaterals showed significantly worse autoregulation than primary collaterals and contra-lateral hemisphere, in line with the fact that leptomeningeal signals higher stroke recurrence.

11:30 0761.   4D Flow MRI in Arterio-Venous Malformations
Michael Markl1, Tim Carroll1, Parmede Vakil1, Sameer Ansari1, Susanne Schnell1, Michael Hurley1, James Carr1, Bernard Bendok1, and Hunt Batjer1
1Northwestern University, Chicago, IL, United States

The aim of this study was to test the feasibility of 4D flow MRI for the comprehensive characterizations of flow patterns in the complex vasculature of arterio-venous malformations (AVM). 3D blood flow visualization revealed intricate vascularization in 12 patients with AVM of different size, location, and severity as specified by the Spetzler-Martin grade. Different patterns of venous drainage with high variability in regional blood flow velocities indicate the complex nature of AVMs. In three patients, we were able to quantify changes in AVM hemodynamics following staged interventional embolization indicating the sensitivity of the technique for comprehensive hemodynamic monitoring during therapy.

11:42 0762.   Application of a three-dimensional phase-contrast MR sequence to determine blood flow pattern within brain aneurysms
Myriam Edjlali1, Pauline Roca1, Cécile Rabrait2, Kevin M. Johnson3, Oliver Wieben3,4, Denis Trystram1, Olivier Naggara1, Jean-François Meder1, and Catherine Oppenheim1
1Department of Neuroradiology, Sainte-Anne Hospital, University of Paris Descartes, UMR S894, Paris, France, 2GE Healthcare, Vélizy, France, 3Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, United States, 4Department of Radiology, University of Wisconsin, Madison, Wisconsin, United States

We present the first application of a three-dimensional phase-contrast MR sequence (PC VIPR) for the study of flow pattern within human brain aneurysms (n=14, diameter 4-24 mm) and its comparison to Digital Subtraction Angiography (DSA). High spatial resolution (0.85 mm3) PC VIPR velocity maps were informative for all patients, allowing blood flow tracking within all aneurysms. PC VIPR blood flow patterns were consistent with DSA patterns when informative (n=7/14). This new insight in flow tracking allowed us to distinguish in-vivo and non-invasively three flow patterns: a recirculation pattern (n=8), a direct inflow jet (n=1), and a lateral flow pattern (n=5).

11:54 0763.   New Insights of Carotid High-Risk Atherosclerotic Plaques Determined by Proportion of the Arterial Wall Occupied by the Lipid-Rich Necrotic Core in Symptomatic Patients: A 3.0T MRI study permission withheld
Xihai Zhao1, Huilin Zhao2, Jinnan Wang3, Feiyu Li4, Jie Sun5, Jianrong Xu2, and Chun Yuan1,5
1Department of Biomedical Engineering, Tsinghua University School of Medicine, Beijing, China, 2Department of Radiology, Shanghai Jiao Tong University Renji Hospital, Shanghai, China, 33. Philips Research North America, Briarcliff Manor, NY, United States, 4Department of Radiology, Peking University First Hospital, Beijing, China, 5Department of Radiology, University of Washington, Seattle, WA, United States

Neurological symptoms caused by advanced carotid atherosclerosis with intraplaque hemorrhage (IPH) or fibrous cap rupture (FCR) may exist as these lesions detection. As such, investigation of carotid lesions before advanced stage might be helpful for stroke prevention. Recently, Underhill et al proposed carotid atherosclerosis score (CAS) that effectively stratifies plaque¡¯s risk of developing future IPH/ FCR. This study investigated the incidence of high-risk lesions determined by CAS in symptomatic patients. We found a substantial number of lesions with higher CAS value exist in carotid arteries with low grade stenosis, suggesting the necessity of direct characterizing LRNCs using black-blood MRI techniques.

12:06 0764.   Serial monitoring of intracranial aneurysms and correlation of aneurysm evolution with hemodynamics
David Saloner1, Vitaliy Rayz2, Alastair Martin2, Sahand Sohrabi2, William Young3, Michael Lawton4, Wade Smith5, and Randall Higashida2
1Radiology, UCSF, San Francisco, CA, United States, 2Radiology, UCSF, 3Anesthesiology, UCF, 4Neurosurgery, UCSF, 5Neurology, UCSF

Sixty seven patients with untreated intracranial aneurysms were followed with serial imaging to determine changes in aneurysm morphology over time and to correlate those changes with hemodynamics

12:18 0765.   First Results of Quantitative Cerebrovascular Reserve with MRI
Renee Qian1, Parmede Vakil1, Michael C Hurley2, Sameer A Ansari2, Christina Sammet2, Jessy Mouannes-Srour2, H. Hunt Batjer3, Bernard R Bendok3, and Timothy J Carroll1,2
1Biomedical Engineering, Northwestern University, Evanston, IL, United States, 2Neuroradiology, Northwestern University, Chicago, IL, United States, 3Neurosurgery, Northwestern University, Chicago, IL, United States

Cerebrovascular reserve (CVR) measures the autoregulatory dilatation of intracranial vessels in the setting of ischemic pathologies. Quantitative cerebral blood flow scans prior to and 10 after acetazolamide injection in patients were retrospectively acquired. Healthy volunteers without Diamox injection were used as controls. QCVR was calculated as the percentage change between the two scans. We found that quantification of CVR is possible in MRI with ACZ challenge. We proposed an index correlating with the presence of hemodynamic compromise resulting from neurovascular disease. Assigning a quantitative CVR score has the potential to track longitudinal changes in hemodynamic status in response to therapy.