Kartheeban Nargenthiraja¹, Lars Riisgaard Ribe¹, Kristina Dupont Hougaard^1,2, 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 Mouridsen^1
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)

Roland Bammer¹, Matus Straka¹, and Gregory W Albers^2,3
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.

Ona Wu¹, Lawrence L Latour², Shlee S Song³, Karen L Furie⁴, Steven Warach², and Lee H. Schwamm^4
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’ =0.89 compared to =0.74 using simple FLAIR assessments. MR WITNESS algorithm is a robust, and reproducible approach.

James Qiupeng Zhan¹, Alan Moody¹, and Cristina Nasui^2
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.

Nolan S. Hartkamp¹, Jeroen Hendrikse¹, Reinoud P.H. Bokkers¹, Matthias J.P. van Osch², and Esben T. Petersen^1
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.

Michael Markl¹, Tim Carroll¹, Parmede Vakil¹, Sameer Ansari¹, Susanne Schnell¹, Michael Hurley¹, James Carr¹, Bernard Bendok¹, and Hunt Batjer^1
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.

Myriam Edjlali¹, Pauline Roca¹, Cécile Rabrait², Kevin M. Johnson³, Oliver Wieben^3,4, Denis Trystram¹, Olivier Naggara¹, Jean-François Meder¹, and Catherine Oppenheim^1
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).

Xihai Zhao¹, Huilin Zhao², Jinnan Wang³, Feiyu Li⁴, Jie Sun⁵, Jianrong Xu², and Chun Yuan^1,5
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.

David Saloner¹, Vitaliy Rayz², Alastair Martin², Sahand Sohrabi², William Young³, Michael Lawton⁴, Wade Smith⁵, and Randall Higashida^2
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

Renee Qian¹, Parmede Vakil¹, Michael C Hurley², Sameer A Ansari², Christina Sammet², Jessy Mouannes-Srour², H. Hunt Batjer³, Bernard R Bendok³, and Timothy J Carroll^1,2
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.