Stroke - Clinical Studies
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Wednesday May 11th
Room 512A-G  16:00 - 18:00 Moderators: Fernando Calamante

16:00 458.   Ischemic penumbra in acute MCA stroke: comparison of the PWI-DWI mismatch and the ADC-based NEURINFARCT methods 
Aurelie Drier1,2, Thomas Tourdias3, Igor Sibon4, Yohan Attal5, Gurkan Mutlu6, Stéphane Lehéricy1,2, Yves Samson6, Jacques Chiras1, Didier Dormont1, Jean-Marc Orgogozo4, Vincent Dousset3, and Charlotte Rosso6
1Neuroradiology, Pitié Salpêtrière Hospital, Paris, France, 2Centre de NeuroImagerie de Recherche - CENIR,CRICM U795, Paris, France, 3Neuroradiology, CHU Pellegrin, Bordeaux, France, 4Neurology, CHU Pellegrin, Bordeaux, France, 5CRICM, CNRS, UMR7225 équipe NEMESIS, Paris, France, 6Urgences cérébro-vasculaires, Pitié Salpêtrière Hospital, Paris, France

The MRI prediction of the risk of infarct growth is essential for decision making in acute stroke treatment. A method only based on DWI and ADC maps has been recently developped to identify the at-risk tissue. In this study, this new method is compared to the gold standard, the PWI/DWI mismatch. It is as efficient as the PWI/DWI mismatch for the prediction of infarct growth and more efficient for the prediction of infarct volume. The ADC-based method‘s performances are similar during and after the therapeutic window (4H30) whereas they are significantly lower after 4h30 after stroke onset with the PWI/DWI mismatch.

16:12 459.   Bolus Delay and Dispersion in Predictor Models in Acute Stroke 
Lisa Willats1, Alan Connelly1,2, Soren Christensen3,4, Geoffrey Donnan2,5, Stephen Davis4,6, and Fernando Calamante1,2
1Brain Research Institute, Florey Neuroscience Institutes, Melbourne, Australia, 2Department of Medicine, University of Melbourne, Australia, 3Department of Radiology, University of Melbourne, Australia, 4Royal Melbourne Hospital, Melbourne, Australia, 5Florey Neuroscience Institutes, Melbourne, Australia, 6Department of Neurology, University of Melbourne, Australia

Recent studies have suggested that in addition to perfusion deficits, delay and dispersion (D/D) of blood flow may also increase the risk of permanent tissue damage. We investigate the infarct risk associated with D/D using generalised linear models (GLM) formed with delay insensitive global-AIF and local-AIF perfusion estimates, together with independent D/D parameters. Including D/D parameters was found to improve the GLM predictions. The global-AIF models performed better summarised over all risk thresholds. However, for a single risk threshold (as would be used clinically), the local-AIF models would perform closer to optimum for a larger proportion of patients.

16:24 460.   Comparison of Pseudo-Continuous Arterial Spin-Labeled and Dynamic Susceptibility Contrast Enhanced Perfusion Imaging in Acute Ischemic Stroke 
Danny JJ Wang1, David S Liebeskind1, Qing Hao1, Joe X Qiao2, Rana Fiazv1, Matthias Gunther3,4, Whitney B Pope2, Samuel Hou2, Lirong Yan1, Jeffrey L Saver1, Noriko Salamon2, and Jeffry R Alger1,2
1Neurology, UCLA, Los Angeles, CA, United States, 2Radiology, UCLA, Los Angeles, CA, United States, 3Faculty of Physics and Electronics, University of Bremen, Bremen, Germany, 4Fraunhofer MEVIS-Institute for Medical Image Computing, Bremen, Germany

Pseudo-continuous arterial spin labeling (ASL) and dynamic susceptibility contrast enhanced (DSC) perfusion imaging were carried out in 27 cases of acute ischemic stroke. ASL CBF and DSC CBF, Tmax maps provided largely consistent results in delineating hypoperfusion lesions. ASL CBF, nevertheless, was more sensitive than DSC CBF in delineating hyperemic lesions which Tmax and MTT maps were unable to demonstrate. After calibration using CBF in control regions, a strong correlation emerged between mean ASL and DSC CBF values in the penumbral zones defined by Tmax>4s. This study illustrated the potential for combined ASL and DSC perfusion imaging in acute stroke.

16:36 461.   Reversal of abnormal ADC lags reperfusion and does not necessarily represent tissue salvage 
Hongyu An1, Andria L Ford2, Katie D Vo3, William J Powers4, Jin-Moo Lee2, and Weili Lin1
1Radiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 2Neurology, Washington University in St. Louis, St. Louis, MO, United States,3Radiology, Washington University in St. Louis, St. Louis, MO, United States, 4Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

A temporal dissociation between ADC change and perfusion alterations, with ADC changes lagging behind reperfusion, was observed. Moreover, ADC recovery subsequent to reperfusion does not necessarily predict tissue salvage and it depends on whether and when reperfusion may occur.

16:48 462.   Consequences of Multi-echo Fits in Perfusion MRI for the Determination of MTT in Presence of T1-Effects. 
Matus Straka1, Heiko Schmiedeskamp1, Greg Zaharchuk1, Jalal B Andre1, Jean-Marc Olivot2, Nancy J Fischbein1, Maarten G Lansberg2, Michael E Moseley1, Gregory W Albers2, and Roland Bammer1
1Radiology, Stanford University, Stanford, CA, United States, 2Stanford Stroke Center, Stanford University, Stanford, CA, United States

Typical PWI exam employs single-echo acquisitions, but accuracy of perfusion parameters from such data can be severely flawed by T1 shortening. While CBV inaccuracies are widely understood, errors in MTT are not expected as temporal parameters are assumed to be immune to these effects. We give an explanation of the problem using simulations and exemplify it on a clinical scan. We conclude that MTT can be largely underestimated if T1-effects (e.g. due to tracer leakage) are not accounted for. As a solution we present an advanced imaging scheme based on multi-echo SAGE PWI sequence that can correct these problems.

17:00 463.   Operatively defined ischemic core, penumbra and oligemia in human acute stroke using sequential MR perfusion images 
Hongyu An1, Andria L Ford2, Cihat Eldeniz1, Yang Yang1, Yasheng Chen1, Katie D Vo3, William J Powers4, Jin-Moo Lee2, and Weili Lin1
1Radiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 2Neurology, Washington University in St. Louis, St. Louis, MO, United States,3Radiology, Washington University in St. Louis, St. Louis, MO, United States, 4Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

Tissue survival rate as a function of 3 hr and 6hr MTT prolongation revealed that distinct patterns of perfusion and subsequent perfusion changes can be utilized to separate tissue into ischemic core (MTT prolongation >15 seconds), penumbra (MTT prolongation: 5-15 seconds) and oligemia (MTT prolongation <5 seconds) using MR perfusion. Moreover, the more severely damaged tissue needs larger perfusion improvement to survive when compared to mildly injured tissue.

17:12 464.   Cerebrovascular reactivity measured with arterial spin labeling MRI in the caudate nucleus, lentiform nucleus, and thalamus in patients with steno-occlusive internal carotid artery disease 
Nolan S Hartkamp1, R P H Bokkers1, H B van der Worp2, M J P van Osch3, and J Hendrikse1
1Radiology, UMC Utrecht, Utrecht, Netherlands, 2Neurology, UMC Utrecht, Utrecht, Netherlands, 3C.J. Gorter Center, Leiden UMC, Leiden, Netherlands

Lacunar infarcts are small lesions in the deep white matter, basal ganglia or brainstem. It is hypothesized that this is a manifestation of small vessel disease and that it has a different pathogenesis than cortical stroke. An association is suggested with impaired hemodynamic autoregulation. It was previously shown that steno-occlusive internal carotid artery disease leads to hemodynamic impairement of the brain. We investigate the impact of large vessel disease upon the autoregulative hemodynamics in the deep brain structures by investigating cerebrovascular reactivity in subcortical regions in patients with steno-occlusive internal carotid artery disease and compare this with healthy control subjects.

17:24 465.   Whole-brain arterial spin labeling perfusion MR imaging in patients with acute stroke  -permission withheld
Reinoud P.H. Bokkers1, Steven Warach2, Daymara Hernandez2, Matthias J van Osch3, Jeroen Hendrikse1, Raymond V. Mirasol2, José G. Merino2, and Lawrence L. Latour2
1Department of Radiology, UMCU, Utrecht, Utrecht, Netherlands, 2Section of Stroke Diagnostics and Therapeutics, NINDS, NIH, Bethesda, Maryland, United States, 3C.J. Gorter Institute for High Field MRI, LUMC, Leiden, Netherlands

The aim of our study was to test the feasibility of using arterial spin labeling (ASL) perfusion MRI for evaluating hyperacute stroke in patients where limited time is available and to evaluate the ability of ASL for detecting perfusion deficits and perfusion-diffusion mismatch as compared with dynamic susceptibility contrast (DSC) perfusion imaging. Our study shows that ASL can depict large perfusion deficits and perfusion/diffusion mismatches in correspondence with DSC and that a fast 2½ minute ASL perfusion scan may be adequate for screening patients with contraindications to gadolinium-based contrast agents.

17:36 466.   An Automated Tool for Prediction of Secondary Hemorrhage in Stroke. 
Matus Straka1, Bruce C Campbell2, Maarten G Lansberg3, Greg Zaharchuk1, Michael Mlynash3, Stephanie M Kemp3, Demi Thai3, Gregory W Albers3, and Roland Bammer1
1Radiology, Stanford University, Stanford, CA, United States, 2Neurology, Royal Melbourne Hospital, Melbourne, Australia, 3Stanford Stroke Center, Stanford University, Stanford, CA, United States

Possible occurrence of secondary hemorrhage is an important consideration in stroke treatment. Based on previous research, we present a tool that can fully-automatically and in short time provide hemorrhage prediction maps based on standard DWI and PWI images. Acquired PWI data are automatically postprocessed to obtain maps cerebral blood volume (CBV) and coregistered with the DWI. The CBV maps are then mirrored about the A/P axis to obtain estimates of contralateral CBV. Hemorrhage is ultimately predicted in regions that manifest diffusion lesions together with very low CBV. An initial test on 19 stroke cases showed 83% specificity and 86% specificity.

17:48 467.   Carotid Atherosclerotic Lesion Distribution in Patients with Cerebrovascular Events: A 3.0 Tesla Magnetic Resonance Vessel Wall Imaging Study Using Three-dimensional, Isotropic, Fast Sequence with Large Coverage  -permission withheld
Xihai Zhao1, Niranjan Balu2, Jinnan Wang3, Huilin Zhao4, Jianrong Xu4, and Chun Yuan1,2
1Department of Biomedical Engineering & Center for Biomedical Imaging Research, School of Medicine, Tsinghua University, Beijing, China, People's Republic of,2Department of Radiology, University of Washington, Seattle, WA, United States, 3Philips Research North America, Briarcliff Manor, NY, United States, 4Department of Radiology, Renji hospital, Shanghai Jiao Tong University, Shanghai, China, People's Republic of

Multicontrast vessel wall imaging has been widely used for characterizing carotid atherosclerosis. However, this imaging protocol could not assess the full spectrum of carotid atherosclerotic lesion distribution due to its limited longitudinal coverage (40 mm). Recently, 3D fast sequence ¡®MERGE¡¯ with isotropic resolution, large-coverage (> 80 mm) and short-scan-time (2 min) is emerging as a promising approach for identification of carotid plaques. In this study, we used 3D MERGE sequence to determine carotid lesion distribution and found that near one fourth of lesions occurred in proximal common carotid artery which is beyond the imaging coverage of current multicontrast protocol.