Multiparametric Approaches to Clinical Stroke Imaging
Monday 20 April 2009
Room 311 11:00-13:00


Jeffry R. Alger and Lawrence Latour

11:00  32.

Comparison of ASL and PWI Perfusion in Stroke Patients


Esben Thade Petersen1,2, Tchoyoson C.C. Lim2, N Venketasubramanian2, Xavier Golay2,3
Center of Functionally Integrative Neuroscience, University of Aarhus, Aarhus, Denmark; 2National Neuroscience Institute, Singapore; 3Institute of Neurology, University College London, UK

    One obvious problem of ASL in stroke imaging is the limited duration of the label, which makes it arguable whether ASL will have a chance as compared to PWI when it comes to penumbra estimation and subsequent risk-benefit weighting of possible intervention. In this work we show that ASL acquired at multiple time-points provides similar information to PWI in the affected areas. In addition, ASL can probe the existence of collateral perfusion and combined they could potentially be valuable in this risk assessment. However it still remains to future studies of hyperacute stroke to tell whether ASL can prove sufficient.
11:12 33.   

3 T Pulsed Arterial Spin Labeling MRI Reveals Perfusion Deficits in Patients with Minor Stroke or Transient Ischaemic Attack

    Bradley J. MacIntosh1, Alistair C. Lindsay2, Ilias Kylintireas2, Justin M. Lee2, Matthew D. Robson2, James Kennedy3, Robin P. Choudhury2, Peter Jezzard1
Clinical Neurology, FMRIB Centre, Oxford, Oxfordshire, UK; 2Department of Cardiovascular Medicine, John Radcliffe; 3Acute Stroke Programme, Nuffield Department of Clinical Medicine, John Radcliffe
    Dynamic susceptibility contrast (DSC) is the clinical-standard perfusion MRI technique for acute ischaemic stroke. Arterial spin labeling (ASL) is a complementary non-invasive perfusion MRI technique and has demonstrated promise in a limited number of clinical ASL studies. The purpose of the current study is test the feasibility of acute multiple-inflow pulsed ASL in a group of minor stroke patients. An automated clustering technique is used to visualise voxels where the arterial transit times are delayed and produce low CBF levels. We argue that ASL has the sensitivity to detect perfusion deficits even in patients that have low impairment.
11:24 34. 

Comparison of CBF Measurement by ASL and SPECT in Patients with Internal Carotid Artery Stenosis

    Yoshito Uchihashi1, Kohkichi Hosoda1, Ivan Zimine2, Atsushi Fujita1, Satoshi Inoue1, Hideo Aihara1, Hideaki Kawamitsu3, Nobukazu Aoyama3, Hajime Aoki3, Masahiko Fujii3, Eiji Kohmura1
Dept. of OrganTherapeutics, Neurosurgery, Kobe University graduate school of Medicine, Kobe, Hyogo, Japan; 2Philips Healthcare Japan; 3Dept. of Radiology, Kobe University graduate school of Medicine, Kobe, Hyogo, Japan
    ASL tecknique provide quantative CBF measurement of brain perfusion in good agreement with SPECT which is already established method for making decision for Neurosurgical interventions.
11:36  35. 

Predictive Value of Structural Integrity of Affected Corticospinal Tracts in Motor Function Outcome of Affected Upper Extremities in Patients with Subcortical Ischemic Stroke: A Diffusion Spectrum Imaging Tractography Study

    Miao-Chi Lo1, Yi-Hsin Ko2, Pei-Fang Tang2,3, Wen-Yih Isaac Tseng1,4
Center for Optoetectronic Biomedicine, National Taiwan University College of Medicine, Taipei, Taiwan; 2School and Graduate Institute of Physical Therapy, National Taiwan University College of Medicine, Taipei, Taiwan; 3Physical Therapy Center, National Taiwan University Hospital, Taipei, Taiwan; 4Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan
    We used diffusion spectrum imaging (DSI) tractography to investigate whether the structural integrity of the corticospinal tract (CST) of the affected upper extremity can predict the motor outcome in patients with subcortical ischemic stroke. The entire CST of each subject was reconstructed and the mean generalized fractional anisotropy (GFA) values of the tract were analyzed. The tract-specific quantitative analysis of the relative GFA (rGFA) values of different segments of bilateral CSTs was derived to indicate the structural integrity of CST in various segments. The rGFA values in the IC segment of CST at D30 were highly correlated with the FMA-UE scores at D180 (N = 7, r = -.802, p = .030). In conclusion, the structural integrity of the affected CST early after stroke appears to have predictive value for late motor recovery.
11:48  36. 

Predicting Tissue Outcome in Acute Ischemic Stroke Using Projection Pursuit Regression


Kartheeban Nagenthiraja1, Kristjana Yr Jonsdottir1, Leif Østergaard1, Kim Mouridsen1
Dept. of Neuroradiology, Århus University Hospital, CFIN, Århus C, Denmark

    We have presented a flexible procedure for predicting final tissue outcome combining a dimension reduction method with efficient regression modeling of the resulting low-dimensional projections using smooth non-linear ridge functions. Increase in performance was observed for PPR notably in single-subject models, while performance in data pooled across patients was similar to LR, possibly owing to increased heterogeneity (reperfusion status, time of scan). We speculate that PPR in combination with techniques for identifying homogenous patient subgroups could further improve quantification of regional risk of infarct progression.
12:00 37. 

ADC Values in the Corticospinal Tract at the Acute Stage Can Help Predict Stroke Outcome

    Charlotte Rosso1,2, Olivier Colliot2, Christine Delmaire3, Romain Valabregue3, Sylvain Baillet2, Sophie Crozier1, Didier Dormont2,4, Yves Samson1, Stéphane Lehéricy3,4
Stroke Center, Pitie Salpetriere Hospital, University Pierre and Marie Curie, Paris, France; 2Cognitive neuroscience and Brain Imaging Laboratory, CNRS-UPR 640 LENA, Pitie Salpetriere Hospital, University Pierre and Marie Curie, Paris, France; 3Center for NeuroImaging Research, Pitie Salpetriere Hospital, University Pierre and Marie Curie, Paris, France; 4Department of Neuroradiology, Pitie Salpetriere Hospital, University Pierre and Marie Curie, Paris, France
    We used DWI and ADC maps acquired in the first six hours of stroke onset-H6 and the day after-D1 to predict ischemic stroke outcome at three months in 76 patients. Normalized ADC maps were analyzed for differences between patients with good and poor outcome. ADC values in the corticospinal tract were measured in both groups and used to classify patients according to outcome. ADC values were lower in the CST of patients with poor than patients with good outcomes at both examinations (p<0.05). ADC values in the “damaged” CST predicted outcome with 65% accuracy at H6 and 71% at D1.
12:12 38. 

Identifying Stroke Patients Most Likely to Benefit from Reperfusion Therapy Using Acute MRI


Ona Wu1,2, Søren Christensen2, Niels Hjort2, Anders Neumann2, A Gregory Sorensen1, Gotz Thomalla3, Jens Fiehler4, Thomas Kucinski4, Joachim Rother3, Leif Østergaard2
Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; 2Center for Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark; 3Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; 4Neuroradiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany

    Identification of patients most likely to benefit from reperfusion therapy is a key question in the management of acute stroke patients. Algorithms combining DWI/PWI for predicting infarction in stroke patients (< 6h) were trained on patients receiving standard non-thrombolytic treatment and then applied to patients who received thrombolysis. Predicted lesion volumes were significantly higher in patients without early reperfusion compared to patients who did reperfuse. Our results show that for patients given thrombolytic therapy, the likelihood of reperfusion depends on the degree and extent of the ischemic injury at the time of treatment, which we measured using multiparametric predictive algorithms.
12:24 39. 

Oxygen Metabolic Index as a Predictor of Tissue Viability in Acute Ischemic Stroke Patients


Hongyu An1, Andria L. Ford2, Katie Vo3, William J. Powers4, Jin-Moo Lee2, Weili Lin1
Radiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; 2Neurology, Washington University in St. Louis, St. Louis, MO, USA; 3Radiology, Washington University in St. Louis, St. Louis, MO, USA; 4Neurology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

    We have utilized MR_OMI to assess the cerebral oxygen metabolic activity sequentially (<3.5 hours and at 6 hours) in hyper-acute stroke patients. By using the reperfusion and final infarct status, tissue with different outcomes (dead or alive) were examined in regions either with or without reperfusion. We found that dead tissue had much lower MR_OMI values than alive tissue independent of reperfusion status, suggesting that MR_OMI is capable of predicting tissue outcome in hyper-acute ischemic stroke.
12:36 40.

Diffusion Time Dependent Kurtosis Maps Visualize Ischemic Lesions in Stroke Patients

    Jimmy Lätt1, Danielle van Westen1, Markus Nilsson2, Ronnie Wirestam2, Freddy Ståhlberg2,3, Stig Holtås1,3, Sara Brockstedt1,2
MR Department, Center for Medical Imaging and Physiology, Lund University Hospital, Lund, Sweden; 2Department of Medical Radiation Physics, Lund University, Lund, Sweden; 3Department of Diagnostic Radiology, Lund University, Lund, Sweden
    Diffusion time dependence of the diffusion weighted signal for high b-values in ischemic stroke lesions was recently reported, allowing for the extraction of more information on the tissue microstructure. Here, we express the diffusion time dependence as a change kurtosis, where kurtosis reflects the degree of deviation from free diffusion. The changes in kurtosis for different diffusion times were calculated for nine ischemic stroke patients, examined at a 3T clinical scanner. The change in kurtosis successfully visualized the lesions. Changes in kurtosis are suggested to reflect changes in cell sizes as well as in cell physiology (cellular membrane functionality).
12:48 41.   

Functional MRI Exploration of Visuospatial Attention in Acute Neglect and Non-Neglect Stroke Patients


Roza M. Umarova1, Dorothee Saur2, Christoph Kaller1, Magnus-Sebastian Vry1, Volkmar Glauche2, Irina Mader3, Cornelius Weiller1
Department of Neurology, University Medical Center , Freiburg, Germany; 2Department of Neurology, University Medical Center, Freiburg, Germany; 3Department of  Neuroradilogy, University Medical Center , Freiburg, Germany


We aimed to explore what distinguishes patients with and without neglect after acute stroke in the right hemisphere using fMRI with visuospatial attention task. Patients without neglect showed spared function of key attentional centers in the left hemisphere and post-Rolandic structures in the right hemisphere. Neglect patients presented a down-regulation in most of attentional centers, while the infrequent left targets detection correlated with involvement of the left hemisphere structures. Thus, the spared function of the attention relevant regions in non-neglect patients enabled the modulation of the right primary and association visual areas with a subsequent left targets detection.