Advanced Stroke Imaging

Tuesday 23 April 2013

Irene Klaerke Mikkelsen¹, Lars Riisgaard Ribe¹, Susanne Lise Bekke¹, Kim Mouridsen¹, and Leif Østergaard^1
1Center for Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark

In patients with acute ischemic stroke, millions of neurons die by the minute. For those who are eligible for thrombolytic therapy, the duration of diagnostic DSC-scans are therefore reduced to a minimum. This study shows that this practice may lead to severe underestimation of the perfusion abnormality, and therefore the therapeutic target. The degree of underestimation is investigated for three different deconvolution techniques.

Danny J.J. Wang^1,2, David S. Liebeskind¹, Joe X. Qiao², Matthias Günther³, Whitney B. Pope², Jeffrey L. Saver¹, Noriko Salamon², and Jeffry R. Alger^1,2
1Neurology, UCLA, Los Angeles, CA, United States, ²Radiology, UCLA, Los Angeles, CA, United States, ³Institute for Medical Image Computing, University of Bremen, Bremen, Germany

A novel multi-delay multi-parametric pseudo-continuous ASL (pCASL) protocol was presented. Its accuracy was evaluated by comparison with dynamic susceptibility contrast (DSC) enhanced perfusion MRI in 29 patients with acute and subacute ischemic stroke. Consistent results between multiple hemodynamic parameters derived using ASL and DSC were demonstrated.

Blaise Frederick^1,2, Yunjie Tong^1,2, Megan Strother³, Lisa Nickerson^1,2, Kim Lindsey^1,2, and Manus Donahue^3
1Brain Imaging Center, McLean Hospital, Belmont, MA, United States, ²Department of Psychiatry, Harvard Medical School, Boston, MA, United States,³Department of Radiology, Vanderbilt University, Nashville, TN, United States

We present a novel analysis technique which allows the extraction of detailed cerebrovascular flow information from fMRI data acquired during a hypercarbia challenge. Flow data is derived in 20 subjects, and comparison of flow before and after surgical intervention is performed.

Manus J. Donahue¹, Paul Clemmons¹, Ricardo Andal¹, Robert Singer¹, Diane Brown¹, Morgan Anderson¹, Dan Claassen¹, John Connors¹, Lisa Hermann¹, Lori Jordan¹, Howard Kirshner¹, J. Mocco¹, Ryan Moore¹, Anne O'Duffy¹, Derek Riebau¹, Allen Sills¹, and Megan Strother^1
1Vanderbilt University, Nashville, TN, United States

The purpose of this work is to develop and clinically implement a noninvasive MRI protocol for quantifying the relationship between key hemodynamic compensation mechanisms including cerebrovascular reactivity (CVR), baseline cerebral blood flow (CBF), CBF reactivity, and CBF territory dynamics in patients with cerebrovascular disease. This approach was implemented in 50 patients and results illuminated impairment not clear from structural imaging.

Henry Rusinek¹, Jenny Ha², Po Lai Yau², Aziz Tirsi², Wai Hon Tsui², and Antonio Convit^2
1Radiology, NYU School of Medicine, New York, New York, United States, ²Psychiatry, NYU School of Medicine, New York, New York, United States

The obesity epidemic is responsible for the increasing prevalence of Type 2 diabetes (DB). Using a high-resolution ASL we present evidence that brain perfusion and vascular reactivity are affected in the early stage of DB. Insulin resistant (IR) subjects had significantly lower (p=0.008) resting gray matter flow (60.0±4.5) compared to healthy controls (63.6±6.4), with a trend for hypoperfusion in DB. There was a significant detrimental effect of obesity on vascular reactivity. Our findings suggest that cerebral blood flow and vascular reactivity changes resulting from obesity and insulin resistance are reversible.

Julien Bouvier^1,2, Olivier Detante¹, Irène Troprès³, Sylvie Grand^1,4, David Chechin², Jean-François Le Bas^3,4, Alexandre Krainik^1,4, and Emmanuel Luc Barbier^1
1INSERM U836, Grenoble Institute of Neurosciences, Grenoble, France, ²Philips Healthcare, Suresnes, France, ³Plate-forme IRMaGe, UJF – INSERM US17 – CNRS UMS 3552, Grenoble, France, ⁴CHU de Grenoble, Clinique Universitaire de Neuroradiologie et d’IRM, Grenoble, France

In stroke, Perfusion Weigthed Imaging (PWI) allows the identification of hypoperfused tissues. MRI characterization of the ischemic penumbra, defined by the diffusion-perfusion mismatch, can delineate penumbral and irreversibly infarcted fields with a similar degree of reliability to the gold standard, positron-emission tomography (PET). The presence of a diffusion-perfusion mismatch could justify thrombolysis therapy beyond 3h. The assessment of the penumbra using MRI remains controversial, however. The aim of this study is to evaluate how tissular oxygen saturation (StO2), assessed with a multiparametric qBOLD approach, fits between diffusion and perfusion acute stroke patients.

Xin Hong¹, Yan Zhi Ong², Irvin Teh³, Fatima Ali Nasrallah¹, Zhong Kang Lu⁴, Wei Peng Teo⁵, Cuntai Guan⁴, Kai Keng Ang⁴, Kok Soon Phua⁴, Ling Zhao⁵, Effie Chew⁵, and Kai-Hsiang Chuang^1
1Singapore Bioimaging Consortium, Singapore, Singapore, ²Department of Biological Sciences, National University of Singapore, Singapore, Singapore, ³A*STAR-NUS Clinical Imaging Research Centre, Singapore, Singapore, ⁴Institute for Infocomm Research, Singapore, Singapore, ⁵The Division of Neurology and Rehabilitation Medicine, National University Hospital System, Singapore, Singapore

Perfusion and diffusion MRI were used to understand the plasticity in gray and white matters after motor training in stroke patients with impaired upper extremity. Robot-assisted motor imagery and brain-computer interface (MI-BCI) combined with or without transcranial direct current stimulation (tDCS) were conducted. Brain CBF change and FA changes along motor related fiber tracts are found after 2 weeks of training and correlate with clinical improvement. tDCS did not show significant effects on motor recovery. These findings will be helpful in understanding the role of neuroplasticity in motor recovery, and in the development of effective therapeutic approach for stroke rehabilitation.

Samantha J. Holdsworth¹, Stefan Skare², Kristen Yeom¹, Michael U. Antonucci¹, Jalal B. Andre³, Jarrett Rosenberg¹, Matus Straka¹, Nancy J. Fischbein¹, Greg Zaharchuk¹, and Roland Bammer^1
1Department of Radiology, Stanford University, Palo Alto, CA, United States, ²Karolinska Institute, Clinical Neuroscience, Stockholm, Sweden, ³Department of Radiology, University of Washington, Seattle, WA, United States

Here we investigate an alternative approach to diffusion-weighting imaging (DWI) with the use of a parallel-imaging enhanced dual-echo sequence. It was found that dual-echo DWI is a powerful method for evaluating diffusion-restricting lesions. The long echo time of Echo 2 gives rise to DW images that exhibit superior sensitivity to diffusion lesions than DW images acquired at a shorter echo time; Echo 1 provides high SNR ADC maps for specificity to acute stroke; and the information from both echoes is a potential source of complementary information for the assessment of blood and mineralization products.

Jamie M. Kawadler¹, Jonathan D. Clayden², Fenella J. Kirkham³, and Christopher A. Clark^2
1Imaging & Biophysics Unit, UCL Institute of Child Health, London, United Kingdom, ²Imaging & Biophysics Unit, University College London, London, United Kingdom,³Neurosciences Unit, UCL Institute of Child Health, London, United Kingdom

This work investigates for the first time specific subcortical structure volumes in children and adolescents with sickle cell disease, which has been shown to affect cortical grey matter and deep white matter.

Takashi Yoshiura¹, Akio Hiwatashi¹, Osamu Togao², Jochen Keupp³, Koji Yamashita¹, Kazufumi Kikuchi¹, Yuriko Suzuki⁴, Makoto Obara⁴, and Hiroshi Honda^1
1Department of Clinical Radiology, Kyushu University, Fukuoka, NA, Japan, ²Department of Molecular Imaging and Diagnosis, Kyushu University, Fukuoka, NA, Japan, ³Technical Systems, Philips Research Laboratories, Hamburg, NA, Germany, ⁴Philips Electronics Japan, Tokyo, NA, Japan

Animal experiments have shown that APT imaging can detect lowered pH in acute cerebral infarction, but evidence for human stroke patients is extremely limited in amount. Our purpose was to test the feasibility of APT imaging in assessing clinical acute infarction. APT imaging data from 8 patients with acute infarctions showed significantly reduced APT signal in infarcted tissue compared to normal tissue, demonstrating the clinical feasibility of APT imaging. Moreover, we found that APT contrast between normal ad infarcted tissues was critically dependent on the saturation time, suggesting the importance of imaging parameter optimization.