Christine Preibisch^1,2, Monika Ankenbrank¹, Alexandra Gersing¹, Vivien Toth¹, Nuria Hirsch¹, Hendrik Kooijman³, Silke Wunderlich², and Claus Zimmer^1
1Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany, ²Neurologische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, Munich, Germany, ³Philips Healthcare, Hamburg, Germany

Purpose of this study was to evaluate a protocol for measurement of a relative oxygen extraction fraction (rOEF) with separate quantification of T2, T2* and CBV for improved penumbra estimation in patients with ischemia. Compared to rOEF in healthy appearing tissue (0.59 ± 0.19), rOEF presented a stronger increase in areas with prolonged TTP without diffusion restriction (1.44 ± 0.85) than in regions with diffusion restriction (1.03 ± 0.62). rOEF measurement allows to identify ischemic areas and detects differences in rOEF between ischemic core and surrounding tissue. Further work is needed to delineate utility of rOEF for the penumbra concept.

Xiao Wang¹, Xiao-Hong Zhu¹, Afshin A Divani², Yi Zhang¹, and Wei Chen^1
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, United States,²Neurology, University of Minnesota, Minnesota, United States

Ischemic stroke is a leading cause of death and long-term disability in the United States. Tremendous effort has been taken and great progress has been made to detect and treat the ischemic lesion at an early stage. The use of thrombolytic agent such as tissue plasminogen activator (tPA) can be helpful to restore the function of salvageable tissues, however, reperfusion paradoxically may also lead to the secondary cell death concurrently. The severity of the reperfusion lesion was evaluated with the ADC, CVR images at a relatively early stage (24 hours after a 1-hour MCA occlusion) of rat brain and the corresponding histology images were obtained on day 7 of the post-occlusion. The results show that the spatial pattern of declined ADC correlates well with the actual lesion region determined by the histology images, while the compromised CVR with normal ADC turns out to be histologically intact. Therefore, three regions regarding the lesion severity can be identified with combined ADC and CVR images: severe lesion region with both ADC and CVR decreased; mild lesion region with impaired CVR but normal ADC and the normal brain region with intact CVR and ADC. The mismatched areas with compromised CVR but intact ADC at the early stage of reperfusion potentially could serve as the treatment target to improve the clinical outcomes.

Jeroen C.W. Siero¹, Nolan Hartkamp¹, Anita A. Harteveld¹, Annette Compter¹, Bart van der Worp¹, Manus J. Donahue², Esben T. Petersen¹, and Jeroen Hendrikse^1
1University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, ²Radiology and Radiological Sciences, Vanderbilt University, TN, United States

We acquired CBF and BOLD data in patients with cerebrovascular disease (stenosis/occlusion of vertebral basilar artery) during visual stimulation before and after acetazolamide (ACZ) administration. One third of the patients showed negative BOLD responses post-ACZ while CBF remained positive. As the conventionally assumed one-to-one relationship between BOLD and CBF responses seems compromised, caution is warranted when inferring cortical activation and neurovascular coupling in these patients when solely using BOLD fMRI. Our findings indicate altered neurovascular and/or metabolic coupling in these patients and could potentially be valuable marker for clinical outcome.

Amit Mehndiratta¹, Chang Sub Park¹, David E Crane², Bradley J MacIntosh², Stephen J Payne¹, and Michael A Chappell^1
1Institute of Biomedical Engineering, University of Oxford, Oxford, Oxfordshire, United Kingdom, ²Medical Biophysics, Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada

Estimation of capillary haemodynamics has historically been a challenge in DSC-MRI analysis. With the Control Point Interpolation method it is now possible to study variation in residue function and haemodynamics in-vivo. This study examined the changes in tissue haemodynamics, maximum potential oxygen delivery corresponding maximum potential tissue metabolic activity in a cohort of seventeen patients with atherosclerotic diseases both pre- and post-carotid endarterectomy. It was found that capillary heterogeneity increased in ischemic tissue, which would be associated with an increase in maximum tissue oxygen extraction fraction that could assist the tissue to maintain normal metabolic activity.

Olivier Heck^1,2, Johan Pietras³, Thomas Perret⁴, Agnès Aghetti^1,3, Marie-Charlotte Plichta^1,3, Irène Troprès^4,5, Sylvie Grand¹, Olivier Detante^5,6, Assia Jaillard^3,7, and Alexandre Krainik^1,5
1Department of Neuroradiology and MRI, University Hospital of Grenoble, Grenoble, France, ²Department of Neuroradiology, University Hospital of Nancy, Nancy, France, ³UMS IRMaGe, Grenoble, France, ⁴Inserm U836, Grenoble Institute of Neurosciences, Grenoble, France, ⁵University Joseph Fourier, Grenoble, France, ⁶Stroke Unit, University Hospital of Grenoble, Grenoble, France, ⁷Research Department, University Hospital of Grenoble, Grenoble, France

Purpose: To investigate changes over time of cerebral perfusion and CO2 vasoreactivity (CVR) after anterior stroke using MRI. Methods: Basal perfusion with dynamic susceptibility contrast, and CVR with BOLD contrast measured in 16 stroke subjects at 35, 50, and 180 days after stroke onset. Results: Basal perfusion decreased in both necrotic and perinecrotic rim. In the undamaged MCA territory, perfusion remained stable over time. CVR increased in the perinecrotic rim, but remained stable in the necrosis and the undamaged MCA territory. Conclusion: These preliminary results suggest functional improvement of the perilesional vasculature during the first 180 days after stroke.

Yang Li¹, Denise C. Park², Karen M. Rodrigue², Yamei Cheng¹, and Hanzhang Lu^1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, ²Center for Vital Longevity, School of Behavioral and Brain Sciences, Uiversity of Texas at Dallas, Dallas, Texas, United States

Age is the single most important risk factor for stroke and associated cerebrovascular diseases. To date, the most direct vascular marker in vivo has been shown to be cerebrovascular reactivity (CVR), which reflects the ability of the vessel to dilate when challenged. In this work, we present four-year longitudinal follow-up CVR data in 80 healthy individuals ranging from 20 to 85 years old. The findings from the longitudinal data were compared to those from the cross-sectional data. Regional differences were also investigated.