22. European Stroke Conference 6 Brain imaging A 15:20 - 15:30 pH-weighted imaging in acute stroke: can metabolic imaging help us better understand the penumbra? G.W.J. Harston1, Y.K. Tee2, M. Chappell3, N. Blockley4, T. Okell5, J. Levman6, I. Reckless7, G. Pope8, F. Sheerin9, M. Cellerini10, N. Rane11, P. Jezzard12, S. Payne13, J. Kennedy14 University of Oxford, Oxford, UNITED KINGDOM1,University of Oxford, Oxford, UNIT-ED KINGDOM2, University of Oxford, Oxford, UNITED KINGDOM3, University of Oxford, Oxford, UNITED KINGDOM4, University of Oxford, Oxford, UNITED KINGDOM5, Univer-sity of Oxford, Oxford, UNITED KINGDOM6, Oxford University Hospitals NHS Trust, Ox-ford, UNITED KINGDOM7, Oxford University Hospitals NHS Trust, Oxford, UNITED KING-DOM8, Oxford University Hospitals NHS Trust, Oxford, UNITED KINGDOM9, Oxford University Hospitals NHS Trust, Oxford, UNITED KINGDOM10, Oxford University Hospitals NHS Trust, Oxford, UNITED KINGDOM11, University of Oxford, Oxford, UNITED KINGDOM12, University of Oxford, Oxford, UNITED KINGDOM13, University of Oxford, Oxford, UNITED KINGDOM14 Objectives MRI characterization of cerebral pH changes may provide an indication of metabolic stress and improve the understanding of the evolution of the ischemic penumbra. The objective of this study is to examine how pH-weighted imaging changes are linked to tissue outcome in acute stroke. Methods Patients with ischemic stroke are recruited within 6hrs of symptom onset and undergo serial MRI, on presentation, at 1 day, and 1 week. MRI protocols include diffusion-weighted imaging (DWI), fluid attenuated inversion recovery (FLAIR), and single slice pH-weighted imaging us-ing chemical exchange saturation transfer (CEST) MRI. pH signal is normalized relative to the unaffected, contralateral hemisphere. Tissue outcome was defined using co-registered DWI le-sion on presentation and at 24hrs, and FLAIR lesion at 7 days. Final infarct volume was defined by the day 7 FLAIR scan. Core infarct was defined as DWI positive, FLAIR positive and the mismatch between core and final infarct as DWI negative, FLAIR positive. Results Immediate and delayed tissue outcome appears to be predicted by thresholds of intracellular pH reduction. Core infarct on presentation is predicted by a greater than 15% relative pH signal reduction. A 10-15% relative reduction identified DWI-FLAIR+ tissue. pH tends to normalize by 24hrs. However, despite pH normalization, the depth of initial pH reduction appears to be linked to the eventual tissue outcome, with progression to infarction by 1 week. Conclusions These data suggest that intracellular acidosis occurs early in ischemic stroke and initial pH drop may predict final infarct volume better than DWI. The data suggest that the magnitude of acido-sis predicts tissue outcome. Further study is ongoing to assess whether tissue acidosis can iden-tify reversibly injured penumbral tissue amenable to intervention. 5 Brain imaging A 15:10 - 15:20 Optimizing Acute Stroke Imaging for Maximizing information and Minimizing Acquisi-tion, Post processing and Interpretation times: Analysis of data from a prospective imag-ing cohort study. M. Goyal1, B.K. Menon2 University of Calgary, Calgary, CANADA1,University of Calgary, Calgary, CANADA2 Introduction: We intend to compare the utility and efficiency of perfusion CT (PCT) to NCCT/ multiphase CTA (mCTA) paradigm in making treatment decisions (both IV and IA) in patients with acute ischemic stroke. Methods: mCTA (patent pending) is a new technique capable of identifying site of arterial oc-clusions and degree of pial collateralization distal to occlusion significantly better than conven-tional CTA. Data is from PROVE-IT, an ongoing prospective imaging based cohort study of pa-tients presenting with acute ischemic stroke to our center. All patients undergo NCCT followed by mCTA and PCT (8 cm coverage). Two readers interpreted NCCT and mCTA by consensus. PCT was processed using proprietary software. Data is analyzed using Stata version 12. Results: In 70 patients (median age 67, 49.3% male), median baseline NIHSS was 10 (IQR 13), median onset to CT time in those with witnessed stroke onset was 101 mins (IQR 138) and median baseline ASPECTS was 10 (IQR 3). Acquisition and interpretation took < 2 mins for NCCT, < 5 mins for mCTA and < 20 mins for PCT. Uncertainty for IV tPA treatment was pres-ent in 10.1% of patients with NCCT, 1.4% with mCTA and 15.9% with PCT. Uncertainty for IA treatment was present in 66.7% of patients with NCCT but only in 2.9% with mCTA. Patient motion affected image interpretation in 1.4% of patients with NCCT and mCTA when com-pared to 7.2% with PCT. Agreement between mCTA and PCT for IV tPA was seen in 91.2% patients (k=0.41, p<0.001). In 2 patients with sub-acute infarcts on NCCT, PCT suggested treat-ment. In 3 other patients, NCCT and mCTA suggested futile recanalization whereas PCT sug-gested treatment. These patients all had large infarcts on follow-up imaging. Conclusion: NCCT with mCTA is a robust tool for making IV and IA treatment decisions in pa-tients with acute ischemic stroke. Whole brain coverage, speedy interpretation and being unaf-fected by patient motion are advantages in the acute stroke milieu when compared to PCT. 46 © 2013 S. Karger AG, Basel Scientific Programme
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