Gersing AS, Faymonville AM, Schwaiger BJ, Leypoldt F, Siemonsen S, Zimmer C, Magnus T, Fiehler J.

BACKGROUND: Oxyhemoglobin-sensitive sequences, namely T2*, can indirectly depict changes in oxygen extraction. Purpose of this study was to investigate the dynamics of T2* changes in ischemic tissue. NEW METHOD: We investigated earliest temporo-spatial dynamics within ischemic tissue, measured with quantitative T2* imaging in the histologically defined infarct core and surrounding surviving tissue. Middle cerebral artery occlusion (MCAO) was induced by a filament model in mice. Serial multiple gradient-echo T2* sequences and diffusion-weighted images were acquired for 60min after MCAO and repeated for 60min after recanalization. T2* maps were co-registered with histology and T2* changes were compared to the contralateral hemisphere. RESULTS: Within the histologically defined infarct core, relative T2* values decreased significantly by -10.8±2.8% (P=0.003) compared to the contralateral hemisphere within 3.5±0.7min after MCAO. Relative T2* values in volume exceeding the histologically determined infarct core were significantly less decreased (-6.7±2.1%; P=0.02) and increased after recanalization (+3.9±1.9%; P=0.045). Volume with T2* decrease showed continuous growth over 60min after MCAO (P=0.002) and decreased during 60min after recanalization (P=0.026), showing most significant correlations between infarct core volume and T2* abnormality volume (r=0.66; P=0.037) of the last image acquired after recanalization. COMPARISON WITH EXISTING METHOD(S): To our best knowledge, this is the first application of non-invasive quantitative T2* measurements to assess changes in levels of deoxyhemoglobin as an indirect biomarker for metabolic impairment in ischemic tissue. CONCLUSIONS: Quantitative T2* imaging might be a feasible tool to indicate change of oxygenation in acute stroke imaging, without administration of contrast agent.

J Neurosci Methods. 2016;259:83-9

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