Basic neuroscienceQuantitative T2* mapping reveals early temporo-spatial dynamics in an ischemic stroke model

- This study investigated temporo-spatial dynamics of T2* changes in ischemic tissue.
- T2* detects infarct core and surrounding tissue within 60 min of ischemia.
- T2* values of affected tissue were lower compared to the contralateral hemisphere.
- After 60 min of recanalization of MCAO, T2* normalized in surrounding tissue.
- T2* mapping may be feasible to indicate change of oxygenation in acute stroke.

BackgroundOxyhemoglobin-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 methodWe 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 60 min after MCAO and repeated for 60 min after recanalization. T2* maps were co-registered with histology and T2* changes were compared to the contralateral hemisphere.ResultsWithin 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 ± 0.7 min 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 60 min after MCAO (P = 0.002) and decreased during 60 min 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.ConclusionsQuantitative T2* imaging might be a feasible tool to indicate change of oxygenation in acute stroke imaging, without administration of contrast agent.