Quantitative T2′-Mapping in Acute Ischemic Stroke

Background and Purpose— Quantitative T2′-mapping detects regional changes in the relation of oxygenated and deoxygenated haemoglobine and might reflect areas with increased oxygen extraction. T2′-mapping in conjunction with an elaborate algorithm for motion correction was performed in patients with acute large-vessel stroke, and quantitative T2′-values were determined within the diffusion-weighted imaging lesion and perfusion-restricted tissue. Methods— Eleven patients (median age, 71 years) with acute middle cerebral or internal carotid artery occlusion underwent MRI before scheduled endovascular treatment. MR-examination included diffusion- and perfusion-weighted imaging and quantitative, motion-corrected mapping of T2′. Time-to-peak maps were thresholded for different degrees of perfusion delays (eg, ≥0 s, ≥ 2s) when compared with a reference time-to-peak value from healthy contralateral tissue. Mean T2′-values in areas with reduced apparent diffusion coefficient and in areas with impaired perfusion were compared with T2′-values in corresponding contralateral areas. Results— Median time between symptom onset and MRI was 238 minutes. T2′-values were significantly reduced within the apparent diffusion coefficient -lesion when compared with contralateral healthy tissue (83 ms [67, 97] versus 97 ms [91, 111]; P <0.003). In perfusion-restricted tissue, T2′-values were also significantly lower when compared with contralateral healthy tissue (ie, for time to peak, ≥0 s 93 ms [86, 102] versus 104 [90, 110]; P =0.008) but were significantly higher than within the apparent diffusion coefficient lesion. The severity of the perfusion impairment had no influence on median T2′-values. Conclusions— Motion-corrected T2′-mapping reveals significant and gradually declining values from healthy to perfusion-disturbed to apparent diffusion coefficient-restricted tissue. Current T2′-mapping can differentiate between the ischemic core and the perfusion-impaired areas but not on its own between penumbral and oligemic tissue.