Multiparametric MRI tissue characterization in clinical stroke with correlation to clinical outcome - Part 2

Background and Purpose-Multiparametric MRI generates different zones within the lesion that may reflect heterogeneity of tissue damage in cerebral isc hemia. This study presents the application of a novel model of tissue chara cterization based on an angular separation between tissues obtained with th e use of an objective (unsupervised) computer segmentation algorithm implem enting a modified version of the Iterative Self-Organizing Data Analysis Te chnique (ISODATA). We test the utility of this model to identify ischemic t issue in clinical stroke. Methods-MR parameters diffusion-, T2-, and T1-weighted imaging (DWI, T2WI, and T1WI, respectively) were obtained from 10 patients at 3 time points (30 studies) after stroke: acute (less than or equal to 12 hours), subacute (3 to 5 days), and chronic (3 months). The National Institutes of Health Stro ke Scale (NIHSS) was measured, and volumes were obtained from the ISODATA, DWI, and T2WI maps on patients at each time point. Results-The acute (less than or equal to 12 hours) multiparametric ISODATA volume was significantly correlated with the acute (less than or equal to 1 2 hours) DWI (r=0.96. P <0.05; n=10) and chronic (3 months) T2WI volume (r= 0.69, P <0.05; n=10). The ISODATA-defined tissue regions exhibited MR indic es consistent with ischemic and/or infarcted tissue at each time point. The acute (less than or equal to 12 hours) multiparametric ISODATA volumes wer e significantly correlated (r=0.82, P <0.009; 10) with the final NIHSS scor e. In comparison, the acute (less than or equal to 12 hours) DWI volumes we re less correlated (p =0.77, P <0.05; n=10) and T2WI volume (less than or e qual to 12h) exhibited a marginal correlation (r=0.66, P <0.05; n=10) with the final NIHSS score. Conclusions-The integrated ISODATA approach to tissue segmentation and clas sification discriminated abnormal from normal tissue at each time point. Th e ISODATA volume was significantly correlated with the current MR standards used in the clinical setting and the 3-month clinical status of the patien t.