Abstract T P29: Arterial-Spin Labeled MRI After Endovascular Stroke Therapy: Validation of a Novel Scale to Quantify the Degree and Heterogeneity of Reperfusion

Abstract

Background: The degree of reperfusion in acute stroke is a key predictor of clinical outcome, yet validation of a noninvasive imaging technique such as arterial spin-labeled MRI (ASL) that can quantify both hypo- and hyperperfusion is needed. Methods: Consecutive series of endovascular therapy for acute stroke and ASL-MRI within 36 hours after treatment start during a 3-year period were analyzed. Reperfusion on DSA was scored with TICI and mTICI (2b definitions of 2/3 and ½, respectively). ASL cerebral blood flow was graded with a scale analogous to mTICI (0=none, 1=< ½, 2=>½, 3=complete) separately for hypo- and hyperperfusion based on occlusion site, yet blinded to TICI/mTICI results. Results: 64 patients (mean age 67.7 ± 13.9 years; 53% women; median baseline NIHSS 15 (2-38)) had ASL acquired within 36 hours (median 7.07 hours (2.69-33.08)) from start of IV thrombolysis or thrombectomy over a 3-year period. 31/64 (48%) patients received IV tPA before endovascular therapy. DSA revealed 32 M1, 18 ICA, 10 M2, and 4 basilar occlusions. After endovascular treatment, TICI0/mTICI0 (6%), TICI1/mTICI1 (2%), TICI2a/mTICI2a (30%), TICI2a/mTICI2b (22%), TICI2b/mTICI2b (39%) and TICI3/mTICI3 (2%) results were noted. ASL revealed hypoperfusion (0 (19%); 1 (59%); 2 (14%); 3 (8%)) and hyperperfusion (0 (69%); 1 (27%); 3 (5%)). 7 combined patterns of hypo- and hyperperfusion were noted on ASL, all unrelated to baseline clinical variables. ASL mTICI hypoperfusion strongly correlated with DSA mTICI (R=-0.77, p<0.001) and TICI (R=-0.71, p<0.001). ASL hyperperfusion was noted only with TICI2a/mTICI2a (9%), TICI2a/mTICI2b (14%), TICI2b/mTICI2b (9%) and was more common with increased time from DSA to ASL (p=0.017). Conclusions: ASL hypoperfusion within 36 hours of acute stroke therapy strongly correlates with reperfusion scores on DSA, providing a novel means to accurately quantify degree of reperfusion. ASL hyperperfusion, concomitant with hypoperfusion, affects a substantial number of cases, predominantly affecting the TICI2a/mTICI2b reperfusion category on DSA.