First-pass quantitative CT perfusion identifies thresholds for salvageable penumbra in acute stroke patients treated with intra-arterial therapy.

BACKGROUND AND PURPOSE: The purpose of this study was to determine whether, in acute stroke patients treated with intra-arterial (IA) recanalization therapy, CT perfusion (CTP) can distinguish ischemic brain tissue destined to infarct from that which will survive.

METHODS: Dynamic CTP was obtained in 14 patients within 8 hours of stroke onset, before IA therapy. Initial quantitative cerebral blood volume (CBV) and flow (CBF) values were visually segmented and normalized in the "infarct core" (region 1: reduced CBV and CBF, infarction on follow-up), "penumbra that infarcts" (region 2: normal CBV, reduced CBF, infarction on follow-up), and "penumbra that recovers" (region 3: normal CBV, reduced CBF, normal on follow-up). Normalization was accomplished by dividing the ischemic region of interest value by that of a corresponding, contralateral, uninvolved region, which resulted in CBV and CBF "ratios." Separate CBV and CBF values were obtained in gray matter (GM) and white matter (WM).

RESULTS: Mean CBF ratios for regions 1, 2, and 3 were 0.19 +/- 0.06, 0.34 +/- 0.06, and 0.46 +/- 0.09, respectively (all P < .001). Mean CBV ratios for regions 1, 2, and 3 were similarly distinct (all P < .05). Absolute CBV and CBF values for regions 2 and 3 were not significantly different. All regions with CBF ratio <0.32, CBV ratio <0.68, CBF <12.7 mL/100 g/min, or CBV <2.2 mL/100 g infarcted. No region with CBF ratio >0.44 infarcted. GM versus WM CBF and CBV values were significantly different for region 2 compared with region 3 (P < .05).

CONCLUSIONS: In acute stroke patients, quantitative CTP can distinguish ischemic tissue likely to infarct from that likely to survive.