Do Acute Diffusion- and Perfusion-Weighted MRI Lesions Identify Final Infarct Volume in Ischemic Stroke?

Abstract

Background and Purpose— An acute mismatch on diffusion-weighted MRI (DWI) and perfusion-weighted MRI (PWI) may represent the “tissue-at-risk.” It is unclear which “semiquantitative” perfusion parameter most closely identifies final infarct volume. Methods— Acute stroke patients underwent DWI and PWI (dynamic-susceptibility contrast imaging) on admission (baseline), and T 2 -weighted imaging (T 2 WI) at 1 or 3 months after stroke. “Semiquantitative” mean transit time (MTT sq =first moment of concentration/time curve), cerebral blood volume (CBV sq =area under concentration/time curve), and cerebral blood flow (CBF sq =CBV sq /MTT sq ) were calculated. DWI and PWI lesions were measured at baseline and final infarct volume on T 2 WI acquired ≥1 month after stroke. Baseline DWI, CBF sq , and MTT sq lesion volumes were compared with final T 2 WI lesion volume. Results— Among 46 patients, baseline DWI and CBF sq lesions were not significantly different from final T 2 WI lesion volume, but baseline MTT sq lesions were significantly larger. The correlation with final T 2 WI lesion volume was strongest for DWI (Spearman rank correlation coefficient ρ=0.68), intermediate for CBF sq (ρ=0.55), and weakest for MTT sq (ρ=0.49) baseline lesion volumes. Neither DWI/CBF sq nor DWI/MTT sq mismatch predicted lesion growth; lesion growth was equally common in those with and without mismatch. Conclusions— Of the 2 PWI parameters, CBF sq lesions most closely identifies, and MTT sq overestimates, final T 2 WI lesion volume. “DWI/PWI mismatch” does not identify lesion growth. Patients without “DWI/PWI mismatch” are equally likely to have lesion growth as those with mismatch and should not be excluded from acute stroke treatment.