OBJECTIVEThe value of combined diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) for detecting ischemic lesions of patients with acute ischemic injury was analyzed. Combined pre- and posttreatment DWI and PWI studies were used to assess the efficacy of intra-arterial thrombolysis.METHODSIntra-arterial thrombolysis was performed within 6 hours of onset in 10 patients who presented with acute middle cerebral artery or internal carotid artery occlusion. DWI and PWI obtained before and after treatment were studied. The final T2-weighted magnetic resonance scans were obtained 1 month after onset. Thrombolysis resulted in recanalization in seven patients. The mismatch ratio percentage ([initial PWI − initial DWI/initial PWI] × 100) and the rescued ratio percentage ([initial PWI − final T2/initial PWI] × 100) were calculated. The National Institutes of Health Stroke Scale (NIHSS) was used for neurological assessment of stroke severity at admission and at 1 month after onset.RESULTSIn all patients, the mismatch ratio was greater than 60% (mean ± standard deviation, 81.7 ± 16.7%) and was significantly correlated with initial NIHSS score (−0.74;P= 0.03), and the rescued ratio was significantly correlated with the NIHSS score 1 month after the insult (r= −0.83;P= 0.01). In patients who exhibited recanalization of the occluded artery (n = 7), the mean rescued ratio was 89.6 ± 12.8% (range, 63–100%). In addition, the lesion volume on posttreatment DWI scans and final T2-weighted magnetic resonance images was not enlarged; on posttreatment PWI scans, it was significantly decreased. The NHISS score at 1 month after the insult (2.3 ± 2.1) was markedly improved as compared with the initial NHISS score (10.7 ± 3.9).CONCLUSIONIn a small number of patients who presented with internal carotid artery or middle cerebral artery occlusion, the DWI/PWI mismatch ratio correlated with the initial neurological severity. The rescued ratio may be an objective indicator of the efficacy of treatment.