Characterizing the diffusion/perfusion mismatch in experimental focal cerebral ischemia

Abstract

Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) can rapidly detect lesions in acute ischemic stroke patients. The PWI volume is typically substantially larger than the DWI volume shortly after onset, that is, a diffusion/ perfusion mismatch. The aims of this study were to follow the evolution of the diffusion/ perfusion mismatch in permanent and 60- minute temporary focal experimental ischemia models in Sprague-Dawley rats using the intraluminal middle cerebral artery occlusion (MCAO) method. DWI and arterial spin-labeled PWI were performed at 30, 60, 90, 120, and 180 minutes after occlusion and lesion volumes (mm(3)) calculated At 24 hours after MCAO, and infarct volume was determined using triphenyltetrazolium chloride staining. In the permanent MCAO group, the lesion volume on the ADC maps was significantly smaller than that on the cerebral blood flow maps through the first 60 minutes after MCAO; but not after 90 minutes of occlusion. With 60 minutes of transient ischemia, the diffusion/perfusion mismatch was similar, but after reperfusion, the lesion volumes on ADC and cerebral blood flow maps became much smaller. There was a significant difference in 24- hour infarct volumes between the permanent and temporary occlusion groups.

Fig 1

(A) Temporal evolution of apparent diffusion coefficient (ADC)– and cerebral blood flow (CBF)–derived ischemic lesion volumes (mm³) in Group 2 (n = 6) subjected to permanent suture middle cerebral artery occlusion (MCAO) based on ADC and CBF reduction thresholds of 30 ± 2% and 57 ± 11%, respectively. The ADC- and CBF-derived lesion volumes are compared with the 2,3,4-triphenyltetrazolium chloride (TTC)–derived infarct volume at 24 hours. The error bars are standard error of the mean. *p < 0.01, **p < 0.005. (B) Temporal evolution of ADC- and CBF-derived ischemic lesion volumes (mm³) in Groups 1 and 2 (n = 11) subjected to permanent suture MCAO based on ADC and CBF reduction thresholds of 30 ± 2% and 57 ± 11%, respectively. The ADC- and CBF-derived lesion volumes are compared with the TTC-derived infarct volume at 24 hours. The error bars are standard error of the mean. *p < 0.01; **p < 0.001.

Fig 2

Temporal evolution of apparent diffusion coefficient (ADC)– and cerebral blood flow (CBF)–derived ischemic lesion volumes (mm³) in Group 3 (n = 6) subjected to 60 minutes of suture MCAO based on ADC and CBF reduction thresholds of 30 ± 2% and 57 ± 11%, respectively. The ADC- and CBF-derived lesion volumes are compared with the 2,3,4-triphenyltetrazolium chloride–derived infarct volume at 24 hours. The error bars are standard error of the mean. Arrow indicates reperfusion (REP). *p < 0.005; **p <0.001.