Diffusion and Perfusion MRI in Predicting Final Infarct Volume: A Study of 81 Patients with Acute Stroke
Purpose: To assess the utility of diffusion weighted imaging, cerebral blood volume, cerebral blood flow and mean transit time mapping in predicting final infarct volume in 81 patients with acute ischemic stroke. Methods: DWI, CBV, CBF and MTT images were obtained in 81 patients within 53 hours of stroke onset. Follow-up CT or T2 weighted MR images were obtained at 1 day to 4 months. Ischemic region volumes were measured on all images. An analysis of covariance with the variables of age, sex, treatment, time from stroke onset to imaging, and lesion type was performed. Linear regressions of DWI, CBV, CBF and MTT versus final infarct volume were obtained. A mismatch was determined if there was greater than 20% difference in volume between the diffusion and perfusion images. Results: Analysis of covariance demonstrated that DWI best predicts final infarct volume and that CBV alone of the other variables significantly improves the DWI prediction of final infarct volume. Linear regression analysis yielded an R2 of 0.90, slope of 1.24 for DWI versus follow-up, R2 of 0.84, slope of 1.22 for CBV versus follow-up, R2 of 0.37, slope of 0.44 for CBF versus follow-up and R2 of 0.25, slope of 0.33 for MTT versus follow-up. 13/81 patients had a DWI - CBV mismatch with mean lesion growth of 121 % while 68/81 patients had a DWI - CBV match with mean lesion growth of 15%. 36/81 had a DWI - CBF mismatch with mean lesion growth of 56% while 45/81 had a DWI - CBF match with mean lesion growth of 13%. 43/81 had a DWI - MTT mismatch with mean lesion growth of 47%. 38/81 had a DWI - MTT match with mean lesion growth of 16%. Conclusions: Both DWI and CBV are very good predictors of final infarct volume. CBF and MTT maps identify tissue at risk of infarction not identified on DWI or CBV maps. Since this tissue does not always infarct, these maps greatly overestimate final infarct size.The identification of a DWI - CBV, DWI - CBF or DWI - MTT mismatch predicts much more lesion growth compared with a diffusion perfusion match. This is most dramatic for DWI - CBV mismatches. This information may be valuable in the assessment of new therapeutic strategies.