Threshold-based Identification of Persistent Infarction after Successful Endovascular Treatment: Re-evaluating the “Core”
Authors: Meier Raphael , Lux Paula , McKinley Richard , Jung Simon , Fischer Urs , Gralla Jan , Wiest Roland , Kaesmacher Johannes 
Published: April 2020

Objectives

The objectives of this study included the volumetric analysis of persistent infarction and lesion reversal in Diffusion-Weighted Imaging (DWI), as well as the assessment of accuracy of ADC thresholds to identify regions of persistent infarction in patients with acute ischemic stroke after successful endovascular treatment (EVT).

Materials and Methods

A retrospective analysis of patients with M1 or proximal M2 occlusions, treated between 01/2012 and 07/2017, who underwent successful EVT (≥TICI 2b) and both pre- and post-interventional Magnetic Resonance Imaging (MRI), led to the inclusion of N=90 patients. Administration of recombinant tissue plasminogen activator (rTPA) for intra-venous thrombolysis was performed ahead of intervention in 45 cases (N=45/90, 50%). The majority of patients (N=78/90, 86.7%) were treated with second-generation thrombectomy devices with or without intra-arterial urokinase. DWI at admission and 24-hour follow-up DWI data were co-registered. Acute ischemic changes at baseline DWI, 24-hour DWI lesion, and the affected gray/white matter regions were manually annotated. Persistent infarction was defined as acute ischemic changes on baseline DWI, which were sustained on 24-hour follow-up DWI. Based on the manual annotations, persistent infarction and DWI reversal were quantified in a voxel-wise analysis. Thresholds for the identification of persistent infarction using baseline ADC images were estimated by maximizing Youden’s J statistic (ROC-analysis).

Results

Median age of the patients was 71.9 years (IQR 60.4–79.7 years), 55.6% were female, and NIHSS at admission was 11 (IQR 6–14). The median DWI lesion volume at baseline was 9.9 mL (IQR 3–23.6 mL) and the median DWI lesion volume around 24 hours was 12.1 mL (IQR 3.6–23.7 mL). Reversal of acute ischemic changes occurred frequently (49.8%, IQR 31.7%–65.4%; percentage of initial DWI lesion volume per subject). Sizeable DWI reversal (i.e. >10 mL and >10%) was observed in 26.7% (N=24/90) of the cases. Relative DWI reversal was significantly higher in white matter (58.6%, IQR 35.3–81.5%) than in gray matter (39.2%, IQR 24.9–56.6%; p<0.001). The volume of persistent infarction and DWI reversal were both significantly correlated with the DWI lesion volume at baseline (R=0.873–0.945, p<0.001), however, no correlations with time to reperfusion were found (relative volumes: R=-/+0.058, p=0.607). ROC analyses of ADC thresholds yielded optimal values which differed significantly for gray and white matter (p=0.003), and were lower than previously reported thresholds while having significantly improved accuracy (p≤0.015). No correlations between the estimated ADC thresholds and different covariates were found (time from imaging to reperfusion, time from baseline to follow-up imaging, volume of acute ischemic changes).

Conclusions

DWI reversal occurs frequently in successfully reperfused patients treated with modern EVT. Identification of persistent infarction using ADC thresholds in baseline DWI remains challenging with notable differences for gray and white matter.