Background: The degree of variability in the rate of early diffusion-weighted imaging expansion in acute stroke has not been well characterized. Aim: We hypothesized that patients with slowly expanding diffusion-weighted imaging lesions would have more penumbral salvage and better clinical outcomes following endovascular reperfusion than patients with rapidly expanding diffusion-weighted imaging lesions. Methods: In the first part of this substudy of DEFUSE 2, growth curves were constructed for patients with >90% reperfusion and 50% reduction in perfusion-weighted imaging after endovascular therapy) were categorized into tertiles according to their initial diffusion-weighted imaging growth rates. For each tertile, penumbral salvage [comparison of final volume to the volume of perfusion-weighted imaging (Tmax > 6 s)/diffusion-weighted imaging mismatch prior to endovascular therapy], favorable clinical response (National Institutes of Health Stroke Scale improvement of ≥8 points or 0–1 at 30 days), and good functional outcome (90-day modified Rankin score of ≤2) were calculated. A multivariate model assessed whether infarct growth rates were an independent predictor of clinical outcomes. Results: Sixty-five patients were eligible for this study; the median initial growth rate was 3·1 ml/h (interquartile range 0·7–10·7). Target mismatch patients ( n = 42) had initial growth rates that were significantly slower than the growth rates in malignant profile ( n = 9 patients, P < 0·001). In patients who achieved reperfusion ( n = 38), slower early diffusion-weighted imaging growth rates were associated with better clinical outcomes ( P < 0·05) and a trend toward more penumbral salvage ( n = 31, P = 0·103). A multivariate model demonstrated that initial diffusion-weighted imaging growth rate was an independent predictor of achieving a 90-day modified Rankin score of ≤2. Conclusions: The growth rate of early diffusion-weighted imaging lesions in acute stroke patients is highly variable; malignant profile patients have higher growth rates than patients with target mismatch. A slower rate of early diffusion-weighted imaging growth is associated with a greater degree of penumbral salvage and improved clinical outcomes following endovascular reperfusion.

Background and Purpose—: It is hypothesized that early diffusion-weighted imaging (DWI) lesions accurately estimate the size of the irreversibly injured core and thresholded perfusion-weighted imaging (PWI) lesions (time to maximum of tissue residue function [Tmax] >6 seconds) approximate the volume of critically hypoperfused tissue. With incomplete reperfusion, the union of baseline DWI and posttreatment PWI is hypothesized to predict infarct volume. Methods—: This is a substudy of Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution Study 2 (DEFUSE 2); all patients with technically adequate MRI scans at 3 time points were included. Baseline DWI and early follow-up PWI lesion volumes were determined by the RAPID software program. Final infarct volumes were assessed with 5-day fluid-attenuated inversion recovery and were corrected for edema. Reperfusion was defined on the basis of the reduction in PWI lesion volume between baseline and early follow-up MRI. DWI and PWI volumes were correlated with final infarct volumes. Results—: Seventy-three patients were eligible. Twenty-six patients with >90% reperfusion show a high correlation between early DWI volume and final infarct volume ( r =0.95; P <0.001). Nine patients with 6 seconds) volume and final infarct volume ( r =0.86; P =0.002). Using all 73 patients, the union of baseline DWI and early follow-up PWI is highly correlated with final infarct volume ( r =0.94; P 6 seconds) volumes provide a reasonable approximation of final infarct volume after endovascular therapy.

Background and Purpose—: The aim of this study was to assess the frequency and extent of early diffusion-weighted imaging (DWI) lesion reversal after endovascular therapy and to determine whether early reversal is sustained or transient. Methods—: MRI with DWI perfusion imaging was performed before (DWI 1) and within 12 hours after (DWI 2) endovascular treatment; follow-up MRI was obtained on day 5. Both DWIs were coregistered to follow-up MRI. Early DWI reversal was defined as the volume of the DWI 1 lesion that was not superimposed on the DWI 2 lesion. Permanent reversal was the volume of the DWI 1 lesion not superimposed on the day 5 infarct volume. Associations between early DWI reversal and clinical outcomes in patients with and without reperfusion were assessed. Results—: A total of 110 patients had technically adequate DWI before endovascular therapy (performed median [interquartile range], 4.5 [2.8–6.2] hours after onset); 60 were eligible for this study. Thirty-two percent had early DWI reversal >10 mL; 17% had sustained reversal. The median volume of permanent reversal at 5 days was 3 mL (interquartile range, 1.7–7.0). Only 2 patients (3%) had a final infarct volume that was smaller than their baseline DWI lesion. Early DWI reversal was not an independent predictor of clinical outcome and was not associated with early reperfusion. Conclusions—: Early DWI reversal occurred in about one third of patients after endovascular therapy; however, reversal was often transient and was not associated with a significant volume of tissue salvage or favorable clinical outcome.

Purpose To determine the tracking factor by studying the relationship between kidney and diaphragm motions and to compare the efficiency of the gating‐and‐following and gating‐only algorithms in reducing motion artifacts in navigator‐gated scans. Materials and Methods Diaphragm and kidney motions were measured by using real‐time TrueFISP sequences from 10 healthy human volunteers to determine tracking factors at different acceptance windows. Mean tracking factors were used to calculate mean residual errors and improvement factors for the gating‐and‐following and gating‐only algorithms. Results Mean tracking factors for ±4, ±6, ±8 mm and full acceptance windows ranged from 0.6 to 0.7, with large interindividual variations. Acceptance rates increased as the size of the acceptance window increased (acceptance rate for a 4 mm window ∼50%). There was a greater reduction of motion errors by gating‐and‐following (maximum of 1.86 mm) than gating‐only (maximum of 7.05 mm). Conclusion Mean tracking factors obtained in this study can be used as a guideline for using the gating‐and‐following algorithm in navigator‐gated kidney scans. The gating‐and‐following and gating‐only algorithms were quantitatively compared, and it was found that the former is more effective in reducing motion errors. J. Magn. Reson. Imaging 2011;33:143–148.