Background: For acute stroke assessment, apparent diffusion coefficient (ADC) obtained from diffusion-weighted imaging (DWI) provides sensitive detection of infarct volume. Identification of infarct growth in patients with acute ischemic stroke (AIS) is important for determining the efficacy of stroke therapy. Reported ADC thresholds for detecting AIS vary from 550 to 650 x10^-6mm^2/s. Therefore, the measurement of infarct growth is not standardized.
Hypothesis: Measurement of the rate of infarct growth after stroke is independent of the ADC threshold used.
Methods: 38 AIS patients (age; 71.5±17.0) were imaged acutely (within 4h) after stroke symptoms (Time1-Baseline) and repeated at 24h (Time2) on a 3T MR scanner. DTI data with 15 directions was acquired and used for ADC map calculations. Lesion volumes were calculated with ADC thresholds of 550, 600, 630 and 650 x10^-6mm^2/s using ANTONIA software. Rate (r) of infarct growth was calculated by r=Δvolume(ADC2-ADC1)/Δtime(time2-time1).
Results: ADC volume and rate of infarct growth is reported in table 1. No significant difference was found in the rate of infarct growth between the two time points (one way ANOVA).
Conclusion: Quantification of infarct evolution is critical for determining the efficacy of stroke therapy. Although absolute lesion volumes vary considerably, the rate of infarct growth is independent of the ADC threshold and should be the preferred measure of acute infarct growth.