Final infarct volume estimation on 1-week follow-up MR imaging is feasible and is dependent on recanalization status

Abstract

Purpose: We aim to characterize infarct volume evolution within the first month post-ischemic stroke and to determine the effect of recanalization status on early infarct volume estimation.

Methods: Ischemic stroke patients recruited for the MONITOR and VISION studies were retrospectively screened and patients who had infarcts on diffusion-weighted imaging (DWI) at baseline and had at least two follow-up MR scans (n = 56) were included. Pre-defined target imaging time points, obtained on a 3-T MR scanner, were 12 hours (h), 24 h, 7 days, and ≥30 days post-stroke. Infarct tissue was manually traced blinded to the images at the other time points. Infarct expansion index was calculated by dividing infarct volume at each follow-up time point by the baseline DWI infarct volume. Recanalization was assessed within 24 h post-stroke. Correlation and statistical comparison analysis were done using the Spearman, Mann-Whitney, and Kruskal-Wallis tests.

Results: Follow-up infarct volumes were positively correlated with the baseline infarct volume (ρ > 0.81; p < 0.001) where the strongest correlation existed between baseline and 7-day post-stroke infarct volumes (ρ = 0.92; p < 0.001). The strongest correlation among the follow-up imaging was found between infarct volumes 7-day post-stroke and ≥30-day time points (ρ = 0.93; p < 0.001). Linear regression showed a close-to unity slope between 7-day and final infarct volumes (slope = 1.043; p < 0.001). Infarct expansion was higher in the non-recanalized group than the recanalized group at the 7-day (p = 0.001) and ≥30-day (p = 0.038) time points.

Conclusions: Final infarct volume can be approximated as early as 7 days post-stroke. Final infarct volume approximation is significantly associated with recanalization status.

Keywords: Infarct volume; Ischemic stroke; MRI; Recanalization; Sub-acute.

Fig. 1

Infarct volume changes in a 79-year-old male patient presented with left-sided weakness and occlusion of the superior division of the right MCA. This figure represents diffusion-weighted imaging (DWI) at 5 hours after onset (A) and consecutive fluid attenuated inversion recovery (FLAIR) imaging sessions obtained 12 hours (B), 28 hours (C), 5 days (D) and 40 days (E) post stroke.

Fig. 2

Infarct volume distribution measured at consecutive imaging time points. In this box plot, the ends of the boxes define the 25th and 75th percentiles, with a line at the median and error bars extending to the 10th and 90th percentiles.

Fig. 3

Infarct expansion index, calculated as the infarct volume divided by lesion size on the baseline DWI, declines after the sub-acute phase within the first week post-stroke. Ends of the boxes define the 25th and 75th percentiles, with a line representing the median value and error bars extending to the 10th and 90th percentiles.

Fig. 4

Linear regression analysis of 7-day and final infarct volumes. The solid line represents the regression line and dashed lines represent the 95% prediction and confidence intervals. Calculated p values for slope (1.043) and intercept (3.734) were <0.001 and 0.009, respectively.

Fig. 5

Bland-Altman analysis of infarct expansion at 7-day and final assessment time points.

Fig. 6

Infarct expansion was significantly different in recanalized (R) and non-recanalized (NR) groups at both 7-day and final (>30-day) time points. Ends of the boxes define the 25th and 75th percentiles, with a line at the median and error bars extending to the 10th and 90th percentiles.