Preliminary observations of increased diffusional kurtosis in human brain following recent cerebral infarction

Abstract

By application of the MRI method of diffusional kurtosis imaging, a substantially increased diffusional kurtosis was observed within the cerebral ischemic lesions of three stroke subjects, 13-26 h following the onset of symptoms. This increase is interpreted as probably reflecting a higher degree of diffusional heterogeneity in the lesions when compared with normal-appearing contralateral tissue. In addition, for two of the subjects with white matter infarcts, the increase had a strong fiber tract orientational dependence. It is proposed that this effect is consistent with a large drop in the intra-axonal diffusivity, possibly related to either axonal varicosities or alterations associated with the endoplasmic reticulum.

Copyright © 2010 John Wiley & Sons, Ltd.

Figures

Figure 1

T2-weighted (b = 0) images for a single slice from each of the three subjects. The red arrows indicate the lesion areas used for the analysis of the diffusion metrics.

Figure 2

Parametric maps of the four conventional diffusion metrics for the three subjects. The regions of interest (ROIs) for the ischemic lesions are shown in red, and the contralateral ROIs are shown in blue. The calibration bars for the diffusivities are in units of μm2/ms, whereas those for the fractional anisotropy (FA) are dimensionless. D⊥, radial diffusivity; D||, axial diffusivity; MD, mean diffusivity.

Figure 3

Parametric maps of the three diffusional kurtosis metrics for the same slices as shown in Fig. 2. All metrics in Figs 2 and 3 for a given subject are derived from a single diffusional kurtosis imaging (DKI) dataset. Note the relatively larger differences between the ischemic and contralateral sides for the axial kurtosis (K||) relative to the radial kurtosis (K⊥) for Subjects 2 and 3. The calibration bars for the kurtoses are dimensionless. MK, mean kurtosis.

Figure 4

(a–g) Values of the diffusion metrics averaged over the regions of interest (ROIs). The error bars indicate the standard deviations. Note the particularly large differences between the contralateral and ischemic ROIs for D|| and K||. (h) Percentage changes for the diffusion metrics in the ischemic ROI relative to the contralateral ROI, averaged over all three subjects. The error bars indicate the standard errors. D⊥, radial diffusivity; D||, axial diffusivity; FA, fractional anisotropy; K⊥, radial kurtosis; K||, axial kurtosis; MD, mean diffusivity; MK, mean kurtosis.