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.

Visualizing Non-Gaussian Diffusion: Clinical Application of q-Space Imaging and Diffusional Kurtosis Imaging of the Brain and Spine

“…MK is deˆned as the average of the kurtosis over all possible diŠusion directions; K ¿ is deˆned, by analogy to D ¿ , as the kurtosis in the direction of the diŠusion tensor eigenvector with the largest diŠusion eigenvalue; and K ⊥ is dened as the average of the kurtosis over all directions perpendicular to the diŠusion eigenvector with the largest eigenvalues. 29 Figure 2 shows maps of these metrics. Jensen and Helpern emphasized that, unlike in QSI, the maximum b-value for DKI should be carefully chosen because the DKI formula is valid only for DWI data obtained in normal brain tissue with bº3500 s/mm 2 27 (Fig.…”

“…18,21 However, for q-space analysis, QSI-analyzer was introduced for calculating the FWHM of the PDF and the mean displacement of water molecules. 22,26,30,31 For diŠusional kurtosis analysis, diffusion kurtosis estimator (DKE) 29,32 and the combination of dTV¿FZR (http://www.ut-radiology. umin.jp/people/masutani/dTV.htm) and VOLUME-ONE software (http://www.volume-one.org/) have been introduced in the literature 33,34 (Fig.…”

“…43 Conventional DTI measurements using the Gaussian diŠu-sion tensor model can only be used to evaluate latestage remodeling that is generally characterized by well-organized axons, whereas QSI can better detect axonal remodeling at the early stage, when ax- Jensen's group reported substantial increases in MK within ischemic lesions for 3 patients with stroke. 29 For theˆrst time, they determined the changes in K ¿ and K ⊥ for human focal cerebral infarction. For lesions with strongly oriented axon bundles, i.e., large contralateral FA values, the change was much greater in K ¿ than K ⊥ , suggesting a large decrease in the intra-axonal diŠusivity.…”

Abnormalities in Diffusional Kurtosis Metrics Related to Head Impact Exposure in a Season of High School Varsity Football

“…Similar changes have been seen previously in ischemic regions of stroke patients. 38,39 The significant increase in MK also has been demonstrated in axonal injury and astrogliosis.25 Astrogliosis is the increase of reactive astrocytes due to the destruction of nearby neurons. This abnormal increase in astrocytes increases the microcellular complexity and has been shown to significantly elevate the measured MK in animal models.…”

“…Similar changes have been seen previously in ischemic regions of stroke patients. 38,39 The significant increase in MK also has been demonstrated in axonal injury and astrogliosis.…”