Diffusion Tensor Imaging of Neural Tissue Organization: Correlations between Radiologic and Histologic Parameters

Abstract

Summary Objective This study examined the relationship between histological variables and DTI values in a normal canine brain. We hypothesized that radial diffusivity (RD) would correlate with myelin density and fractional anisotropy (FA) would correlate with white matter fiber coherence Specimens and methods We acquired DTI maps of a normal canine brain post mortem on a 7T MR scanner (TR = 100 ms, TE = 18.1 ms, NEX = 1, width [d] = 4 ms, separation [D] = 8.9 ms, gradient amplitude = 600 mT/m, b=1,565 s/mm2) and generated maps of FA, RD, and axial diffusivity. The brain was subsequently sectioned and stained for myelin with gold chloride, which also allowed for measurement of fiber coherence. DTI metrics were then directly compared with optical density of the myelin stain and the coherence of stained fibers. Results Multivariate linear regression demonstrated that RD, but not FA, significantly correlated with both myelin stain intensity (p = 0.031) and fiber coherence (p = 0.035). The Pearson correlation coefficient between these two histological variables and FA was 0.122; and was 0.607 for the histological variables and RD. Conclusion We found that RD significantly correlated with both optical density of myelinated fibers and fiber coherence, but FA correlated with neither histological finding. Factors other than degree of myelination and fiber coherence should be considered to fully account for regional variation in FA.

Widespread white matter but focal gray matter alterations in depressed individuals with thoughts of death

“…Alterations in astrocyte morphometry and function are associated with suicide (Ernst et al, 2011, Torres-Platas et al, 2011). Additionally, as RD is thought to be a marker of myelination (Song et al, 2002, Wei et al, 2013), our findings may reflect oligodendrocyte dysfunction and myelination deficits, which are themselves associated with suicide (Klempan et al, 2009a, Klempan et al, 2009b). The gray matter findings were more focal and limited.…”

Diffusion tensor imaging and myelin composition analysis reveal abnormal myelination in corpus callosum of canine mucopolysaccharidosis I

“…A number of studies have used DTI to follow serial changes in the brain after therapy (McGraw et al, 2005). However, few studies have validated DTI metrics by providing histological correlates of the major DTI parameters, such as FA and radial diffusivity (Song et al, 2002; Wei et al, 2013). One investigator has previously shown that radial diffusivity, but not FA, correlated with degree of demyelination based on Luxol fast blue-stained slides of spinal cord derived from multiple sclerosis patients (Klawiter et al, 2011), However, unlike our study, that investigation was based on a semi-quantitative grading system for degree of demyelination (rather than on a quantitative analysis of myelin content) and also did not measure response to a treatment.…”

Imaging Ischemic and Hemorrhagic Disease of the Brain in Dogs

“…Fractional anisotropy has been demonstrated to reflect features that constrain water diffusion in white matter, including myelination and other microstructural factors (201). With optimization of these parameters, DTI may become a more useful tool in diagnosing strokes in dogs (200)(201)(202).…”