Correlation of Diffusion Tensor Imaging Parameters in the Canine Brain

Abstract

The goal of this study was to determine the degree to which ex vivo diffusion tensor imaging (DTI) parameters correlate to one another in white matter regions on very high resolution MR scans. Specifically, we hypothesized that radial diffusivity (RD) and apparent diffusion coefficient (ADC) would correlate more closely than either would correlate with fractional anisotropy (FA). We performed post mortem DTI imaging on three canine brains on a 7 T MR scanner (TR = 100 ms, NEX = 1, gradient amplitude = 600 mT/m, b = 1492-1,565 s/mm²) and generated maps of FA, RD, and ADC. We measured RD, FA and ADC within 14 regions of interest representative of various portions of white matter. We compared the three combinations of values, i.e., FA vs ADC, FA vs RD and ADC vs RD, using linear regression models. Linear regression demonstrated that RD was significantly correlated with FA (p << 0.01; R² = 0.3053) and also with ADC (p << 0.01; R² = 0.6755), but to a much greater degree. However, ADC was not significantly correlated with FA (p = 0.526; R² = 0.101). Our findings suggest that both RD and ADC reflect similar cytoarchitectural features, most likely that of myelination, whereas FA values likely reflect both myelination and additional microstructural features that constrain the diffusion of water in white matter.

Normal diffusivity of the domestic feline brain

“…The majority of significant differences identified in the statistical evaluation in our study were between white matter and grey matter regions. This is consistent with that documented in the dog (Leong et al, ). The linear axonal bundles of the white matter cause water diffusion to be highly anisotropic, when compared to diffusion within grey matter.…”

Disruption of Accumbens and Thalamic White Matter Connectivity Revealed by Diffusion Tensor Tractography in Young Men with Genetic Risk for Obesity

“…This discrepancy might be due to the different sensitivity that ADC and FA have toward different neural maturation processes, such as fiber organization, myelination, and proliferation and maturation of glial cell bodies and intracellular compartments (Provenzale et al, 2010 ), particularly during neurogenesis. Indeed, ADC and FA do not necessarily correlate with each other (Provenzale et al, 2010 ; Leong et al, 2015 ), and the relationship between ADC and FA values varies for different WM tracts (Provenzale et al, 2010 ). The FTO gene has been reported to be involved in neurogenesis in mice (Li et al, 2017 ).…”

Developmental Alterations of Cerebral Gray and White Matter in Children with Congenital Cyanotic Heart Disease

“…21 LD can vary with fiber diameter and axon coherence. 22 Animal studies show that FA, RD, and MD are more related to progress of myelination and axonal packing, 23 whereas increased LD could indicate increased fiber coherence in adolescence and older ages, as axons straighten and coalesce further within the bundle. 24 According to our results, this process might be disturbed or retarded in children suffering from cyanotic cardiac malformations.…”