Diffusion tensor MRI as a biomarker in axonal and myelin damage

Abstract

Diffusion tensor imaging has been used extensively as a research tool to understand the structural changes associated with white matter pathology. Using water diffusion as the basis to construct anatomic details, diffusion tensor imaging offers the potential to identify structural and functional adaptations before gross anatomical changes, such as lesions and tumors, become apparent on conventional MRI. Over the past 10 years, further parameters, such as axial and radial diffusivity, have been developed to characterize white matter changes specific to axons and myelin. In this paper, the potential application and outstanding issues on the use of diffusion tensor imaging directional diffusivity as a biomarker in axonal and myelin damage in neurological disorders will be reviewed. Keywordsacute and chronic CNS disorders; acute disseminated encephalomyelitis; Alzheimer's disease; axial diffusivity; axonal injury; diffusion tensor imaging; leukodystrophy; MRI; multiple sclerosis; myelin damage; radial diffusivity Principles of diffusion tensor imagingDiffusion tensor imaging (DTI) is a noninvasive, quantitative MRI technique that measures the rate and direction of movement of water molecules within tissues. In the CNS, axonal

Brain magnetic resonance metabolic and microstructural changes in adult-onset autosomal dominant leukodystrophy

“…Our DTI data analysis showed a significant reduction of FA, an increase in RD and no significant changes in AD values in CC genu in subjects with LMNB1 gene duplication, consistent with myelin disruption and relative axonal preservation (Aung et al, 2013). A reduction in FA values in CC has already been reported in one ADLD patient (Potic et al, 2013).…”

“…Macro-and microstructural changes in CC are typically related to different degrees of cognitive impairment as in Alzheimer's Disease (Di Paola et al, 2010), Fronto-Temporal Dementia (Tartaglia et al, 2012) and in white matter disorders such as Hereditary Diffuse Leukoencephalopathy with Neuroaxonal Spheroids (Kinoshita et al, 2014), Pelizaeus-Merzbacher disease (Laukka et al, 2013) and Metachromatic leukodystrophy (Groeschel et al, 2011). The genu of the CC regulates inter-hemispheric connections between pre-frontal associative areas that are involved in working memory, executive and attentive functions (Aung et al, 2013). It consists of fibers that myelinate later during physiological brain development, compared to the callosal body and splenium.…”

Cerebral Mitochondrial Microangiopathy Leads to Leukoencephalopathy in Mitochondrial Neurogastrointestinal Encephalopathy

“…ROIs of the splenium of the corpus callosum and PLIC showed a selective increase in radial diffusivity with unchanged axial diffusivity. Radial diffusivity is considered a measure of myelin integrity, 26 as demonstrated by its selective increase in the corpus callosum of animal models with cuprizone-induced demyelination 27,28 and in the optic nerves of mice with demyelination resulting from retinal ischemia. 29 Similarly, in patients with relapsing-remitting multiple sclerosis, tract-specific DTI analysis of the optic radiations showed selective increases in RD only within the T2 lesions and, therefore, related to local myelin disruption.…”

Current Developments In Mri For Assessing Rodent Models of Multiple Sclerosis

“…AD and RD measurements are potentially more sensitive than MD in diagnosis of MS lessions due to characteristic high diffusion anisotropy in the WM [132,138]. In MS studies using the cuprizone rodent model [139,140], decreasing AD and increasing RD were robust surrogate markers for axonal damage and demyelination, respectively.…”

“…MD describes the average of diffusivity components within each voxel [131]. The diffusion tensor parametric FA is more commonly used than RA in the DTI literature [132]. FA values range from 0 to 1 to describe the degree of the anisotropy of the intra--voxel diffusivity [133].…”