Diffusion tensor and restriction spectrum imaging reflect different aspects of neurodegeneration in Parkinson’s disease

Abstract

To meet the need for Parkinson’s disease biomarkers and evidence for amount and distribution of pathological changes, MRI diffusion tensor imaging (DTI) has been explored in a number of previous studies. However, conflicting results warrant further investigations. As tissue microstructure, particularly of the grey matter, is heterogeneous, a more precise diffusion model may benefit tissue characterization. The purpose of this study was to analyze the diffusion-based imaging technique restriction spectrum imaging (RSI) and DTI, and their ability to detect microstructural changes within brain regions associated with motor function in Parkinson’s disease. Diffusion weighted (DW) MR images of a total of 100 individuals, (46 Parkinson’s disease patients and 54 healthy controls) were collected using b-values of 0–4000s/mm 2 . Output diffusion-based maps were estimated based on the RSI-model combining the full set of DW-images (Cellular Index (CI), Neurite Density (ND)) and DTI-model combining b = 0 and b = 1000 s/mm 2 (fractional anisotropy (FA), Axial-, Mean- and Radial diffusivity (AD, MD, RD)). All parametric maps were analyzed in a voxel-wise group analysis, with focus on typical brain regions associated with Parkinson’s disease pathology. CI, ND and DTI diffusivity metrics (AD, MD, RD) demonstrated the ability to differentiate between groups, with strongest performance within the thalamus, prone to pathology in Parkinson’s disease. Our results indicate that RSI may improve the predictive power of diffusion-based MRI, and provide additional information when combined with the standard diffusivity measurements. In the absence of major atrophy, diffusion techniques may reveal microstructural pathology. Our results suggest that protocols for MRI diffusion imaging may be adapted to more sensitive detection of pathology at different sites of the central nervous system.

Diffusion tensor imaging‐based pontine damage as a degeneration marker in synucleinopathy

“…These pathological findings are in accordance with phenotypic progression in PD, as many nonmotor symptoms precede the motor features of PD (Marras & Chaudhuri, 2016). Therefore, demonstrating pontine damage in patients with PD would provide in vivo evidence for Braak's hypothesis, although there are conflicting reports (Blain et al., 2006; Hope et al., 2019; Surova et al., 2015; Taylor et al., 2018). The pons is also an important neuropathological substrate of RBD (Iranzo, 2018; Knudsen et al., 2018), and a few neuroimaging studies have reported gray matter volume reduction or altered DTI parameters in the pons (Hanyu et al., 2012; Scherfler et al., 2011; Unger et al., 2010).…”

White matter microstructure across the adult lifespan: A mixed longitudinal and cross-sectional study using advanced diffusion models and brain-age prediction

“…We selected 20 scalar metrics from the six models (DTI, DKI, NODDI, RSI, SMT mc, WMTI) based on recent studies (Benitez et al, 2018;De Santis et al, 2011;Hope et al, 2019;Jelescu et al, 2015;Kaden, Kelm, et al, 2016;Maximov et al, 2019;Pines et al, 2020). NODDI: ICVF (intracellular volume fraction), ISOVF (isotropic volume fraction), OD (oriental dispersion).…”

Modern Brainstem MRI Techniques for the Diagnosis of Parkinson's Disease and Parkinsonisms

“…Restriction spectrum imaging (RSI) (80,81) is a new diffusion model based on high angular resolution diffusion imaging (HARDI), acquired in multiple directions at different high b values. RSI highlights hindered and restricted diffusion in extracellular and intracellular compartments.…”

“…With the development of several new metrics, RSI can now provide information about neurite density and orientation. Hope et al ( 81 ) were the first to compare RSI with DTI in patients with PD. They defined a cellularity index and a neurite density index.…”