Abstract
Most diffusion magnetic resonance imaging (dMRI) techniques use the mono-exponential model to describe the diffusion process of water in the brain. However, the observed dMRI signal decay curve deviates from the mono-exponential form. To solve this problem, the fractional motion (FM) model has been developed, which is regarded as a more appropriate model for describing the complex diffusion process in brain tissue. It is still unclear in the identification and classification of Alzheimer’s disease (AD) patients using the FM model. The purpose of this study was to investigate the potential feasibility of FM model for differentiating AD patients from healthy controls and grading patients with AD. Twenty-four patients with AD and 11 healthy controls were included. The left and right hippocampus were selected as regions of interest (ROIs). The apparent diffusion coefficient (ADC) values and FM-related parameters, including the Noah exponent (α), the Hurst exponent (H), and the memory parameter (μ=H−1/α), were calculated and compared between AD patients and healthy controls and between mild AD and moderate AD patients using a two-sample t-test. The correlations between FM-related parameters α, H, μ, and ADC values and the cognitive functions assessed by mini-mental state examination (MMSE) and Montreal cognitive assessment (MoCA) scales were investigated using Pearson partial correlation analysis in patients with AD. The receiver-operating characteristic analysis was used to assess the differential performance. We found that the FM-related parameter α could be used to distinguish AD patients from healthy controls (P < 0.05) with greater sensitivity and specificity (left ROI, 0.917 and 0.636; right ROI, 0.917 and 0.727) and grade AD patients (P < 0.05) showed higher sensitivity and specificity (right ROI, 0.917, 0.75). The α was found to be positively correlated with MMSE (P < 0.05) and MoCA (P < 0.05) scores in patients with AD, indicating that the α values in the bilateral hippocampus were a potential MRI-based biomarker of disease severity in AD patients. This novel diffusion model may be useful for further understanding neuropathologic changes in patients with AD.
Highlights
Alzheimer’s disease (AD) is the most common neurodegenerative disease and is characterized by memory loss and cognitive decline (Reddy and Oliver, 2019)
There was a significant difference in the Montreal cognitive assessment (MoCA) score between the mild AD group and the moderate AD group (P < 0.05) since a MoCA scale was not collected in the healthy group
We found that the α values of the hippocampus were positively correlated with mini-mental state examination (MMSE) and MoCA scores in the AD patients, while there were no significant correlations in apparent diffusion coefficient (ADC) values
Summary
Alzheimer’s disease (AD) is the most common neurodegenerative disease and is characterized by memory loss and cognitive decline (Reddy and Oliver, 2019). As the most common type of dementia, AD may account for 60–70% of these cases (Wortmann, 2012; Alzheimer’s Association, 2016; Khan et al, 2017) and has a significant impact on the life quality of patients and societal costs. The pathogenesis of AD is extremely complicated, mainly including the deposition of amyloid-β (Aβ) and hyperphosphorylation of tau protein, which results in the formation of Aβ-plaques and intracellular neurofibrillary tangles (NFTs) separately (Kidd, 1963; Hyman et al, 1984; Braak and Braak, 1991; Wegmann et al, 2010; Aisen et al, 2017), causes neuronal death. The diagnosis of AD is complicated and the accuracy is difficult. It is of great significance to develop an effective diagnostic method for AD in clinical research (Cummings, 2017)
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