[p4–230]: Longitudinal Neurite Orientation Dispersion and Density Imaging in Young‐onset Alzheimer's Disease
Year: 2017
Type: article
Study design: Observational Study
Abstract: Longitudinal white matter damage in Alzheimer's disease (AD) has been identified using diffusion tensor imaging (DTI). However, DTI indices are not tissue-specific and cannot differentiate between axonal loss and changes in axonal morphology. We used neurite orientation dispersion and density imaging (NODDI) to investigate longitudinal changes in white matter neurite density index (NDI), thought to be a specific measure of axonal loss, in a cohort of patients with young-onset Alzheimer's disease (YOAD). Twenty-four patients with YOAD (age: 61.4±5.7 yrs, 38% male) and 19 controls (age 60.7±6.3yrs, 53% male) were imaged on the same 3T Siemens Trio scanner at baseline and after one year using a sequence optimised for NODDI (64, 32, and 8 diffusion-weighted directions at b=2000, 700 and 300s/mm2; 14 b=0 images; 55 slices; voxel size 2.5x2.5x2.5mm; TR/TE=7000/92ms; TA=15mins). After motion and eddy-current distortion correction using FSL, neurite density index (NDI) was estimated using the NODDI toolbox. An optimised longitudinal framework implemented in DTI-TK was used for spatial normalization. Cross-sectional between-group comparisons of NDI were performed at each time point using Tract-Based Spatial Statistics (TBSS), co-varying for age and gender (5000 permutations corrected for multiple comparisons with Threshold-Free Cluster Enhancement p<0.05). Annualised rate of change in NDI indices within groups was computed as follow-up NDI minus baseline, divided by the between-scan interval, and then rates of change between groups compared using TBSS. At baseline, individuals with YOAD had extensive NDI reduction relative to controls in the cingulum, corpus callosum, superior and inferior longitudinal fasciculi, fronto-occipital fasciculus and fornix (A). After one year, this NDI reduction was more extensive and additionally involved the internal capsule and brainstem white matter tracts (B). The annualized rate of NDI reduction in YOAD was significantly greater in patients in the cingulum, splenium of corpus callosum, inferior and superior longitudinal fasciculi, fornix and fronto-occipital fasciculus (C).
Source: Alzheimer s & Dementia
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2765866937