ABSTRACT
BACKGROUND AND PURPOSE: With the aim of facilitating the early detection of Alzheimer's disease, the Alzheimer's Disease Neuroimaging Initiative proposed two stages based on the memory performance: early mild cognitive impairment (EMCI) and late mild cognitive impairment (LMCI). The current study was designed to investigate structural differences in terms of surface atrophy and microstructural changes of the hippocampus in EMCI and LMCI. METHODS: Hippocampal shape modeling based on progressive template surface deformation was performed on T1-weighted MRI images obtained from 20 cognitive normal (CN) subjects, 17 EMCI patients, and 20 LMCI patients. A template surface in CN was used as a region of interest for diffusion-tensor imaging (DTI) voxel-based morphometry (VBM) analysis. Cluster-wise group comparison was performed based on DTI indices within the hippocampus. Linear regression was performed to identify correlations between DTI metrics and clinical scores. RESULTS: The hippocampal surface analysis showed significant atrophies in bilateral CA1 regions and the right ventral subiculum in EMCI, in contrast to widespread atrophy in LMCI. DTI VBM analysis showed increased diffusivity in the CA2–CA4 regions in EMCI and additionally in the subiculum region in LMCI. Hippocampal diffusivity was significantly correlated with scores both for the Mini Mental State Examination and on the Modified Alzheimer Disease Assessment Scale cognitive subscale. However, the hippocampal diffusivity did not vary significantly with the fractional anisotropy. CONCLUSIONS: EMCI showed hippocampal surface changes mainly in the CA1 region and ventral subiculum. Diffusivity increased mainly in the CA2–CA4 regions in EMCI, while it decreased throughout the hippocampus in LMCI. Although axial diffusivity showed prominent changes in the right hippocampus in EMCI, future studies need to confirm the presence of this laterality difference. In addition, diffusivity is strongly correlated with the cognitive performance, indicating the possibility of using diffusivity as a biomarker for disease progression.
Subject(s)
Humans , Alzheimer Disease , Anisotropy , Atrophy , Biomarkers , Disease Progression , Hippocampus , Linear Models , Magnetic Resonance Imaging , Memory , Cognitive Dysfunction , NeuroimagingABSTRACT
BACKGROUND: Carotid intima media thickness (CIMT) and the presence of carotid plaque have been used for risk stratification of cardiovascular disease (CVD). To date, however, the association between multi-directional functional properties of carotid artery and CVD has not been fully elucidated. We sought to explore the multi-directional mechanics of the carotid artery in relation to cardiovascular risk. METHODS: Four hundred one patients who underwent carotid ultrasound were enrolled between January 2010 and April 2013. A high risk of CVD was defined as more than 20% of 10-year risk based on the Framingham risk score. Using a speckle-tracking technique, the longitudinal and radial movements were analyzed in the B-mode images. Peak longitudinal and radial displacements, strain and strain rate were also measured. Beta stiffness and elastic modulus index were calculated from the radial measurements. RESULTS: Of the overall sample, 13% (52) of patients comprised the high-risk group. In multivariate logistic regression, CIMT and elastic modulus index were independently associated with a high-risk of CVD {odds ratio (OR): 1.810 [95% confidence interval (CI) 1.249–2.622] and OR: 1.767 (95% CI: 1.177–2.652); p = 0.002, 0.006, respectively}. The combination of CIMT and elastic modulus index correlated with a high-risk of CVD more so than CIMT alone. CONCLUSION: The elastic modulus index of the carotid artery might serve as a novel surrogate marker of high-risk CVD. Measurement of the multi-directional mechanics of the carotid artery using the speckle tracking technique has potential for providing further information over conventional B-mode ultrasound for stratification of CVD risk.