Discriminative analysis of early-stage Alzheimer's disease and normal aging with automatic segmentation technique in subcortical gray matter structures: a multicenter in vivo MRI volumetric and DTI study.

Background: Previous studies have revealed that amyloid depositions exist in not only the hippocampus but in other subcortical gray matter structures as well. Diffusion-tensor imaging (DTI) parameters might be more sensitive measures of early degeneration in Alzheimer's disease (AD) than conventional magnetic resonance imaging (MRI) techniques.

Purpose: To evaluate the significance of the volumes and the mean diffusivity (MD) values of subcortical gray matter structures in discrimination between early-stage AD and normal subjects using the Integrated Registration and Segmentation Tool in FMRIB's Software Library.

Material And Methods: Fifty-three cases of early-stage AD and 30 normal aging volunteers from two hospitals were scanned with 3D-FSPGRIR and SSSE-EPI sequences using two similar 1.5T MR systems. The mean relative volumes and mean MD values of subcortical gray matter structures were compared between early-stage AD and control groups. Binary logistic regression analysis and receiver-operating characteristic (ROC) curves were applied to assess the diagnostic significance of every structure's relative volume, MD value, and combination of both.

Results: The relative volumes of the left hippocampus, right amygdala, bilateral thalamus, right caudate, left putamen, and bilateral pallidum were significantly lower in the early-stage AD group than in the control group (P < 0.05). The MD values of the bilateral hippocampus and pallidum, and of the right thalamus and caudate were significantly elevated in the early-stage AD group (P < 0.05). In binary logistic regression analysis, the relative volume of left hippocampus and age entered the final model of volumetric analysis. The MD values of bilateral hippocampi and pallidums entered the final model of MD analysis. The MD values of bilateral hippocampi and pallidums, and the relative volume of left pallidum, entered the final model of combination analysis. The accuracy of three models was 84.7%, 88.9%, and 93.1%, respectively.

Conclusion: Pathological changes takes place in the hippocampus and other subcortical gray matter structures in early-stage AD. Diffusive imaging has great diagnostic significance in early-stage AD. The combination of both imaging modalities can lead to better discrimination between early-stage AD and normal aging.