Quantitative Diffusion-Weighted MRI Metrics in the Differential Diagnosis of Alzheimer's Disease and Vascular Dementia

Abstract

Background:
Early differential diagnosis of neurodegenerative dementias remains a clinical challenge, where non-invasive mapping of cerebral microstructural changes plays a central role.
Objectives: To evaluate the diagnostic utility of diffusion-weighted MRI (DW-MRI) and apparent diffusion coefficient (ADC) values in differentiating Alzheimer's disease from vascular dementia.
Materials and methods: A total of 120 participants were evaluated (50 with Alzheimer's disease [AD], 45 with vascular dementia [VaD], and 25 healthy controls). All subjects underwent brain MRI with quantitative ADC measurements in the hippocampus, temporal lobes, and periventricular white matter.
Results: Patients with AD demonstrated significantly elevated hippocampal ADC values (1.08 ± 0.06 × 10⁻³ mm²/s) compared with the VaD group (0.91 ± 0.05 × 10⁻³ mm²/s) and controls (0.81 ± 0.04 × 10⁻³ mm²/s; p < 0.001). Conversely, VaD was characterized by significantly higher ADC values in periventricular white matter. A hippocampal ADC cutoff > 0.98 × 10⁻³ mm²/s yielded a sensitivity of 86.0% and specificity of 82.2% for detecting AD (AUC = 0.89).
Conclusions: Quantitative DW-MRI metrics effectively differentiate Alzheimer's disease from vascular dementia based on localized microstructural tissue damage patterns.

Keywords:
Dementia; DW-MRI; apparent diffusion coefficient; ADC; Alzheimer's disease; vascular dementia; hippocampus.