MRI-Based Medial Temporal Atrophy May Reflect Amyloid PET Positivity in Cognitively Normal Individuals: A Preliminary Study

This study investigated whether magnetic resonance imaging (MRI)-based medial temporal morphometry can predict amyloid positron emission tomography (PET) positivity in cognitively normal individuals. Sixteen consecutive participants (eight amyloid PET-positive and eight PET-negative) were retrospectively identified, all within the normal cognitive range (Mini-Mental State Examination 28-30). Amyloid PET was performed using florbetapir, with visual interpretation as the primary diagnostic criterion and Centiloid values as supportive measures. MRI-derived volumetric analysis was conducted using the voxel-based specific regional analysis system for Alzheimer's disease (AD) to quantify medial temporal atrophy. Although between-group differences in hippocampal indices did not reach statistical significance, the PET-positive group showed a trend toward greater atrophy, and centiloid values correlated positively with medial temporal indices. Receiver operating characteristic analysis indicated fair discrimination, highest for the volume-of-interest-to-gray-matter ratio (area under the curve = 0.83). These preliminary findings suggest that subtle hippocampal alterations on routine structural MRI may mirror early amyloid pathology even before cognitive impairment, supporting the potential of MRI-based morphometric assessment as an adjunctive biomarker for early AD detection.