miR-Trace-NP is a radiolabeled nanoparticle probe for early Alzheimer’s detection, targeting the inflammatory microRNA miR-146a to visualize activated microglia via PET. Built from 18F-FDG liposomes with antisense oligonucleotides plus an AI-based InflammaScore, it enables early, precise assessment of disease activity. In AD models, it delivered a 4–8× stronger signal and showed high accuracy, safety, fast clearance, and low cost, offering scalable early diagnosis.