Therefore, the objectives of this study were 1) to evaluate the signal enhancement using our developed Gd-DOTA-ob5 aptamer MRI contrast agent in 3xTg, APP/PS/Tau, and control C57BL/6 mouse models for early diagnosis of AD using MRI and 2) to evaluate the time-dependent signal changes after injection of the contrast agent. Here, APP is linked to Alzheimer disease.