P3‐261: Synthesis and IN VIVO Spect Evaluation of a Novel Butyrylcholinesterase Diagnostic Radioligand for Alzheimer’S Disease

vasogenic edema in several WM regions (tapetum was chosen as a representative example, Fig. 1A). Significantly reduced DBSIderived axial diffusivity suggested the presence of axonal injury at this early AD dementia stage (Fig. 1B). In comparison, the significantly increased DTI-derived axial diffusivity suggested the failure of DTI to detect axonal injury, probably due to the confounding effect of vasogenic edema (Fig. 1B, red arrow). DTI-/DBSI-derived radial diffusivity and FA increased (Fig. 1C) and decreased (Fig. 1D), respectively, in the early AD dementia group, suggesting demyelination and white matter abnormality. However, DBSIderived radial diffusivity and FA were not affected by vasogenic edema contamination and therefore reflected the white matter integrity with higher specificity and accuracy. Conclusions: Our data suggest that DBSI can separately quantify WM structural abnormalities and vasogenic edema in early symptomatic AD. In comparison, conventional DTI cannot separate the effect off WM abnormality from edema, limiting its usage in accurately characterizing the complicated pathological substrates in AD.