P4‐370: Relationship between cerebral glucose metabolism and [C‐11]BF‐227 accumulation in the stages from cognitively normal to Alzheimer's disease

relationship of atrophy in central olfactory structures to their functional deficit in AD by quantitatively determine the relationship of olfactory fMRI activation with local atrophy in the POC and hippocampus. Methods: 12 AD and 20 age-matched normal controls (NC) participated in this study. All AD and NC participants completed the University of Pennsylvania Smell Identification Test (UPSIT). The anatomical and fMRI images were acquired using a 3T MRI scanner. The olfactory stimulation paradigm consisted of three concentrations (0.10%, 0.32% and 1.0%) of the odorant (lavender) administered sequentially with three repetitions for each concentration. Each odor stimulation lasted for 6s, followed by 42s of baseline with odorless air. The hippocampus and POC were manually segmented and were saved as ROIs for subsequent fMRI activation voxels in those two local regions. Results: The UPSIT scores were significantly different (21.17 6 7.94 for AD and 30.85 6 5.69 for NC). The volumes and activation voxels of POC and hippocampus are showed in Fig. 1. The AD group showed prominent atrophy in both hippocampus and POC. Compared to NC group, the average volumes of the POC and hippocampus in the AD group were reduced by 39% and 44%. There was a high correlation between the atrophy of POC and hippocampus (p <0.001). Olfactory activations in the corresponding structures show a much greater reduction in AD: 98% in POC and 95% in hippocampus. The activation reduction and local atrophy in these two regions were significantly correlated (P 1⁄4 0.008 for POC and P 1⁄4 0.033 for hippocampus). Fig. 2 demonstrated olfactory fMRI activation difference in POC, hippocampus and insula between the two groups. Conclusions: In this study, we determined the morphological and functional changes in the brain areas most susceptible to AD pathology. We revealed that the reduction of BOLD response due to the disease in POC and hippocampus was much greater than the structural changes in the corresponding areas. These results indicate that olfactory fMRI can be a more sensitive marker for detection and evaluation of AD.