O1-05-03: PET measurements of posterior cingulate glucose metabolism are superior to MRI measurements of hippocampal volume in distinguishing cognitively normal persons at differential genetic risk for Alzheimer’s disease

Abstract

developed which accomplishes entirely non-invasive CBF measurements in 3 dimensions within 24 seconds, allowing calculating other flow dynamics, including arterial transit time (ATT). Objective: To determine CBF, ATT and other parameters of perfusion dynamics in normal ageing, AD and MCI using the new ASL-MRI technique. Methods: Fifteen cognitively normal subjects, 6 patients with AD and 4 subjects with MCI were studied on a 4 Tesla MRI scanner. The dynamic ASL-MRI series contained 12 serial 3D GRASE image frames of the brain with variable delay times after labeling. CBF and ATT were obtained from fitting a two-compartment perfusion model to the data. CBF and ATT of the PC as a function of age and disease were determined by linear regressions. Results: Figure 1 depicts CBF and ATT maps from a 65y control subject and 72y AD patient, showing substantial CBF reduction and ATT prolongation in the patient. In CN, CBF is negatively correlated with age (R 0.55, p 0.002), declining 1.5% per year, while ATT increases with age (R 0.27, p 0.04) 0.5% per year. Independent of age, AD was associated with significant CBF reductions (35% lower than controls, p 0.04) while MCI had CBF reductions intermediate between controls and AD. Independent of age, AD was furthermore associated with marked increase of ATT (34% longer than CN, p 0.005). Increased ATT in MCI was a trend (18% longer, p 0.06). CBF alone correctly classified 82% of the patients and 67% of the MCI. Adding ATT improved classification to 100% for AD and 78% for MCI. Conclusions: The new finding is prolonged ATT in AD and MCI. Furthermore, the ATT changes were independent of CBF changes and improved the classification of AD and MCI.