White matter lesion load is associated with resting state functional MRI activity and amyloid PET but not FDG in mild cognitive impairment and early Alzheimer's Disease patients

Purpose: To quantify and investigate the interactions between multimodal MRI/positron emission tomography (PET) imaging metrics in elderly patients with early Alzheimer's disease (AD), mild cognitive impairment (MCI) and healthy controls.

Materials and Methods: Thirteen early AD, 17 MCI patients, and 14 age-matched healthy aging controls from the Alzheimer's Disease Neuroimaging Initiative database were selected based on availability of data. Default mode network (DMN) functional connectivity and fractional amplitude of low frequency fluctuation (fALFF) were obtained for resting state functional MRI (RS-fMRI). White matter lesion load (WMLL) was quantified from MRI T2- weighted FLAIR images. Amyloid deposition with PET [¹⁸F]-Florbetapir tracer and metabolism of glucose by means of [¹⁸F]-fluoro-2-deoxyglucose (FDG) images were quantified using ratio of standard uptake values (rSUV).

Results: Whole-brain WMLL and amyloid deposition were significantly higher (P<0.005) in MCI and AD patients compared with controls. RS-fMRI results showed significantly reduced (corrected P<0.05) DMN connectivity and altered fALFF activity in both MCI and AD groups. FDG uptake results showed hypometabolism in AD and MCI patients compared with controls. Correlations (P<0.05) were found between WMLL and amyloid load, FDG uptake and amyloid load, as well as between amyloid load (rSUV) and fALFF.

Conclusion: Our quantitative results of four MRI and PET imaging metrics (fALFF/DMN, WMLL, amyloid, and FDG rSUV values) agree with published values. Significant correlations between MRI metrics, including WMLL/ functional activity and PET amyloid load suggest the potential of MRI and PET-based biomarkers for early detection of AD.