Sensitivity of unconstrained quantitative magnetization transfer MRI to Amyloid burden in preclinical Alzheimer's disease.

INTRODUCTION: Magnetization transfer MRI is sensitive to semi-solid macromolecules, including amyloid beta, and has been used to discriminate Alzheimer's disease (AD) patients from controls. Here, we utilize an unconstrained 2-pool quantitative MT (qMT) approach that quantifies the longitudinal relaxation rates of free water and semi-solids separately, and investigate its sensitivity to amyloid accumulation in preclinical subjects.

METHODS: We recruited 15 cognitively normal subjects, of which nine were amyloid positive by [ 18 F]Florbetaben PET. A 12 min qMT scan was used to estimate the unconstrained 2-pool qMT parameters. Group comparisons and correlations were analyzed at the lobar level.

RESULTS: The exchange rate and semi-solid pool's were sensitive to the amyloid concentration. The former finding is consistent with previous reports in clinical AD, but the latter is novel as its value is typically constrained.

DISCUSSION: qMT MRI may be a promising surrogate marker of amyloid beta without the need for contrast agents or radiotracers.