Comparison of T 1 Rho MRI, Glucose Metabolism, and Amyloid Burden Across the Cognitive Spectrum: A Pilot Study.

Objective: The pathological cascades associated with the development of Alzheimer's disease (AD) have a common element: acidosis. T ₁ rho MRI is a pH-sensitive measure, with higher values associated with greater neuropathological burden. The authors investigated the relationship between T ₁ rho imaging and AD-associated pathologies as determined by available diagnostic imaging techniques.
Methods: Twenty-seven participants (men, N=13, women, N=14; ages 55-90) across the cognitive spectrum (healthy control subjects [HCs] with normal cognition, N=17; participants with mild cognitive impairment [MCI], N=7; participants with mild AD, N=3) underwent neuropsychological testing, MRI (T ₁ -weighted and T ₁ rho [spin-lattice relaxation time in the rotating frame]), and positron emission tomography imaging ([ ¹¹ C]Pittsburg compound B for amyloid burden [N=26] and [ ¹⁸ F]fluorodeoxyglucose for cerebral glucose metabolism [N=12]). The relationships between global T ₁ rho values and neuropsychological, demographic, and imaging measures were explored.
Results: Global mean and median T ₁ rho were positively associated with age. After controlling for age, higher global T ₁ rho was associated with poorer cognitive function, poorer memory function (immediate and delayed memory scores), higher amyloid burden, and more abnormal cerebral glucose metabolism. Regional T ₁ rho values, when controlling for age, significantly differed between HCs and participants with MCI or AD in select frontal, cingulate, and parietal regions.
Conclusions: Higher T ₁ rho values were associated with greater cognitive impairment and pathological burden. T ₁ rho, a biomarker that varies according to a feature common to each cascade rather than one that is unique to a particular pathology, has the potential to serve as a metric of neuropathology, theoretically providing a measure for assessing pathological status and for monitoring the neurodegeneration trajectory.