T_1ρ MRI in Alzheimer's Disease: Detection of Pathological Changes in Medial Temporal Lobe

BACKGROUND: The need of an early and noninvasive diagnosis of AD requires the development of imaging-based techniques. As an alternative, the magnetic resonance image (MRI) relaxation time constant (T_1ρ) was measured in brains of Alzheimer's disease (AD), mild-cognitive impairment (MCI), and age-matched controls in order to determine whether T_1ρ values correlated with the neurological diagnosis. METHODS: MRI was performed on AD (n= 48), MCI (n= 45), and age-matched control (n= 41), on a 1.5 Tesla Siemens clinical MRI scanner. T_1ρ maps were generated by fitting each pixel's intensity as a function of the duration of the spin-lock pulse. T_1ρ values were calculated from the gray matter (GM) and white matter (WM) of medial temporal lobe (MTL). RESULTS: GM and WM T_1ρ values were 87.5 ± 1.2 ms and 80.5 ± 1.4 ms, respectively, in controls, 90.9 ± 1.3 ms and 84.1 ± 1.7 ms in MCI, and 91.9 ± .8 ms and 88.3 ± 1.3 ms in AD cohorts. Compared to control, AD patients showed 9% increased WM T_1ρ and 5% increased GM T_1ρ. Compared to control, MCI individuals showed 4% increased T_1ρ both in WM and GM. A 5% increased T_1ρ was found in WM of AD over MCI. CONCLUSION: The increased T_1ρ in WM and GM of MTL in AD may be associated with the pathological changes that are not evident on conventional MRI.