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 (T1ρ) was measured in brains of Alzheimer's disease (AD), mild-cognitive impairment (MCI), and age-matched controls in order to determine whether T1ρ 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. T1ρ maps were generated by fitting each pixel's intensity as a function of the duration of the spin-lock pulse. T1ρ values were calculated from the gray matter (GM) and white matter (WM) of medial temporal lobe (MTL).

Results: GM and WM T1ρ 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 T1ρ and 5% increased GM T1ρ. Compared to control, MCI individuals showed 4% increased T1ρ both in WM and GM. A 5% increased T1ρ was found in WM of AD over MCI.

Conclusions: The increased T1ρ in WM and GM of MTL in AD may be associated with the pathological changes that are not evident on conventional MRI.