T(1ρ) MRI in Alzheimer's disease: detection of pathological changes in medial temporal lobe

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.

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).

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.

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.