Quantitative MR imaging R2 relaxometry in elderly participants reporting memory loss

Area of Science:

• Neuroimaging
• Biochemistry
• Neurology

Background:

• Alzheimer's disease (AD) is associated with altered brain iron homeostasis and demyelination.
• Elevated iron in gray matter and increased water content in white matter are observed in AD.

Purpose of the Study:

• To investigate differences in the transverse proton relaxation rate (R2) in elderly individuals with cognitive impairment compared to healthy controls.
• To assess R2 as a potential biomarker for early AD-related changes in brain iron and myelin.

Main Methods:

• Single-spin-echo MR imaging was performed on 12 participants with memory complaints and 11 healthy controls.
• Neuropsychological testing was conducted, and R2 data were analyzed from 14 brain regions.
• Participants with memory complaints were categorized into subgroups based on objective cognitive impairment levels.

Main Results:

• Mean R2 values correlated strongly with reference brain iron concentrations in controls.
• Significantly higher R2 values were observed in the right temporal cortex for both memory complaint subgroups compared to controls.
• Significantly lower R2 values were found in the left internal capsule and specific white matter regions (left temporal and frontal) in the cognitively impaired subgroup (MC2).

Conclusions:

• R2 differences indicate increased iron in the temporal cortex and myelin loss in white matter regions in individuals with memory complaints.
• These findings are consistent with incipient Alzheimer's disease pathogenesis and support biochemical data.
• R2 may serve as a sensitive imaging marker for early neuropathological changes in Alzheimer's disease.