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Quantitative MR imaging R2 relaxometry in elderly participants reporting memory loss
M J House1, T G St Pierre, J K Foster
1School of Physics, University of Western Australia.
Background And Purpose:
In Alzheimer disease (AD), elevated brain iron concentrations in gray matter suggest a disruption in iron homeostasis, while demyelination processes in white matter increase the water content. Our aim was to assess whether the transverse proton relaxation rate, or R2, an MR imaging parameter affected by changes in brain iron concentration and water content, was different in elderly participants with mild to severe levels of cognitive impairment compared with healthy controls.
Methods:
Twelve elderly participants reporting memory problems and 11 healthy volunteers underwent single-spin-echo MR imaging in a 1.5T scanner, with subsequent neuropsychological testing. R2 data were collected from 14 brain regions in cortical and subcortical gray and white matter. Those with memory complaints were separated into 2 further subgroups: MC1 (no objective cognitive impairment) and MC2 (mild to severe objective cognitive impairment).
Results:
Mean brain R2 values from the 11 controls correlated strongly (r = 0.94, P < .0001) with reference brain iron concentrations for healthy adults. R2 values in the MC1 and MC2 subgroups were significantly higher in the right temporal cortex and significantly lower in the left internal capsule, compared with healthy controls. R2 values in the MC2 subgroup were significantly lower in the left temporal and frontal white matter, compared with healthy controls.
Conclusions:
R2 differences between both subgroups and the healthy controls suggest iron has increased in the temporal cortex, and myelin has been lost from several white matter regions in those with memory complaints, consistent with incipient AD pathogenesis and biochemical data.
Insights
In individuals with memory complaints, MRI analysis revealed increased brain iron in the temporal cortex and myelin loss in white matter, suggesting early Alzheimer's disease changes.
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.
