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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 27:430-439, February 2006
© 2006 American Society of Neuroradiology

BRAIN

Quantitative MR Imaging R₂ Relaxometry in Elderly Participants Reporting Memory Loss

M.J. House^a, T.G. St. Pierre^a, J.K. Foster^b,c, R.N. Martins^b and R. Clarnette^d

^a School of Physics, University of Western Australia
^b School of Exercise, Biomedical and Sports Sciences, Health Department of Western Australia
^c Edith Cowan University and Neurosciences Unit, Health Department of Western Australia
^d Department of Community and Geriatric Medicine, Fremantle Hospital

Address correspondence to Michael J. House, School of Physics, Mailbag M013, University of Western Australia, Crawley, Western Australia 6009, 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.

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