Quantitative magnetization transfer imaging in Alzheimer disease.
OBJECTIVE
To prospectively measure magnetization transfer (MT) parameters, along with established atrophy parameters, in patients with Alzheimer disease (AD) and in age- and sex-matched control subjects.


METHODS
Participants provided informed consent, and additional assent was obtained from next of kin of all patients with AD. The study was approved by the local ethics committee. Fourteen patients with AD (seven men; mean age, 67.2 years+/-6.5 [standard deviation]) and 14 control subjects (nine men; mean age, 65.5 years+/-9.4) underwent volumetric T1-weighted magnetic resonance and MT imaging. Whole-brain and total hippocampal volumes were adjusted for total intracranial volume. MT images were processed to derive four fundamental parameters in the hippocampal region by using the two-pool model of the MT phenomenon. Pearson correlation coefficients were used to assess the association between volumetric and MT parameters and Mini-Mental State Examination (MMSE) results. Logistic regression models were used to investigate whether combinations of parameters associated with MMSE could help provide better group discrimination.


RESULTS
Patients with AD had significantly reduced whole-brain (P=.001) and total hippocampal (P<.001) volumes compared with those of control subjects. Two MT parameters were significantly reduced in the hippocampal region of patients: 1/(RAT2A)--that is, ratio of relaxation times of free proton pool, where RA equals 1/T1A and is the inverse of the longitudinal relaxation time of the free proton pool (P=.01)--and f*b, which equals fb/[RA(1-fb)], where fb is the restricted proton fraction (P<.001). Among patients with AD, whole-brain volume and hippocampal were correlated with MMSE results. When both parameters were included in a logistic regression model, only hippocampal was significantly associated with case-control status (P=.03).


CONCLUSIONS
Certain MT parameters may serve as useful biomarkers of AD.
Ridha
Basil H
BH
Dementia Research Centre, NMR Research Unit, and Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, 8-11 Queen Square, London, WC1N 3BG, England. bridha@dementia.ion.ucl.ac.uk
Tozer
Daniel J
DJ
Symms
Mark R
MR
Stockton
Katherine C
KC
Lewis
Emma B
EB
Siddique
Musib M
MM
MacManus
David G
DG
Rossor
Martin N
MN
Fox
Nick C
NC
Tofts
Paul S
PS
D000368:Aged; D000544:Alzheimer Disease / Q000473:pathology*; D001284:Atrophy / Q000473:pathology; D001921:Brain / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016015:Logistic Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity