title: Regional analysis of the magnetization transfer ratio of the brain in mild Alzheimer disease and amnestic mild cognitive impairment.
abstract: OBJECTIVE
  Manually drawn VOI-based analysis shows a decrease in magnetization transfer ratio in the hippocampus of patients with Alzheimer disease. We investigated with whole-brain voxelwise analysis the regional changes of the magnetization transfer ratio in patients with mild Alzheimer disease and patients with amnestic mild cognitive impairment.
  
  
  METHODS
  Twenty patients with mild Alzheimer disease, 27 patients with amnestic mild cognitive impairment, and 30 healthy elderly control subjects were examined with high-resolution T1WI and 3-mm-thick magnetization transfer images. Whole-brain voxelwise analysis of magnetization transfer ratio maps was performed by use of Statistical Parametric Mapping 8 software and was supplemented by the analysis of the magnetization transfer ratio in FreeSurfer parcellation-derived VOIs.
  
  
  RESULTS
  Voxelwise analysis showed 2 clusters of significantly decreased magnetization transfer ratio in the left hippocampus and amygdala and in the left posterior mesial temporal cortex (fusiform gyrus) of patients with Alzheimer disease as compared with control subjects but no difference between patients with amnestic mild cognitive impairment and either patients with Alzheimer disease or control subjects. VOI analysis showed that the magnetization transfer ratio in the hippocampus and amygdala was significantly lower (bilaterally) in patients with Alzheimer disease when compared with control subjects (ANOVA with Bonferroni correction, at P < .05). Mean magnetization transfer ratio values in the hippocampus and amygdala in patients with amnestic mild cognitive impairment were between those of healthy control subjects and those of patients with mild Alzheimer disease. Support vector machine-based classification demonstrated improved classification performance after inclusion of magnetization transfer ratio-related features, especially between patients with Alzheimer disease versus healthy subjects.
  
  
  CONCLUSIONS
  Bilateral but asymmetric decrease of magnetization transfer ratio reflecting microstructural changes of the residual GM is present not only in the hippocampus but also in the amygdala in patients with mild Alzheimer disease.
authors.affiliation: Quantitative and Functional Neuroradiology Research Unit, Department of Experimental and Clinical Biomedical Sciences.
authors.forename: M
authors.initials: M
authors.lastname: Mascalchi
authors.forename: A
authors.initials: A
authors.lastname: Ginestroni
authors.forename: V
authors.initials: V
authors.lastname: Bessi
authors.forename: N
authors.initials: N
authors.lastname: Toschi
authors.forename: S
authors.initials: S
authors.lastname: Padiglioni
authors.forename: S
authors.initials: S
authors.lastname: Ciulli
authors.forename: C
authors.initials: C
authors.lastname: Tessa
authors.forename: M
authors.initials: M
authors.lastname: Giannelli
authors.forename: L
authors.initials: L
authors.lastname: Bracco
authors.forename: S
authors.initials: S
authors.lastname: Diciotti
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications / Q000473:pathology*; D000647:Amnesia / Q000150:complications / Q000473:pathology*; D000679:Amygdala / Q000473:pathology*; D060825:Cognitive Dysfunction / Q000150:complications; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity