title: Decreased brain stiffness in Alzheimer's disease determined by magnetic resonance elastography.
abstract: OBJECTIVE
  To test patient acceptance and reproducibility of the 3D magnetic resonance elastography (MRE) brain exam using a soft vibration source, and to determine if MRE could noninvasively measure a change in the elastic properties of the brain parenchyma due to Alzheimer's disease (AD).
  
  
  METHODS
  MRE exams were performed using an accelerated spin-echo echo planar imaging (EPI) pulse sequence and stiffness was calculated with a 3D direct inversion algorithm. Reproducibility of the technique was assessed in 10 male volunteers, who each underwent four MRE exams separated into two imaging sessions. The effect of AD on brain stiffness was assessed in 28 volunteers, 7 with probable AD, 14 age- and gender-matched PIB-negative (Pittsburgh Compound B, a PET amyloid imaging ligand) cognitively normal controls (CN-), and 7 age- and gender-matched PIB-positive cognitively normal controls (CN+).
  
  
  RESULTS
  The median stiffness of the 10 volunteers was 3.07 kPa with a range of 0.40 kPa. The median and maximum coefficients of variation for these volunteers were 1.71% and 3.07%. The median stiffness of the 14 CN- subjects was 2.37 kPa (0.44 kPa range) compared to 2.32 kPa (0.49 kPa range) within the CN+ group and 2.20 kPa (0.33 kPa range) within the AD group. A significant difference was found between the three groups (P = 0.0055, Kruskal-Wallis one-way analysis of variance). Both the CN+ and CN- groups were significantly different from the AD group.
  
  
  CONCLUSIONS
  3D MRE of the brain can be performed reproducibly and demonstrates significantly reduced brain tissue stiffness in patients with AD.
authors.affiliation: Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Murphy
authors.forename: John
authors.initials: J
authors.lastname: Huston
authors.forename: Clifford R
authors.initials: CR
authors.lastname: Jack
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Glaser
authors.forename: Armando
authors.initials: A
authors.lastname: Manduca
authors.forename: Joel P
authors.initials: JP
authors.lastname: Felmlee
authors.forename: Richard L
authors.initials: RL
authors.lastname: Ehman
mesh_terms: D000328:Adult; D000544:Alzheimer Disease / Q000473:pathology* / Q000503:physiopathology*; D001921:Brain / Q000473:pathology* / Q000503:physiopathology*; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity