title: Multicenter R2* mapping in the healthy brain.
abstract: OBJECTIVE
  The R2* relaxation rate constant has been suggested as a sensitive measure for iron accumulation. The aim of this multi-center study was to assess the inter-scanner and inter-subject variability of R2* mapping and to investigate the relationship between brain volume and R2* in specific structures.
  
  
  METHODS
  R2* mapping was performed in 81 healthy subjects in seven centers using different 3 T systems. R2* was calculated from a dual-echo gradient echo sequence and was assessed in several deep gray matter structures. The inter-scanner and inter-subject variability of R2* was calculated by means of the coefficient of variation before and after correcting for age.
  
  
  RESULTS
  Significant center effects were seen in some regions which get lost after age correction. The coefficient of variation for the inter-center variability was much lower (<5.6%) than for the intra-subject variability (6.7%-11.7%). R2* in the putamen and red nucleus scaled with cortical volume while R2* in the globus pallidus and the substantia nigra was negatively associated with white matter volume.
  
  
  CONCLUSIONS
  R2* is a robust and reproducible measure in a multicenter setting provided that a standardized MRI protocol is used. The relationship between iron concentration in deep gray matter and volume of specific brain compartments needs further investigation.
authors: Department of Neurology, Medical University of Graz, Graz, Austria.
authors: Stefan
authors: S
authors: Ropele
authors: Mike P
authors: MP
authors: Wattjes
authors: Christian
authors: C
authors: Langkammer
authors: Iris D
authors: ID
authors: Kilsdonk
authors: Wolter L
authors: WL
authors: Graaf
authors: Jette L
authors: JL
authors: Frederiksen
authors: Dan
authors: D
authors: Fuglø
authors: Marios
authors: M
authors: Yiannakas
authors: Claudia A M
authors: CA
authors: Wheeler-Kingshott
authors: Christian
authors: C
authors: Enzinger
authors: Maria A
authors: MA
authors: Rocca
authors: Till
authors: T
authors: Sprenger
authors: Michael
authors: M
authors: Amman
authors: Ludwig
authors: L
authors: Kappos
authors: Massimo
authors: M
authors: Filippi
authors: Alex
authors: A
authors: Rovira
authors: Olga
authors: O
authors: Ciccarelli
authors: Frederik
authors: F
authors: Barkhof
authors: Franz
authors: F
authors: Fazekas
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000033:anatomy & histology*; D005060:Europe; D005260:Female; D066128:Gray Matter / Q000033:anatomy & histology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D066127:White Matter / Q000033:anatomy & histology*; D055815:Young Adult