title: Validation of intracranial area as a surrogate measure of intracranial volume when using clinical MRI.
abstract: OBJECTIVE
  We sought to determine whether mid-sagittal intracranial area (ICA) is a valid surrogate of intracranial volume (ICV) when using retrospective data with relatively thick (6-7 mm) sagittal slices.
  
  
  METHODS
  Data were retrospectively analyzed from 47 subjects who had two MRI scans taken at least nine months apart. Twenty-three subjects had manual segmentation of ICV on the T2-weighted sequence for comparison.
  
  
  RESULTS
  Intraclass correlation coefficient (ICC) for intraobserver, interobserver, and intraobserver scan-rescan comparisons were 0.96, 0.97 and 0.95. Pearson correlation coefficients between ICV and ICA, averaging the cumulative 1, 2, 3, and 4 most midline slices, were 0.89, 0.94, 0.93, and 0.95. There was a significant marginal increase in explained variance of ICV by measuring two, rather than one, slices (P= 0.001).
  
  
  CONCLUSIONS
  These data suggest that ICA, even measured without high-resolution imaging, is a reasonable substitute for ICV.
authors.affiliation: Department of Neurology, Neurology Clinical Trials Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: R N Kaveer
authors.initials: RN
authors.lastname: Nandigam
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Chen
authors.forename: Mahmut E
authors.initials: ME
authors.lastname: Gurol
authors.forename: Jonathan
authors.initials: J
authors.lastname: Rosand
authors.forename: Steven M
authors.initials: SM
authors.lastname: Greenberg
authors.forename: Eric E
authors.initials: EE
authors.lastname: Smith
mesh_terms: D000368:Aged; D001921:Brain / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D015588:Observer Variation; D009929:Organ Size; D015203:Reproducibility of Results; D012886:Skull / Q000033:anatomy & histology