title: A statistical investigation of normal regional intra-subject heterogeneity of brain metabolism and perfusion by F-18 FDG and O-15 H2O PET imaging.
abstract: BACKGROUND
  The definite evaluation of the regional cerebral heterogeneity using perfusion and metabolism by a single modality of PET imaging has not been well addressed. Thus a statistical analysis of voxel variables from identical brain regions on metabolic and perfusion PET images was carried out to determine characteristics of the regional heterogeneity of F-18 FDG and O-15 H2O cerebral uptake in normal subjects.
  
  
  METHODS
  Fourteen normal subjects with normal CT and/or MRI and physical examination including MMSE were scanned by both F-18 FDG and O-15 H2O PET within same day with head-holder and facemask. The images were co-registered and each individual voxel counts (Q) were normalized by the global maximal voxel counts (M) as R = Q/M. The voxel counts were also converted to z-score map by z = (Q - mean)/SD. Twelve pairs of ROIs (24 total) were systematically placed on the z-score map at cortical locations 15-degree apart and identically for metabolism and perfusion. Inter- and intra-subject correlation coefficients (r) were computed, both globally and hemispherically, from metabolism and perfusion: between regions for the same tracer and between tracers for the same region. Moments of means and histograms were computed globally along with asymmetric indices as their hemispherical differences.
  
  
  RESULTS
  Statistical investigations verified with data showed that, for a given scan, correlation analyses are expectedly alike regardless of variables (Q, R, z) used. The varieties of correlation (r's) of normal subjects, showing symmetry, were mostly around 0.8 and with coefficient of variations near 10%. Analyses of histograms showed non-Gaussian behavior (skew = -0.3 and kurtosis = 0.4) of metabolism on average, in contrast to near Gaussian perfusion.
  
  
  CONCLUSIONS
  The co-registered cerebral metabolism and perfusion z maps demonstrated regional heterogeneity but with attractively low coefficient of variations in the correlation markers.
authors.affiliation: Nuclear Medicine, William Beaumont Hospital, Royal Oak, MI, USA. owong@beaumont.edu
authors.forename: Ching-yee Oliver
authors.initials: CY
authors.lastname: Wong
authors.forename: Joseph
authors.initials: J
authors.lastname: Thie
authors.forename: Marianne
authors.initials: M
authors.lastname: Gaskill
authors.forename: Richard
authors.initials: R
authors.lastname: Ponto
authors.forename: Jack
authors.initials: J
authors.lastname: Hill
authors.forename: Hai-yan
authors.initials: HY
authors.lastname: Tian
authors.forename: Helena
authors.initials: H
authors.lastname: Balon
authors.forename: Dafang
authors.initials: D
authors.lastname: Wu
authors.forename: Darlene
authors.initials: D
authors.lastname: Fink-Bennett
authors.forename: Conrad
authors.initials: C
authors.lastname: Nagle