title: Partial correlation analyses of global diffusion tensor imaging-derived metrics in glioblastoma multiforme: Pilot study.
abstract: OBJECTIVE
  To determine existing correlates among diffusion tensor imaging (DTI)-derived metrics in healthy brains and brains with glioblastoma multiforme (GBM).
  
  
  METHODS
  Case-control study using DTI data from brain magnetic resonance imaging of 34 controls (mean, 41.47; SD, ± 21.94 years; range, 21-80 years) and 27 patients with GBM (mean, SD; 48.41 ± 15.18 years; range, 18-78 years). Image postprocessing using FSL software calculated eleven tensor metrics: fractional (FA) and relative anisotropy; pure isotropic (p) and anisotropic diffusions (q), total magnitude of diffusion (L); linear (Cl), planar (Cp) and spherical tensors (Cs); mean (MD), axial (AD) and radial diffusivities (RD). Partial correlation analyses (controlling the effect of age and gender) and multivariate Mancova were performed.
  
  
  RESULTS
  There was a normal distribution for all metrics. Comparing healthy brains vs brains with GBM, there were significant very strong bivariate correlations only depicted in GBM: [FA↔Cl (+)], [FA↔q (+)], [p↔AD (+)], [AD↔MD (+)], and [MD↔RD (+)]. Among 56 pairs of bivariate correlations, only seven were significantly different. The diagnosis variable depicted a main effect [F-value (11, 23) = 11.842, P ≤ 0.001], with partial eta squared = 0.850, meaning a large effect size; age showed a similar result. The age also had a significant influence as a covariate [F (11, 23) = 10.523, P < 0.001], with a large effect size (partial eta squared = 0.834).
  
  
  CONCLUSIONS
  DTI-derived metrics depict significant differences between healthy brains and brains with GBM, with specific magnitudes and correlations. This study provides reference data and makes a contribution to decrease the underlying empiricism in the use of DTI parameters in brain imaging.
authors.affiliation: David Cortez-Conradis, Magnetic Resonance Unit, Medica Sur Clinic and Foundation, Mexico City CP 14050, Mexico.
authors.forename: David
authors.initials: D
authors.lastname: Cortez-Conradis
authors.affiliation: David Cortez-Conradis, Magnetic Resonance Unit, Medica Sur Clinic and Foundation, Mexico City CP 14050, Mexico.
authors.forename: Camilo
authors.initials: C
authors.lastname: Rios
authors.affiliation: David Cortez-Conradis, Magnetic Resonance Unit, Medica Sur Clinic and Foundation, Mexico City CP 14050, Mexico.
authors.forename: Sergio
authors.initials: S
authors.lastname: Moreno-Jimenez
authors.affiliation: David Cortez-Conradis, Magnetic Resonance Unit, Medica Sur Clinic and Foundation, Mexico City CP 14050, Mexico.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Roldan-Valadez
keywords: Brain neoplasms; Diffusion tensor imaging; Magnetic resonance imaging; Software tools; Statistics as topic