title: Diffusion tensor histogram analysis of pediatric diffuse intrinsic pontine glioma.
abstract: OBJECTIVE
  To evaluate tumor structure in children with diffuse intrinsic pontine glioma (DIPG) using histogram analyses of mean diffusivity (MD), determine potential treatment and corticosteroid-related effects on MD, and monitor changes in MD distributions over time.
  
  
  METHODS
  DTI was performed on a 1.5T GE scanner. Regions of interest included the entire FLAIR-defined tumor. MD data were used to calculate histograms. Patterns in MD distributions were evaluated and fitted using a two-normal mixture model. Treatment-related effects were evaluated using the R (2) statistic for linear mixed models and Cox proportional hazards models.
  
  
  RESULTS
  12 patients with DIPG underwent one or more DTI exams. MD histogram distributions varied among patients. Over time, histogram peaks became shorter and broader (P = 0.0443). Two-normal mixture fitting revealed large lower curve proportions that were not associated with treatment response or outcome. Corticosteroid use affected MD histograms and was strongly associated with larger, sharper peaks (R(2) = 0.51, P = 0.0028).
  
  
  CONCLUSIONS
  MD histograms of pediatric DIPG show significant interpatient and intratumoral differences and quantifiable changes in tumor structure over time. Corticosteroids greatly affected MD and must be considered a confounding factor when interpreting MD results in the context of treatment response.
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, Center for Cancer Research, National Institutes of Health, Building 10, Room 1-5750, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Emilie A
authors.initials: EA
authors.lastname: Steffen-Smith
authors.affiliation: In Vivo NMR Center, National Institute of Neurological Disorders and Stroke, National Institutes of the Health, Bethesda, MD 20892, USA.
authors.forename: Joelle E
authors.initials: JE
authors.lastname: Sarlls
authors.affiliation: Program on Pediatric Imaging and Tissue Sciences, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Carlo
authors.initials: C
authors.lastname: Pierpaoli
authors.affiliation: Biostatistics and Data Management Section, National Cancer Institute, Center for Cancer Research, National Institutes of the Health, Bethesda, MD 20892, USA.
authors.forename: Joanna H
authors.initials: JH
authors.lastname: Shih
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, Center for Cancer Research, National Institutes of Health, Building 10, Room 1-5750, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Robyn S
authors.initials: RS
authors.lastname: Bent
authors.affiliation: Program on Pediatric Imaging and Tissue Sciences, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA ; Center for Biomedical Engineering, School of Engineering, Brown University, Providence, RI 02912, USA.
authors.forename: Lindsay
authors.identifier: 0000-0001-6394-5050
authors.initials: L
authors.lastname: Walker
authors.affiliation: Pediatric Oncology Branch, National Cancer Institute, Center for Cancer Research, National Institutes of Health, Building 10, Room 1-5750, 9000 Rockville Pike, Bethesda, MD 20892, USA.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Warren
mesh_terms: D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D020295:Brain Stem Neoplasms / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D005910:Glioma / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology; D006801:Humans; D008297:Male; D013997:Time Factors
chemical_list: D000305:Adrenal Cortex Hormones