title: Common pediatric cerebellar tumors: correlation between cell densities and apparent diffusion coefficient metrics.
abstract: OBJECTIVE
  To test whether there is correlation between cell densities and apparent diffusion coefficient (ADC) metrics of common pediatric cerebellar tumors.
  
  
  METHODS
  This study was reviewed for issues of patient safety and confidentiality and was approved by the Institutional Review Board of the University of Texas Southwestern Medical Center and was compliant with HIPAA. The need for informed consent was waived. Ninety-five patients who had preoperative magnetic resonance imaging and surgical pathologic findings available between January 2003 and June 2011 were included. There were 37 pilocytic astrocytomas, 34 medulloblastomas (23 classic, eight desmoplastic-nodular, two large cell, one anaplastic), 17 ependymomas (13 World Health Organization [WHO] grade II, four WHO grade III), and seven atypical teratoid rhabdoid tumors. ADCs of solid tumor components and normal cerebellum were measured. Tumor-to-normal brain ADC ratios (hereafter, ADC ratio) were calculated. The medulloblastomas and ependymomas were subcategorized according to the latest WHO classification, and tumor cellularity was calculated. Correlation was sought between cell densities and mean tumor ADCs, minimum tumor ADCs, and ADC ratio.
  
  
  RESULTS
  When all tumors were considered together, negative correlation was found between cellularity and mean tumor ADCs (ρ = -0.737, P < .05) and minimum tumor ADCs (ρ = -0.736, P < .05) of common pediatric cerebellar tumors. There was no correlation between cellularity and ADC ratio. Negative correlation was found between cellularity and minimum tumor ADC in atypical teratoid rhabdoid tumors (ρ = -0.786, P < .05). In atypical teratoid rhabdoid tumors, no correlation was found between cellularity and mean tumor ADC and ADC ratio. There was no correlation between the ADC metrics and cellularity of the pilocytic astrocytomas, medulloblastomas, and ependymomas.
  
  
  CONCLUSIONS
  Negative correlation was found between cellularity and ADC metrics of common pediatric cerebellar tumors. Although ADC metrics are useful in the preoperative diagnosis of common pediatric cerebellar tumors and this utility is generally attributed to differences in cellularity of tumors, tumor cellularity may not be the sole determinant of the differences in diffusivity.
authors.affiliation: Department of Radiology, University of Texas Southwestern Medical Center and Children's Medical Center, 1935 Medical District Dr, Dallas, TX 75235, USA. korgun.koral@utsouthwestern.edu
authors.forename: Korgün
authors.initials: K
authors.lastname: Koral
authors.forename: Derek
authors.initials: D
authors.lastname: Mathis
authors.forename: Barjor
authors.initials: B
authors.lastname: Gimi
authors.forename: Lynn
authors.initials: L
authors.lastname: Gargan
authors.forename: Bradley
authors.initials: B
authors.lastname: Weprin
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Bowers
authors.forename: Linda
authors.initials: L
authors.lastname: Margraf
mesh_terms: D001927:Brain Diseases / Q000175:diagnosis*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans