title: MRI Evaluation of Non-Necrotic T2-Hyperintense Foci in Pediatric Diffuse Intrinsic Pontine Glioma.
abstract: OBJECTIVE
  The conventional MR imaging appearance of diffuse intrinsic pontine glioma suggests intralesional histopathologic heterogeneity, and various distinct lesion components, including T2-hypointense foci, have been described. Here we report the prevalence, conventional MR imaging semiology, and advanced MR imaging features of non-necrotic T2-hyperintense foci in diffuse intrinsic pontine glioma.
  
  
  METHODS
  Twenty-five patients with diffuse intrinsic pontine gliomas were included in this study. MR imaging was performed at 3T by using conventional and advanced MR imaging sequences. Perfusion (CBV), vascular permeability (ve,Ktrans), and diffusion (ADC) metrics were calculated and used to characterize non-necrotic T2-hyperintense foci in comparison with other lesion components, namely necrotic T2-hyperintense foci, T2-hypointense foci, peritumoral edema, and normal brain stem. Statistical analysis was performed by using Kruskal-Wallis and Wilcoxon rank sum tests.
  
  
  RESULTS
  Sixteen non-necrotic T2-hyperintense foci were found in 12 tumors. In these foci, ADC values were significantly higher than those in either T2-hypointense foci (P= .002) or normal parenchyma (P= .0002), and relative CBV values were significantly lower than those in either T2-hypointense (P= .0002) or necrotic T2-hyperintense (P= .006) foci. Volume transfer coefficient values in T2-hyperintense foci were lower than those in T2-hypointense (P= .0005) or necrotic T2-hyperintense (P= .0348) foci.
  
  
  CONCLUSIONS
  Non-necrotic T2-hyperintense foci are common, distinct lesion components within diffuse intrinsic pontine gliomas. Advanced MR imaging data suggest low cellularity and an early stage of angioneogenesis with leaky vessels resulting in expansion of the extracellular space. Because of the lack of biopsy validation, the underlying histoarchitectural and pathophysiologic changes remain unclear; therefore, these foci may correspond to a poorly understood biologic event in tumor evolution.
authors.affiliation: From the Departments of Diagnostic Imaging (O.C.-L., W.E.R., A.E., J.O.G., Z.P.).
authors.forename: O
authors.identifier: http://orcid.org/0000-0002-1204-2385
authors.initials: O
authors.lastname: Clerk-Lamalice
authors.affiliation: From the Departments of Diagnostic Imaging (O.C.-L., W.E.R., A.E., J.O.G., Z.P.).
authors.forename: W E
authors.identifier: http://orcid.org/0000-0002-1054-1201
authors.initials: WE
authors.lastname: Reddick
authors.affiliation: Biostatistics (X.L., Y.L.), St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: X
authors.identifier: http://orcid.org/0000-0003-1653-4886
authors.initials: X
authors.lastname: Li
authors.affiliation: Biostatistics (X.L., Y.L.), St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Y
authors.identifier: http://orcid.org/0000-0002-7046-4316
authors.initials: Y
authors.lastname: Li
authors.affiliation: From the Departments of Diagnostic Imaging (O.C.-L., W.E.R., A.E., J.O.G., Z.P.).
authors.forename: A
authors.identifier: http://orcid.org/0000-0003-2979-5508
authors.initials: A
authors.lastname: Edwards
authors.affiliation: From the Departments of Diagnostic Imaging (O.C.-L., W.E.R., A.E., J.O.G., Z.P.).
authors.forename: J O
authors.identifier: http://orcid.org/0000-0001-9679-2054
authors.initials: JO
authors.lastname: Glass
authors.affiliation: From the Departments of Diagnostic Imaging (O.C.-L., W.E.R., A.E., J.O.G., Z.P.) zoltan.patay@stjude.org.
authors.forename: Z
authors.identifier: http://orcid.org/0000-0003-1479-9864
authors.initials: Z
authors.lastname: Patay