title: Perilesional edema in radiation necrosis reflects axonal degeneration.
abstract: BACKGROUND
  Recently, we characterized a Gamma Knife® radiation necrosis mouse model with various magnetic resonance imaging (MRI) protocols to identify biomarkers useful in differentiation from tumors. Though the irradiation was focal to one hemisphere, a contralateral injury was observed that appeared to be localized in the white matter only. Interestingly, this injury was identifiable in T2-weighted images, apparent diffusion coefficient (ADC), and magnetization transfer ratio (MTR) maps, but not on post-contrast T1-weighted images. This observation of edema independent of vascular changes is akin to the perilesional edema seen in clinical radiation necrosis.
  
  
  RESULTS
  The pathology underlying the observed white-matter MRI changes was explored by performing immunohistochemistry for healthy axons and myelin. The presence of both healthy axons and myelin was reduced in the contralateral white-matter lesion.
  
  
  CONCLUSIONS
  Based on our immunohistochemical findings, the contralateral white-matter injury is most likely due to axonal degeneration.
authors: Department of Radiology, Washington University, Campus Box 8227, 4525 Scott Avenue, Saint Louis, MO, 63110, USA. pereztorresc@wustl.edu.
authors: Carlos J
authors: CJ
authors: Perez-Torres
authors: Department Neurosurgery, Washington University, Saint Louis, MO, USA. YuanL@wudosis.wustl.edu.
authors: Liya
authors: L
authors: Yuan
authors: Department of Neuropathology, Washington University, Saint Louis, MO, USA. reschmidt@pathology.wustl.edu.
authors: Robert E
authors: RE
authors: Schmidt
authors: Department Neurosurgery, Washington University, Saint Louis, MO, USA. RichK@wudosis.wustl.edu.
authors: Keith M
authors: KM
authors: Rich
authors: Department of Radiology, Washington University, Campus Box 8227, 4525 Scott Avenue, Saint Louis, MO, 63110, USA. ackerman@wustl.edu.|Department of Chemistry, Washington University, Saint Louis, MO, USA. ackerman@wustl.edu.|Alvin J Siteman Cancer Center, Washington University School of Medicine, St Louis, MO, USA. ackerman@wustl.edu.
authors: Joseph J H
authors: JJ
authors: Ackerman
authors: Department of Radiology, Washington University, Campus Box 8227, 4525 Scott Avenue, Saint Louis, MO, 63110, USA. garbow@wustl.edu.|Alvin J Siteman Cancer Center, Washington University School of Medicine, St Louis, MO, USA. garbow@wustl.edu.
authors: Joel R
authors: JR
authors: Garbow
mesh_terms: D000818:Animals; D001369:Axons / Q000473:pathology* / Q000528:radiation effects; D001921:Brain / Q000473:pathology* / Q000528:radiation effects; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004487:Edema / Q000209:etiology / Q000473:pathology*; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D009336:Necrosis; D011832:Radiation Injuries / Q000209:etiology / Q000473:pathology*
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