title: MRI patterns of T1 enhancing radiation necrosis versus tumour recurrence in high-grade gliomas.
abstract: BACKGROUND
  Despite the emergence of new imaging technologies, the differentiation of treatment-related changes from recurrent tumour in patients with high-grade gliomas remains a difficult challenge. We evaluated whether specific MRI (magnetic resonance imaging) T1 post-contrast enhancement patterns can help to distinguish between radiation necrosis and tumour recurrence.
  
  
  METHODS
  This study was approved by local institutional review board. Fifty-one patients with World Health Organization grade III-IV glioma underwent reoperation after prior chemoradiation. The percentage of radiation necrosis versus recurrent tumour in reoperation specimens was estimated by an experienced neuropathologist. Enhancement patterns on T1 post-contrast sequences from the MRIs obtained prior to reoperation were evaluated according to pathology.
  
  
  RESULTS
  T1 contrast enhancement patterns correlating with recurrent tumour included focal solid nodules and solid uniform enhancement with distinct margins. Eighty-five per cent (17/20) of patients with ≥70% recurrent tumour at reoperation demonstrated one of these patterns on preoperative MRI. Enhancement patterns correlating with radiation necrosis included a hazy mesh-like diffuse enhancement and rim enhancement with feathery indistinct margins. Ninety-four per cent (17/18) of patients with ≥70% radiation necrosis demonstrated one of these two patterns. Thirteen cases had more mixed pathology (>30% of tumour/necrosis) and demonstrated patterns associated with recurrence and/or necrosis. Compared to MR spectroscopy performed in 10 patients, enhancement patterns on MRI were just as accurate in predicting pathologic diagnosis.
  
  
  CONCLUSIONS
  Identifying distinct patterns of contrast enhancement on MRI may help to differentiate between radiation necrosis and tumour recurrence in high-grade gliomas.
authors.affiliation: Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA. Krishna.Reddy@ucdenver.edu
authors.forename: Krishna
authors.initials: K
authors.lastname: Reddy
authors.forename: David
authors.initials: D
authors.lastname: Westerly
authors.forename: Changhu
authors.initials: C
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D001930:Brain Injuries / Q000453:epidemiology / Q000473:pathology*; D001932:Brain Neoplasms / Q000453:epidemiology / Q000473:pathology / Q000532:radiotherapy*; D015897:Comorbidity; D003937:Diagnosis, Differential; D005260:Female; D005910:Glioma / Q000453:epidemiology / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D015994:Incidence; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D009336:Necrosis / Q000473:pathology; D009364:Neoplasm Recurrence, Local / Q000473:pathology* / Q000517:prevention & control; D009520:New Zealand / Q000453:epidemiology; D011832:Radiation Injuries / Q000453:epidemiology / Q000473:pathology*; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016896:Treatment Outcome