title: Accuracy of magnetic resonance spectroscopy in distinction between radiation necrosis and recurrence of brain tumors.
abstract: BACKGROUND
  Distinction between radiation necrosis and recurrence of intraparenchymal tumors is necessary to select the appropriate treatment, but it is often difficult based on imaging features alone. We developed an algorithm for analyzing magnetic resonance spectroscopy (MRS) findings and studied its accuracy in differentiation between radiation necrosis and tumor recurrence.
  
  
  METHODS
  Thirty-three patients with a history of intraparenchymal brain tumor resection and radiotherapy, which had developed new enhancing lesion were evaluated by MRS and subsequently underwent reoperation. Lesions with Choline (Cho)/N-acetyl aspartate (NAA) > 1.8 or Cho/Lipid > 1 were considered as tumor recurrence and the remaining as radiation necrosis. Finally, pre-perative MRS diagnoses were compared with histopathological report.
  
  
  RESULTS
  The histological diagnosis was recurrence in 25 patients and necrosis in 8 patients. Mean Cho/NAA in recurrent tumors was 2.72, but it was 1.46 in radiation necrosis (P < 0.01). Furthermore, Cho/Lipid was significantly higher in recurrent tumors (P < 0.01) with the mean of 2.78 in recurrent tumors and 0.6 in radiation necrosis. Sensitivity, specificity, and diagnostic accuracy of the algorithm for detecting tumor recurrence were 84%, 75% and 81%, respectively.
  
  
  CONCLUSIONS
  MRS is a safe and informative tool for differentiating between tumor recurrence and radiation necrosis.
authors: Department of Neurosurgery, School of Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors: Mousa Reza
authors: MR
authors: Anbarloui
authors: Department of Neurosurgery, School of Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors: Seyed Mohammad
authors: SM
authors: Ghodsi
authors: Department of Neurosurgery, School of Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors: Alireza
authors: A
authors: Khoshnevisan
authors: Department of Neurosurgery, School of Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors: Masoud
authors: M
authors: Khadivi
authors: Department of Neurosurgery, School of Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors: Sina
authors: S
authors: Abdollahzadeh
authors: Department of Neurosurgery, School of Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors: Ahmad
authors: A
authors: Aoude
authors: Department of Neurosurgery, School of Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors: Soheil
authors: S
authors: Naderi
authors: Department of Pediatrics, School of Medicine AND Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran.
authors: Zeynab
authors: Z
authors: Najafi
authors: Department of Neurosurgery, School of Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors: Morteza
authors: M
authors: Faghih-Jouibari
keywords: Magnetic Resonance Spectroscopy; Radiation Necrosis; Tumor Recurrence