accuracy of magnetic resonance spectroscopy in distinction between radiation necrosis and recurrence of brain tumors.

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. m e t hod s :    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. r es u l t s : 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. conclusion: mrs is a safe and informative tool for differentiating    between   tumor   recurrence   and radiation necrosis.