title: Proton magnetic resonance spectroscopy in the distinction of high-grade cerebral gliomas from single metastatic brain tumors.
abstract: BACKGROUND
  Brain metastases and primary high-grade gliomas, including glioblastomas multiforme (GBM) and anaplastic astrocytomas (AA), may be indistinguishable by conventional magnetic resonance (MR) imaging. Identification of these tumors may have therapeutic consequences.
  
  
  OBJECTIVE
  To assess the value of MR spectroscopy (MRS) using short and intermediate echo time (TE) in differentiating solitary brain metastases and high-grade gliomas on the basis of differences in metabolite ratios in the intratumoral and peritumoral region.
  
  
  METHODS
  We performed MR imaging and MRS in 73 patients with histologically verified intraaxial brain tumors: 53 patients with high-grade gliomas (34 GBM and 19 AA) and 20 patients with metastatic brain tumors. The metabolite ratios of Cho/Cr, Cho/NAA, and NAA/Cr at intermediate TE and the presence of lipids at short TE were assessed from spectral maps in the tumoral core, peritumoral edema, and contralateral normal-appearing white matter. The differences in the metabolite ratios between high-grade gliomas/GBM/AA and metastases were analyzed statistically. Cutoff values of Cho/Cr, Cho/NAA, and NAA/Cr ratios in the peritumoral edema, as well as Cho/Cr and NAA/Cr ratios in the tumoral core for distinguishing high-grade gliomas/GBM/AA from metastases were determined by receiver operating characteristic (ROC) curve analysis.
  
  
  RESULTS
  Significant differences were noted in the peritumoral Cho/Cr, Cho/NAA, and NAA/ Cr ratios between high-grade gliomas/GBM/AA and metastases. ROC analysis demonstrated a cutoff value of 1.24 for peritumoral Cho/Cr ratio to provide sensitivity, specificity, positive (PPV), and negative predictive values (NPV) of 100%, 88.9%, 80.0%, and 100%, respectively, for discrimination between high-grade gliomas and metastases. By using a cutoff value of 1.11 for peritumoral Cho/NAA ratio, the sensitivity was 100%, the specificity was 91.1%, the PPV was 83.3%, and the NPV was 100%.
  
  
  CONCLUSIONS
  The results of this study demonstrate that MRS can differentiate high-grade gliomas from metastases, especially with peritumoral measurements, supporting the hypothesis that MRS can detect infiltration of tumor cells in the peritumoral edema.
authors.affiliation: Section of Neuroradiology, Department of Medical Imaging and Intervention, Oslo University Hospital, Ullevaal, University of Oslo, Oslo, Norway. a.s.alonso@medisin.uio.no
authors.forename: Andrès
authors.initials: A
authors.lastname: Server
authors.forename: Roger
authors.initials: R
authors.lastname: Josefsen
authors.forename: Bettina
authors.initials: B
authors.lastname: Kulle
authors.forename: Jan
authors.initials: J
authors.lastname: Maehlen
authors.forename: Till
authors.initials: T
authors.lastname: Schellhorn
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Gadmar
authors.forename: Theresa
authors.initials: T
authors.lastname: Kumar
authors.forename: Monika
authors.initials: M
authors.lastname: Haakonsen
authors.forename: Carl W
authors.initials: CW
authors.lastname: Langberg
authors.forename: Per H
authors.initials: PH
authors.lastname: Nakstad
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000556:secondary*; D002794:Choline / Q000378:metabolism; D003287:Contrast Media; D003401:Creatine / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D019786:Gadolinium DTPA; D005910:Glioma / Q000378:metabolism* / Q000473:pathology / Q000556:secondary*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D050356:Lipid Metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D003287:Contrast Media; D001224:Aspartic Acid; C000179:N-acetylaspartate; D019786:Gadolinium DTPA; D003401:Creatine; D002794:Choline