title: Spectroscopy imaging in intraoperative MR suite: tissue characterization and optimization of tumor resection.
abstract: BACKGROUND
  MR spectroscopy (MRS) measurements are common practice in the preoperative diagnostic regimen, but no evidence exists concerning their value in intraoperative MRI (iMRI) setting. We sought to examine the feasibility of intraoperative MRS and to assess the clinical value of the method in optimizing the gliomas resection.
  
  
  METHODS
  Forty-five patients with low- and high-grade gliomas underwent iMRI-assisted surgery, including pre- and intraoperative MRS measurements. During the intraoperative control scan, MRS was performed at the resection margin. Peak areas under the major metabolites (N-acetyl-aspartate: NAA; choline: Cho; and creatine: Cr) resonances were estimated, and their ratios entered in the statistical analysis.
  
  
  RESULTS
  Concerning preoperative MRS imaging, mean Cho/NAA and Cho/Cr ratios in low-grade gliomas were 2.3 and 1.2, respectively. The average Cho/NAA and Cho/Cr ratios in the high-grade gliomas were 3.9 and 2.3, respectively. In 12 out of 20 cases with low-grade gliomas, intraoperative conventional MR imaging showed suspected tumor remnant and MRS diagnosed correctly the tissue signal alterations in 10 out of those 12 cases. MRS could characterize gadolinium-enhancing or non-enhancing tumor remnants in all cases with high-grade tumors. Thus, it could help achieve total tumor resection unless the latter was contraindicated due to increased risk of neurological complications.
  
  
  CONCLUSIONS
  MR spectroscopy (MRS) in an iMRI setting is feasible, facilitating preoperative glioma staging as well as satisfactory characterization of suspected tumor remnants. Thus, it may be helpful tool for an extended tumor resection.
authors.affiliation: Department of Neurosurgery, Eberhard Karls University, Tübingen, Germany.
authors.forename: Constantin
authors.initials: C
authors.lastname: Roder
authors.forename: Marco
authors.initials: M
authors.lastname: Skardelly
authors.forename: Kristofer Fingerle
authors.initials: KF
authors.lastname: Ramina
authors.forename: Rudi
authors.initials: R
authors.lastname: Beschorner
authors.forename: Jürgen
authors.initials: J
authors.lastname: Honneger
authors.forename: Thomas
authors.initials: T
authors.lastname: Nägele
authors.forename: Marcos Soares
authors.initials: MS
authors.lastname: Tatagiba
authors.forename: Ulrike
authors.initials: U
authors.lastname: Ernemann
authors.forename: Sotirios
authors.initials: S
authors.lastname: Bisdas
mesh_terms: D000328:Adult; D000368:Aged; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001921:Brain / Q000378:metabolism / Q000601:surgery*; D001932:Brain Neoplasms / Q000378:metabolism / Q000601:surgery*; D002794:Choline / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D005260:Female; D005910:Glioma / Q000378:metabolism / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline