title: Proton MR spectroscopic evaluation of suspicious brain lesions after stereotactic radiotherapy.
abstract: OBJECTIVE
  The radiologic assessment of suspicious brain lesions after stereotactic radiotherapy of brain tumors is difficult. The purpose of our study was to define parameters from single-voxel proton MR spectroscopy that provide a probability measure for differentiating neoplastic from radiation-induced, nonneoplastic lesions.
  
  
  METHODS
  Seventy-two lesions in 56 patients were examined using a combined MR imaging and MR spectroscopy protocol (point-resolved spectroscopy, TE = 135 ms). Signal intensities of cholines, creatines, N-acetyl aspartate, and the presence of lactate and lipid resonances were correlated to final diagnoses established by clinical and MR imaging follow-up, positron emission tomography studies, or biopsy/surgery. Statistical analysis was performed using the t test, linear discriminant analysis, and k nearest-neighbor method.
  
  
  RESULTS
  Significantly increased signal intensity ratios I(tCho)/I(tCr) (P <.0001) and I(tCho)/I(NAA) (P <.0001) were observed in neoplastic (n = 34) compared with nonneoplastic lesions (n = 32) and contralateral normal brain (n = 33). Analysis of I(tCho)/I(tCr) and I(tCho)/I(NAA) data yielded correct retrospective classification as neoplastic and nonneoplastic in 82% and 81% of the lesions, respectively. Neither I(NAA)/I(tCr) nor signal intensitities of lactate or lipids were useful for differential diagnosis.
  
  
  CONCLUSIONS
  Metabolic information provided by proton MR spectroscopy is useful for the differentiation of neoplastic and nonneoplastic brain lesions after stereotactic radiotherapy of brain tumors.
authors.affiliation: Department of Oncological Diagnostics and Therapy, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors.forename: H P
authors.initials: HP
authors.lastname: Schlemmer
authors.forename: P
authors.initials: P
authors.lastname: Bachert
authors.forename: K K
authors.initials: KK
authors.lastname: Herfarth
authors.forename: I
authors.initials: I
authors.lastname: Zuna
authors.forename: J
authors.initials: J
authors.lastname: Debus
authors.forename: G
authors.initials: G
authors.lastname: van Kaick
mesh_terms: D000328:Adult; D001254:Astrocytoma / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D001932:Brain Neoplasms / Q000175:diagnosis / Q000556:secondary / Q000601:surgery*; D003937:Diagnosis, Differential; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D005909:Glioblastoma / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008577:Meningeal Neoplasms / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D008579:Meningioma / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000503:physiopathology; D016609:Neoplasms, Second Primary / Q000175:diagnosis* / Q000503:physiopathology; D011183:Postoperative Complications / Q000175:diagnosis* / Q000503:physiopathology; D016634:Radiosurgery