title: Proton magnetic resonance spectroscopy imaging in the evaluation of patients undergoing gamma knife surgery for Grade IV glioma.
abstract: OBJECTIVE
  The purpose of this study was to assess the differences in spatial extent and metabolic activity in a comparison of a radiosurgical target defined by conventional strategies that utilize the enhancing lesion and a metabolic lesion defined by proton magnetic resonance spectroscopy (MRS) imaging. The authors evaluated whether these differences manifest themselves in the clinical outcome of patients and assessed the value of incorporating 1H-MRS imaging-derived spatial information into the treatment planning process for gamma knife surgery (GKS).
  
  
  METHODS
  Twenty-six patients harboring Grade IV gliomas who had previously been treated with external-beam radiation therapy were evaluated by comparing the radiosurgically treated lesion volume with the volume of metabolically active tumor defined on 1H-MRS imaging. The cohort was evenly divided into two groups based on the percentage of overlap between the radiosurgical target and the metabolic lesion volumes. Patients with a percentage of overlap greater than 50% with respect to the metabolic lesion volume were classified as low risk and those with an overlap less than 50% were classified as high risk. Kaplan-Meier estimators were calculated using time to progression and survival as dependent variables. The metabolite levels within the metabolic lesion were significantly greater than those within the radiosurgical target (p < or = 0.001). The median survival was 15.7 months for patients in the low-risk group and 10.4 months for those in the high-risk group. This difference was statistically significant (p < 0.01).
  
  
  CONCLUSIONS
  Analysis of the results of this study indicates that patients undergoing GKS may benefit from the inclusion of 1H-MRS imaging in the treatment planning process.
authors.affiliation: Department of Radiology, University of California, San Francisco, California 94107-1739, USA.
authors.forename: Antoinette A
authors.initials: AA
authors.lastname: Chan
authors.forename: Aubrey
authors.initials: A
authors.lastname: Lau
authors.forename: Andrea
authors.initials: A
authors.lastname: Pirzkall
authors.forename: Susan M
authors.initials: SM
authors.lastname: Chang
authors.forename: Lynn J
authors.initials: LJ
authors.lastname: Verhey
authors.forename: David
authors.initials: D
authors.lastname: Larson
authors.forename: Michael W
authors.initials: MW
authors.lastname: McDermott
authors.forename: William P
authors.initials: WP
authors.lastname: Dillon
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Nelson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001921:Brain / Q000503:physiopathology / Q000601:surgery; D001931:Brain Mapping; D001932:Brain Neoplasms / Q000401:mortality / Q000503:physiopathology / Q000532:radiotherapy / Q000601:surgery*; D002794:Choline / Q000378:metabolism; D015331:Cohort Studies; D003131:Combined Modality Therapy; D016371:Cranial Irradiation; D003401:Creatine / Q000378:metabolism; D018450:Disease Progression; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005909:Glioblastoma / Q000401:mortality / Q000503:physiopathology / Q000532:radiotherapy / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019344:Lactic Acid / Q000378:metabolism; D050356:Lipid Metabolism; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000503:physiopathology / Q000532:radiotherapy / Q000601:surgery; D038361:Neuronavigation; D011379:Prognosis; D016634:Radiosurgery; D012086:Reoperation; D012306:Risk; D016019:Survival Analysis
chemical_list: D001224:Aspartic Acid; D019344:Lactic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline