title: Volumetric Analysis of F-18-FET-PET Imaging for Brain Metastases.
abstract: BACKGROUND
  The knowledge of exact tumor margins is of importance for the treating neurosurgeon, radiotherapist, and oncologist alike. The aim of this study was to investigate whether tumor volume and tumor margins acquired by magnetic resonance imaging (MRI) are congruent with the findings acquired by O-(2-(18F)-fluoroethyl)-L-tyrosine-positron emission tomography (FET-PET).
  
  
  METHODS
  Patients received FET-PET and MRI before surgery for brain metastases. Metastases were quantified by calculating tumor-to-background uptake ratios using FET uptake. PET and MRI-based tumor volumes, as well as areas of intersection, were assessed.
  
  
  RESULTS
  Forty-one patients were enrolled in the study. The maximum tumor-to-background uptake ratio measured in all of our patients harboring histologically proven viable tumor tissue was >1.6. Absolute tumor volumes acquired by FET-PET and MRI were not congruent in our patient cohort, and tumors identified in FET-PET and MRI only partially overlapped. The ratio of intersection (intersection of tumor defined by MRI and tumor defined by FET-PET at the ratio of tumor defined by FET-PET) was within a range of 0.27-0.68 when applying the different thresholds.
  
  
  CONCLUSIONS
  Our study therefore indicates that treatment planning based on MRI or PET only might have a substantial risk of undertreatment at the tumor margins. These findings could have important implications for the planning of surgery as well as radiotherapy, although they have to be validated in further studies.
authors.affiliation: Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany. Electronic address: Jens.Gempt@tum.de.
authors.forename: Jens
authors.initials: J
authors.lastname: Gempt
authors.affiliation: Abteilung für Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Bette
authors.affiliation: Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Niels
authors.initials: N
authors.lastname: Buchmann
authors.affiliation: Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Yu-Mi
authors.initials: YM
authors.lastname: Ryang
authors.affiliation: Abteilung für Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Förschler
authors.affiliation: Nuklearmedizinische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pyka
authors.affiliation: Nuklearmedizinische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Wester
authors.affiliation: Nuklearmedizinische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Förster
authors.affiliation: Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Meyer
authors.affiliation: Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Ringel
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000008:administration & dosage; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods; D011237:Predictive Value of Tests; D011379:Prognosis; D019275:Radiopharmaceuticals / Q000008:administration & dosage*; D047368:Tumor Burden; D014443:Tyrosine / Q000008:administration & dosage / Q000031:analogs & derivatives*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C545932:(18F)fluoroethyltyrosine; D014443:Tyrosine
keywords: Brain irradiation; Brain metastasis; Brain metastasis resection; FET-PET; MRI