title: Clinical evaluation of stereotactic target localization using 3-Tesla MRI for radiosurgery planning.
abstract: OBJECTIVE
  Increasing the magnetic resonance imaging (MRI) field strength can improve image resolution and quality, but concerns remain regarding the influence on geometric fidelity. The objectives of the present study were to spatially investigate the effect of 3-Tesla (3T) MRI on clinical target localization for stereotactic radiosurgery.
  
  
  METHODS
  A total of 39 patients were enrolled in a research ethics board-approved prospective clinical trial. Imaging (1.5T and 3T MRI and computed tomography) was performed after stereotactic frame placement. Stereotactic target localization at 1.5T vs. 3T was retrospectively analyzed in a representative cohort of patients with tumor (n = 4) and functional (n = 5) radiosurgical targets. The spatial congruency of the tumor gross target volumes was determined by the mean discrepancy between the average gross target volume surfaces at 1.5T and 3T. Reproducibility was assessed by the displacement from an averaged surface and volume congruency. Spatial congruency and the reproducibility of functional radiosurgical targets was determined by comparing the mean and standard deviation of the isocenter coordinates.
  
  
  RESULTS
  Overall, the mean absolute discrepancy across all patients was 0.67 mm (95% confidence interval, 0.51-0.83), significantly <1 mm (p < .010). No differences were found in the overall interuser target volume congruence (mean, 84% for 1.5T vs. 84% for 3T, p > .4), and the gross target volume surface mean displacements were similar within and between users. The overall average isocenter coordinate discrepancy for the functional targets at 1.5T and 3T was 0.33 mm (95% confidence interval, 0.20-0.48), with no patient-specific differences between the mean values (p >.2) or standard deviations (p >.1).
  
  
  CONCLUSIONS
  Our results have provided clinically relevant evidence supporting the spatial validity of 3T MRI for use in stereotactic radiosurgery under the imaging conditions used.
authors.affiliation: University of Toronto Faculty of Medicine, Toronto, ON, Canada.
authors.forename: Derek
authors.initials: D
authors.lastname: MacFadden
authors.forename: BeiBei
authors.initials: B
authors.lastname: Zhang
authors.forename: Kristy K
authors.initials: KK
authors.lastname: Brock
authors.forename: Mojgan
authors.initials: M
authors.lastname: Hodaie
authors.forename: Normand
authors.initials: N
authors.lastname: Laperriere
authors.forename: Michael
authors.initials: M
authors.lastname: Schwartz
authors.forename: May
authors.initials: M
authors.lastname: Tsao
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Stainsby
authors.forename: Gina
authors.initials: G
authors.lastname: Lockwood
authors.forename: David
authors.initials: D
authors.lastname: Mikulis
authors.forename: Cynthia
authors.initials: C
authors.lastname: Ménard
mesh_terms: D001932:Brain Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D011446:Prospective Studies; D016634:Radiosurgery; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D047368:Tumor Burden