title: Can images obtained with high field strength magnetic resonance imaging reduce contouring variability of the prostate?
abstract: OBJECTIVE
  The objective of this study is to determine whether there is less contouring variability of the prostate using higher-strength magnetic resonance images (MRI) compared with standard MRI and computed tomography (CT).
  
  
  METHODS
  Forty patients treated with prostate brachytherapy were accrued to a prospective study that included the acquisition of 1.5-T MR and CT images at specified time points. A subset of 10 patients had additional 3.0-T MR images acquired at the same time as their 1.5-T MR scans. Images from each of these patients were contoured by 5 radiation oncologists, with a random subset of patients repeated to quantify intraobserver contouring variability. To minimize bias in contouring the prostate, the image sets were placed in folders in a random order with all identifiers removed from the images.
  
  
  RESULTS
  Although there was less interobserver contouring variability in the overall prostate volumes in 1.5-T MRI compared with 3.0-T MRI (p < 0.01), there was no significant differences in contouring variability in the different regions of the prostate between 1.5-T MRI and 3.0-T MRI. MRI demonstrated significantly less interobserver contouring variability in both 1.5-T and 3.0-T compared with CT in overall prostate volumes (p < 0.01, p = 0.01), with the greatest benefits being appreciated in the base of the prostate. Overall, there was less intraobserver contouring variability than interobserver contouring variability for all of the measurements analyzed.
  
  
  CONCLUSIONS
  Use of 3.0-T MRI does not demonstrate a significant improvement in contouring variability compared with 1.5-T MRI, although both magnetic strengths demonstrated less contouring variability compared with CT.
authors.affiliation: Department of Radiation Oncology, Cross Cancer Institute, Edmonton, AB, Canada. Nawaid.Usmani@albertahealthservices.ca
authors.forename: Nawaid
authors.initials: N
authors.lastname: Usmani
authors.forename: Ron
authors.initials: R
authors.lastname: Sloboda
authors.forename: Wafa
authors.initials: W
authors.lastname: Kamal
authors.forename: Sunita
authors.initials: S
authors.lastname: Ghosh
authors.forename: Nadeem
authors.initials: N
authors.lastname: Pervez
authors.forename: John
authors.initials: J
authors.lastname: Pedersen
authors.forename: Don
authors.initials: D
authors.lastname: Yee
authors.forename: Brita
authors.initials: B
authors.lastname: Danielson
authors.forename: Albert
authors.initials: A
authors.lastname: Murtha
authors.forename: John
authors.initials: J
authors.lastname: Amanie
authors.forename: Tara
authors.initials: T
authors.lastname: Monajemi
mesh_terms: D000368:Aged; D001918:Brachytherapy; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009929:Organ Size; D011446:Prospective Studies; D011467:Prostate / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy; D014057:Tomography, X-Ray Computed