title: Variability in prostate and seminal vesicle delineations defined on magnetic resonance images, a multi-observer, -center and -sequence study.
abstract: BACKGROUND
  The use of magnetic resonance (MR) imaging as a part of preparation for radiotherapy is increasing. For delineation of the prostate several publications have shown decreased delineation variability using MR compared to computed tomography (CT). The purpose of the present work was to investigate the intra- and inter-physician delineation variability for prostate and seminal vesicles, and to investigate the influence of different MR sequence settings used clinically at the five centers participating in the study.
  
  
  METHODS
  MR series from five centers, each providing five patients, were used. Two physicians from each center delineated the prostate and the seminal vesicles on each of the 25 image sets. The variability between the delineations was analyzed with respect to overall, intra- and inter-physician variability, and dependence between variability and origin of the MR images, i.e. the MR sequence used to acquire the data.
  
  
  RESULTS
  The intra-physician variability in different directions was between 1.3 - 1.9 mm and 3 - 4 mm for the prostate and seminal vesicles respectively (1 std). The inter-physician variability for different directions were between 0.7 - 1.7 mm and approximately equal for the prostate and seminal vesicles. Large differences in variability were observed for individual patients, and also for individual imaging sequences used at the different centers. There was however no indication of decreased variability with higher field strength.
  
  
  CONCLUSIONS
  The overall delineation variability is larger for the seminal vesicles compared to the prostate, due to a larger intra-physician variability. The imaging sequence appears to have a large influence on the variability, even for different variants of the T2-weighted spin-echo based sequences, which were used by all centers in the study.
authors.forename: Tufve
authors.initials: T
authors.lastname: Nyholm
authors.forename: Joakim
authors.initials: J
authors.lastname: Jonsson
authors.forename: Karin
authors.initials: K
authors.lastname: Söderström
authors.forename: Per
authors.initials: P
authors.lastname: Bergström
authors.forename: Andreas
authors.initials: A
authors.lastname: Carlberg
authors.forename: Gunilla
authors.initials: G
authors.lastname: Frykholm
authors.forename: Claus F
authors.initials: CF
authors.lastname: Behrens
authors.forename: Poul Flemming
authors.initials: PF
authors.lastname: Geertsen
authors.forename: Redas
authors.initials: R
authors.lastname: Trepiakas
authors.forename: Scott
authors.initials: S
authors.lastname: Hanvey
authors.forename: Azmat
authors.initials: A
authors.lastname: Sadozye
authors.forename: Jawaher
authors.initials: J
authors.lastname: Ansari
authors.forename: Hazel
authors.initials: H
authors.lastname: McCallum
authors.forename: John
authors.initials: J
authors.lastname: Frew
authors.forename: Rhona
authors.initials: R
authors.lastname: McMenemin
authors.forename: Björn
authors.initials: B
authors.lastname: Zackrisson
mesh_terms: D006801:Humans; D008279:Magnetic Resonance Imaging / Q000592:standards*; D008297:Male; D015588:Observer Variation; D011471:Prostatic Neoplasms / Q000473:pathology*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods / Q000592:standards*; D012669:Seminal Vesicles / Q000473:pathology*