title: [Interobserver variability study for daily cone beam computed tomography registration of prostate volumetric modulated arc therapy].
abstract: OBJECTIVE
  This work evaluated the interobserver variability in cone beam computed tomography (CBCT) registration for prostate cancers treated with intensity-modulated radiotherapy.
  
  
  METHODS
  Twelve technologists realized 286 CBCT/CT registrations (bone registration followed by prostate to prostate registration). The registration results were compared to those obtained by two radiation oncologists (reference). Each technologist reported the shifts calculated by the software in all three axes. A statistical analysis allowed us to calculate the minimum threshold under which 95% of the observers found similar values. A variance analysis followed by the post hoc test were used to find differences in interobserver registration variability and determine whether any individual users performed registrations which differed significantly from those of the other users.
  
  
  RESULTS
  The registration differences compared to the reference in the three directions in terms of 95th percentile are: 2.1mm left-right, 3.5mm target-gun, 7.3mm anterior-posterior. In the posterior direction, 4% of the observers have found differences superior to 8mm, margin used in routine without the use of a daily CBCT. The variance test revealed a P-value <0.05 only for target-gun and for all observers there was no significant difference compared to the reference.
  
  
  CONCLUSIONS
  This study confirmed the interest of a 3D tissue registration for prostate treatments. The registration study showed a good interobserver reproducibility. This showed the importance of a daily CBCT/CT registration in prostate treatment with the possibility of a planning target volume margin reduction in the three directions. An evaluation of a partial delegation of registration to technologists should be done by the radiation oncologists.
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France. Electronic address: m.n.zahra@gmail.com.
authors.forename: N
authors.initials: N
authors.lastname: Zahra
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France.
authors.forename: C
authors.initials: C
authors.lastname: Monnet
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France.
authors.forename: E
authors.initials: E
authors.lastname: Bartha
authors.affiliation: Institut Curie, hôpital René-Huguenin, 35, rue Dailly, 92210 Saint-Cloud, France.
authors.forename: G
authors.initials: G
authors.lastname: Bouilhol
authors.affiliation: Laboratoire de traitement des signaux 5 (LTS5), école polytechnique fédérale de Lausanne (EPFL), EPFL-STI-IEL-LTS5 Station 11, 1015 Lausanne, Suisse.
authors.forename: C
authors.initials: C
authors.lastname: Boydev
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France.
authors.forename: M
authors.initials: M
authors.lastname: Courbis
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France.
authors.forename: M
authors.initials: M
authors.lastname: Le Grévellec
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France.
authors.forename: M
authors.initials: M
authors.lastname: Bosset
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France.
authors.forename: M
authors.initials: M
authors.lastname: Zouai
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France.
authors.forename: B
authors.initials: B
authors.lastname: Fleury
authors.affiliation: Centre de radiothérapie Marie-Curie, 159, boulevard Maréchal-Juin, 26000 Valence, France.
authors.forename: S
authors.initials: S
authors.lastname: Clippe
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000532:radiotherapy; D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D015588:Observer Variation; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods
keywords: Arcthérapie volumétrique modulée; CBCT imaging; Erreur interobservateurs; Interobserver error; Prostate; Prostate VMAT; Tomographie conique