title: Toward an individualized target motion management for IMRT of cervical cancer based on model-predicted cervix-uterus shape and position.
abstract: OBJECTIVE
  To design and evaluate a 3D patient-specific model to predict the cervix-uterus shape and position.
  
  
  METHODS
  For 13 patients lying in prone position, 10 variable bladder filling CT-scans were acquired, 5 at planning and 5 after 40Gy. The delineated cervix-uterus volumes in 2-5 pre-treatment CT-scans were used to generate patient-specific models that predict the cervix-uterus geometry by bladder volume. Model predictions were compared to delineations, excluding those used for model construction. The prediction error was quantified by the margin required around the predicted volumes to accommodate 95% of the delineated volume and by the predicted-to-delineated surface distance.
  
  
  RESULTS
  The prediction margin was significantly smaller (average 50%) than the margin encompassing the cervix-uterus motion. The prediction margin could be decreased (from 7 to 5mm at planning and from 10 to 8mm after 40Gy) by increasing (from 2 to 5) the number of CT-scans used for the model construction.
  
  
  CONCLUSIONS
  For most patients, even with a model based on only two CT-scans, the prediction error was well below the margin encompassing the cervix-uterus motion. The described approach could be used to create prior to treatment, an individualized treatment strategy.
authors.affiliation: Department of Radiation Oncology, Erasmus-MC Daniel den Hoed Cancer Center, Rotterdam, The Netherlands. m.bondar@erasmusmc.nl
authors.forename: Luiza
authors.initials: L
authors.lastname: Bondar
authors.forename: Mischa
authors.initials: M
authors.lastname: Hoogeman
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Mens
authors.forename: Glenn
authors.initials: G
authors.lastname: Dhawtal
authors.forename: Ilse
authors.initials: I
authors.lastname: de Pree
authors.forename: Rozilawati
authors.initials: R
authors.lastname: Ahmad
authors.forename: Sandra
authors.initials: S
authors.lastname: Quint
authors.forename: Ben
authors.initials: B
authors.lastname: Heijmen
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008875:Middle Aged; D009068:Movement; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D016684:Prone Position; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*