title: Impact of organ shape variations on margin concepts for cervix cancer ART.
abstract: Target and organ movement motivate adaptive radiotherapy for cervix cancer patients. We investigated the dosimetric impact of margin concepts with different levels of complexity on both organ at risk (OAR) sparing and PTV coverage.
  
  
  
  Weekly CT and daily CBCT scans were delineated for 10 patients. The dosimetric impact of organ shape variations were evaluated for four (isotropic) margin concepts: two static PTVs (PTV6mmand PTV15mm), a PTV based on ITV of the planning CT and CBCTs of the first treatment week (PTVART ITV) and an adaptive PTV based on a library approach (PTVART Library).
  
  
  
  Using static concepts, OAR doses increased with large margins, while smaller margins compromised target coverage. ART PTVs resulted in comparable target coverage and better sparing of bladder (V40Gy: 15% and 7% less), rectum (V40Gy: 18 and 6cc less) and bowel (V40Gy: 106 and 15cc less) compared to PTV15mm. Target coverage evaluation showed that for elective fields a static 5mm margin sufficed.
  
  
  
  PTVART Libraryachieved the best dosimetric results. However when weighing clinical benefit against workload, ITV margins based on repetitive movement evaluation during the first week also provide improvements over static margin concepts.
authors.affiliation: Department of Radiation Oncology, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Wien, Austria. Electronic address: Yvette.Seppenwoolde@meduniwien.ac.at.
authors.forename: Yvette
authors.initials: Y
authors.lastname: Seppenwoolde
authors.affiliation: Department of Radiation Oncology, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Wien, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Stock
authors.affiliation: Department of Radiation Oncology, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Wien, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Buschmann
authors.affiliation: Department of Radiation Oncology, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Wien, Austria.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Georg
authors.affiliation: Department of Radiation Oncology, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Wien, Austria.
authors.forename: Kwei-Yuang
authors.initials: KY
authors.lastname: Bauer-Novotny
authors.affiliation: Department of Radiation Oncology, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Wien, Austria.
authors.forename: Richard
authors.initials: R
authors.lastname: Pötter
authors.affiliation: Department of Radiation Oncology, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/AKH Wien, Austria.
authors.forename: Petra
authors.initials: P
authors.lastname: Georg
mesh_terms: D005260:Female; D006801:Humans; D009068:Movement; D059351:Organ Sparing Treatments / Q000379:methods; D058958:Organs at Risk / Q000528:radiation effects; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D014599:Uterus / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D016526:Workload
keywords: Adaptive radiotherapy; Cervix cancer; Organs at risk sparing