title: Position shifts and volume changes of pelvic and para-aortic nodes during IMRT for patients with cervical cancer.
abstract: OBJECTIVE
  To evaluate volume changes and position shifts and their contribution to treatment margins of pelvic and para-aortic lymph nodes during Intensity Modulated Radiation Therapy (IMRT) for advanced cervical cancer.
  
  
  METHODS
  Seventeen patients with visible nodes on MR images underwent T2-weighted MR scans before and weekly during the course of IMRT. Thirty-nine pelvic and para-aortic nodes were delineated on all scans. Margins accommodating for volume and position changes were taken from the boundaries of the nodal volumes in the six main directions.
  
  
  RESULTS
  Nodal volume regression from the pre-treatment situation to week 4 was 58% on average (range: 11.7% increase to 100% decrease). Nodal volumes partly increased between the pre-treatment scans and the scans in weeks 1-3, but in week 4 all nodes except one had regressed. Around the nodal volumes manually derived ITV margins accounting for volume changes and position shifts of 7.0, 4.0, 7.0, 8.0, 7.0 and 9.0mm to the medial, lateral, anterior, posterior, superior and inferior directions were needed to cover 95% of all nodes.
  
  
  CONCLUSIONS
  We used weekly MR scans to derive inhomogeneous margins that accommodate for nodal volume and position changes during treatment. These margins should be taken into consideration when planning external beam radiotherapy (EBRT) boosts, especially for highly conformal boosting techniques.
authors.affiliation: Department of Radiation Oncology, University Medical Centre Utrecht, The Netherlands.
authors.forename: Maaike G A
authors.initials: MG
authors.lastname: Schippers
authors.affiliation: Department of Radiation Oncology, University Medical Centre Utrecht, The Netherlands.
authors.forename: Gijsbert H
authors.initials: GH
authors.lastname: Bol
authors.affiliation: Department of Radiation Oncology, University Medical Centre Utrecht, The Netherlands.
authors.forename: Astrid A C
authors.initials: AA
authors.lastname: de Leeuw
authors.affiliation: Department of Radiation Oncology, University Medical Centre Utrecht, The Netherlands.
authors.forename: Uulke A
authors.initials: UA
authors.lastname: van der Heide
authors.affiliation: Department of Radiation Oncology, University Medical Centre Utrecht, The Netherlands.
authors.forename: Bas W
authors.initials: BW
authors.lastname: Raaymakers
authors.affiliation: Department of Radiology, University Medical Centre Utrecht, The Netherlands; Julius Center for Health Sciences and Primary Care, University Medical Centre Utrecht, The Netherlands.
authors.forename: Helena M
authors.initials: HM
authors.lastname: Verkooijen
authors.affiliation: Department of Radiation Oncology, University Medical Centre Utrecht, The Netherlands. Electronic address: i.m.schulz@umcutrecht.nl.
authors.forename: Ina M
authors.initials: IM
authors.lastname: Jürgenliemk-Schulz
mesh_terms: D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology / Q000528:radiation effects; D008279:Magnetic Resonance Imaging; D010388:Pelvis / Q000473:pathology / Q000528:radiation effects; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D061089:Radiotherapy, Image-Guided; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
keywords: Cervix cancer; ITV margins; Image-guided radiotherapy; Lymph nodes; Target volume changes