title: Structure-based deformable image registration: Added value for dose accumulation of external beam radiotherapy and brachytherapy in cervical cancer.
abstract: Structure-based deformable image registration (DIR) can be used to calculate accumulated brachytherapy (BT) and external-beam radiation therapy (EBRT) dose-volume histogram (DVH) parameters in cervical cancer. Since direct parameter addition does not take dose non-uniformity into account, the added value of DIR over addition methods was investigated for bladder and rectum.
  
  
  
  For twelve patients (EBRT: 46Gy, EBRT+BT: D9085-90GyEQD2in equivalent dose in 2Gy fractions) the EBRT planning CT and BT planning MRI were registered using DIR. Affected lymph nodes, located far from the BT boost region, received an EBRT boost (9.2Gy) not contributing to the BT boost dose. Cumulative bladder/rectum D2cm3/D1cm3were calculated and compared to direct addition methods, assuming uniform EBRT doses (UD), or overlapping high dose volumes (OHD).
  
  
  
  Between the three methods, the maximum differences in the cumulative DVH parameters were 3.2GyEQD2(bladder) and 3.3GyEQD2(rectum). The difference between DIR and UD was <1.8GyEQD2for both organs.
  
  
  
  The UD method provides a better estimate of D2cm3/D1cm3than the OHD method. There is no added value of DIR since differences with direct addition methods are clinically insignificant. EBRT dose distributions can be considered uniform in bladder and rectum for the evaluated dose parameters.
authors.affiliation: Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands. Electronic address: l.e.vanheerden@amc.uva.nl.
authors.forename: Laura E
authors.initials: LE
authors.lastname: van Heerden
authors.affiliation: Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
authors.forename: Antonetta C
authors.initials: AC
authors.lastname: Houweling
authors.affiliation: Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
authors.forename: Kees
authors.initials: K
authors.lastname: Koedooder
authors.affiliation: Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
authors.forename: Zdenko
authors.initials: Z
authors.lastname: van Kesteren
authors.affiliation: Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
authors.forename: Niek
authors.initials: N
authors.lastname: van Wieringen
authors.affiliation: Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
authors.forename: Coenraad R N
authors.initials: CRN
authors.lastname: Rasch
authors.affiliation: Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Pieters
authors.affiliation: Department of Radiation Oncology, Academic Medical Center/University of Amsterdam, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Bel
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
keywords: Brachytherapy; Cervical cancer; Deformable image registration; Dose accumulation