title: Quantification of delineation errors of the gross tumor volume on magnetic resonance imaging in uterine cervical cancer using pathology data and deformation correction.
abstract: BACKGROUND
  To safely optimize target volumes using magnetic resonance imaging (MRI) for uterine cervical cancer radiation therapy, MRI findings need to be validated. The aim of this study was to correlate pre-operatively acquired MRI and surgical specimen imaging for uterine cervical cancer patients using deformable image registration and quantify gross tumor volume (GTV) delineation discrepancies.
  
  
  METHODS
  For 16 retrospectively selected early-stage uterine cervical cancer patients, the cervix-uterus structure, uterine cavity and the GTV were delineated on 2D pathology photos after macroscopic intersection and corresponding pre-operatively acquired T2-weighted 2D sagittal MR images. Segmentations of pathology photos and MR images were simultaneously registered using a three-step multi-image registration strategy. The registration outcome was evaluated by the Dice similarity coefficient (DSC) and the surface distance error (SDE). In addition, GTV expansions within the cervix-uterus structure needed to obtain 95% GTV coverage were determined.
  
  
  RESULTS
  After three-step multi-image registration, the median DSC and median SDE were 0.98 and 0.4 mm (cervix-uterus) and 0.90 and 0.4 mm (uterine cavity), respectively. The average SDE around the GTV was 0.7 mm (range, 0.1 mm - 2.6 mm). An underestimation of MRI-based GTV delineations was found when no margin was applied, indicated by a mean GTV coverage of 61%. To obtain 95% GTV coverage for 90% of the patients, a minimum 12.0 mm margin around MRI-based GTVs was needed.
  
  
  CONCLUSIONS
  The presented three-step multi-image registration strategy was suitable and accurate to correlate MRI and pathology data for uterine cervical cancer patients. To cover the pathology-based GTV, a margin of at least 12.0 mm around GTV delineations on T2-weighted MRI is needed.
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam , Amsterdam , The Netherlands.
authors.forename: Agustinus J A J
authors.initials: AJ
authors.lastname: van de Schoot
authors.forename: Peter
authors.initials: P
authors.lastname: de Boer
authors.forename: Marrije R
authors.initials: MR
authors.lastname: Buist
authors.forename: Jaap
authors.initials: J
authors.lastname: Stoker
authors.forename: Maaike C G
authors.initials: MC
authors.lastname: Bleeker
authors.forename: Lukas J A
authors.initials: LJ
authors.lastname: Stalpers
authors.forename: Coen R N
authors.initials: CR
authors.lastname: Rasch
authors.forename: Arjan
authors.initials: A
authors.lastname: Bel
mesh_terms: D000465:Algorithms; D002584:Cervix Uteri / Q000473:pathology*; D005260:Female; D006801:Humans; D007044:Hysterectomy; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009367:Neoplasm Staging; D015588:Observer Variation; D010781:Photography; D047368:Tumor Burden; D002583:Uterine Cervical Neoplasms / Q000473:pathology* / Q000601:surgery