title: Magnetic resonance imaging- versus computed tomography-based target volume delineation of the glandular breast tissue (clinical target volume breast) in breast-conserving therapy: an exploratory study.
abstract: OBJECTIVE
  To examine MRI and CT for glandular breast tissue (GBT) volume delineation and to assess interobserver variability.
  
  
  METHODS
  Fifteen breast cancer patients underwent a planning CT and MRI, consecutively, in the treatment position. Four observers (two radiation oncologists and two radiologists) delineated the GBT according to the CT and separately to the MR images. Volumes, centers of mass, maximum extensions with standard deviations (SD), and interobserver variability were quantified. Observers viewed delineation differences between MRI and CT and delineation differences among observers.
  
  
  RESULTS
  In cranio-lateral and cranio-medial directions, GBT volumes were delineated larger using MRI when compared with those delineated with CT. Center of mass on MRI shifted a mean (SD) 17% (4%) into the cranial direction and a mean 3% (4%) into the dorsal direction when compared with that on the planning CT. Only small variations between observers were noted. The GBT volumes were approximately 4% larger on MRI (mean [SD] ratio MRI to CT GBT volumes, 1.04 [0.06]). Findings were concordant with viewed MRI and CT images and contours. Conformity indices were only slightly different; mean conformity index was 77% (3%) for MRI and 79% (4%) for CT. Delineation differences arising from personal preferences remained recognizable irrespective of the imaging modality used.
  
  
  CONCLUSIONS
  Contoured GBT extends substantially further into the cranio-lateral and cranio-medial directions on MRI when compared with CT. Interobserver variability is comparable for both imaging modalities. Observers should be aware of existing personal delineation preferences. Institutions are recommended to review and discuss target volume delineations and to design supplementary guidelines if necessary.
authors.affiliation: Radiotherapy Center West, The Hague, The Netherlands. marinagiezen@zonnet.nl
authors.forename: Marina
authors.initials: M
authors.lastname: Giezen
authors.forename: Erik
authors.initials: E
authors.lastname: Kouwenhoven
authors.forename: Astrid N
authors.initials: AN
authors.lastname: Scholten
authors.forename: Emile G
authors.initials: EG
authors.lastname: Coerkamp
authors.forename: Mark
authors.initials: M
authors.lastname: Heijenbrok
authors.forename: Wim P A
authors.initials: WP
authors.lastname: Jansen
authors.forename: Mirjam E
authors.initials: ME
authors.lastname: Mast
authors.forename: Anna L
authors.initials: AL
authors.lastname: Petoukhova
authors.forename: Henk
authors.initials: H
authors.lastname: Struikmans
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008327:Mammography / Q000379:methods; D015412:Mastectomy, Segmental; D008875:Middle Aged; D015588:Observer Variation; D018787:Radiation Oncology; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden