title: Target volume delineation in breast conserving radiotherapy: are co-registered CT and MR images of added value?
abstract: BACKGROUND
  In breast conserving radiotherapy differences of target volume delineations between observers do occur. We evaluated whether delineations based on co-registered computed tomography (CT) and magnetic resonance (MR) imaging may result in an improved consistency between observers. We used the delineation conformity index (CI) to compare clinical target volumes of glandular breast tissue (CTV breast) and lumpectomy cavity (LC) on both imaging modalities.
  
  
  METHODS
  Four observers delineated CTV breast and LC on co-registered CTMR images in ten breast cancer patients. CIs were determined for CT and CTMR. Furthermore, the Cavity Visualization Score (CVS) of LC was taken into account.
  
  
  RESULTS
  The mean CI for CTV breast (CICT;CTV: 0.82 and CICT-CTMR;CTV: 0.80) and LC (CICT;LC: 0.52 and CICT-CTMR;LC: 0.48) did not differ significantly (p=0.07 and p=0.33, respectively). Taking CVS into account for the LC, with a CVS ≥ 4 the mean CI was 0.62 for both CICT;LC and CICT-CTMR;LC.
  
  
  CONCLUSIONS
  The mean volume of the delineated glandular breast tissue based on CT was significantly larger compared to the volume based on CTMR. For patients with a CVS ≥ 4, the mean CIs of the LC were higher compared to CVS<4 for volumes delineated on both CT as well as CTMR images. In our study cohort no significant differences between the CIs of the CTV breast and the LC delineated on CTMR co-registered images were found compared to the CIs on CT images only. Adding MR images does not seem to improve consistency of the delineation of the CTV breast and the LC, even though the volumes were copied from CT images. Since we included only ten patients, caution should be taken with regard to the results of our study.
authors.affiliation: Radiotherapy Centre West, Lijnbaan 32, The Hague, 2501 CK, The Netherlands. m.mast@mchaaglanden.nl.
authors.forename: Mirjam
authors.initials: M
authors.lastname: Mast
authors.forename: Emile
authors.initials: E
authors.lastname: Coerkamp
authors.forename: Mark
authors.initials: M
authors.lastname: Heijenbrok
authors.forename: Astrid
authors.initials: A
authors.lastname: Scholten
authors.forename: Wim
authors.initials: W
authors.lastname: Jansen
authors.forename: Erik
authors.initials: E
authors.lastname: Kouwenhoven
authors.forename: Jasper
authors.initials: J
authors.lastname: Nijkamp
authors.forename: Stephanie
authors.initials: S
authors.lastname: de Waard
authors.forename: Anna
authors.initials: A
authors.lastname: Petoukhova
authors.forename: Henk
authors.initials: H
authors.lastname: Struikmans
mesh_terms: D001943:Breast Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D015412:Mastectomy, Segmental; D008875:Middle Aged; D059351:Organ Sparing Treatments / Q000379:methods; D011237:Predictive Value of Tests; D011379:Prognosis; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden