title: Atlas-based segmentation in breast cancer radiotherapy: Evaluation of specific and generic-purpose atlases.
abstract: OBJECTIVE
  Atlas-based automatic segmentation (ABAS) addresses the challenges of accuracy and reliability in manual segmentation. We aim to evaluate the contribution of specific-purpose in ABAS of breast cancer (BC) patients with respect to generic-purpose libraries.
  
  
  METHODS
  One generic-purpose and 9 specific-purpose libraries, stratified according to type of surgery and size of thorax circumference, were obtained from the computed tomography of 200 BC patients. Keywords about contralateral breast volume and presence of breast expander/prostheses were recorded. ABAS was validated on 47 independent patients, considering manual segmentation from scratch as reference. Five ABAS datasets were obtained, testing single-ABAS and multi-ABAS with simultaneous truth and performance level estimation (STAPLE). Center of mass distance (CMD), average Hausdorff distance (AHD) and Dice similarity coefficient (DSC) between corresponding ABAS and manual structures were evaluated and statistically significant differences between different surgeries, structures and ABAS strategies were investigated.
  
  
  RESULTS
  Statistically significant differences between patients who underwent different surgery were found, with superior results for conservative-surgery group, and between different structures were observed: ABAS of heart, lungs, kidneys and liver was satisfactory (median values: CMD<2 mm, DSC≥0.80, AHD<1.5 mm), whereas chest wall, breast and spinal cord obtained moderate performance (median values: 2 mm ≤ CMD<5 mm, 0.60 ≤ DSC<0.80, 1.5 mm ≤ AHD<4 mm) and esophagus, stomach, brachial plexus and supraclavicular nodes obtained poor performance (median CMD≥5 mm, DSC<0.60, AHD≥4 mm). The application of STAPLE algorithm generally yields higher performance and the use of keywords improves results for breast ABAS.
  
  
  CONCLUSIONS
  The homogeneity in the selection of atlases based on multiple anatomical and clinical features and the use of specific-purpose libraries can improve ABAS performance with respect to generic-purpose libraries.
authors.affiliation: Department of Radiation Oncology, European Institute of Oncology, Milan, Italy.
authors.forename: Delia
authors.initials: D
authors.lastname: Ciardo
authors.affiliation: Department of Radiation Oncology, European Institute of Oncology, Milan, Italy.
authors.forename: Marianna Alessandra
authors.initials: MA
authors.lastname: Gerardi
authors.affiliation: Unit of Medical Physics, European Institute of Oncology, Milan, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Vigorito
authors.affiliation: Department of Radiation Oncology, European Institute of Oncology, Milan, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Morra
authors.affiliation: Department of Radiation Oncology, European Institute of Oncology, Milan, Italy.
authors.forename: Veronica
authors.initials: V
authors.lastname: Dell'acqua
authors.affiliation: Medical Radiation Oncology, Mevaterapia, Buenos Aires, Argentina.
authors.forename: Federico Javier
authors.initials: FJ
authors.lastname: Diaz
authors.affiliation: Unit of Medical Physics, European Institute of Oncology, Milan, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Cattani
authors.affiliation: Department of Experimental and Clinical Medicine, Magna Graecia University, Catanzaro, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Zaffino
authors.affiliation: Department of Radiation Oncology, European Institute of Oncology, Milan, Italy.
authors.forename: Rosalinda
authors.initials: R
authors.lastname: Ricotti
authors.affiliation: Department of Experimental and Clinical Medicine, Magna Graecia University, Catanzaro, Italy.
authors.forename: Maria Francesca
authors.initials: MF
authors.lastname: Spadea
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy; Bioengineering Unit, National Center for Oncologic Hadrontherapy, CNAO Foundation, Pavia, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Riboldi
authors.affiliation: Scientific Direction, European Institute of Oncology, Milan, Italy; Department of Oncology and Hemato-oncology, University of Milan, Milan, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Orecchia
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy; Bioengineering Unit, National Center for Oncologic Hadrontherapy, CNAO Foundation, Pavia, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Baroni
authors.affiliation: Department of Radiation Oncology, European Institute of Oncology, Milan, Italy. Electronic address: cristina.leonardi@ieo.it.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Leonardi
authors.affiliation: Department of Radiation Oncology, European Institute of Oncology, Milan, Italy; Department of Oncology and Hemato-oncology, University of Milan, Milan, Italy.
authors.forename: Barbara Alicja
authors.initials: BA
authors.lastname: Jereczek-Fossa
mesh_terms: D000328:Adult; D000465:Algorithms; D019412:Anatomy, Cross-Sectional / Q000379:methods*; D001271:Atlases as Topic; D001940:Breast / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D013909:Thorax / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed
keywords: Atlas-based segmentation; Automatic contouring; Breast cancer radiotherapy; STAPLE contours