title: A cardiac contouring atlas for radiotherapy.
abstract: The heart is a complex anatomical organ and contouring the cardiac substructures is challenging. This study presents a reproducible method for contouring left ventricular and coronary arterial segments on radiotherapy CT-planning scans.
  
  
  
  Segments were defined from cardiology models and agreed by two cardiologists. Reference atlas contours were delineated and written guidelines prepared. Six radiation oncologists tested the atlas. Spatial variation was assessed using the DICE similarity coefficient (DSC) and the directed Hausdorff average distance (d→H,avg). The effect of spatial variation on doses was assessed using six different breast cancer regimens.
  
  
  
  The atlas enabled contouring of 15 cardiac segments. Inter-observer contour overlap (mean DSC) was 0.60-0.73 for five left ventricular segments and 0.10-0.53 for ten coronary arterial segments. Inter-observer contour separation (mean d→H,avg) was 1.5-2.2mm for left ventricular segments and 1.3-5.1mm for coronary artery segments. This spatial variation resulted in <1Gy dose variation for most regimens and segments, but 1.2-21.8Gy variation for segments close to a field edge.
  
  
  
  This cardiac atlas enables reproducible contouring of segments of the left ventricle and main coronary arteries to facilitate future studies relating cardiac radiation doses to clinical outcomes.
authors.affiliation: Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, UK; Medical Research Council Population Health Research Unit, Nuffield Department of Population Health, University of Oxford, UK. Electronic address: fran.duane@ndph.ox.ac.uk.
authors.forename: Frances
authors.initials: F
authors.lastname: Duane
authors.affiliation: Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, UK.
authors.forename: Marianne C
authors.initials: MC
authors.lastname: Aznar
authors.affiliation: Department of Oncology and Haematology, Queen Alexandra Hospital, Portsmouth, UK.
authors.forename: Freddie
authors.initials: F
authors.lastname: Bartlett
authors.affiliation: Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Cutter
authors.affiliation: Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, UK.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Darby
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, USA.
authors.forename: Reshma
authors.initials: R
authors.lastname: Jagsi
authors.affiliation: Laboratory of Radiation Physics, Odense University Hospital, Denmark.
authors.forename: Ebbe L
authors.initials: EL
authors.lastname: Lorenzen
authors.affiliation: St. Luke's Radiation Oncology Network, Dublin, Ireland.
authors.forename: Orla
authors.initials: O
authors.lastname: McArdle
authors.affiliation: Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: McGale
authors.affiliation: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, UK.
authors.forename: Saul
authors.initials: S
authors.lastname: Myerson
authors.affiliation: George Institute for Global Health, University of Oxford, UK.
authors.forename: Kazem
authors.initials: K
authors.lastname: Rahimi
authors.affiliation: CRUK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, University of Oxford, UK.
authors.forename: Sindu
authors.initials: S
authors.lastname: Vivekanandan
authors.affiliation: University of Birmingham NHS Foundation Trust, Birmingham, UK.
authors.forename: Samantha
authors.initials: S
authors.lastname: Warren
authors.affiliation: Clinical Trial Service Unit, Nuffield Department of Population Health, University of Oxford, UK.
authors.forename: Carolyn W
authors.initials: CW
authors.lastname: Taylor
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D003331:Coronary Vessels / Q000528:radiation effects; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects*; D006352:Heart Ventricles / Q000528:radiation effects; D006801:Humans; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Atlas; Cardiac structures; Contouring; Radiotherapy CT-planning scans