title: Development of a standardized method for contouring the larynx and its substructures.
abstract: OBJECTIVE
  Limiting radiation dose to the larynx can diminish effects of laryngeal dysfunction. However, no clear guidelines exist for defining the larynx and its substructures consistently on cross-sectional imaging. This study presents computed tomography (CT)- and magnetic resonance imaging (MRI)-based guidelines for contouring laryngeal organs-at-risk (OARs).
  
  
  METHODS
  Standardized guidelines for delineating laryngeal OARs were devised and used to delineate on CT and MRI for head-and-neck cancer patients. Volumetric comparisons were performed to evaluate consistency and reproducibility of guideline-based contours.
  
  
  RESULTS
  For the initial 5 patients the mean CT and MRI based larynx volume did not differ significantly between imaging modalities; 34.39 ± 9.85 vs. 35.01 ± 9.47 (p = .09). There was no statistical difference between the CT based mean laryngeal volume in the subsequent 44 patients compared to the initial 5 patients outlined on CT and the MRI scan (p = 0.53 and 0.62). The OAR volume for laryngeal substructures were not statistically different among patients or between imaging modalities. Once established, the guidelines were easy to follow.
  
  
  CONCLUSIONS
  The guidelines developed provide a precise method for delineating laryngeal OARs. These guidelines need to be validated and clinical significance of outlining laryngeal substructures and dose-volume constraints should be investigated before routine implementation in clinic practice.
authors.affiliation: Department of Radiation Oncology, Northwestern University, Robert H. Lurie Comprehensive Cancer Center, 251 E Huron, LC-178, Chicago, IL, 60611, USA. mehee.choi@gmail.com.|Department of Radiation Oncology, Stritch School of Medicine Loyola University Chicago, Cardinal Bernardin Cancer Center, Chicago, Illinois, USA. mehee.choi@gmail.com.
authors.forename: Mehee
authors.initials: M
authors.lastname: Choi
authors.affiliation: Department of Radiation Oncology, Northwestern University, Robert H. Lurie Comprehensive Cancer Center, 251 E Huron, LC-178, Chicago, IL, 60611, USA. tamer.refaat@northwestern.edu.|Department of Clinical Oncology, Faculty of medicine, Alexandria University, Alexandria, Egypt. tamer.refaat@northwestern.edu.
authors.forename: Tamer
authors.initials: T
authors.lastname: Refaat
authors.affiliation: Department of Radiology, Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois, USA. mlester@nmff.org.
authors.forename: Malisa S
authors.initials: MS
authors.lastname: Lester
authors.affiliation: Department of Radiation Oncology, Northwestern University, Robert H. Lurie Comprehensive Cancer Center, 251 E Huron, LC-178, Chicago, IL, 60611, USA. ian.bacchus@northwestern.edu.
authors.forename: Ian
authors.initials: I
authors.lastname: Bacchus
authors.affiliation: Preventive Medicine, Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois, USA. rademaker@northwestern.edu.
authors.forename: Alfred W
authors.initials: AW
authors.lastname: Rademaker
authors.affiliation: Department of Radiation Oncology, Northwestern University, Robert H. Lurie Comprehensive Cancer Center, 251 E Huron, LC-178, Chicago, IL, 60611, USA. bmittal@nmh.org.
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Mittal
mesh_terms: D000328:Adult; D000368:Aged; D001271:Atlases as Topic; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods / Q000592:standards; D007830:Larynx / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods / Q000592:standards; D058958:Organs at Risk / Q000033:anatomy & histology*; D011832:Radiation Injuries / Q000517:prevention & control*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods / Q000592:standards*; D000077195:Squamous Cell Carcinoma of Head and Neck; D014057:Tomography, X-Ray Computed