title: Atlas-based semiautomatic target volume definition (CTV) for head-and-neck tumors.
abstract: OBJECTIVE
  To develop a new semiautomatic method to improve target delineation in head-and-neck cancer.
  
  
  METHODS
  We implemented an atlas-based software program using fourteen anatomic landmarks as well as the most superior and inferior computerd tomography slices for automatic target delineation, using an advanced laryngeal carcinoma as an example. Registration was made by an affine transformation. Evaluation was performed with manually drawn contours for comparison. Three physicians sampled and further applied a target volume atlas to ten other computer tomography data sets. In addition, a rapid three-dimensional (3D) correction program was developed.
  
  
  RESULTS
  The mean time to the first semiautomatic target delineation proposal was 2.7 minutes. Manual contouring required 20.2 minutes per target, whereas semiautomatic target volume definition with the rapid 3D correction was completed in only 9.7 minutes. The net calculation time for image registration of the target volume atlas was negligible (approximately 0.6 seconds). Our method depicted a sufficient adaptation of the target volume atlas on the new data sets, with a mean similarity index of 77.2%. The similarity index increased up to 85% after 3D correction performed by the physicians.
  
  
  CONCLUSIONS
  We have developed a new, feasible method for semiautomatic contouring that saves a significant amount (51.8%) of target delineation time for head-and-neck cancer patients. This approach uses a target volume atlas and a landmark model. The software was evaluated by means of laryngeal cancer but has important implications for various tumor types whereby target volumes remain constant in form and do not move with respiration.
authors.affiliation: Department of Radiotherapy and Radiation Oncology, University of Marburg, Marburg, Germany. gstrassmann@t-online.de
authors.forename: Gerd
authors.initials: G
authors.lastname: Strassmann
authors.forename: Soulimane
authors.initials: S
authors.lastname: Abdellaoui
authors.forename: Detlef
authors.initials: D
authors.lastname: Richter
authors.forename: Fayzal
authors.initials: F
authors.lastname: Bekkaoui
authors.forename: Marlene
authors.initials: M
authors.lastname: Haderlein
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Fokas
authors.forename: Nina
authors.initials: N
authors.lastname: Timmesfeld
authors.forename: Birgitt
authors.initials: B
authors.lastname: Vogel
authors.forename: Martin
authors.initials: M
authors.lastname: Henzel
authors.forename: Rita
authors.initials: R
authors.lastname: Engenhart-Cabillic
mesh_terms: D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D006801:Humans; D007822:Laryngeal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D008488:Medical Illustration; D008953:Models, Anatomic; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012984:Software; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*