title: IMRT for image-guided single vocal cord irradiation.
abstract: OBJECTIVE
  We have been developing an image-guided single vocal cord irradiation technique to treat patients with stage T1a glottic carcinoma. In the present study, we compared the dose coverage to the affected vocal cord and the dose delivered to the organs at risk using conventional, intensity-modulated radiotherapy (IMRT) coplanar, and IMRT non-coplanar techniques.
  
  
  METHODS
  For 10 patients, conventional treatment plans using two laterally opposed wedged 6-MV photon beams were calculated in XiO (Elekta-CMS treatment planning system). An in-house IMRT/beam angle optimization algorithm was used to obtain the coplanar and non-coplanar optimized beam angles. Using these angles, the IMRT plans were generated in Monaco (IMRT treatment planning system, Elekta-CMS) with the implemented Monte Carlo dose calculation algorithm. The organs at risk included the contralateral vocal cord, arytenoids, swallowing muscles, carotid arteries, and spinal cord. The prescription dose was 66 Gy in 33 fractions.
  
  
  RESULTS
  For the conventional plans and coplanar and non-coplanar IMRT plans, the population-averaged mean dose ± standard deviation to the planning target volume was 67 ± 1 Gy. The contralateral vocal cord dose was reduced from 66 ± 1 Gy in the conventional plans to 39 ± 8 Gy and 36 ± 6 Gy in the coplanar and non-coplanar IMRT plans, respectively. IMRT consistently reduced the doses to the other organs at risk.
  
  
  CONCLUSIONS
  Single vocal cord irradiation with IMRT resulted in good target coverage and provided significant sparing of the critical structures. This has the potential to improve the quality-of-life outcomes after RT and maintain the same local control rates.
authors.affiliation: Department of Radiation Oncology, Erasmus Medical Center-Daniel den Hoed Cancer Center, Rotterdam, The Netherlands. s.osman@erasmusmc.nl
authors.forename: Sarah O S
authors.initials: SO
authors.lastname: Osman
authors.forename: Eleftheria
authors.initials: E
authors.lastname: Astreinidou
authors.forename: Hans C J
authors.initials: HC
authors.lastname: de Boer
authors.forename: Fatma
authors.initials: F
authors.lastname: Keskin-Cambay
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: Breedveld
authors.forename: Peter
authors.initials: P
authors.lastname: Voet
authors.forename: Abrahim
authors.initials: A
authors.lastname: Al-Mamgani
authors.forename: Ben J M
authors.initials: BJ
authors.lastname: Heijmen
authors.forename: Peter C
authors.initials: PC
authors.lastname: Levendag
mesh_terms: D000465:Algorithms; D001193:Arytenoid Cartilage / Q000000981:diagnostic imaging; D019583:Dose Fractionation, Radiation; D006801:Humans; D007821:Laryngeal Muscles / Q000000981:diagnostic imaging; D007822:Laryngeal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D009010:Monte Carlo Method; D058958:Organs at Risk / Q000000981:diagnostic imaging; D010609:Pharyngeal Muscles / Q000000981:diagnostic imaging; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D047368:Tumor Burden; D014827:Vocal Cords / Q000000981:diagnostic imaging