title: Dosimetric effects of residual uncertainties in carbon ion treatment of head chordoma.
abstract: OBJECTIVE
  To investigate dose distribution variations due to setup errors and range uncertainties in image-guided carbon ion radiotherapy of head chordoma.
  
  
  METHODS
  Ten treatment plans were retrospectively tested with TRiP98 against ±1.0 mm and ±1.0° setup errors, as observed in clinical routine, and 2.6% range uncertainty when 2mm CTV-to-PTV margins were applied. Single-fraction simulations were compared with the total treatment dose in terms of DVH bands, conformity and inhomogeneity. The contribution of image processing artifacts on reported results was also discussed, as a function of the imaging dataset resolution.
  
  
  RESULTS
  Results showed that safety margins grant the conformal target coverage in presence of setup errors with D95(CTV) variations below 10% in 7 patients out of 10. Instead, the inclusion of range uncertainty yielded to appreciable dose degradation, reporting larger effects for CTV and dose conformity, whereas reduced impact is found on the organ-at-risk. The fractionation scheme positively affects dose conformity and inhomogeneity; conversely its influence on DVH bands is strongly related to the patient anatomy.
  
  
  CONCLUSIONS
  Besides safety margins, setup and range uncertainties lead to non-negligible combined contribution. Systematical treatment plan robustness assessment against expected uncertainties is thus encouraged, selecting beam settings and fractionation schemes where homogeneity is preserved.
authors.affiliation: Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy. Electronic address: giovanni.fattori@polimi.it.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Fattori
authors.affiliation: Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy; CNAO Centro Nazionale di Adroterapia Oncologica, Pavia, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Riboldi
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Abt. Biophysik, Darmstadt, Germany.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Scifoni
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Abt. Biophysik, Darmstadt, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Krämer
authors.affiliation: CNAO Centro Nazionale di Adroterapia Oncologica, Pavia, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Pella
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung GmbH, Abt. Biophysik, Darmstadt, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Durante
authors.affiliation: CNAO Centro Nazionale di Adroterapia Oncologica, Pavia, Italy; University of Milan, Milano, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Ronchi
authors.affiliation: CNAO Centro Nazionale di Adroterapia Oncologica, Pavia, Italy; University of Milan, Milano, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Bonora
authors.affiliation: CNAO Centro Nazionale di Adroterapia Oncologica, Pavia, Italy; European Institute of Oncology , Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Orecchia
authors.affiliation: Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy; CNAO Centro Nazionale di Adroterapia Oncologica, Pavia, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Baroni
mesh_terms: D002817:Chordoma / Q000532:radiotherapy*; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D063193:Heavy Ion Radiotherapy; D006801:Humans; D008297:Male; D018365:Neoplasm, Residual; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods; D012189:Retrospective Studies; D035501:Uncertainty
keywords: Carbon ion radiotherapy; Image-guided patient positioning; Range uncertainties; Setup errors; Treatment planning