title: Four-dimensional computed tomography in accelerated partial breast irradiation planning: single series from a phase III trial.
abstract: OBJECTIVE
  The aim of our study was to evaluate the usefulness of the four-dimensional computed tomography (4DCT) in accelerated partial breast irradiation (aPBI) planning.
  
  
  METHODS
  At our Institute, we have been treating the index quadrant with external intensity-modulated radiation therapy in a phase III trial. For this study, we selected a sample of 10 patients with right- or left-sided breast cancer and surgical clips at the excision site. Contouring of the target was performed both using three-dimensional computed tomography (3DCT) and 4DCT imaging. On both 3DCT and 4DCT, we recorded the clinical target volume (CTV) and the planning target volume (PTV) and the coordinates of the PTV centroid. We calculated the treatment plans, according to our protocol, using the contours drawn on the 3DCT and 4DCT and evaluated target coverage and sparing of organs at risk (OAR).
  
  
  RESULTS
  Median age of the patients was 63.5 years (range 52-75). The comparison between the 3DCT and 4DCT PTV volumes was not statistically significant (p = 0.79). Concerning centroid coordinates, the average absolute differences were 0.1 mm in the latero-lateral, 0.7 mm in the antero-posterior and 0.3 mm in the supero-inferior direction. No statistically significant differences were observed both in PTV coverage and OAR sparing; the 4D PTV contour is adequately covered when the plan based on the 3D contours is used. Target coverage was reduced on average by 1 % and no statistically significant difference was observed (p = 0.93).
  
  
  CONCLUSIONS
  In our experience, no significant differences between PTV volumes, PTV coverage, OAR sparing and centroid position are evidenced when comparing 3DCT and 4DCT plans. Conventional 3DCT-based planning is adequate for aPBI.
authors.affiliation: Radiotherapy Unit, Azienda Ospedaliero-Universitaria Careggi, Largo G. A. Brambilla 3, 50134, Florence, Italy. icro.meattini@unifi.it.
authors.forename: Icro
authors.initials: I
authors.lastname: Meattini
authors.affiliation: Medical Physics Unit, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.
authors.forename: Livia
authors.initials: L
authors.lastname: Marrazzo
authors.affiliation: University of Florence, Florence, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Zani
authors.affiliation: Radiotherapy Unit, Azienda Ospedaliero-Universitaria Careggi, Largo G. A. Brambilla 3, 50134, Florence, Italy.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Paiar
authors.affiliation: Medical Physics Unit, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.|University of Florence, Florence, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Pallotta
authors.affiliation: Radiotherapy Unit, Azienda Ospedaliero-Universitaria Careggi, Largo G. A. Brambilla 3, 50134, Florence, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Simontacchi
authors.affiliation: Medical Physics Unit, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.|University of Florence, Florence, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Bucciolini
authors.affiliation: Radiotherapy Unit, Azienda Ospedaliero-Universitaria Careggi, Largo G. A. Brambilla 3, 50134, Florence, Italy.|University of Florence, Florence, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Livi
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*
keywords: Breast cancer; Breathing motion; Four-dimensional computed tomography; IMRT; Partial breast irradiation