title: Is ExacTrac x-ray system an alternative to CBCT for positioning patients with head and neck cancers?
abstract: OBJECTIVE
  To evaluate the usefulness of a six-degrees-of freedom (6D) correction using ExacTrac robotics system in patients with head-and-neck (HN) cancer receiving radiation therapy.
  
  
  METHODS
  Local setup accuracy was analyzed for 12 patients undergoing intensity-modulated radiation therapy (IMRT). Patient position was imaged daily upon two different protocols, cone-beam computed tomography (CBCT), and ExacTrac (ET) images correction. Setup data from either approach were compared in terms of both residual errors after correction and punctual displacement of selected regions of interest (Mandible, C2, and C6 vertebral bodies).
  
  
  RESULTS
  On average, both protocols achieved reasonably low residual errors after initial correction. The observed differences in shift vectors between the two protocols showed that CBCT tends to weight more C2 and C6 at the expense of the mandible, while ET tends to average more differences among the different ROIs.
  
  
  CONCLUSIONS
  CBCT, even without 6D correction capabilities, seems preferable to ET for better consistent alignment and the capability to see soft tissues. Therefore, in our experience, CBCT represents a benchmark for positioning head and neck cancer patients.
authors: Department of Radiation Oncology, IRCCS CROB, 1 Padre Pio Street, 85028 Rionero in Vulture, PZ, Italy.
authors: Stefania
authors: S
authors: Clemente
authors: Costanza
authors: C
authors: Chiumento
authors: Alba
authors: A
authors: Fiorentino
authors: Vittorio
authors: V
authors: Simeon
authors: Mariella
authors: M
authors: Cozzolino
authors: Caterina
authors: C
authors: Oliviero
authors: Giorgia
authors: G
authors: Califano
authors: Rocchina
authors: R
authors: Caivano
authors: Vincenzo
authors: V
authors: Fusco
mesh_terms: D000465:Algorithms; D001842:Bone and Bones / Q000000981:diagnostic imaging; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging; D054893:Cone-Beam Computed Tomography; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008334:Mandible / Q000528:radiation effects; D019300:Medical Errors / Q000517:prevention & control; D056888:Patient Positioning / Q000379:methods*; D011786:Quality Control; D011857:Radiographic Image Interpretation, Computer-Assisted; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D015203:Reproducibility of Results; D014965:X-Rays