title: Dose calculation accuracy of different image value to density tables for cone-beam CT planning in head & neck and pelvic localizations.
abstract: OBJECTIVE
  We aimed to identify the most accurate combination of phantom and protocol for image value to density table (IVDT) on volume-modulated arc therapy (VMAT) dose calculation based on kV-Cone-beam CT imaging, for head and neck (H&N) and pelvic localizations.
  
  
  METHODS
  Three phantoms (Catphan(®)600, CIRS(®)062M (inner phantom for head and outer phantom for body), and TomoTherapy(®) "Cheese" phantom) were used to create IVDT curves of CBCT systems with two different CBCT protocols (Standard-dose Head and Standard Pelvis). Hounsfield Unit (HU) time stability and repeatability for a single On-Board-Imager (OBI) and compatibility of two distinct devices were assessed with Catphan(®)600. Images from the anthropomorphic phantom CIRS ATOM(®) for both CT and CBCT modalities were used for VMAT dose calculation from different IVDT curves. Dosimetric indices from CT and CBCT imaging were compared.
  
  
  RESULTS
  IVDT curves from CBCT images were highly different depending on phantom used (up to 1000 HU for high densities) and protocol applied (up to 200 HU for high densities). HU time stability was verified over seven weeks. A maximum difference of 3% on the dose calculation indices studied was found between CT and CBCT VMAT dose calculation across the two localizations using appropriate IVDT curves. One IVDT curve per localization can be established with a bi-monthly verification of IVDT-CBCT.
  
  
  CONCLUSIONS
  The IVDT-CBCTCIRS-Head phantom with the Standard-dose Head protocol was the most accurate combination for dose calculation on H&N CBCT images. For pelvic localizations, the IVDT-CBCTCheese established with the Standard Pelvis protocol provided the best accuracy.
authors.affiliation: Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Centre, F-33000 Bordeaux, France.
authors.forename: Anaïs
authors.initials: A
authors.lastname: Barateau
authors.affiliation: Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Centre, F-33000 Bordeaux, France.
authors.forename: Christopher
authors.initials: C
authors.lastname: Garlopeau
authors.affiliation: Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Centre, F-33000 Bordeaux, France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Cugny
authors.affiliation: Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Centre, F-33000 Bordeaux, France.
authors.forename: Bénédicte Henriques
authors.initials: BH
authors.lastname: De Figueiredo
authors.affiliation: Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Centre, F-33000 Bordeaux, France.
authors.forename: Charles
authors.initials: C
authors.lastname: Dupin
authors.affiliation: Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Centre, F-33000 Bordeaux, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Caron
authors.affiliation: Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Centre, F-33000 Bordeaux, France. Electronic address: m.antoine@bordeaux.unicancer.fr.
authors.forename: Mikaël
authors.initials: M
authors.lastname: Antoine
mesh_terms: D000328:Adult; D054893:Cone-Beam Computed Tomography; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D009333:Neck / Q000000981:diagnostic imaging*; D010388:Pelvis / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D015203:Reproducibility of Results; D013997:Time Factors
keywords: Hounsfield units; IVDT curve; kV-CBCT