title: Dose recalculation in megavoltage cone-beam CT for treatment evaluation: removal of cupping and truncation artefacts in scans of the thorax and abdomen.
abstract: OBJECTIVE
  To correct megavoltage cone-beam CT (MVCBCT) images of the thorax and abdomen for cupping and truncation artefacts to reconstruct the 3D-delivered dose distribution for treatment evaluation.
  
  
  METHODS
  MVCBCT scans of three phantoms, three lung and two rectal cancer patients were acquired. The cone-beam projection images were iteratively corrected for cupping and truncation artefacts and the resulting primary transmission was used for cone-beam reconstruction. The reconstructed scans were merged into the planning CT scan (MVCBCT+). Dose distributions of clinical IMRT, stereotactic and conformal treatment plans were recalculated on the uncorrected and corrected MVCBCT+ scans using the treatment planning system and compared to the planned dose distribution.
  
  
  RESULTS
  The dose distributions on the corrected MVCBCT+ of the phantoms were accurate for 99% of the voxels within 2% or 2mm. Using this method the errors in mean GTV dose reduced from about 10% to 1% for the patients.
  
  
  CONCLUSIONS
  The method corrects cupping and truncation artefacts in cone-beam scans of the thorax and abdomen in addition to head-and-neck (demonstrated previously). The corrected scans can be used to calculate the influence of anatomical changes on the 3D-delivered dose distribution.
authors.affiliation: Department of Radiation Oncology (MAASTRO Clinic), Maastricht University Medical Center (MUMC+), Maastricht, The Netherlands. steven.petit@maastro.nl
authors.forename: Steven F
authors.initials: SF
authors.lastname: Petit
authors.forename: Wouter J C
authors.initials: WJ
authors.lastname: van Elmpt
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
authors.forename: André L A J
authors.initials: AL
authors.lastname: Dekker
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging*; D000465:Algorithms; D016477:Artifacts; D054893:Cone-Beam Computed Tomography; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000532:radiotherapy*; D013909:Thorax / Q000000981:diagnostic imaging*; D016896:Treatment Outcome; D014463:Ultrasonography