title: Evaluation of the impact of dental artefacts on intensity-modulated radiotherapy planning for the head and neck.
abstract: OBJECTIVE
  High density materials create severe artefacts in the computed tomography (CT) scans used for radiotherapy dose calculations. Increased use of intensity-modulated radiotherapy (IMRT) to treat oropharyngeal cancers raises concerns over the accuracy of the resulting dose calculation. This work quantifies their impact and evaluates a simple corrective technique.
  
  
  METHODS
  Fifteen oropharyngeal patients with severe artefacts were retrospectively planned with IMRT using two different CT/density look-up tables. Each plan was recalculated using a corrected CT dataset to evaluate the dose distribution delivered to the patient. Plan quality in the absence of dental artefacts was similarly assessed. A range of dosimetric and radiobiological parameters were compared pre- and post-correction.
  
  
  RESULTS
  Plans using a standard CT/density look-up table (density 1.8 g/cm(3)) revealed inconsistent inter-patient errors, mostly within clinical acceptance, although potentially significantly reducing target coverage for individual patients. Using an extended CT/density look-up table (density 10.0 g/cm(3)) greatly reduced the errors for 13/15 patients. In 2/15 patients with residual errors the CTV extended into the severely affected region and could be corrected by applying a simple manual correction.
  
  
  CONCLUSIONS
  Use of an extended CT/density look-up table together with a simple manual bulk density correction reduces the impact of dental artefacts on head and neck IMRT planning to acceptable levels.
authors.affiliation: North Western Medical Physics, Christie Hospital NHS Foundation Trust, Manchester, UK. Gareth.Webster@physics.cr.man.ac.uk
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Webster
authors.forename: Carl G
authors.initials: CG
authors.lastname: Rowbottom
authors.forename: Ranald I
authors.initials: RI
authors.lastname: Mackay
mesh_terms: D016477:Artifacts; D003723:Dental Amalgam; D006801:Humans; D009959:Oropharyngeal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D014057:Tomography, X-Ray Computed
chemical_list: D003723:Dental Amalgam