title: Single-energy metal artefact reduction with CT for carbon-ion radiation therapy treatment planning.
abstract: OBJECTIVE
  One approach to improving image quality of CT is to use metal artefact reduction image processing, such as single-energy metal artefact reduction (SEMAR). To quantify the impact of image correction on the quality of carbon-ion dose distribution, treatment planning using SEMAR was evaluated.
  
  
  METHODS
  Using a head phantom into which metal screws could be inserted, we acquired standard planning CT images. We calculated dose distributions using phantom images with and without metal added, and with and without SEMAR. Hounsfield unit (HU) and dose distribution variation of these images with and without SEMAR were measured using metal-free image subtraction. We similarly analysed the image data sets of two patients with head and neck cancer who had dental implants.
  
  
  RESULTS
  HU difference between metal-containing images and metal-free images without and with SEMAR were -79.5 ± 97.2 HU and -1.4 ± 19.5 HU on severe artefact area, respectively. The range of dose distribution difference from the prescribed dose between uncorrected and SEMAR-corrected images varied from -19.5% to -3.4% within planning target volume (PTV). PTV-D95 (%) for uncorrected and SEMAR-corrected image data were 82.4% and 95.4%, respectively. For data in patients with metal dental work, PTV-D95 (%) for uncorrected and SEMAR-corrected data were 92.2% and 92.5% (Patient 1), and 90.9% and 95.7% (Patient 2), respectively.
  
  
  CONCLUSIONS
  SEMAR algorithm shows promise in improving CT image quality and in ensuring an accurate representation of dose distribution.
  
  
  CONCLUSIONS
  SEMAR may improve treatment accuracy without the need for dental implant extraction in patients with head and neck cancer.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Kentaro
authors.identifier: http://orcid.org/0000-0003-0060-9919
authors.initials: K
authors.lastname: Miki
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Mori
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Hasegawa
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Naganawa
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Koto
mesh_terms: D016477:Artifacts; D002244:Carbon; D015921:Dental Implants; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D063193:Heavy Ion Radiotherapy / Q000379:methods*; D006801:Humans; D008670:Metals; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants; D008670:Metals; D002244:Carbon