title: Evaluation of a commercial orthopaedic metal artefact reduction tool in radiation therapy of patients with head and neck cancer.
abstract: OBJECTIVE
  To assess the image quality and dosimetric effects of the Philips orthopaedic metal artefact reduction (OMAR) (Philips Healthcare System, Cleveland, OH) function for reducing metal artefacts on CT images of head and neck (H&N) patients.
  
  
  METHODS
  11 patients and a custom-built phantom with metal bead inserts (alumina, titanium, zirconia and chrome) were scanned. The image was reconstructed in two ways: with and without OMAR (OMAR and non-OMAR image). The mean and standard deviation values of CT Hounsfield unit (HU) for selected regions of interest of each case were investigated for both images. Volumetric modulated arc therapy plans were generated for all cases. Gamma analysis of each dose distribution pair in the patient (1%/1 mm criteria) and phantom (2%/2 mm and 3%/3 mm criteria) images was performed. The film measurements in phantom for two metal beads were conducted for evaluating the calculated dose on both OMAR and non-OMAR images.
  
  
  RESULTS
  In the OMAR images, noise values were generally reduced, and the mean HU became closer to the reference value (measured from patients without metal implants) in both patient and phantom cases. Although dosimetric difference was insignificant for the eight closed-mouth patients (γ = 99.4 ± 0.5%), there was a large discrepancy in dosimetric calculation between OMAR and non-OMAR images for the three opened-mouth patients (γ = 91.1%, 94.8% and 96.6%). Moreover, the calculated dose on the OMAR image is closer to the real delivered dose on a radiochromic film than was the dose from the non-OMAR image.
  
  
  CONCLUSIONS
  The OMAR algorithm increases the accuracy of CT HU and reduces the noise such that the entire radiation treatment planning process can be improved, especially for contouring and segmentation.
  
  
  CONCLUSIONS
  OMAR reconstruction is appropriate for the radiotherapy planning process of H&N patients, particularly of patients who use a bite block.
authors.affiliation: 1 Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Republic of Korea.|2 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.|3 Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea.
authors.forename: H
authors.initials: H
authors.lastname: Kwon
authors.affiliation: 4 Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea.|5 Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: K S
authors.initials: KS
authors.lastname: Kim
authors.affiliation: 6 Philips Healthcare Korea, Seoul, Republic of Korea.
authors.forename: Y M
authors.initials: YM
authors.lastname: Chun
authors.affiliation: 3 Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea.|4 Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea.|5 Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: H-G
authors.initials: HG
authors.lastname: Wu
authors.affiliation: 2 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.|3 Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea.|7 Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Suwon, Republic of Korea.
authors.forename: J N K
authors.initials: JN
authors.lastname: Carlson
authors.affiliation: 1 Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Republic of Korea.|2 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.|3 Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea.|8 Center for Convergence Research on Robotics, Advance Institutes of Convergence Technology, Suwon, Republic of Korea.
authors.forename: J M
authors.initials: JM
authors.lastname: Park
authors.affiliation: 1 Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Republic of Korea.|2 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.|3 Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea.|8 Center for Convergence Research on Robotics, Advance Institutes of Convergence Technology, Suwon, Republic of Korea.
authors.forename: J-I
authors.initials: JI
authors.lastname: Kim
mesh_terms: D000465:Algorithms; D016477:Artifacts; D015921:Dental Implants; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008670:Metals; D009983:Orthopedic Equipment; D019047:Phantoms, Imaging; D011874:Radiometry; D012189:Retrospective Studies
chemical_list: D015921:Dental Implants; D008670:Metals