title: Evaluation of a metal artifact reduction technique in tonsillar cancer delineation.
abstract: OBJECTIVE
  Metal artifacts can degrade computed tomographic (CT) simulation imaging and impair accurate delineation of tumors for radiation treatment planning purposes. We investigated a Digital Imaging and Communications in Medicine-based metal artifact reduction technique in tonsillar cancer delineation.
  
  
  METHODS
  Eight patients with significant artifact and tonsil cancer were evaluated. Each patient had a positron emission tomography (PET)-CT and a contrast-enhanced CT obtained at the same setting during radiotherapy simulation. The CTs were corrected for artifact using the metal deletion technique (MDT). Two radiation oncologists independently delineated primary gross tumor volumes (GTVs) for each patient on native (CTnonMDT), metal corrected (CTMDT), and reference standard (CTPET/nonMDT) imaging, 1 week apart. Mixed effects models were used to determine if differences among GTVs were statistically significant. Two diagnostic radiologists and 2 radiation oncologists independently qualitatively evaluated CTs for each patient. Ratings were on an ordinal scale from -3 to +3, denoting that CTMDT was markedly, moderately, or slightly worse or better than CTnonMDT. Scores were compared with a Wilcoxon signed-rank test.
  
  
  RESULTS
  The GTVPET/nonMDT were significantly smaller than GTVnonMDT (P = .004) and trended to be smaller than GTVMDT (P = .084). The GTVnonMDT and GTVMDT were not significantly different (P = .93). There was no significant difference in the extent to which GTVnonMDT or GTVMDT encompassed GTVPET/nonMDT (P = .33). In the subjective assessment of image quality, CTMDT did not significantly outperform CTnonMDT. In the majority of cases, the observer rated the CTMDT equivalent to (53%) or slightly superior (41%) to the corresponding CTnonMDT.
  
  
  CONCLUSIONS
  The MTD modified images did not produce GTVMDT that more closely reproduced GTVPET/nonMDT than did GTVnonMDT. Moreover, the MTD modified images were not judged to be significantly superior when compared to the uncorrected images in terms of subjective ability to visualize the tonsilar tumors. This study failed to demonstrate value of the adjunctive use of a CT corrected for artifacts in the tumor delineation process. Artifacts do make tumor delineation challenging, and further investigation of other body sites is warranted.
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Abelson
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: James D
authors.initials: JD
authors.lastname: Murphy
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Wiegner
authors.affiliation: Department of Radiology, Stanford University, Stanford, California.
authors.forename: Deborah
authors.initials: D
authors.lastname: Abelson
authors.affiliation: Department of Radiology, University of California, San Francisco, California.
authors.forename: David N
authors.initials: DN
authors.lastname: Sandman
authors.affiliation: Department of Radiology, Stanford University, Stanford, California.
authors.forename: F Edward
authors.initials: FE
authors.lastname: Boas
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Dimitre
authors.initials: D
authors.lastname: Hristov
authors.affiliation: Department of Radiology, Stanford University, Stanford, California.
authors.forename: Dominik
authors.initials: D
authors.lastname: Fleischmann
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Megan E
authors.initials: ME
authors.lastname: Daly
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Chang
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Billy W
authors.initials: BW
authors.lastname: Loo
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California.
authors.forename: Wendy
authors.initials: W
authors.lastname: Hara
authors.affiliation: Department of Radiation Oncology, Stanford University, Stanford, California. Electronic address: qle@stanford.edu.
authors.forename: Quynh-Thu
authors.initials: QT
authors.lastname: Le