Purpose: 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 and Materials: 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 (CT nonMDT), metal corrected (CT MDT), and reference standard (CT PET/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 CT MDT was markedly, moderately, or slightly worse or better than CT nonMDT. Scores were compared with a Wilcoxon signed-rank test. Results: The GTV PET/nonMDT were significantly smaller than GTV nonMDT (P =.004) and trended to be smaller than GTV MDT (P =.084). The GTV nonMDT and GTV MDT were not significantly different (P =.93). There was no significant difference in the extent to which GTV nonMDT or GTV MDT encompassed GTV PET/nonMDT (P =.33). In the subjective assessment of image quality, CT MDT did not significantly outperform CT nonMDT. In the majority of cases, the observer rated the CT MDT equivalent to (53%) or slightly superior (41%) to the corresponding CT nonMDT. Conclusions: The MTD modified images did not produce GTV MDT that more closely reproduced GTV PET/nonMDT than did GTV nonMDT. 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.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging