Richard Patrick, Sandison George, Dang Quang, Johnson Bart, Wong Tony, Parvathaneni Upendra
University of Washington, Department of Radiation Oncology, Seattle, Washington.
University of Washington, Department of Radiation Oncology, Seattle, Washington.
Pract Radiat Oncol. 2015 Nov-Dec;5(6):e583-8. doi: 10.1016/j.prro.2015.04.007. Epub 2015 Sep 26.
We evaluated the incidence and impact of dental filling artifacts on the definition of clinical target volume (CTV) for oropharyngeal/oral cavity cancers receiving radiation therapy. We performed phantom proton beam dosimetric analyses using a low-density composite filling to investigate artifact reduction and dose distribution.
We reviewed oral cavity/oropharynx radiation treatment plans between 2010 and 2012. Plans were evaluated for artifacts and impact on CTV visualization. We constructed a head and neck phantom, obtaining planning computed tomography images at baseline (native tooth) and for each filling (composite and metal amalgam) interchanged into a tooth adjacent to the tumor. We performed uniform scanning proton plans with each filling, evaluating for planning target volume (PTV) coverage and overall dose distribution.
A total of 110 treatment plans were reviewed (71 oropharynx, 39 oral cavity). Artifacts were identified in 81 plans (73.6%), including 53 oropharynx (74.6%) and 28 oral cavity (71.8%). Artifacts obscured the CTV in 77 cases (95%), including 49 of 53 oropharynx cases (92.5%) and all 28 oral cavity cases. On phantom testing, the metal amalgam obscured the tumor while the composite did not. Hounsfield unit (HU) values (range, mean) for the tumor were: baseline (-484.0 to 700.0 HU, 104 HU), composite (-728.5 to 1038.0 HU, 105 HU), metal amalgam (-1023.0 to 807.0 HU, 90.74 HU). The percent of planning target volume receiving 95% of prescription dose of the PTV was baseline (100%), composite (100%), and metal amalgam (92.3%). PTV dose ranges were baseline (98%-106%), composite (98%-107%), and metal amalgam (66%-111%). PTV coverage and dose distributions of the composite and native tooth plans were identical.
A high incidence of artifacts was found on the planning scans of oral/oropharyngeal cancer patients, adversely impacting CTV visualization. In our phantom model, metal amalgam impacted tumor and tissue density. The PTV was underdosed with the metal amalgam compared with the composite filling. A potential solution involves exchanging metal fillings with composite before proton treatment planning for improved tumor visualization and dosimetry.
我们评估了牙充填物伪影对口咽/口腔癌接受放射治疗时临床靶区（CTV）定义的发生率及影响。我们使用低密度复合充填物进行了体模质子束剂量学分析，以研究伪影减少及剂量分布情况。
我们回顾了2010年至2012年间的口腔/口咽放射治疗计划。对计划中的伪影及对CTV可视化的影响进行评估。我们构建了一个头颈体模，在基线（天然牙）以及将每种充填物（复合充填物和金属汞合金）替换到肿瘤相邻牙齿的情况下获取计划计算机断层扫描图像。我们对每种充填物进行了均匀扫描质子计划，评估计划靶区（PTV）覆盖情况及总体剂量分布。
共回顾了110个治疗计划（71个口咽，39个口腔）。在81个计划（73.6%）中发现了伪影，其中包括53个口咽计划（74.6%）和28个口腔计划（71.8%）。在77例（95%）中伪影遮挡了CTV，包括53例口咽病例中的49例（92.5%）以及所有28例口腔病例。在体模测试中，金属汞合金遮挡了肿瘤而复合充填物未遮挡。肿瘤的亨氏单位（HU）值（范围，均值）为：基线（-484.0至700.0 HU，104 HU），复合充填物（-728.5至1038.0 HU，105 HU），金属汞合金（-1023.0至807.0 HU，90.74 HU）。接受PTV处方剂量95%的计划靶区体积百分比为基线（100%），复合充填物（100%），金属汞合金（92.3%）。PTV剂量范围为基线（98%-106%），复合充填物（98%-107%），金属汞合金（66%-111%）。复合充填物和天然牙计划的PTV覆盖及剂量分布相同。
在口腔/口咽癌患者的计划扫描中发现伪影发生率很高，对CTV可视化产生不利影响。在我们的体模模型中，金属汞合金影响肿瘤和组织密度。与复合充填物相比，金属汞合金使PTV剂量不足。一种潜在的解决方案是在质子治疗计划前将金属充填物更换为复合充填物，以改善肿瘤可视化及剂量学。
