Kamomae Takeshi, Itoh Yoshiyuki, Okudaira Kuniyasu, Nakaya Takayoshi, Tomida Masashi, Miyake Yoshikazu, Oguchi Hiroshi, Shiinoki Takehiro, Kawamura Mariko, Yamamoto Noriyuki, Naganawa Shinji
Nagoya University Graduate School of Medicine.
J Appl Clin Med Phys. 2016 Jan 8;17(1):234-245. doi: 10.1120/jacmp.v17i1.5870.
Metal dental restoration materials cause dose enhancement upstream and dose disturbance downstream of the high-density inhomogeneous regions in which these materials are used. In this study, we evaluated the impact of a dental metallic crown (DMC) on intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck cancer. Additionally, the possibility of sparing the oral mucosa from dose enhancement using an individual intraoral mouthpiece was evaluated. An experimental oral phantom was designed to verify the dosimetric impact of a DMC. We evaluated the effect on single beam, parallel opposing beam, arc beam, IMRT, and VMAT treatment plans. To evaluate the utility of a 3-mm-thick intraoral mouthpiece, the doses across the mouthpiece were measured. For single beam irradiation, the measured doses at the entrance and exit planes of the DMC were 51% higher and 21% lower than the calculated dose by the treatment planning system, respectively. The maximum dose enhancements were 22% and 46% for parallel opposing beams and the 90° arc rotation beam, respectively. For IMRT and VMAT, the measured doses adjacent to the DMC were 12.2% ± 6.3% (mean ± 1.96SD) and 12.7% ± 2.5% higher than the calculated doses, respectively. With regard to the performance of the intraoral mouthpiece for the IMRT and VMAT cases, the disagreement between measured and calculated doses at the outermost surface of the mouthpieces were -2.0%, and 2.0%, respectively. Dose enhancements caused by DMC-mediated radiation scattering occurred during IMRT and VMAT. Because it is difficult to accurately estimate the dose perturbations, careful consideration is necessary when planning head and neck cancer treatments in patients with DMCs. To spare the oral mucosa from dose enhancement, the use of an individual intraoral mouthpiece should be considered.
金属牙科修复材料会在使用这些材料的高密度非均匀区域的上游导致剂量增强，并在其下游造成剂量干扰。在本研究中，我们评估了牙科金属冠（DMC）对头颈部癌调强放射治疗（IMRT）和容积调强弧形治疗（VMAT）的影响。此外，还评估了使用个体化口腔内口托使口腔黏膜免受剂量增强影响的可能性。设计了一个实验性口腔体模来验证DMC的剂量学影响。我们评估了其对单束、平行对穿束、弧形束、IMRT和VMAT治疗计划的影响。为了评估3毫米厚口腔内口托的效用，测量了口托各处的剂量。对于单束照射，在DMC的入射面和出射面测得的剂量分别比治疗计划系统计算的剂量高51%和低21%。对于平行对穿束和90°弧形旋转束，最大剂量增强分别为22%和46%。对于IMRT和VMAT，在DMC附近测得的剂量分别比计算剂量高12.2%±6.3%（平均值±1.96标准差）和12.7%±2.5%。关于IMRT和VMAT病例中口腔内口托的性能，在口托最外表面测得的剂量与计算剂量之间的差异分别为-2.0%和2.0%。在IMRT和VMAT期间发生了由DMC介导的辐射散射导致的剂量增强。由于难以准确估计剂量扰动，在为佩戴DMC的患者制定头颈部癌治疗计划时需要仔细考虑。为了使口腔黏膜免受剂量增强影响，应考虑使用个体化口腔内口托。
