Radiation and Proton Therapy Center, Shizuoka Cancer Center, 1007 Shimonagakubo, Nagaizumi-cho, Sunto-gun, Shizuoka, 411-8777, Japan.
Radiol Phys Technol. 2021 Mar;14(1):82-92. doi: 10.1007/s12194-021-00606-6. Epub 2021 Jan 23.
A commercially available flat bolus (commercial bolus) would not fully fit the irregular surfaces of the scalp. We developed a transparent and flexible material with good fitting properties, analyzed its physical characteristics, and evaluated the clinical feasibility of the bolus fabricated using a three-dimensional (3D) printer (3D bolus). To evaluate the physical characteristics of the new material, treatment plans with virtual, 3D, and commercial boluses were created for water-equivalent phantoms using a radiation treatment planning system (RTPS). Using a head phantom and the dose volume histogram calculated with RTPS, dose distributions for total scalp irradiation were compared between the three treatment plans. To evaluate the clinical feasibility, the fitness and reproducibility of the 3D bolus were compared with the head phantom and clinical cases using dice similarity coefficient (DSC) measurements. A good agreement was observed between the percentage depth dose (PDD) curves for the virtual, 3D, and commercial boluses. The homogeneity indexes of the planning target volume (PTV) for the 3D and commercial boluses were 0.083 and 0.153, respectively, proving that the former achieved a better dose uniformity of PTV than the latter. Good fitness and reproducibility with the 3D bolus were observed in both the head phantom and two clinical cases, with mean DSC values of 0.854, 0.829, and 0.843, respectively. These results successfully demonstrated and verified the utility of the 3D bolus for total scalp irradiation.
市售的扁平体模（commercial bolus）无法完全贴合头皮的不规则表面。我们开发了一种具有良好贴合性能的透明且灵活的材料，分析了其物理特性，并评估了使用三维（3D）打印机制作体模（3D bolus）的临床可行性。为了评估新材料的物理特性，我们使用放射治疗计划系统（RTPS）为水等效体模创建了带有虚拟、3D 和商业体模的治疗计划。使用头部体模和 RTPS 计算的剂量体积直方图，比较了三种治疗计划下全头皮照射的剂量分布。为了评估临床可行性，我们使用骰子相似系数（DSC）测量值，将 3D 体模的贴合度和可重复性与头部体模和临床病例进行了比较。虚拟、3D 和商业体模的百分深度剂量（PDD）曲线之间观察到了良好的一致性。3D 和商业体模的计划靶区（PTV）的均匀性指数分别为 0.083 和 0.153，这表明前者实现了比后者更好的 PTV 剂量均匀性。在头部体模和两个临床病例中，3D 体模都具有良好的贴合度和可重复性，平均 DSC 值分别为 0.854、0.829 和 0.843。这些结果成功地证明和验证了 3D 体模在全头皮照射中的实用性。
