Department of Medical Physics, Graduate School of Medical Sciences, Kindai University, 377-2, Onohigashi, Osakasayama, Osaka, 589-8511, Japan.
Department of Radiotherapy, Takarazuka City Hospital, 4-5-1, Kohama, Takarazuka, Hyogo, 665-0827, Japan.
Phys Med Biol. 2023 May 5;68(10). doi: 10.1088/1361-6560/acc7e0.
The purpose of this study was to develop a new bolus (HM bolus), with tissue equivalence, transparency, reusability, and free shaping at approximately 40 °C for excellent adhesion, and to evaluate the feasibility of clinically using this bolus as an ideal bolus.We summarized the advantages and disadvantages of existing boluses. To evaluate dose characteristics, a vinyl gel sheet bolus (Gel bolus) and HM bolus placed on a water-equivalent phantom were used to obtain the percentage depth dose (PDD) of electron (6 MeV, 9 MeV) and photon (4 MV, 6 MV) beams. The average dose difference of the HM bolus and Gel bolus was calculated. The Gel bolus, a soft rubber bolus (SR bolus), and HM bolus were placed in adherence to a pelvic phantom. CT images taken after shaping and 1, 2, and 3 weeks after shaping were used to evaluate the adhesion and reproducibility using air gap and dice similarity coefficient (DSC).The average dose difference for electron beams was 0.16% ± 0.79% and photon beams was 0.06% ± 0.34%, both within 1% of the PDD results. The HM bolus showed the same build-up effect and dose characteristics as the Gel bolus. The mean air gap values for the Gel bolus, SR bolus, and HM bolus were 96.02 ± 43.77 cm, 34.93 ± 21.44 cm, and 4.40 ± 1.50 cm, respectively. The mean DSC values compared to initial images for the Gel bolus, SR bolus, and HM bolus were 0.363 ± 0.035, 0.556 ± 0.042, and 0.837 ± 0.018, respectively. Excellent adhesion was observed in the CT simulation and during the treatment period.The HM bolus has unique features, such as tissue equivalence, transparency, reusability, and free shaping for excellent adhesion, and is thus an ideal bolus for use in clinical cases.
本研究旨在开发一种新的组织等效、透明、可重复使用、在大约 40°C 下可自由成型且具有极好黏附性的 bolus（HM bolus），并评估将其作为理想 bolus 用于临床的可行性。我们总结了现有的 bolus 的优缺点。为了评估剂量特性，将乙烯基凝胶片 bolus（Gel bolus）和置于水等效体模上的 HM bolus 用于获取电子（6 MeV、9 MeV）和光子（4 MV、6 MV）射束的百分深度剂量（PDD）。计算了 HM bolus 和 Gel bolus 的平均剂量差异。将 Gel bolus、软橡胶 bolus（SR bolus）和 HM bolus 置于骨盆体模中，贴合在一起。用于评估粘附性和可重复性的空气间隙和骰子相似系数（DSC）是使用成型后的 CT 图像以及成型后 1、2 和 3 周时的 CT 图像获得的。电子束的平均剂量差异为 0.16%±0.79%，光子束的平均剂量差异为 0.06%±0.34%，均在 PDD 结果的 1%以内。HM bolus 表现出与 Gel bolus 相同的建成效应和剂量特性。Gel bolus、SR bolus 和 HM bolus 的平均空气间隙值分别为 96.02±43.77cm、34.93±21.44cm 和 4.40±1.50cm。Gel bolus、SR bolus 和 HM bolus 与初始图像相比的平均 DSC 值分别为 0.363±0.035、0.556±0.042 和 0.837±0.018。在 CT 模拟和治疗期间观察到极好的粘附性。HM bolus 具有独特的特性，例如组织等效性、透明性、可重复使用性和极好的粘附性的自由成型性，因此是临床应用的理想 bolus。
