State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P. R. China.
Shenzhen United Imaging Research Institute of Innovative Medical Equipment, Shenzhen, Guangdong Province, China.
Technol Cancer Res Treat. 2024 Jan-Dec;23:15330338241293267. doi: 10.1177/15330338241293267.
This study assesses the physical properties of the silicone rubber (SR) bolus, compares its dosimetric characterization with those of gel and thermoset boluses, aiming to evaluate the feasibility and stability of utilizing SR bolus for head photon-beam radiotherapy.
Three types of boluses (gel, thermoset, and SR) were prepared with same dimensions. Firstly, the physical properties of SR bolus (density, tensile strength and hardness) were assessed pre-irradiation and post-irradiation. Secondly, the percentage of depth dose (PDD) curve was calculated using the treatment planning system (TPS) and measured with a plane-parallel. Thirdly, these three boluses were individually placed on the head phantom, followed by computed tomography (CT) scans to delineate the customized target area and organs at risk (OARs) for treatment planning. Over the subsequent three weeks, fan-beam CT (FBCT) images were obtained weekly and registered with the initial CT to modify the target area and OARs. Fourthly, the adhesion differences, dose distributions, and inter-fraction reproducibility of the three boluses were compared and evaluated.
The results observed that post-irradiated SR bolus exhibited higher hardness values (< .01) than the pre-irradiated one, with no significant differences in tensile strength and density. The PDD curves of all three boluses showed similarity within a difference range less than ±1%. The air gaps between the SR, thermoset, and gel boluses and skin surfaces were measured as 0.07 cm, 2.96 cm, and 4.82 cm, respectively. Compared with gel bolus and thermoset bolus, the SR bolus demonstrated noticeable inter-fraction reproducibility.
The SR bolus can be fabricated at room temperature, adheres to irregular body surfaces, and retains its physical properties post-irradiation. Additionally, this bolus has comparable dosimetric characterization to other commercial boluses, and may provide notable protection for OARs. Therefore, the SR bolus is recommended as a feasible and stable material for head photon-beam radiotherapy.
本研究评估了硅橡胶（SR）挡块的物理特性，比较了其与凝胶和热固性挡块的剂量学特征，旨在评估将 SR 挡块用于头部光子束放射治疗的可行性和稳定性。
制备了三种尺寸相同的挡块（凝胶、热固性和 SR）。首先，在辐照前后评估了 SR 挡块的物理特性（密度、拉伸强度和硬度）。其次，使用治疗计划系统（TPS）计算了百分深度剂量（PDD）曲线，并使用平面平行仪进行了测量。然后，将这三种挡块分别放置在头部体模上，然后进行计算机断层扫描（CT）扫描，以描绘定制的靶区和危及器官（OARs）进行治疗计划。在接下来的三周内，每周进行一次扇束 CT（FBCT）图像采集，并与初始 CT 进行配准，以修改靶区和 OARs。第四，比较和评估了三种挡块的粘附差异、剂量分布和分次间可重复性。
结果观察到，辐照后的 SR 挡块的硬度值（<.01）高于辐照前的硬度值，而拉伸强度和密度没有显著差异。所有三种挡块的 PDD 曲线在差异范围内相似，差异小于±1%。SR、热固性和凝胶挡块与皮肤表面之间的空气间隙分别测量为 0.07cm、2.96cm 和 4.82cm。与凝胶挡块和热固性挡块相比，SR 挡块具有明显的分次间可重复性。
SR 挡块可以在室温下制造，粘附在不规则的身体表面上，并在辐照后保持其物理性能。此外，该挡块具有与其他商业挡块相当的剂量学特征，并可为 OAR 提供显著的保护。因此，SR 挡块被推荐为头部光子束放射治疗的一种可行且稳定的材料。
