Kaplan L P, Høye E M, Balling P, Muren L P, Petersen J B B, Poulsen P R, Yates E S, Skyt P S
Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark.
Phys Med Biol. 2017 Jun 14;62(14):5612-5622. doi: 10.1088/1361-6560/aa70cd.
New treatment modalities in radiotherapy (RT) enable delivery of highly conformal dose distributions in patients. This creates a need for precise dose verification in three dimensions (3D). A radiochromic silicone-based 3D dosimetry system has recently been developed. Such a dosimeter can be used for dose verification in deformed geometries, which requires knowledge of the dosimeter's mechanical properties. In this study we have characterized the dosimeter's elastic behaviour under tensile and compressive stress. In addition, the dose response under strain was determined. It was found that the dosimeter behaved as an incompressible hyperelastic material with a non-linear stress/strain curve and with no observable hysteresis or plastic deformation even at high strains. The volume was found to be constant within a 2% margin at deformations up to 60%. Furthermore, it was observed that the dosimeter returned to its original geometry within a 2% margin when irradiated under stress, and that the change in optical density per centimeter was constant regardless of the strain during irradiation. In conclusion, we have shown that this radiochromic silicone-based dosimeter's mechanical properties make it a viable candidate for dose verification in deformable 3D geometries.
放射治疗（RT）中的新治疗模式能够为患者提供高度适形的剂量分布。这就需要在三维（3D）空间中进行精确的剂量验证。最近开发了一种基于放射变色硅酮的3D剂量测定系统。这种剂量计可用于变形几何形状中的剂量验证，这需要了解剂量计的机械性能。在本研究中，我们对剂量计在拉伸和压缩应力下的弹性行为进行了表征。此外，还测定了应变下的剂量响应。结果发现，该剂量计表现为不可压缩的超弹性材料，应力/应变曲线呈非线性，即使在高应变下也没有明显的滞后或塑性变形。在高达60%的变形范围内，体积在2%的容差内保持恒定。此外，观察到剂量计在应力下照射后能在2%的容差内恢复到原始几何形状，并且每厘米光密度的变化在照射期间与应变无关，保持恒定。总之，我们已经表明，这种基于放射变色硅酮的剂量计的机械性能使其成为可变形3D几何形状中剂量验证的可行候选者。
