Instituto de Física, Universidade Federal de Goiás - UFG, Goiás, Brazil.
Instituto Federal de Educação, Ciência e Tecnologia de Goiás - IFG, Goiás, Brazil.
Med Eng Phys. 2019 Apr;66:102-106. doi: 10.1016/j.medengphy.2019.02.011. Epub 2019 Mar 4.
Commonly dose-responses of conventional dosimetric methods are affected by a saturation dose and are known to be limited when the delivered dose is relatively high. In contrast, elastic properties of polymer-gel dosimeter phantoms play major roles in a new dosimetry technique using magnetic resonance elastography (MRE). A single volume of polymer-gel dosimeter solution containing methacrylic and ascorbic acid in gelatin initiated by copper was prepared. The material was subsequently stored in cylindrical containers for future use as a biological tissue-mimicking phantom material. The phantom material was irradiated with gamma rays, where absorbed doses of 10-50 Gy were delivered. To study the dynamic elastic behaviour, periodic mechanical external forces of 100-400 Hz were applied to generate shear waves in the samples. The radiation-induced changes in the shear modulus of the samples were estimated from wave-displacement images and converted to elastograms. The smallest and largest shear modulus values were approximately 2.10 ± 0.64 and 35.26 ± 2.85 kPa, respectively. The dynamic elastic response of the polymer-gel dosimeters showed an increased dependency with frequency. A linear relationship (R = 0.996) was observed between the integrated area and the absorbed dose of the samples. The elastograms clearly showed that the largest shear modulus values were in the irradiated region of the polymer-gel dosimeter phantoms. Quantitative values of the shear modulus of polymer-gel dosimeters were estimated using MRE.
常规剂量测定方法的剂量反应通常受到饱和剂量的影响，并且当所给予的剂量相对较高时，其作用受到限制。相比之下，聚合物凝胶剂量计模型的弹性特性在使用磁共振弹性成像（MRE）的新剂量测定技术中起着重要作用。我们制备了含有甲基丙烯酰基和抗坏血酸的聚合物凝胶剂量计溶液，该溶液以明胶中的铜作为引发剂。随后，将该材料储存在圆柱形容器中，以备将来用作生物组织模拟模型材料。用伽马射线辐照该模型材料，其中传递的吸收剂量为 10-50Gy。为了研究动态弹性行为，对样品施加了 100-400Hz 的周期性机械外力，以在样品中产生剪切波。从波位移图像中估计了样品的剪切模量的辐射诱导变化，并将其转换为弹性图。最小和最大剪切模量值分别约为 2.10±0.64kPa 和 35.26±2.85kPa。聚合物凝胶剂量计的动态弹性响应显示出与频率的依赖性增加。在样品的积分面积与吸收剂量之间观察到线性关系（R=0.996）。弹性图清楚地表明，聚合物凝胶剂量计模型的辐照区域的最大剪切模量值最高。使用 MRE 估计了聚合物凝胶剂量计的剪切模量的定量值。
