Department of Physics and Electronics, CHRIST (Deemed to be University), Bangalore Central Campus, Bengaluru - 560029, Karnataka, India.
Biomed Phys Eng Express. 2020 Jul 20;6(5):055008. doi: 10.1088/2057-1976/aba209.
The efficacy of synthetic polymers as hydrogel phantoms for radiation therapy and dosimetry has been investigated for photon and charged particle (electron, proton and alpha particle) interactions. Tissue equivalence has been studied in terms of photon mass energy-absorption coefficients, KERMA (kinetic energy released per unit mass), equivalent atomic number and energy absorption build-up factors, relative to human tissues (skin, soft tissue, cortical bone and skeletal muscle), in the energy range 0.015-15 MeV. For charged particle interactions, ratio of effective atomic number is examined for tissue-equivalence in the energy region of 10 keV-1 GeV. Well established theoretical formulations are used for computation of photon mass-energy absorption effective atomic number, electron density and KERMA. Five-parameter geometric progression (G-P) fitting approximation is used to compute the values of energy absorption build-up factors. Effective atomic number for charged particle interaction is determined using logarithmic interpolation method. Using the analytical methodology, it has been revealed that all the selected synthetic polymers have good tissue-equivalence relative to all tissue except cortical bone. In particular, polyglycolic acid (PGA) and poly-lactic-co-glycolic acid (PLGA) prove to be best substitute material for photon interactions. On the other hand, % difference between effective atomic number for charged particle relative to human tissues is found least for polyethylene glycol (PEG) demonstrating adequate tissue-equivalence. Therefore, the present study is expected to be useful to choose most appropriate phantom material for radiation therapy.
合成聚合物作为辐射治疗和剂量学的水凝胶模型的功效已经针对光子和带电粒子（电子、质子和阿尔法粒子）相互作用进行了研究。从光子质量能量吸收系数、KERMA（每单位质量释放的动能）、等效原子数和能量吸收积累因子的角度研究了与人体组织（皮肤、软组织、皮质骨和骨骼肌）的组织等效性，能量范围为 0.015-15 MeV。对于带电粒子相互作用，在 10 keV-1 GeV 的能量区域检查有效原子数比以实现组织等效性。使用成熟的理论公式来计算光子质量-能量吸收有效原子数、电子密度和 KERMA。使用五参数几何级数（G-P）拟合逼近来计算能量吸收积累因子的值。使用对数插值方法确定带电粒子相互作用的有效原子数。使用分析方法，结果表明，除了皮质骨外，所有选定的合成聚合物与所有组织相比都具有良好的组织等效性。特别是聚乙醇酸（PGA）和聚乳酸-乙醇酸共聚物（PLGA）被证明是光子相互作用的最佳替代材料。另一方面，与人体组织相比，带电粒子的有效原子数的差异最小，证明聚乙二醇（PEG）具有足够的组织等效性。因此，本研究有望有助于选择最适合辐射治疗的体模材料。
