Evaluation of the physical and radiological properties of different Fricke gel formulations as water-equivalent materials and biological tissues.

Fricke gel dosimeters, also known as hydrogels, have emerged as attractive tools in clinical dosimetry due to the stringent requirements of quality assurance protocols and radiation protection programs. The performance of these materials strongly depends on the characteristics of the polymeric matrices that constitute them. Their ability to mimic reference materials, such as water and biological tissue, has been widely investigated for applications as simulators in radiotherapy procedures. This study aims to evaluate the physical and radiological properties of Fricke gel formulations prepared with different polymeric matrices: porcine skin gelatin (GEL), sodium carboxymethylcellulose (CMC), guar gum (GGU), and poly(vinyl alcohol) (PVA). Key-parameters, including the linear and mass attenuation coefficients (and), the mass energy-absorption (), the electronic stopping power (Stpe), and the effective atomic number (), were determined using both experimental and computational methods. The physical investigations included the evaluation of thermal decomposition, determined by thermogravimetric analysis and kinetic analysis, incorporating isoconversional models based on multilayer perceptron (MLP) neural networks. The results obtained experimentally and through computational tools such as Phy-X, XCOM, TOPAS, EGSnrc, and ESTAR, for the different Fricke gel formulations, revealed that all gel formulations exhibit radiological parameters comparable to those of reference materials (water and biological tissue), in accordance with ICRU Report 44. Thermal analysis revealed distinct stability characteristics among the Fricke gel compositions. The GGU and PVA formulations exhibited greater thermal resistance compared with the GEL and CMC compositions. Kinetic analysis indicated that the average activation energy values for all formulations were below 40 kJ mol, suggesting that the thermal degradation processes initiate at relatively low temperatures. The application of MLP mathematical method proved valuable for accurately modeling the observed thermal kinetics. This study demonstrates that Fricke gel formulations (GEL, CMC, GGU, and PVA) effectively mimic the radiological response of biological tissue and water. Their performance in the field of radiotherapy is relevant for applications in three-dimensional dosimetry and radiological simulations due to their tissue-equivalent properties.