Radiation Shielding Evaluation of Carbohydrate Hydrogel Radiotherapy Pads Containing High-Z Fillers: A Geant4 Study

This work analyzes the radiation shielding effectiveness of biocompatible hydrogel pads containing carbohydrate-based polymer matrices (Alginate, Chitosan, and Cellulose) integrated with the high atomic number (Z) fillers Bismuth Oxide (Bi2O3) and Zinc Oxide (ZnO). The Monte Carlo-based toolkit, Geant4, was used to simulate the deposition of the dose throughout a multilayer phantom that mimics the skin (Epidermis, Dermis, Subcutaneous, and Muscle) with a pad on top irradiated with photon and electron beams from 50 keV to 1000 keV. The results indicated that Bi2O3 succeeded in causing greater absorption of photons at doses, particularly in deep-layer tissues, from the increase in the filler content as well as the pad thickness. The Cellulose–Bi2O3 composites (10 mm thick) not only showed the best deep-shielding property among all investigated combinations but also the Alginate-based pads generally performed better with regard to the surface dose attenuation. The results demonstrate the promising potential of high-Z-doped hydrogels in serving as flexible, light, and biocompatible shielding materials for superficial radiotherapy.