Abstract

This study aimed to develop epoxy-barium sulfate (BaSO₄) composites as bone-equivalent materials for the mandibular and cervical vertebral regions of a Rando phantom and to evaluate their radiological and dosimetric accuracy in radiotherapy planning. Epoxy-based composite samples were prepared by incorporating BaSO₄ into the epoxy matrix to obtain bone-equivalent materials for the mandibular and cervical vertebral regions. The samples were imaged using a planning computed tomography (CT) system, and the resulting Hounsfield Unit (HU) values were analysed. Planning CT scans were acquired for both the original Rando phantom and the phantom incorporating epoxy-BaSO₄ inserts. Based on these images, treatment plans were recalculated in the treatment planning system while maintaining identical monitor unit (MU) settings and beam geometry. Isodose distributions and dose-volume histogram (DVH) parameters were comparatively evaluated between the original and modified phantom configurations. Strong linear relationship was observed between BaSO₄ content and HU values (R²>0.95). Composites containing 5% and 3% BaSO₄ produced HU values consistent with the reference ranges for the mandibular and cervical vertebral regions, respectively. Dose parameters for the planning target volume (PTV) and organs at risk (OARs) remained within ±2% clinical acceptance limits, and a high degree of overlap was observed in the isodose distributions. Epoxy-BaSO4 composites demonstrated region-specific HU values and yielded dosimetric results within clinically acceptable limits in the treatment planning system. These findings suggest that epoxy-BaSO₄-based materials provide a feasible approach for radiotherapy planning-oriented quality assurance and educational phantom development. Future studies incorporating different beam energies and experimental dose verification may further clarify the applicability of these materials.

Key words: Epoxy, epoxy-barium sulfate, bone-equivalent phantom, computed tomography, hounsfield unit, radiotherapy planning, dose-volume histogram