PHITS-Based Investigation of 6 MV Photon Beam in Wood-Based Phantoms for Radiotherapy Applications

This study aims to investigate the dosimetric characteristics of a 6 MV photon beam when interacting with wood-based phantom materials using Particle and Heavy Ion Transport code System (PHITS) simulation tool. Specifically, the study aims to evaluate the feasibility of using wood-based materials as potential alternatives to conventional tissue-equivalent phantoms for radiotherapy applications by analyzing their radiation attenuation, distribution, and energy deposition properties. PHITS version 3.30 was employed to investigate the dosimetric behavior of a 6 MV photon beam interacting with selected wood-based phantom materials such as Binderless Rhizophora (ρ = 0.992 g/cm3), Corn starch Rhizophora (ρ = 1.0 g/cm3), Tannin-added Rhizophora (ρ = 1.0 g/cm3), 6% soy-lignin Rhizophora (ρ = 0.98 g/cm3), 12% soy-lignin Rhizophora (ρ =0.94 g/cm3), Untreated Rhizophora (SPI0) (ρ = 0.962 g/cm3), SPI5 (ρ = 1.05 g/cm3), SPI10 (ρ = 1.10 g/cm3), SPI15 (ρ = 1.15 g/cm3), SPI20 (ρ = 1.20 g/cm3), including solid water (ρ = 1.04 g/cm3), polymethyl methacrylate (PMMA) (ρ = 1.19 g/cm3), and water hyacinth (ρ = 0.99 g/cm3 ). All phantom models were constructed as slabs with identical dimensions of 30 × 30 × 30 cm³ to ensure consistency in the simulations. The elemental compositions and densities of the materials were adopted from National Institute of Standards and Technology (NIST) (https://www.nist.gov/) database and previously published studies to maintain accuracy and comparability with existing research. Dose differences and TPR20,10 values were analyzed to evaluate the potential of wood-based materials. The results indicate that several wood-based phantom materials, especially SPI20, SPI10, and water hyacinth, with TPR20,10 values of 0.78, 0.95, 1.00, respectively. These results closely replicate the dose deposition and attenuation characteristics of conventional phantoms, making them promising candidates for tissue-equivalent applications in 6 MV photon beam radiotherapy.