Development and clinical applications of an all-in-one Monte Carlo-based independent dose calculation system for carbon-ion radiation therapy

Abstract

Purpose: This study aimed to develop a Monte-Carlo (MC)-based independent dose calculation system (IDCS) for carbon-ion radiation therapy (CIRT) capable of simultaneously computing the physical dose, biological dose, and linear energy transfer (LET) distributions. This study evaluated the clinical applicability through treatment plan verification and patient-specific quality assurance. Method: The developed IDCS utilizes the TOPAS MC code that incorporates automated beam modeling, and dose/ LET calculations. The system was validated by comparing the IDCS-calculated physical dose, biological dose, and LET distributions with those from a treatment planning system (TPS) in a water phantom. The clinical feasibility of this method was assessed in a patient case. Results: The automated beam-modeling was performed using 32 nominal energies that converged after 20.5 iterations. The gamma evaluation (2%/2 mm) demonstrated high agreement between the IDCS and TPS dose in the water phantom validation, with passing rates exceeding 99.9%. LET volume histograms confirmed the reliability of the LET calculations. In a clinical application test, the IDCS achieved a gamma passing rate >97.0% for dose distributions. It also exhibited close agreement with LET within the target, whereas discrepancies were observed in the surrounding organs-at-risk. Conclusions: The MC-based IDCS demonstrated high accuracy in calculating the physical dose, biological dose, and LET distributions for CIRT. Its agreement with the TPS calculations in water phantom validations and its robust performance in clinical plan verification confirmed its reliability as an independent verification tool. This system can be easily adapted for implementation in other particle therapy centers, further enhancing its clinical applicability.