Simulation of stopping power for therapeutic proton beams in dental amalgam

Amalgam has been widely used as a common dental material and has existed in head and neck proton therapy cases. The stopping power of dental materials is still a limited study. This study aims to simulate and validate the stopping power of therapeutic proton beams through dental amalgam.

Proton beam parameters in FLUKA Monte Carlo (MC) simulation for two energies (150 and 200 MeV) were determined, including energy, momentum spread, spot size (in the x- and y-axis), and divergence. Amalgam was analyzed using an EDX spectrometer to acquire the material compositions. The stopping powers were simulated using FLUKA for monoenergetic proton beams penetrating through the amalgam materials and compared with the measurement values from multi-layer ionization chambers.

The material compositions of amalgam were reported by weight proportions: Ag = 0.31, Hg = 0.28, As = 0.19, Sn = 0.15, Cu = 0.05, and Si = 0.02. The stopping power for 150 and 200 MeV proton beams in dental amalgam were 23.6 and 21.3 MeV/cm for MC simulation and 24.9 and 21.5 MeV/cm for measurements, respectively. The simulation stopping power of protons with 200 MeV agreed well with the measurement, while a larger deviation with 1.3 MeV/cm was observed for 150 MeV.

The determined proton beam parameters and acquired material compositions from the EDX spectrometer could be employed for FLUKA MC simulation. At 200 MeV, the stopping power of amalgam shows good agreement with measurement.