Therapeutic Proton Beam Range Measurement with EBT3 Film and Comparison with Tool for Particle Simulation

Purpose: The advantages of ocular proton therapy are that it spares the optic nerve and delivers the minimal dose to normal surrounding tissues.In this study, it developed a solid eye phantom that enabled us to perform quality assurance (QA) to verify the dose and beam range for passive single scattering proton therapy using a single phantom.For this purpose, a new solid eye phantom with a polymethyl-methacrylate (PMMA) wedge was developed using film dosimetry and an ionization chamber.Methods: The typical beam shape used for eye treatment is approximately 3 cm in diameter and the beam range is below 5 cm.Since proton therapy has a problem with beam range uncertainty due to differences in the stopping power of normal tissue, bone, air, etc, the beam range should be confirmed before treatment.A film can be placed on the slope of the phantom to evaluate the Spread-out Bragg Peak based on the water equivalent thickness value of PMMA on the film.In addition, an ionization chamber (Pin-point, PTW 31014) can be inserted into a hole in the phantom to measure the absolute dose.Results: The eye phantom was used for independent patient-specific QA.The differences in the output and beam range between the measurement and the planned treatment were less than 1.5% and 0.1 cm, respectively.Conclusions: An eye phantom was developed and the performance was successfully validated.The phantom can be employed to verify the output and beam range for ocular proton therapy.