Proton dose assessment to the human eye using Monte Carlo n-particle transport code (MCNPX)

Abstract

The objective of this project was to develop a simple MCNPX model of the human eye to approximate dose delivered from proton therapy. The calculated dose included that due to proton interactions and secondary interactions, which included multiple coulombic energy scattering, elastic and inelastic scattering, and non-elastic nuclear reactions (i.e., the production of secondary particles). After benchmarking MCNPX with a known proton simulation, the proton therapy beam used at Laboratori Nazionali del Sud-INFN was modeled for simulation. A virtual water phantom was used and energy tallies were found to correspond with the direct measurements from the therapy beam in Italy. A simple eye model was constructed and combined with the proton beam to measure dose distributions. Two treatment simulations were considered. The first simulation was a typical treatment scenario-where dose was maximized to a tumor volume and minimized elsewhere. The second case was a worst case scenario to simulate a patient gazing directly into the treatment beam during therapy. Dose distributions for the typical treatment yielded what was expected, but the worst case scenario showed the bulk of dose deposited in the cornea and lens region. The study concluded that MCNPX is a capable platform for patient planning but laborious for programming multiple simulation configurations.