X-ray radiation simulation of a head tetrahedral phantom with intraoral metal using PHITS

Nagano, Takuya*; Matsuya, Yusuke  ; Kaida, Atsushi*; Nojima, Hitomi*; Furuta, Takuya   ; Sato, Kaoru   ; Yoshimura, Ryoichi*; Miura, Masahiko*

A dental prosthesis such as a metal crown exists in radiation field when performing head and neck cancer radiotherapy. In our previous studies, we have evaluated the sensitizing effect ratio (SER) of the radiobiological effects around metal crowns by in vitro analysis. However, it is uncertain how much SER is actually expected in complex geometry in clinical practice. Here, we simulated the treatment plan using a head phantom with a metal crown, and evaluated the dose distributions around the metal crown in a realistic patient system by simulation. The simulation results using PHITS agree well with the SER values obtained in vitro. It has been known that localized mucositis occurs around metal crowns during radiotherapy, and this outcome is expected to provide a precise understanding of the mechanism on inflammation in tissues around metals.