Ambient neutron and photon dose equivalent H*(10) around a pencil beam scanning proton therapy facility.

Objectives: To measure leakage ambient dose equivalent H*(10) from stray secondary neutron and photon radiation around proton therapy (PT) facility and evaluate adequacy of shielding design.

Methods And Materials: H*(10) measurement were carried out at 149 locations around cyclotron vault (CV), beam transport system (BTS) and first treatment room (GTR3) of a multiroom PT facility using WENDI-II and SmartIon survey meter. Measurement were performed under extreme case scenarios wherein maximum secondary neutrons and photons were produced around CV, BTS and GTR3 by stopping 230MeV proton of 300nA on beam degrader, end of BTS and isocenter of GTR3.