Development of a New Monte-Carlo Treatment Planning System for Boron Neutron Capture Therapy

To improve treatment planning in boron neutron capture therapy (BNCT), a new Monte-Carlo radiotherapy planning system is under development at Japan Atomic Energy Agency (JAEA). This system (developing code: JCDS-FX) builds on fundamental technologies of JCDS (JAEA Computation Dosimetry System) which has been applied to actual BNCT trials at Japan Research Reactor No.4 (JRR-4). Basic technologies of JCDS have been taken over to JCDS-FX, and some new functions have been built into the system. One of features of the JCDS-FX is that PHITS as a multi-purpose particle Monte-Carlo transport code has been applied to particle transport calculation. Application of PHITS enables to evaluate doses for neutrons and photons as well as protons and heavy ions. Therefore, the JCDS-FX with PHITS can perform treatment planning for not only BNCT but also particle radiotherapy. To verify calculation accuracy of the JCDS-FX with PHITS, dose evaluations for neutron irradiation of a cylindrical water phantom and for an actual clinical trial conducted at JRR-4 were performed. The verification results indicated that JCDS-FX is applicable to BNCT treatment planning in practical use. Further verifications of the system are being performed to achieve practical application of the system in the future. And in addition to the BNCT, investigations for application of the system to any other particle radiotherapy like proton therapy are carried forward.