An overview on the developments and improvements of a new treatment planning system for BNCT

Boron neutron capture therapy (BNCT) is a radiation therapy for cancer that employs a neutron beam and ¹⁰B-loaded drugs to selectively kill tumor cells sparing surrounding healthy tissues (HT). The task is to give the maximum dose to tumor, containing the HT dose within the allowed limits. This must be evaluated prior to irradiation by means of treatment planning systems (TPSs) based on radiation transport simulation. Since 1996 our team has been involved in research on BNCT TPS. The innovation lies in the use in the simulation of a 3D map of the real boron distribution in tissues, obtained through PET scanning of the target region (Kyoto BNCT team, 1995). This approach differs markedly from the "standard" one, in which the target organ is subdivided into "regions"; each region is then assigned a single value of boron concentration indirectly estimated by an "educated guess". The first result of this research was the prototype software "CARONTE", employed to test the feasibility of the new approach and to carry out a comparative study that showed significant differences (doses and fluences) when both the approaches are applied to the same TPS. These results led to the development of "BDTPS", an original, complete TPS software. This research activity was introduced and described in some previous works, but in this one we particularly point out the comparison between ours and standard results and the experimental validation, which required the design, construction, CT and PET scanning and irradiation in a nuclear reactor (HFR-Petten) of a special phantom.