Development of JCDS, a computational dosimetry system at JAEA for boron neutron capture therapy

Clinical trials of boron neutron capture therapy (BNCT) are being carried out using several research reactors throughout the world. In Japan, many medical groups perform clinical trials of BNCT using Japan Research Reactor No.4 (JRR-4) in Japan Atomic Energy Agency (JAEA). JAEA has developed a treatment planning system, JCDS, in order to evaluate radiation dose given to a patient in the BNCT. JCDS employs a voxel calculation method to compute the radiation dose given to a patient. An initial version of JCDS created a voxel model, dividing a space into 1x1x1cm(3) voxel cells. JCDS was improved to create a detailed voxel model consisting of minute voxel cells such as 2x2x2mm(3) voxel cells. Verification of accuracy of calculations with the detailed voxel mode demonstrated that the detailed voxel model enables JCDS to evaluate more accurately the radiation doses to a patient undergoing BNCT. Furthermore, the calculation code of JCDS is being incorporated into the PHITS system as a Monte-Carlo transport code. By employing the PHITS system in the dose evaluation, total doses given to a patient by combined modality therapy such as BNCT and X-ray therapy can be estimated accurately. Here, an outline and the performances of the latest version of JCDS are presented, and a future system integrated with JCDS is introduced.