Neutronics Analyses of the Radiation Field at the Accelerator-Based Neutron Source of Nagoya University for the BNCT Study

Abstract

The Nagoya University Accelerator-driven Neutron Source (NUANS) is an accelerator-based neutron source by 7Li(p,n)7Be reaction with a 2.8 MeV proton beam up to 15 mA. The fast neutrons are moderated and shaped to beam with a Beam Shaping Assembly (BSA). NUANS is aiming at the basic study of the Boron Neutron Capture Therapy (BNCT) such as an in vitro cell-based irradiation experiment using a water phantom. Moreover, the BSA is developed as a prototype of one for human treatment. We have evaluated the radiation field of NUANS by a Monte Carlo code PHITS. It is confirmed that the radiation characteristics at the BNCT outlet meet the requirement of IAEA TECDOC-1223. Additionally, the radiation field in the water phantom located just in front of the BSA outlet is calculated. In the in vitro irradiation experiment, the boron dose of 30 Gy-eq, which is the dose to kill tumor cells, is expected for 20 min of irradiation at the beam current of 15 mA.

A Compact Neutron Generator for the Niort® Treatment of Severe Solid Cancers

“…(6) The monoenergetic neutron spectrum of the nIORT® would set the OER to about the plateau of @1.45 15 because of the radiobiology effect of the neutrons in biological tissues: therefore, nIORT® is less affected by the tumour hypoxic microenvironment. (7) The potential appearance of the Radiation Induced Abscopal Effect (RIAE) on distant nonirradiated cells due to the adaptive immune system 42,43 , that is also favoured by the epithermal and thermal tails of the neutron flux spreading out around the tumour bed. (8) It should be intriguing to investigate in preclinical tests if neutrons of 2.45 MeV energy could inhibit the Epithelial-Mesenchymal Transitions (EMTs) in solid cancers.…”

“…The basic idea in the nIORT® is to irradiate tumour beds "directly" with the monoenergetic 2.45 MeV neutrons emitted by the DD source, e.g., without moderating to epithermal or thermal energies as in the BNCT. 5,6,7 This high energy neutrons are very effective in cancer cells killing because of their high LET and RBE: @16 for 2.45 MeV neutrons. 9,30 This RBE value is significantly higher than of the proton in the Spread Out Bragg Peak (SOBP, estimated to be 1.1 to 1.2) and of the currently used 50 kV Xrays medical devices for IORT, which are 1.26 to 1.42 as measured in a phantom model.…”

“…Indeed, the almost spherically symmetric IR on the tumour bed has the advantages to be less sensitive to the margins of the surgery cavity and to the possible intra-tumour heterogeneity of the solid tumour cells since the neutron irradiator behaves like an IR "foam" within the cavity. Differently from the Boron Neutron Capture Therapy (BNCT) exploiting thermal and epithermal neutrons to induce (n, a) reactions in boron carriers injected into patients 5,6,7 , the fast neutrons interact directly and efficiently with the hydrogen nuclei, producing recoil protons that ionize the tissues. Monte Carlo simulations have shown that the nIORT® delivers on the tumour bed a fast-neutron IR with a high linear energy transfer (LET) 8 and a relative biological effectiveness (RBE) 9 significantly higher than all other IRs such as X-rays, electrons and protons, thus resulting very efficient in producing DNA double strand breaks (DSBs) of the cancer cells.…”

Next generation of boron neutron capture therapy (BNCT) agents for cancer treatment

“…The creation of new accelerators has rekindled interest in creating new medications and treatment methods that using BNCT 12 but further scientific and clinical research is required to get to an era of accelerator‐based BNCT, when more patients with resistant tumors will be treated 13 …”

“…The creation of new accelerators has rekindled interest in creating new medications and treatment methods that using BNCT 12 but further scientific and clinical research is required to get to an era of accelerator-based BNCT, when more patients with resistant tumors will be treated. 13 F I G U R E 1 (A) The principles of boron neutron capture therapy; (B) Chemical structures and characteristics of p-boro-L-phenylalanine 1 (L-BPA) and sodium borocaptate 2 (BSH).…”