Designing an Epithermal Neutron Beam for Boron Neutron Capture Therapy for the Fusion Reactions 2H(d,n)3He and 3H(d,n)4He

DESIGNING AN EPITHERMAL NEUTRON BEAM FOR BORON NEUTRON CAPTURE THERAPY FOR THE FUSION REACTIONS 2 H ( d n ) 3 H e AND 3 H ( d n ) 4 H e 1 . a J.M. Verbeke , S.V. Costes , D. Bleuel , J. Vujic and K.N. Leung Nuclear Engineering Department, University of California, Berkeley Lawrence Berkeley National Laboratory Berkeley, CA 94720 a b a b a b a b b Abstract A beam shaping assembly has been designed to mod- erate high energy neutrons from the fusion reactions 2 H(d n) 3 He and 3 H(d n) 4 He for use in boron neu- tron capture therapy. The low neutron yield of the 2 H(d n) 3 He reaction led to unacceptably long treat- ment times. However, a 160 mA deuteron beam of en- ergy 400 keV led to a treatment time of 120 minutes with the reaction 3 H(d n) 4 He. Equivalent doses of 9.6 Gy-Eq and 21.9 Gy-Eq to the skin and to a 8 cm deep tumor respectively have been computed. ergy required for DD and DT lies between 100 keV and 400 keV. Due to this lower energy, smaller accelerators with higher currents can be utilized. In this paper we present a preliminary study to determine which moder- ators, if any, are the most suitable to decrease the initial neutron energies to therapeutically useful regions, with- out large losses in neutron beam intensity. The Monte- Carlo codes MCNP 2] and BNCT RTPE 3] are used for the neutron transport calculation through the mod- erators and for the treatment planning, respectively. I INTRODUCTION The main goal of this study is to identify some alter- native accelerator-based reactions that could result in an accelerator and target system simpler and less ex- pensive than current ones, while satisfying all of the re- quirements for boron neutron capture therapy (BNCT). The need for epithermal neutrons with energy distribu- tion peaking around 10 keV 1] has led di erent groups to focus their research on the two candidate reactions 7 Li(p n) and 9 Be(p n) that generate neutrons in the energy range of hundreds of keV. To the best of au- thors knowledge, the feasibility of generating neutrons for BNCT with the fusion reactions 2 H(d n) 3 He (DD) and 3 H(d n) 4 He (DT) has not been investigated in de- tail so far, due to the di culty of moderating high en- ergy neutrons of 2.43 and 14.1 MeV respectively. The advantage of these neutron sources is the low energy required for the deuteron beam. While the protons for the 7 Li(p n) or 9 Be(p n) reactions need to be acceler- ated between 2.5 and 4.0 MeV, the deuteron beam en- 1 This work is supported by the US Department of Energy under contract number DE-AC03-76SF00098 II BACKGROUND Boron Neutron Capture Therapy (BNCT) is a binary cancer therapy modality which is very appealing due to its potential for selective cell killing 4]. This ther- apy is being investigated for several types of cancers including Glioblastoma Multiforme, a highly malignant and therapeutically persistent brain tumor, for which conventional therapies like chemotherapy, surgery, and radiotherapy are not successful. BNCT brings together two components which as- sume selectivity in cell killing. The rst component is the delivery of 10 B | a stable isotope of boron with a large cross-section for thermal neutron absorp- tion | preferentially to the tumor cells with help of tumor-seeking compounds. The second component is a beam of low energy neutrons reaching the tumor cells. When a thermal neutron is captured by 10 B, the re- action 10 B(n ) 7 Li occurs, releasing two high-energy ions. Due to the high LET and RBE of these ions, only tumor cells in close proximity to the ssion reaction are damaged, leaving adjacent healthy cells una ected. Glioblastoma Multiforme is characterized by a tumor mass often located near the center of the brain with accompanying microscopic ngerlets spreading