In-phantom dosimetry for the C-13(d,n)N-14 reaction as a source for accelerator-based BNCT

The use of the C-13(d,n) N-14 reaction at E-d = 1.5 MeV for accelerator-bas ed boron neutron capture therapy (AB BNCT) is investigated. Among the deute ron-induced reactions at low incident energy, the C-13(d,n)N-14 reaction tu rns out to be one of the best for AB-BNCT because of beneficial materials p roperties inherent to carbon and its relatively large neutron production cr oss section. The deuteron beam was produced by a tandem accelerator at MIT' s Laboratory for Accelerator Beam Applications (LABA) and the neutron beam shaping assembly included a heavy water moderator and a lead reflector. The resulting neutron spectrum was dosimetrically evaluated at different depth s inside a water-filled brain phantom using the dual ionization chamber tec hnique for fast neutrons and photons and bare and cadmium-covered gold foil s for the thermal neutron flux. The RBE doses in tumor and healthy tissue w ere calculated from experimental data assuming a tumor B-10 concentration o f 40 ppm and a healthy tissue B-10 concentration of 11.4 ppm (corresponding to a reported ratio of 3.5:1). All results were simulated using the code M CNP, a general Monte Carlo radiation transport code capable of simulating e lectron, photon, and neutron transport. Experimental and simulated results are presented at 1, 2, 3, 4, 6, 8, and 10 cm depths along the brain phantom centerline. An advantage depth of 5.6 cm was obtained for a treatment time of 56 min assuming a 4 mA deuteron current and a maximum healthy tissue do se of 12.5 RBE Gy. (C) 2001 American Association of Physicists in Medicine.