Designing accelerator‐based epithermal neutron beams for boron neutron capture therapy

Abstract

The 7Li(p,n)7Be reaction has been investigated as an accelerator-driven neutron source for proton energies between 2.1 and 2.6 MeV. Epithermal neutron beams shaped by three moderator materials, Al/AlF3, 7LiF, and D2O, have been analyzed and their usefulness for boron neutron capture therapy (BNCT) treatments evaluated. Radiation transport through the moderator assembly has been simulated with the Monte Carlo N-particle code (MCNP). Fluence and dose distributions in a head phantom were calculated using BNCT treatment planning software. Depth-dose distributions and treatment times were studied as a function of proton beam energy and moderator thickness. It was found that an accelerator-based neutron source with Al/AlF3 or 7LiF as moderator material can produce depth-dose distributions superior to those calculated for a previously published neutron beam design for the Brookhaven Medical Research Reactor, achieving up to approximately 50% higher doses near the midline of the brain. For a single beam treatment, a proton beam current of 20 mA, and a 7LiF moderator, the treatment time was estimated to be about 40 min. The tumor dose deposited at a depth of 8 cm was calculated to be about 21 Gy-Eq.

Optimization of an accelerator-based epithermal neutron source for neutron capture therapy

“…Spatialenergy distributions of neutrons `from 7 Li(p,n) 7 Be reaction from thick metallic lithium target are calculated by using methods and programs previously described [10]. Main investigations were carried out for initial proton energies of 2.3, 2.4, and 2.8 MeV.…”

“…The sphere moderator model was chosen for investigating characteristics of different materials for creating epithermal neutron sources based on 7 Li(p,n) 7 Be reaction. In the center of the sphere was placed a source as a thin disk with a diameter of 4 cm, which is connected to the beam-line tube of the same diameter.…”

“…2 shows epithermal neutrons spectra from the surface of a sphere moderator with a radius of 20 cm made from different materials. Neutron source is based on 7 Li(p,n) 7 Be reaction in a thick More detailed characteristic of epithermal neutron beam was derived in calculation of inphantom absorbed-dose distribution. In this calculation, a cube beam-shaping assembly, with a size of 40x40x40 cm, was used.…”

“…To be presented at the 11th World Congress on Neutron Capture Therapy (ISNCT-11), Boston, October 11-15, 2004 2 and investigations of creating neutron sources for neutron capture therapy based on proton accelerators with beam energy 2-3 MeV and power 10-20 kW, which are more cost-effective and readily acceptable in oncology clinics [5][6][7][8]. The most promising nuclear reaction for neutron generation on such an accelerator is 7 Li(p,n) 7 Be [9].…”

“…The most promising nuclear reaction for neutron generation on such an accelerator is 7 Li(p,n) 7 Be [9]. Calculations show that with such a neutron source and a compact moderator it is possible to create neutron beams suitable for neutron capture therapy purposes.…”