Epithermal Neutron Beam For BNCT Research Articles

A novel design of beam shaping assembly to use D-T neutron generator for BNCT

In order to use 14.1MeV neutrons produced by d-T neutron generators, two special and novel Beam Shaping Assemblies (BSA), including multi-layer and hexagonal lattice have been suggested and the effect of them has been investigated by MCNP4C Monte Carlo code. The results show that the proposed BSA can provide the qualified epithermal neutron beam for BNCT. The final epithermal neutron flux is about 6e9 n/cm2.s. The final proposed BSA has some different advantages: 1) it consists of usual and well-known materials (Pb, Al, Fluental and Cd); 2) it has a simple geometry; 3) it does not need any additional gamma filter; 4) it can provide high flux of epithermal neutrons. As this type of neutron source is under development in the world, it seems that they can be used clinically in a hospital considering the proposed BSA.

Simulation study of accelerator based quasi-mono-energetic epithermal neutron beams for BNCT

Filtered neutron techniques were applied to produce quasi-mono-energetic neutron beams in the energy range of 1.5–7.5keV at the accelerator port using the generated neutron spectrum from a Li (p, n) Be reaction. A simulation study was performed to characterize the filter components and transmitted beam lines. The feature of the filtered beams is detailed in terms of optimal thickness of the primary and additive components. A computer code named “QMNB-AS” was developed to carry out the required calculations. The filtered neutron beams had high purity and intensity with low contamination from the accompanying thermal, fast neutrons and γ-rays.

Improvement of Activation-Detector-Based Spectrum Unfolding Technique for BNCT

Energy spectrum determination of an epithermal neutron beam for BNCT is always a critical issue to its dose accuracy. The spectrum is generally determined by multiple activation foils with few-channel unfolding codes. This study aims to make improvement to the activation-detector-based unfolding technique via introducing specially designed detector complexes in addition to the commonly applied multiple activation foils. The extra detector complexes can obtain valuable information from planned, artificial perturbations posed on the incident epithermal neutron beam, without the need of modifying the unfolding algorithm. Two different types of BNCT beams, one is based on nuclear reactor and the other one is based on low energy accelerator, with two different conditions were tested: under- and over-moderated cases. The spectra adjusted by using the original foil package containing 11 foils and the improved system are compared based on the square root of the sum of deviation squares. The specially designed detector complexes have shown the great ability to significantly reduce the deviations between the unfolded spectra and standard solutions. For a seriously under-moderated case tested in this work, the improvement can even reach more than 400% in deviation reduction.

Optimized therapeutic neutron beam for accelerator-based BNCT by analyzing the neutron angular distribution from 7Li(p,n) 7Be reaction

Perpendicular neutrons (i.e., solid angle bin of 50–150°) among ones generated from 7Li(p,n) 7Be reaction were used to produce an optimized therapeutic neutron beam for accelerator-based BNCT. A new beam port assembly was also designed to shape the fast neutrons into epithermal ones and to reduce unnecessary radiation including gammas. As a result of a simulation, it is found that a tumor at a depth of 60 mm from the head skin could be treated within 5 minutes, if a typical tumor is assumed to be taken about 20 RBE Gy for therapeutic treatment. It is, thus, expected that the neutrons emitted into the solid angle bin of 50–150° from 7Li(p,n) 7Be reaction are very effective in producing epithermal neutron beams for BNCT.

The epithermal neutron beam for BNCT under construction at TAPIRO: Physics

A column to provide an epithermal neutron beam suitable for experimental and clinical BNCT is nearing completion at the TAPIRO reactor (ENEA Casaccia, Rome). TAPIRO is a compact, low power (5 kW), helium-cooled, fast reactor. It has a hard neutron spectrum relative even to other fast reactors. In this paper some of the basic physics aspects of designing an epithermal neutron beam are considered, with reference to the TAPIRO beam.

Renovation of epithermal neutron beam for BNCT at THOR

Heading for possible use for clinical trial, THOR (Tsing Hua Open-pool Reactor) at Taiwan was shutdown for renovation of a new epithermal neutron beam in January 2003. In November 2003, concrete cutting was finished for closer distance from core and larger treatment room. This article presents the design base that the construction of the new beam is based on. The filter/moderator design along the beam is Cd(0.1 cm)+Al(10 cm)+FLUENTAL™(16 cm)+Al(10 cm)+FLUENTAL(24 cm)+Void(18 cm)+Cd(0.1 cm)+Bi(10 cm) with 6 cm Pb as reflector. Following the filter/moderator is an 88 cm long, 6 cm thick Bi-lined collimator with Li 2CO 3-PE at the end. The collimator is surrounded by Li 2CO 3-PE and Pb. The calculated beam parameters under 2 MW at the beam exit is φ epi=3.4×10 9 n/cm 2/s, D f/ φ epi=2.8×10 −11 cGy cm 2/n, D γ / φ epi=1.3×10 −11 cGy cm 2/n, and J +/ φ= 0.8. For a phantom placed 10 cm from beam exit, MCNP calculation shows that the advantage depth is 8.9 cm, and advantage ratio is 5.6 if boron concentration in tumor and normal tissue are assumed to be 65 and 18 ppm. The maximum dose rate for normal tissue is 50 cGy/min. The maximum therapeutic ratio is 6. The construction of the beam is scheduled to be finished by the end of April 2004.

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

A modeling investigation was performed to choose moderator material and size for creating optimal epithermal neutron beams for BNCT based on a proton accelerator and the 7Li(p,n) 7Be reaction as a neutrons source. An optimal configuration is suggested for the beam shaping assembly made from polytetrafluoroethylene and magnesium fluorine to be placed on high current IPPE proton accelerator KG-2.5. Results of calculation were experimentally tested and are in good agreement with measurements.

Determination of the γ-ray component of a neutron beam for medical irradiation applications at the HFR in Petten

The spectrum of γ-rays contaminating the epithermal neutron beam for BNCT at the HFR in Petten has been measured with a HPGe-detector. These measurements show that the main γ-ray component is in the energy range between 3 and 7 MeV. This γ-ray component contributes to the dose in healthy tissue at patient irradiations. Knowledge of the energy spectrum of the beam is important for correct treatment planning. Furthermore, it gives an insight into the origin of these γ-rays, it determines the influence of irradiation experiments in the reactor core on the γ-ray component and this contribution may be reduced. The measurements were feasible without causing damage to the detector by the high neutron intensity of 3.8×10 8 n/ cm 2 s . There are two ways to do this. The first is to measure directly in the beam, removing most of the neutrons by scattering in polythene. The second way is to measure the Compton scattered γ-rays at an angle of 90°, after they have scattered in a slab of polythene. In this report, direct measurements of the beam γ-rays and a preliminary analysis of the energy distribution are presented. Furthermore, the origin of its components is determined. In a next stage, such measurements in combination with MCNP simulations allow the reconstruction of the energy-dependent γ-ray fluence rate of the beam.

On the optimal energy of epithermal neutron beams for BNCT

The optimal neutron energy for the treatment of deep-seated tumours using boron neutron capture therapy is studied by analysing various figures of merit. In particular, analysis of the therapeutic gain as a function of the neutron energy indicates that, with the currently available 10B carriers, the most useful neutrons for the treatment of deep-seated tumours, in particular glioblastoma multiforme, are those with an energy of a few keV. Based on the results of the simulations, a method is presented which allows us to evaluate the quality of epithermal neutron beams of known energy spectrum, thus allowing us to compare different neutron-producing reactions and beam-shaping assembly configurations used for accelerator-based neutron sources.

The Argonne ACWL, a potential accelerator-based neutron source for BNCT

THE CWDD (Continuous Wave Deuterium Demonstrator) accelerator was designed to accelerate 80 mA cw of D − to 7.5 MeV. Most of the hardware for the first 2 MeV was installed at Argonne and major subsystems had been commissioned when program funding from the Ballistic Missile Defense Organization ended in October 1993. Renamed the Argonne Continuous Wave Linac (ACWL), we are proposing to complete it to accelerate either deuterons to 2 MeV or protons to 3 – 3.5 MeV. Equipped with a beryllium or other light-element target, it would make a potent source of neutrons (on the order of 10 13 n/s) for BNCT and/or neutron radiography. Project status and proposals for turning ACWL into a neutron source are reviewed, including the results of a computational study that was carried out to design a target/moderator to produce an epithermal neutron beam for BNCT.