Beam Shaping Assembly Research Articles

Optimized beam shaping assembly for a 2.1-MeV proton-accelerator-based neutron source for boron neutron capture therapy

Boron Neutron Capture Therapy (BNCT) is facing a new era where different projects based on accelerators instead of reactors are under development. The new facilities can be placed at hospitals and will increase the number of clinical trials. The therapeutic effect of BNCT can be improved if a optimized epithermal neutron spectrum is obtained, for which the beam shape assembly is a key ingredient. In this paper we propose an optimal beam shaping assembly suited for an affordable low energy accelerator. The beam obtained with the device proposed accomplishes all the IAEA recommendations for proton energies between 2.0 and 2.1 MeV. In addition, there is an overall improvement of the figures of merit with respect to BNCT facilities and previous proposals of new accelerator-based facilities.

Design of Beam Shaping Assemblies for Accelerator-Based BNCT With Multi-Terminals.

To moderate fast neutrons produced by accelerator to appropriate therapeutic energies for boron neutron capture therapy (BNCT), beam shaping assembly (BSA) is required definitely. In this work, based on a model of 2.5 MeV/30 mA proton accelerator, the Monte Carlo simulation software MCNPX was employed to design multi-terminal BSAs. All parameters for both the thermal and epithermal neutron beams at the exit ports of the designed BSAs meet the treatment recommendation values proposed by the International Atomic Energy Agency (IAEA). The clinical parameters of the thermal and epithermal neutron beams were also calculated for clinical indication consideration.

A bi-tapered and air-gapped beam shaping assembly used for AB-BNCT

The 7Li(p,n)7Be reaction, which leads to a soft neutron field, is often chosen as the neutron producing reaction used for accelerator-based boron neutron capture therapy (AB-BNCT). This study aims to design a compact beam shaping assembly (BSA) and auxiliary system for a 7Li(p,n)7Be reaction-based neutron source and to evaluate the relationship between the BSA design and the consequent neutron beam quality for further optimization.In this study, five types of moderator shapes for the BSA model were designed. Both the in-air and in-phantom figures of merit were considered to evaluate the performance of the BSA designs. It was found that the BSA with a bi-tapered and air-gapped design could generate a high-intensity epithermal neutron beam, which could be used to treat deep-seated brain tumors within a reasonable time.

Neutron yields of Be-9(p,xn) reactions and beam characterization for accelerator-based boron neutron capture therapy facility using MCNP6, PHITS, and GEANT4 simulation results

Neutron yields from 9Be(p,xn) reactions with a 2-cm thick beryllium target bombarded by proton beams of 5, 6, 7, 8, 9, and 10 MeV were investigated. Neutron beam characteristics through a pilot design of beam shaping assembly were calculated by using MCNP6, PHITS, and GEANT4. The neutron yield with a 10 MeV beam by MCNP6 was 7.7 times larger than values by the other codes, but close to the experimental data. The neutron spectrum and directionality were different among the codes. These differences could stem from different cross-section libraries and models used in the codes. The epithermal flux at the beam irradiation port by MCNP6 was 1.4 × 109 cm−2 s−1 for a proton current of 8 mA hitting the target. The ratio of thermal and epithermal flux was less than 0.01 and the forward directionality was 0.78. However, we suggest a new criterion regarding a ratio of fast and epithermal flux.

Design of a BNCT irradiation room based on proton accelerator and beryllium target

Preliminary studies for the design of an accelerator-based BNCT clinical facility are presented. The Beam Shaping Assembly neutron activation was evaluated experimentally and with Monte Carlo simulations. The activations of patient, air and walls in the room, the absorbed doses by the patient and the in-air dose distributions were evaluated. Based on these calculations, different walls compositions were tested to optimize the environmental conditions. Borated concrete, advantageously reducing the thermal flux in the room, was proven the best choice.

A simulation study on beam property of 124Sb–Be isotope-based neutron for BNCT

The 9Be(γ,n) neutrons with the energies at 21–24 keV generated by 1.691 MeV photons from 124Sb was investigated as a source of epithermal neutrons for BNCT, using PHITS code. A beam shaping assembly composed of 13 mm thick Be target, a gamma ray shield made of 30 cm thick Bi, and a reflector of 30 cm thick Pb satisfied the beam requirements of IAEA-TECDOC-1223. The needed 124Sb activity was estimated in the order of 1016–1017 Bq. Feasibility of BNCT using 124Sb–Be neutrons would be influenced by the capability of periodic supply of short-lived 124Sb (half-life: 60 days) with such high activity.

Monte Carlo simulation-based design of an electron-linear accelerator-based neutron source for boron neutron capture therapy

Characteristics of a beam-shaping assembly that utilizes photo-neutrons from irradiation of a tungsten target by electrons from an accelerator were examined to produce a beam of neutrons suitable for boron neutron capture therapy. The epithermal neutron flux per kilowatt of electron-beam power almost increased to a maximum as the energy of the initial electrons was increased to 42.5 MeV, but the fast-neutron dose and the photon dose per epithermal neutron hardly changed on varying the energy of the initial electrons.

ANALYSIS OF PARTICLE DISTRIBUTION IN A DOUBLE LAYER BEAM SHAPING ASSEMBLY RESULTED FROM 30 MEV-PROTON REACTIONS WITH BERYLLIUM TARGET USING THE PHITS PROGRAM

An analysis on the distribution of particle flux emanating from reactions of 30 MeV-proton with beryllium target in a double layer beam shaping assembly (BSA) has been carried out using the PHITS program. It studies important parameters relating to the distribution of proton, neutron, and gamma. It is revealed that reactions of proton and beryllium in double layer BSA produce fast neutrons and other protons, resulting from certain reactions, and recoil protons from the interactions of fast neutrons and hydrogen atoms. Fast neutrons are distributed around beryllium target, moderator, reflector, and collimator. They are moderated by Al and LiF material. Epithermal neutrons spread along the moderator, with a distribution that is tapering down as it approaches the end of the collimator (aperture). During its travel along the moderator, an epithermal neutron decreases in energy to become a thermal neutron. The spectrum of neutron beam produced by the double layer BSA is wide, which indicates that the neutron beam exiting the aperture consists of three kinds of neutrons, dominated by epithermal neutronswith energy range 1 eV – 10 keV.

The possibility of an appropriate neutron beam achievement for medical purposes based on GEANT4 calculations

Proton-induced reactions on the 9Be target are considered as a neutron source, and dependence of neutron yield on target thicknesses is investigated. The optimal thickness of the 9Be target with the design and optimization characteristics of a beam shaping assembly (BSA) for neutron flux from the thick target is studied with the GEANT4 program. To create the realistic model of the experiment, there are inserted two physics lists for nuclear and electromagnetic reactions. To get a high flux of neutrons had taken into account usage of special materials as moderators on the base of (n, 2n) nuclear reactions, as well as, moderators which will decrease the energy of neutrons to achieve the appropriate thermal/epithermal neutron flux. The creation of the system, which must be made from reflectors and moderators, is a necessity to explore the possibility of an appropriate neutron flux achievement for medical purposes, especially for boron neutron capture therapy (BNCT). GEANT4 simulations of this scientific paper describe the study of IBA’s C18/18 cyclotron-based neutron sources and its possible usage for therapies.

Characteristics of Thermal Neutron Flux Distribution in a Phantom Irradiated by Epithermal Neutron Beam from Double Layer Beam Shaping Assembly (DBSA)

A simulation study on the Double-layer Beam Shaping Assembly (DBSA) system has been carried out. This study used fast neutron beam resulting from reactions of 30 MeV protons with beryllium target. The MCNPX code was utilized to design the DBSA and the phantom as well as to calculate neutron flux on the phantom. The distribution of epithermal neutron flux and gamma in the DBSA and phantom were computed using the PHITS code. The spectrum of radiation beams generated by the DBSA shows the characteristics that the typical epithermal neutron flux of 1.0 x109 n/(cm2.s), the ratio of epithermal to the thermal and fast neutron flux of 344 and 85, respectively and the ratio of gamma dose to the epithermal neutron flux of 1.82 x 10-13 Gy.cm2. The test of epithermal neutron beams irradiation on the water phantom shows that epithermal neutrons are thermalized and penetrate the phantom up to 12 cm in depth. The maximum value of neutron flux is 1.1 x 109 n/(cm2.s) at a depth of 2 cm in phantom.

Feasibility study on the use of 230MeV proton cyclotron in proton therapy centers as a spallation neutron source for BNCT.

The feasibility of using 230MeV proton cyclotrons in proton therapy centers as a spallation neutron source for Boron Neutron Capture Therapy (BNCT) was investigated. BNCT is based on the neutron irradiation of a 10B-containing compound located selectively in tumor cells. Among various types of neutron generators, the spallation neutron source is a unique way to generate high-energy and high-flux neutrons. Neutron beam was generated by a proton accelerator via spallation reactions and then the produced neutron beam was shaped to be appropriate for BNCT. The proposed Beam Shaping Assembly (BSA) consists of different moderators, a reflector, a collimator, as well as thermal and gamma filters. In addition, the simulated Snyder head phantom was utilized to evaluate the dose distribution in tumor and normal tissue due to the irradiation by the designed beam. MCNPX2.6 Monte Carlo code was used to optimize BSA as well as evaluate dose evaluation. A BSA was designed. With the BSA configuration and a beam current of 104nA, epithermal neutron flux of 3.94×106 [n/cm2] can be achieved, which is very low. Provided that we use the beam current of 5.75μA, epithermal neutron flux of 2.18×108 [n/cm2] can be obtained and the maximum dose of 38.2 Gy-eq can be delivered to tumor tissue at 1.4cm from the phantom surface. Results for 230MeV protons show that with proposed BSA, proton beam current about 5.75μA is required for this purpose.

A feasibility study of the Iranian Sun mather type plasma focus source for neutron capture therapy using MCNP X2.6, Geant4 and FLUKA codes

The purpose of the current study was to evaluate a spectrum formulation set employed to modify the neutron spectrum of D-D fusion neutrons in a IS plasma focus device using GEANT4, MCNPX2.6, and FLUKA codes. The set consists of a moderator, reflector, collimator and filters of fast neutron and gamma radiation, which placed on the path of 2.45 MeV neutron energy. The treated neutrons eliminate cancerous tissue with minimal damage to other healthy tissue in a method called neutron therapy. The system optimized for a total neutron yield of 10 9 (n/s). The numerical results indicate that the GEANT4 code for the cubic geometry in the Beam Shaping Assembly 3 (BSA3) is the best choice for the energy of epithermal neutrons.

WITHDRAWN: Design of a new facility for Boron Neutron Capture Therapy based on the medical room of Tehran Research Reactor

Abstract A new beam line has been designed based on the use of medical room of Tehran Research Reactor (TRR) for Boron Neutron Capture Therapy (BNCT) using MCNP4C Monte Carlo code. The medical room is located behind the east wall of the reactor pool. The designed beam line is an in-pool Beam Shaping Assembly (BSA) which is considered between the reactor core and the medical room wall. It was found that the final designed BSA can provide 2.96×109 n/cm2.s epithermal neutron flux with acceptable beam contaminations.

Characteristics in Water Phantom of Epithermal Neutron Beam Produced by Double Layer Beam Shaping Assembly

A Double Layer Beam Shaping Assembly (DLBSA) was designed to produce epithermal neutrons for BNCT purposes. The Monte Carlo N-Particle eXtended program was used as the software to design the DLBSA and phantom. Distribution of epithermal neutron and gamma flux in the DLBSA and phantom and absorbed dose in the phantom were computed using the Particle and Heavy Ion Transport code System program. Testing results of epithermal neutron beam irradiation of the water phantom showed that epithermal neutrons were thermalized and penetrated the phantom up to a depth of 12 cm. The maximum value of the absorbed dose was 2 × 10-3 Gy at a depth of 2 cm in the phantom.

Optimization and analysis of neutron distribution on 30 MeV cyclotron-based double layer beam shaping assembly (DLBSA)

Optimization and analysis of neutron distribution on 30 MeV cyclotron-based double layer beam shaping assembly (DLBSA)

Beam Shaping Assembly Optimization for Boron Neutron Capture Therapy Facility Based on Cyclotron 30 MeV as Neutron Source

A design of beam shaping assembly (BSA) installed on cyclotron 30 MeV model neutron source for boron neutron capture therapy (BNCT) has been optimized using simulator software of Monte Carlo N-Particle Extended (MCNPX). The Beryllium target with thickness of 0.55 cm is simulated to be bombarded with 30 MeV of proton beam. In this design, the parameter regarding beam characteristics for BNCT treatment has been improved, which is ratio of fast neutron dose and epithermal neutron flux. TiF3 is replaced to 30 cm of 27Al as moderator, and 1.5 cm of 32S is combined with 28 cm of 60Ni as neutron filter. Eventually, this design produces epithermal neutron flux of 2.33 × 109, ratio between fast neutron dose and epithermal neutron flux of 2.12 × 10-13,ratio between gamma dose and epithermal neutron flux of 1.00 × 10-13, ratio between thermal neutron flux and epithermal neutron flux is 0.047, and ration between particle current and total neutron flux is 0.56.

Beam shaping assembly study for BNCT facility based on a 2.5\xa0MeV proton accelerator on Li target

A new study for a boron neutron capture therapy irradiation facility, based on a 2.5 MeV proton accelerator on a thick Li target as neutron converter, is presented here. The beam shaping assembly (BSA) modeling has been performed with the use of the MCNP5 Monte Carlo code. The fast (i.e., > 10 keV) neutron component yielded by the 7Li(p,n)7Be reaction is slowed down through TiF3 neutron spectrum shifter, while to obtain a high-quality epithermal neutron beam at the beam port exit additional layers for thermal neutrons removal and shielding of gamma rays were used. Moreover, 60Ni and Ti6Al14V were selected to filter out and further remove the residual fast neutron component, while cadmium was chosen as thermal neutrons absorber, and bismuth was selected for gamma rays shielding. The therapeutic effectiveness of the proposed BSA was evaluated by performing a set of dose-equivalent distribution calculations in a standard Snyder head phantom. The simulation results show that the proposed BSA modeling meets all the recommended by IAEA criteria and provides one possible technical choice for an accelerator-based BNCT irradiation facility in a hospital environment.

Investigating a proton beam-based neutron source for BNCT using the MCNP simulation

Works in this project are focused on the design and optimization of a beam shaping assembly (BSA) for boron neutron capture therapy (BNCT) based on a 30 MeV proton beam generator. The aim was to maximize the epithermal neutron flux and to prevent the background radiation which are required for the BNCT designation. A set of material and geometry simulations of neutron multiplier, moderator, reflector, and collimator was examined. The final configuration consists of 0.5 cm of beryllium as a p-n converter, 15 cm in radius of uranium as a neutron multiplier, 44 cm of TiF3 and 15 cm of Al2O3 as a first and second layer of moderator, 10 cm thickness of lead as a reflector, and lithium polyethylene as a collimator. According to the results of the calculation, the proposed cylinder BSA provides high epithermal neutron flux at the irradiation area.

Optimization of double layered beam shaping assembly using genetic algorithm

Abstract The genetic algorithm method is a new method used to obtain radiation beams that meet the IAEA requirements. This method is used in optimization of configurations and compositions of materials that compose double layered Beam Shaping Assembly (BSA). The double layered BSA is modeled as having two layers of material for each of the components, which are the moderator, reflector, collimator, and filter. Up to 21st generation, the optimization results in four (4) individuals having the capacity to generate the most optimum radiation beams. The best configuration, producing the most optimum radiation beams, is attained by using combinations of materials, that is by combining Al with either one of CaF2 and PbF2for moderator; combining Pb material with either Ni or Pb for reflector; combining Ni and either FeC or C for collimator, and FeC+LiF and Cd for fast and thermal neutron filter. The parameters of radiation resulted from the four configurations of double layer BSA adequately satisfy the standard of the IAEA.

Design and optimization of two-sided beam based on 7Li(p,n)7Be source using in BNCT for brain and liver tumors

Recent studies in BNCT have focused on investigating appropriate neutron sources based on accelerators. One of the common reactions based on accelerators for neutron production is7Li(p,n)7Be. In this paper we designed and optimized two-sided Beam Shaping Assembly composed of a moderator, a filter, a reflector and a collimator for the perpendicular neutrons with respect to the direction of the incident beam to provide an appropriate neutron beam in BNCT. Calculations for our design show, using a proton beam of 2.5 MeV with a current of 10 mA, will produce proper epithermal neutron flux in both sides of the system. The final optimized flux for the system was calculated to be 2.15×109n∕cm2.s for one side of BSA and the epithermal neutron flux on one of two sides has increased by about 32% with respect to the forward direction. All in-air licensed parameters proposed by the International Atomic Energy Agency (IAEA) have been established. The dose evaluation results and depth dose curves were presented for a simulated head phantom and a human phantom including the liver with a typical tumor. The results confirmed that the designed neutron source and BSAs, can potentially be used to treat deep-seated brain and liver tumors in BNCT.