Beam Shaping Assembly Design Research Articles

Double-layered beam shaping assembly design based on intelligent optimization method coupling neural network and genetic algorithm for BNCT

The beam shaping assembly (BSA) plays a crucial role in the facility of accelerator-based boron neutron capture therapy (AB-BNCT). The quality of the neutron beam utilized for treatment is directly influenced by the design of the BSA. However, conventional step-by-step optimization approaches often encounter challenges in achieving the global optimal solution, as they tend to converge towards local optima. To address this issue, this study proposed an intelligent optimization method that combines neural network and genetic algorithm. The proposed method was applied to optimize a double-layered BSA based on the neutron source resulting from a lithium target bombarding by a 2.8 MeV, 20 mA proton beam. The obtained optimal BSA solution parameters well met the IAEA-TECDOC-1223 report, while also exhibiting significantly higher epithermal neutron flux compared to alternative BSA designs. The performance of the epithermal neutron beam was assessed by calculating the dose distribution and clinical parameters in the Snyder head phantom. The findings suggest that this beam exhibits promising therapeutic potential for treating tumors.

Coin-structured tunable beam shaping assembly design for accelerator-based boron neutron capture therapy for tumors at different depths and sizes

Coin-structured tunable beam shaping assembly design for accelerator-based boron neutron capture therapy for tumors at different depths and sizes

Beam shaping assembly design of Li(p,n) neutron source with a rotating target for boron neutron capture therapy

With rapid development in recent years, the accelerator-based boron neutron capture therapy (AB-BNCT) has been paid more and more attention. Our team designed a set of AB-BNCT facility based on the Li(p,n) reaction. We suppose to use a radio frequency quadrupole field accelerator with a 2.8 MeV, 20 mA proton beam to bombard a rotating lithium target. The generated neutrons were moderated by a beam shaping assembly (BSA) to get an epithermal neutron beam for tumor treatment. This paper introduced the parameter calculation and analysis of back reflector, rotating gap and moderator in BSA, discussed the influence of the density of magnesium fluoride block as a moderator on the outgoing neutron beam in detail, and evaluated epithermal neutron beam with a water and Snyder phantom. Finally, it is concluded that a 20 cm lead as the back reflector, the rotation gap of 6 cm, and the density of magnesium fluoride blocks of above 2.5 g/cm3 could make the neutron beam meet the treatment needs. And the density of 2.8 g/cm3 as a compromise choice could obtain an epithermal neutron beam with good therapeutic potential with consideration of the processing difficulty and cost.

An AB-BNCT epithermal neutron source using 7Li(p,n)7Be reaction

A suitable neutron source is indispensable for boron neutron capture therapy (BNCT). This article proposes a design of beam shaping assembly (BSA) for an accelerator-based BNCT (AB-BNCT) epithermal neutron source facility using 7Li(p,n)7Be reaction, and the results show that all parameters of BSA meet the recommended values of International Atomic Energy Agency (IAEA). The dose distribution and parameters in the Snyder head phantom are calculated using the Monte Carlo simulations to evaluate the performance of the epithermal neutron beam.

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.

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 design of 7Li(p,n)7Be neutron source for boron neutron capture therapy of deep-seated tumor

The development of a medical facility for boron neutron capture therapy at Budker Institute of Nuclear Physics is under way. The neutron source is based on a tandem accelerator with vacuum insulation and lithium target. The proposed accelerator is conceived to deliver a proton beam around 10 mA at 2.3 MeV proton beam.To deliver a therapeutic beam for treatment of deep-seated tumors a typical Beam Shaping Assembly (BSA) based on the source specifications has been explored. In this article, an optimized BSA based on the 7Li(p,n)7Be neutron production reaction is proposed.To evaluate the performance of the designed beam in a phantom, the parameters and the dose profiles in tissues due to the irradiation have been considered.In the simulations, we considered a proton energy of 2.3 MeV, a current of 10 mA, and boron concentrations in tumor, healthy tissues and skin of 52.5 ppm, 15 ppm and 22.5 ppm, respectively. It is found that, for a maximum punctual healthy tissue dose seated to 11 RBE-Gy, a mean dose of 56.5 RBE Gy with a minimum of 52.2 RBE Gy can be delivered to a tumor in 40 min, where the therapeutic ratio is estimated to 5.38.All of these calculations were carried out using the Monte Carlo MCNP code.

Design of beam shaping assembly based on 3.5 MeV radio-frequency quadrupole proton accelerator for boron neutron capture therapy

Boron neutron capture therapy (BNCT) is expected to be an effective method of improving the treatment results on malignant brain glioma and malignant melanoma, for which no successful treatment has been developed so far. The beam shaping assembly (BSA) of accelerator-based boron neutron capture therapy (A-BNCT) consists of a moderator, a reflector, gamma and thermal neutron shielding and a collimator. The BSA moderates the fast neutron produced in target to epithermal energy range. Design of BSA is one of the key jobs in BNCT project. An optimized study was conducted to design a beam shaping assembly for BNCT facility based on 3.5 MeV 10 mA radio-frequency quadrupole proton accelerator at Dongguan Neutron Science Center. In this simulation work, the neutron produced from the 7Li (p, n) 7Be reaction by 3.5 MeV proton is adopted as a neutron source term. In order to search for an optimized beam shaping assembly for accelerator-based BNCT, Monte Carlo simulation is carried out based on the parameters of moderator material and structure, the Gamma shielding, and the thermal neutron filter in the beam shaping assembly. The beam shaping assembly in this work consists of various moderator materials, teflon as reflector, Bi as gamma shielding, 6Li as thermal neutron filter, and lithium polyethylene as collimator. After comparing the simulation results of Fluental and LiF moderator materials, the beam shaping assembly configuration based on sandwich Fluental-LiF configuration is proposed. The sandwich Fluental-LiF configuration is made up of Fluental and LiF layer by layer, like a sandwich structure, and each layer is 2 cm thick. According to the beam quality requirement of the IAEA-tecdoc-1223 report, the optimized epithermal neutron flux in air at the exit of BSA of the sandwich Fluental-LiF configuration is 9.14×108 n/(cm2·s), which is greater than those of the Fluental configuration (7.81×108 n/(cm2·s)) and LiF configuration (8.79×108 n/(cm2·s)), when the ratio of fast neutron component to gamma ray component to thermal neutron is less than the limiting value of IAEA recommendation. Subsequently, the depth distribution of the equivalent doses in the Snyder head phantom is calculated to evaluate the treatment characteristic. The simulation results show that the therapy rate of the beam shaping assembly based on the sandwich Fluental-LiF configuration is basically equal to that of the Fluental configuration and better than that of the LiF configuration, and the therapy time is less than that of the Fluental configuration. This means that the beam shaping assembly based on the sandwich Fluental-LiF configuration is one of the suitable options for our accelerator-based BNCT.

Design and dosimetric evaluation of beam shaping assembly for BNCT of compact D–T neutron generator by Monte Carlo simulation

In this work, FLUKA design of a beam shaping assembly (BSA) has been carried out for sealed D–T neutron generator to have application in BNCT (boron neutron capture therapy). Out of several materials, the design has been optimized for tungsten multiplier, D2O moderator, TiF3 fast neutron filter, cadmium thermal neutron filter and bismuth gamma filter surrounded by lead reflector. The designed BSA would provide appropriate beam intensity and quality at lower source strength. The dosimetric evaluation of BSA carried out with Snyder head phantom is found to be satisfactory for treatment of deeply seated tumor in 115 min. The proposed design of BSA for compact D–T neutron generator can be installed in hospital premises for BNCT treatment with better social acceptance.

2.5 MeV CW 4-vane RFQ accelerator design for BNCT applications

Boron Neutron Capture Therapy (BNCT) promises a bright future in cancer therapy for its highly selective destruction of cancer cells, using the 10B +n→7Li +4 He reaction. It offers a more satisfactory therapeutic effect than traditional methods for the treatment of malignant brain tumors, head and neck cancer, melanoma, liver cancer and so on. A CW 4-vane RFQ, operating at 162.5 MHz, provides acceleration of a 20 mA proton beam to 2.5 MeV, bombarding a liquid lithium target for neutron production with a soft neutron energy spectrum. The fast neutron yield is about 1.73×1013n∕s. We preliminarily develop and optimize a beam shaping assembly design for the 7Li(p, n)7Be reaction with a 2.5 MeV proton beam. The epithermal neutron flux simulated at the beam port will reach up to 1.575×109 n/s/cm2. The beam dynamics design, simulation and benchmark for 2.5 MeV BNCT RFQ have been performed with both ParmteqM (V3.05) and Toutatis, with a transmission efficiency higher than 99.6% at 20 mA. To ease the thermal management in the CW RFQ operation, we adopt a modest inter-vane voltage design (U=65 kV), though this does increase the accelerator length (reaching 5.2 m). Using the well-developed 3D electromagnetic codes, CST MWS and ANSYS HFSS, we are able to deal with the complexity of the BNCT RFQ, taking the contribution of each component in the RF volume into consideration. This allows us to optimize the longitudinal field distribution in a full-length model. Also, the parametric modeling technique is of great benefit to extensive modifications and simulations. In addition, the resonant frequency tuning of this RFQ is studied, giving the tuning sensitivities of vane channel and wall channel as −16.3 kHz/°C and 12.4 kHz/°C, respectively. Finally, both the multipacting level of this RFQ and multipacting suppressing in the coaxial coupler are investigated.

Optimization of Beam Shaping Assembly design for Boron Neutron Capture Therapy based on a transportable proton accelerator

The optimization of a Beam Shaping Assembly design for Boron Neutron Capture Therapy (BNCT), based on a commercial available proton accelerator, has been simulated. The primary goal is to improve the flux of the epithermal neutrons, which is the major drawback in all designed BNCT facilities with portable neutron source, satisfying simultaneously all the other relevant parameters.A BNCT facility has been simulated using the MCNP4B Monte Carlo code. A wide set of material were examined as moderators, while three different materials are used as fast neutron, gamma ray and thermal neutrons filters.Fast neutrons from 9Be(p,n)9B reaction are moderated through the 7LiF and TiF3 moderators and further reduced using 60Ni as fast neutron filter. The undesired gamma rays and thermal neutrons are removed using Bi and Cd filters respectively. The therapeutic efficacy of the proposed facility was calculated through the dosimetric evaluation in a head phantom.According to the results of the calculations the proposed unit satisfies the recommended by IAEA parameters. Only the flux of the epithermal neutrons remains below the recommended threshold, but is significantly improved.

Geant4 Simulations of a Beam Shaping Assembly Design and Optimization for Thermal/Epithermal Neutrons

Geant4 Simulations of a Beam Shaping Assembly Design and Optimization for Thermal/Epithermal Neutrons

A 13C(d,n)-based epithermal neutron source for Boron Neutron Capture Therapy

PurposeBoron Neutron Capture Therapy (BNCT) requires neutron sources suitable for in-hospital siting. Low-energy particle accelerators working in conjunction with a neutron producing reaction are the most appropriate choice for this purpose. One of the possible nuclear reactions is 13C(d,n)14N. The aim of this work is to evaluate the therapeutic capabilities of the neutron beam produced by this reaction, through a 30mA beam of deuterons of 1.45MeV. MethodsA Beam Shaping Assembly design was computationally optimized. Depth dose profiles in a Snyder head phantom were simulated with the MCNP code for a number of BSA configurations. In order to optimize the treatment capabilities, the BSA configuration was determined as the one that allows maximizing both the tumor dose and the penetration depth while keeping doses to healthy tissues under the tolerance limits. ResultsSignificant doses to tumor tissues were achieved up to ∼6cm in depth. Peak doses up to 57Gy-Eq can be delivered in a fractionated scheme of 2 irradiations of approximately 1h each. In a single 1h irradiation, lower but still acceptable doses to tumor are also feasible. ConclusionsTreatment capabilities obtained here are comparable to those achieved with other accelerator-based neutron sources, making of the 13C(d,n)14N reaction a realistic option for producing therapeutic neutron beams through a low-energy particle accelerator.

Optimization of a Beam Shaping Assembly Design for Boron Neutron Capture Cancer Therapy Facility Based on 30 MeV Cyclotron

A series of simulations has been carried out using a Monte Carlo N Particle X code to find out the final composition and configuration of a neutron Beam Shaping Assembly (BSA) to moderate the fast neutron flux which is generated from the thick disk-type beryllium target. The final configuration for neutron BSA design included 35 cm lead as reflector, 39 cm alumina as moderator, 8.2 cm lithium fluoride as fast neutron filter and 0.5 cm boron carbide as thermal neutron filter. Bismuth, lead fluoride, and lead were chosen as the aperture, reflector, and gamma shielding, respectively. The disk-type of beryllium target is 19 cm in diameter with 0.5 cm thickness which is covered by copper plate to hold the water pressured coolant. A higher yield of neutron production requires a higher intensity of proton beams, which generate much heats and causes the target material to melt. Therefore, it is useful to consider the temperature distribution on the target material with flowing water coolant by means of computer modeling while designing the target. ANSYS-Fluent code will be used to estimate the thermal transfer and heat calculation in a solid target during beam irradiation. Epithermal neutron flux in the suggested design were 1,03x10<sup>9</sup> n/cm<sup>2</sup> s, with almost all IAEA parameters for BNCT BSA design has been satisfied.

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.

An evaluation on the design of beam shaping assembly based on the D-T reaction for BNCT

Boron Neutron Capture Therapy (BNCT) can be achieved by using a compact neutron generator such as a compact D-T neutron source, in which neutron energy must be in the epithermal energy range with sufficient flux. For these requirements, a Beam Shaping Assembly (BSA) is needed. In this paper, three BSA designs based on the D-T reaction for BNCT are discussed. It is found that the BSA configuration designed by Rasouli et al. satisfies all of the International Atomic Energy Agency (IAEA) criteria. It consists of 14 cm uranium as multiplier, 23 cm TiF3 and 36 cm Fluental as moderator, 4 cm Fe as fast neutron filter, 1 mm Li as thermal neutron filter, 2.6 cm Bi as gamma ray filter, and Pb as collimator and reflector. It is also found that use of specific filters is important for removing the fast and thermal neutrons and gamma contamination. Moreover, an appropriate neutron source plays a key role in providing a proper epithermal flux.

Evaluation of performance of an accelerator-based BNCT facility for the treatment of different tumor targets

PurposeEncouraging Boron Neutron Capture Therapy (BNCT) clinical results obtained in recent years have stimulated intense research to develop accelerator-based neutron sources to be installed in clinical facilities. In this work an assessment of an accelerator-based BNCT facility for the treatment of different tumor targets was performed, comparing the accelerator-derived results with reported reactor-based trials under similar conditions and subjected to the same clinical protocols. Materials and methodsA set of real image studies was used to cover clinical-like cases of brain and head-and-neck tumors. In addition, two clinical cases of malignant nodular melanoma treated at the RA-6 BNCT facility in Argentina were used to thoroughly compare the clinical dosimetry with the accelerator-derived results. ResultsThe minimum weighted dose delivered to the clinical target volume was higher than 30 Gy and 14 Gy for the brain tumor and head-and-neck cases, respectively, in agreement with those achieved in clinical applications. For the melanoma cases, the minimum tumor doses were equal or higher than those achieved with the RA-6 reactor for identical field orientation and protocol. The whole-body dose assessment showed that the maximum photon-equivalent doses for those normal organs close to the beam direction were below the upper limits considered in the protocols used in the present work. ConclusionsThe obtained results indicate not only the good performance of the proposed beam shaping assembly design associated to the facility but also the potential applicability of accelerator-based BNCT in the treatment of both superficial and deep-seated tumors.

Optimization of a neutron production target and a beam shaping assembly based on the 7Li( p, n) 7Be reaction for BNCT

In this work a thick LiF target was studied through the 7Li( p, n) 7Be reaction as a neutron source for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT) to provide a testing ground for numerical simulations aimed at producing an optimized neutron production target and beam shaping assembly design. Proton beams in the 1.88–2.0 MeV energy range were produced with the tandem accelerator TANDAR ( TANDem ARgentino) at the Comisión Nacional de Energía Atómica (CNEA) in Buenos Aires, Argentina. A cylindrical water-filled head-phantom, containing a boric acid sample, was irradiated to study the resulting neutron flux. The dose deposited in the boric acid sample was inferred through the Compton-suppressed detection of the gamma radiation produced from the 10B( n, αγ) 7Li capture reaction. The thermal neutron flux was evaluated using bare and Cd-covered activation gold foils. In all cases, Monte Carlo simulations have been done showing good agreement with the experimental results. Extensive MCNP simulation trials have then been performed after the preliminary calculation tool validation in order to optimize a neutron beam shaping assembly. These simulations include a thick Li metal target (instead of LiF), a whole-body phantom, two different moderator–reflector assemblies (Al/AlF 3/LiF, Fluental ®, as moderator and lead as reflector and a combination of Al, PTFE (polytetrafluoroethylene) and LiF as moderator and lead as reflector) and the treatment room. The doses were evaluated for proton bombarding energies of 1.92 MeV (near to the threshold of the reaction), 2.0 MeV, 2.3 MeV (near the reaction resonance) and 2.5 MeV, and for three Fluental ® and Al/PTFE/LiF moderator thicknesses (18, 26 and 34 cm). In a later instance, the effect of the specific skin radiosensitivity (an RBE of 2.5 for the 10B( n, α) 7Li reaction) and a 10B uptake 50% greater than the healthy tissue one, was considered for the scalp. To evaluate the doses in the phantom, a comparison of the different assemblies and beam energies was done using a Tumor Control Probability (TCP) model. The simulations show the advantage of irradiating with near-resonance-energy protons (2.3 MeV) because of the relatively high neutron yield at this energy, which at the same time keeps the fast neutron healthy tissue dose limited and leads to the shortest treatment times. A moderator of 34 cm length (either Fluental or Al/PTFE/LiF) has shown the best performance among the studied cases.

An accelerator-based epithermal neutron beam design for BNCT and dosimetric evaluation using a voxel head phantom

The beam shaping assembly design has been investigated in order to improve the epithermal neutron beam for accelerator-based boron neutron capture therapy in intensity and quality, and dosimetric evaluation for the beams has been performed using both mathematical and voxel head phantoms with MCNP runs. The neutron source was assumed to be produced from a conventional 2.5 MeV proton accelerator with a thick (7)Li target. The results indicate that it is possible to enhance epithermal neutron flux remarkably as well as to embody a good spectrum shaping to epithermal neutrons only with the proper combination of moderator and reflector. It is also found that a larger number of thermal neutrons can reach deeply into the brain and, therefore, can reduce considerably the treatment time for brain tumours. Consequently, the epithermal neutron beams designed in this study can treat more effectively deep-seated brain tumours.