A carefully made treatment plan is of paramount importance in order to achieve satisfactory results in treatments based on Boron Neutron Capture Therapy. Different source configurations and positions have to be analyzed, and based on the different dose maps that can be computed, an optimal treatment should be chosen. Nowadays the dose maps are computed using slow and computationally intensive Monte Carlo simulations, which hinder the formulation of an optimized treatment plan. This work proposes a machine learning algorithm based on a convolutional neural network that accelerates the convergence of Monte Carlo neutron transport simulations, drastically reducing computation time without loss of accuracy. A dataset of Monte Carlo simulation was made and used for the training of the proposed model. 97% of the voxels of the set of testing simulations had errors lower than 5% when processed by the neural network, and inference times were reduced by three orders of magnitude. In the future, this tool could allow a real optimization of treatment plans.

Globally, there are several AB-BNCT facilities, either operational and already treating patients and others still under development. These facilities range from high-energy 30 MeV cyclotrons using the 9Be(p,n) reaction, medium-energy RFQ-DTL accelerators operating at 8-10 MeV with the same reaction, low-energy electrostatic machines (Tandem and single-ended) using the 7Li(p,n) reaction at approximately 2.5 MeV. Additionally, the low-energy ESQ accelerator developed in Argentina, employs the 9Be(d,n) or the 13C(d,n) reactions at 1.45 MeV. This paper presents updated insights into Argentina's AB-BNCT project while also providing a global overview of AB-BNCT developments.

(1) Background: The CT-based attenuation correction of SPECT images is essential for obtaining accurate quantitative images in cardiovascular imaging. However, there are still many SPECT cameras without associated CT scanners throughout the world, especially in developing countries. Performing additional CT scans implies troublesome planning logistics and larger radiation doses for patients, making it a suboptimal solution. Deep learning (DL) offers a revolutionary way to generate complementary images for individual patients at a large scale. Hence, we aimed to generate linear attenuation coefficient maps from SPECT emission images reconstructed without attenuation correction using deep learning. (2) Methods: A total of 384 SPECT myocardial perfusion studies that used 99mTc-sestamibi were included. A DL model based on a 2D U-Net architecture was trained using information from 312 patients. The quality of the generated synthetic attenuation correction maps (ACMs) and reconstructed emission values were evaluated using three metrics and compared to standard-of-care data using Bland–Altman plots. Finally, a quantitative evaluation of myocardial uptake was performed, followed by a semi-quantitative evaluation of myocardial perfusion. (3) Results: In a test set of 66 test patients, the ACM quality metrics were MSSIM = 0.97 ± 0.001 and NMAE = 3.08 ± 1.26 (%), and the reconstructed emission quality metrics were MSSIM = 0.99 ± 0.003 and NMAE = 0.23 ± 0.13 (%). The 95% limits of agreement (LoAs) at the voxel level for reconstructed SPECT images were: [−9.04; 9.00]%, and for the segment level, they were [−11; 10]%. The 95% LoAs for the Summed Stress Score values between the images reconstructed were [−2.8, 3.0]. When global perfusion scores were assessed, only 2 out of 66 patients showed changes in perfusion categories. (4) Conclusion: Deep learning can generate accurate attenuation correction maps from non-attenuation-corrected cardiac SPECT images. These high-quality attenuation maps are suitable for attenuation correction in myocardial perfusion SPECT imaging and could obviate the need for additional imaging in standalone SPECT scanners.

Existing and active low-energy Accelerator-Based BNCT programs worldwide will be reviewed and compared. In particular, the program in Argentina will be discussed which consists of the development of an Electro-Static-Quadrupole (ESQ) Accelerator-Based treatment facility. The facility is conceived to operate with the deuteron-induced reactions 9Be(d,n)10B and 13C(d,n)14N at 1.45 MeV deuteron energy, as neutron sources. Neutron production target development status is specified. The present status of the construction of the new accelerator development laboratory and future BNCT centre is shown.

Aim: This work aims at giving an updated report of the worldwide status of Accelerator-Based BNCT (AB-BNCT).Background: There is a generalized perception that the availability of accelerators installed in hospitals, as neutron sources, may be crucial for the advancement of BNCT. Accordingly, in recent years a significant effort has started to develop such machines.Materials and methods: A variety of possible charged-particle induced nuclear reactions and the characteristics of the resulting neutron spectra are discussed along with the worldwide activity in suitable accelerator development.Results: Endothermic Li-7(p,n)Be-7 and Be-9(p,n)B-9 and exothermic Be-9(d,n)B-10 are compared. In addition to having much better thermo-mechanical properties than Li, Be as a target leads to stable products. This is a significant advantage for a hospital-based facility. Be-9(p,n)B-9 needs at least 4-5 MeV bombarding energy to have a sufficient yield, while Be-9(d,n)B-10 can be utilized at about 1.4 MeV, implying the smallest possible accelerator. This reaction operating with a thin target can produce a sufficiently soft spectrum to be viable for AB-BNCT. The machines considered are electrostatic single ended or tandem accelerators or radiofrequency quadrupoles plus drift tube Linacs.Conclusions: Li-7(p,n)Be-7 provides one of the best solutions for the production of epithermal neutron beams for deep-seated tumors. However, a Li-based target poses significant technological challenges. Hence, Be has been considered as an alternative target, both in combination with (p,n) and (d,n) reactions. Be-9(d,n)B-10 at 1.4 MeV, with a thin target has been shown to be a realistic option for the treatment of deep-seated lesions. (C) 2014 Greater Poland Cancer Centre. Published by Elsevier Sp. z o.o. All rights reserved.

In this work we provide some information on the present status of accelerator-based BNCT (AB-BNCT) worldwide and subsequently concentrate on the recent accelerator technology developments in Argentina.

El presente trabajo se enmarca dentro de un proyecto de la Comision Nacional de Energia Atomica para el desarrollo en Argentina de la terapia por captura neutronica en boro o BNCT (por Boron Neutron Capture Therapy) basada en aceleradores de particulas. En particular se describe aqui la metodologia seguida para del diseno de una sala de irradiacion de pacientes que, desde el punto de vista del blindaje, se ajuste a los requerimientos de la Autoridad Regulatoria Nuclear Argentina (ARN) en la materia. Con este fin se partio de un blanco de produccion, moderacion y conformacion del haz de neutrones (o BSA por Beam Shaping Assembly), con geometria sencilla y para la reaccion 7Li(p,n)7Be. Considerando este BSA se realizo un estudio por simulaciones Monte Carlo (utilizando el codigo MCNP) de la radiacion de fuga (neutrones y fotones) a traves de las caras del mismo con el fin de disenar un blindaje recubriendo su superficie. Con el BSA recubierto se procedio al diseno de la sala de irradiacion de pacientes suponiendo una utilizacion con carga de trabajo maxima y la ocupacion continua de los locales vecinos. Se llego a un diseno preliminar con paredes de hormigon en donde la tasa de dosis en el exterior llega, en orden de magnitud, a la restriccion de diseno para el publico (10-4 mSv/h) y que satisface holgadamente las restricciones de diseno para el trabajador (3×10-3 mSv/h). Finalmente se presentan las primeras evaluaciones de la radiacion de fuga de dos nuevos BSA, uno nuevo para la reaccion 7Li(p,n)7Be y otro para la reaccion 9Be(d,n)10B. Palabras claves: radioterapia, BNCT con aceleradores, blindaje, neutrones, sala de tratamiento, simulaciones Monte Carlo

(7)Li(p,n)(7)Be is an endothermic reaction and working near its threshold (1.88 MeV) has the advantage of neutron spectra with maximum energies of about 100 keV, considerably lower than at higher beam energies, or than using other neutron-producing reactions or as for the uranium fission spectrum, relevant for BNCT based on nuclear reactors. With this primary energy it is much easier to obtain the energies needed for treating deep seated tumors by BNCT (about 10 keV). This work studies bombarding energies up to 2.05 MeV, different beam incidence angles and the effect of the undesirable gamma production via the (7)Li(p,γp') (7)Li reaction.

In the frame of accelerator-based BNCT, the Be-9(d,n)B-10 reaction was investigated as a possible source of epithermal neutrons. In order to determine the configuration in terms of bombarding energy, target thickness and Beam Shaping Assembly (BSA) design that results in the best possible beam quality, a systematic optimization study was carried out. From this study, the optimal configuration resulted in tumor doses >= 40 Gy-Eq, with a maximum value of 51 Gy-Eq at a depth of about 2.7 cm, in a 60 min treatment.The optimal configuration was considered for the treatment planning assessment of a real Glioblastoma Multiforme case. From this, the resulted dose performances were comparable to those obtained with an optimized Li-7(p,n)-based neutron source, under identical conditions and subjected to the same clinical protocol. (C) 2013 Elsevier Ltd. All rights reserved.

The activity in accelerator development for accelerator-based BNCT (AB-BNCT) both worldwide and in Argentina is described. Projects in Russia, UK, Italy, Japan, Israel, and Argentina to develop AB-BNCT around different types of accelerators are briefly presented. In particular, the present status and recent progress of the Argentine project will be reviewed. The topics will cover: intense ion sources, accelerator tubes, transport of intense beams, beam diagnostics, the (9)Be(d,n) reaction as a possible neutron source, Beam Shaping Assemblies (BSA), a treatment room, and treatment planning in realistic cases.

A numerical optimization of a Beam Shaping Assembly (BSA) for Accelerator Based-Boron Neutron Capture Therapy (AB-BNCT) has been performed. The reaction 7Li(p,n)7Be has been considered using a proton beam on a lithium fluoride target. Proton energy and the dimensions of a simple BSA geometry have been varied to obtain a set of different configurations. The optimal configuration of this set is shown.

In the frame of accelerator-based BNCT, the 9Be(d,n)10B reaction was investigated as a possible source of epithermal neutrons. In order to determine the configuration in terms of bombarding energy, target thickness and Beam Shaping Assembly (BSA) design that results in the best possible beam quality, a systematic optimization study was carried out. From this study, the optimal configuration resulted in tumor doses ≥40Gy-Eq, with a maximum value of 51Gy-Eq at a depth of about 2.7cm, in a 60min treatment.

The 9 Be(d,n) 10 B reaction as a neutron source for BNCT María E. Capoulat

We highlight some of the results of an ongoing program at the National Atomic Energy Commission (CNEA) in Argentina to develop low energy (0.2 to 2.5 MeV), high current (30-100mA) proton and deuteron electrostatic accelerators for nuclear and medical applications. This activity aims at developing: 1) Low-energy (200 keV) high-current (100mA) deuteron accelerators for D(d,n) and T(d,n) for neutron production for various nuclear applications, among them the injection of a subcritical reactor. 2) The development of a 700kV folded tandem for neutron production using the 9Be(d,n) reaction. 3) The development of a folded 1.2-1.4 MV tandem for epithermal neutron production through the 7Li(p, n) reaction. At the same time this machine can be operated as single-ended with a positive ion source at the terminal to produce 1.4 MeV deuteron beams for the 9Be(d, n) reaction. Development and progress have been made in the areas of mechanical, electromechanical and electronics components (structures, alternators,HV supplies, control systems, etc), ion sources, accelerator tubes, 3D electrostatic and selfconsistent beam transport simulations, high power neutron production targets.

Within the framework of accelerator based Boron Neutron Capture Therapy, a project to develop a folded Tandem-ElectroStatic-Quadrupole accelerator is under way at the Atomic Energy Commission of Argentina.The proposed accelerator is designed to deliver a 30 mA current of protons of up to 2.5 MeV.This work explores the production of neutrons by the 7 Li(p,n) 7 Be reaction in a near threshold ( 1.88MeV) energy regime to obtain neutron beams to treat deep seated tumors.Results show that treatments of high quality can be obtained in this regime.

PURPOSE:Encouraging 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 METHODS:A 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.RESULTS:The 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.CONCLUSIONS:The 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.

There has been increasing interest in combining Boron Neutron Capture Therapy (BNCT) with standard radiotherapy, either concomitantly or as a BNCT treatment of a recurrent tumor that was previously irradiated with a medical electron linear accelerator (LINAC). In this work we report the simulated dosimetry of treatments combining X-rays and BNCT

In the range of low bombarding energies (less than about 1.5 MeV) the (9)Be(d,n)(10)B reaction produces neutron spectra that can be moderated depending on the choice of the target thickness and the deuteron bombarding energy. In this work, a Monte Carlo simulation study to determine the capability of this reaction to deliver enough dose to efficiently control both skin and deep seated tumors has been performed by means of MCNP calculations using eight optimized (9)Be targets.

Within the frame of an ongoing project to develop a folded Tandem-Electrostatic-Quadrupole accelerator facility for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT) a theoretical study was performed to assess the treatment planning capability of different configurations of an optimized beam shaping assembly for such a facility. In particular this study aims at evaluating treatment plans for a clinical case of Glioblastoma.