Accelerator-based BNCT

Development of an affine transformation based treatment control system for accelerator based boron neutron capture therapy

This study developed and validated an adaptive treatment control system based on affine transformation for accelerator-based boron neutron capture therapy. Accelerator-based boron neutron capture therapy is a form of targeted radiotherapy that uses boron-10 to label tumor cells. When these boron-rich cells interact with neutrons, they produce high-linear energy transfer alpha particles and lithium-7 particles, effectively destroying the tumor cells with precision. The newly developed treatment control system integrates real-time stereoscopic x-ray imaging technology, enabling dynamic adjustments to the treatment plan by continuously monitoring changes in tumors and surrounding tissues. To optimize treatment accuracy, the system employs an affine transformation algorithm, ensuring precise dose delivery and accurate patient positioning. Positioning test results demonstrate that the system excels in its core functionality of ensuring patient positioning accuracy, significantly improving treatment adaptability while minimizing damage to healthy tissues. In addition, the study introduces the accelerator-based boron neutron capture therapy device independently designed and constructed by Lanzhou University. This includes a detailed description of the system's architecture, algorithms, and the principles behind its safety interlock functions. Spatial positioning tests of the device confirmed its high overall positioning accuracy, validating the system's reliability and highlighting its potential for broader applications in cancer treatment.

Influence of lung physical density on dose calculation in boron neutron capture therapy for malignant pleural mesothelioma

The boron neutron capture therapy treatment planning systems such as SERA and TSUKUBA Plan, which are mainly based on the Monte Carlo method, require the lung physical density and composition of the tissue for the dose calculation. However, the physical density and composition of lungs may change because of diseases such as pneumonia and emphysema. We investigated the effect of the lung physical density on the neutron flux distribution and dose for the lung and tumor.

Construction of targeted 10B delivery agents and their uptake in gastric and pancreatic cancer cells

Boron Neutron Capture Therapy (BNCT) is a new binary radiation therapy for tumor tissue, which kills tumor cells with neutron capture reaction. Boron neutron capture therapy has become a technical means for glioma, melanoma, and other diseases has been included in the clinical backup program. However, BNCT is faced with the key problem of developing and innovating more efficient boron delivery agents to solve the targeting and selectivity. We constructed a tyrosine kinase inhibitor-L-p-boronophenylalanine (TKI-BPA) molecule, aiming to improve the selectivity of boron delivery agents by conjugating targeted drugs while increasing the molecular solubility by adding hydrophilic groups. It shows excellent selectivity in differential uptake of cells, and its solubility is more than 6 times higher than BPA, leading to the saving of boron delivery agents. This modification method is effective for improving the efficiency of the boron delivery agent and is expected to become a potential alternative with high clinical application value.

Neutron-gamma dosimetry for BNCT using field oxide transistors with gadolinium oxide as neutron converter layer

PURPOSE

A new type of electronic dosimeter is presented, capable of discerning between the doses of gamma photons and neutrons in a mixed beam as found in boron neutron capture therapy (BNCT). We introduce a real-time dosimeter based on a thick gate field oxide field effect transistor (FOXFET) covered with a neutron converter layer containing gadolinium.

METHODS

To sensitize the FOXFET dosimeter to neutron fluxes, a converter layer containing gadolinium oxide particles embedded in photoresines was deposited over the sensor surface. Mixed neutron-gamma field configurations with different neutron energy spectra were used to assess the FOXFET response, considering different thicknesses of the neutron converter layer.

RESULTS

The total gamma sensitivity of the devices resulted to be 43 mV/Gy. The responses of sensors with different converter layer thicknesses irradiated with different neutron spectra are simulated using GEANT4 code. The response to photons is not significantly modified with thin conversion layers when used in water medium.

CONCLUSIONS

A real-time dosimeter comprising a pair of FOXFET sensors-only one of them with a gadolinium neutron converter layer-allows the simultaneous measurement of gamma dose and neutron flux during BNCT irradiations.

A Critical Review of Radiation Therapy: From Particle Beam Therapy (Proton, Carbon, and BNCT) to Beyond

In this paper, we discuss the role of particle therapy—a novel radiation therapy (RT) that has shown rapid progress and widespread use in recent years—in multidisciplinary treatment. Three types of particle therapies are currently used for cancer treatment: proton beam therapy (PBT), carbon-ion beam therapy (CIBT), and boron neutron capture therapy (BNCT). PBT and CIBT have been reported to have excellent therapeutic results owing to the physical characteristics of their Bragg peaks. Variable drug therapies, such as chemotherapy, hormone therapy, and immunotherapy, are combined in various treatment strategies, and treatment effects have been improved. BNCT has a high dose concentration for cancer in terms of nuclear reactions with boron. BNCT is a next-generation RT that can achieve cancer cell-selective therapeutic effects, and its effectiveness strongly depends on the selective ¹⁰B accumulation in cancer cells by concomitant boron preparation. Therefore, drug delivery research, including nanoparticles, is highly desirable. In this review, we introduce both clinical and basic aspects of particle beam therapy from the perspective of multidisciplinary treatment, which is expected to expand further in the future.

Aza-BODIPY: A New Vector for Enhanced Theranostic Boron Neutron Capture Therapy Applications

Boron neutron capture therapy (BNCT) is a radiotherapeutic modality based on the nuclear capture of slow neutrons by stable ¹⁰B atoms followed by charged particle emission that inducing extensive damage on a very localized level (<10 μm). To be efficient, a sufficient amount of ¹⁰B should accumulate in the tumor area while being almost cleared from the normal surroundings. A water-soluble aza-boron-dipyrromethene dyes (BODIPY) fluorophore was reported to strongly accumulate in the tumor area with high and BNCT compatible Tumor/Healthy Tissue ratios. The clinically used ¹⁰B-BSH (sodium borocaptate) was coupled to the water-soluble aza-BODIPY platform for enhanced ¹⁰B-BSH tumor vectorization. We demonstrated a strong uptake of the compound in tumor cells and determined its biodistribution in mice-bearing tumors. A model of chorioallantoic membrane-bearing glioblastoma xenograft was developed to evidence the BNCT potential of such compound, by subjecting it to slow neutrons. We demonstrated the tumor accumulation of the compound in real-time using optical imaging and ex vivo using elemental imaging based on laser-induced breakdown spectroscopy. The tumor growth was significantly reduced as compared to BNCT with ¹⁰B-BSH. Altogether, the fluorescent aza-BODIPY/¹⁰B-BSH compound is able to vectorize and image the ¹⁰B-BSH in the tumor area, increasing its theranostic potential for efficient approach of BNCT.

Status of low-energy accelerator-based BNCT worldwide and in Argentina

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.

Evaluation of the characteristics of the neutron beam of a linac-based neutron source for boron neutron capture therapy

The linac-base neutron source "iBNCT" developed by the Tsukuba team has begun to generate a large intensity of neutrons. To confirm the applicability of the device to BNCT, several characteristic measurements have been implemented. In a water phantom experiment, when the accelerator was operated with an average current of 1.4 mA, the maximum thermal neutron flux was approximately 7.8 × 10⁸ (n/cm²/s). Results demonstrate the stability of the linac over time, showing its promising potential for future patient treatment.

Monitoring patient movement with boron neutron capture therapy and motion capture technology

In boron neutron capture therapy (BNCT), a patient must remain in a fixed position during the irradiation process. In this study, a system was devised that can guide a patient to the correct position and the patient can be monitored during the irradiation process. This is achieved by using motion capture technology that consists of many cameras. The discrepancy of the measured coordinates for each marker on a phantom by the system was less than 5 mm. For practical applications, further research and verification are required.

Neutron beam performance of iBNCT as linac-based neutron source for boron neutron capture therapy

The linac-based neutron source “iBNCT” developed by the Tsukuba team has been shown to generate a large intensity of neutrons. To confirm the applicability of the device to BNCT, several characteristic measurements have been implemented. In a water phantom experiment, when the accelerator was operated with an average current of 1.4 mA, the maximum thermal neutron flux was approximately 7.8 × 108 (cm-2s-1). From estimation of the stability of the linac, the results demonstrate its applicability to actual treatment.

Neutrons production on the IPHI accelerator for the validation of the design of the compact neutron source SONATE

We aim at building a compact accelerator-based neutron source (CANS) which would provide a thermal neutron flux on the order of 4x1012 n.s-1.cm-2.sr-1. Such a brilliance would put compact neutron sources on par with existing medium flux neutron research reactors for neutron scattering experiments. We performed the first neutron production tests on the IPHI proton accelerator at Saclay at a proton energy of 3 MeV. The thermal neutron flux were measured using gold foil activation and 3He detectors. The measured flux were compared with GEANT4 Monte Carlo simulations (10.4) in which the whole experimental setup was modelled. There is a good agreement between the experimental measurements and the Monte-Carlo simulations. The available modelling tools will allow us to optimize the whole Target Moderator Reflector assembly together with the neutron scattering spectrometer geometries for the design of the neutron scattering facility SONATE.

Design and construction of an accelerator-based boron neutron capture therapy (AB-BNCT) facility with multiple treatment rooms at the Southern Tohoku BNCT Research Center

Installation of an accelerator-based boron neutron capture therapy (AB-BNCT) system was started in April 2014 at the Southern Tohoku BNCT Research Center (STBRC), and clinical trials began in January 2016. There are two treatment rooms, which have same specifications, and the beam quality equivalency was confirmed both rooms. Here, we describe the design and construction of the first hospital-based AB-BNCT facility in the world with multiple treatment rooms.

Remarkable Boron Delivery Of iRGD-Modified Polymeric Nanoparticles For Boron Neutron Capture Therapy

Purpose

Boron neutron capture therapy (BNCT) is an emerging binary radiotherapy, which is limited for application due to the challenge of targeted delivery into tumor nowadays. Here, we propose the use of iRGD-modified polymeric nanoparticles for active targeted delivery of boron and doxorubicin (DOX) in BNCT.

Methods

¹⁰B-enriched BSH was covalently grafted to PEG-PCCL to prepare ¹⁰B-polymer, then surface-modified with iRGD. And, DOX was physically incorporated into polymers afterwards. Characterization of prepared polymers and in vitro release profile of DOX from polymers were determined by several methods. Cellular uptake of DOX was observed by confocal microscope. Accumulation of boron in cells and tissues was analyzed by ICP-MS. Biodistribution of DOX was studied by ex vivo fluorescence imaging and quantitative measurement. Tumor vascular normalization of Endostar for promoting delivery efficiency of boron on refractory B16F10 tumor was also studied.

Results

The polymers were monodisperse and spheroidal in water with an average diameter of 24.97 nm, which were relatively stable at physiological pH and showed a sustained release of DOX, especially at endolysosomal pH. Enhanced cellular delivery of DOX was found in iRGD-modified polymer group. Cellular boron uptake of iRGD-modified polymers in A549 cells was remarkably raised fivefold (209.83 ng ¹⁰B/10⁶ cells) compared with BSH. The polymers represented prolonged blood circulation, enhanced tumor accumulation of ¹⁰B against BSH, and favorable tumor:normal tissue boron concentration ratios (tumor:blood = 14.11, tumor:muscle = 19.49) in A549 tumor-bearing mice 24 hrs after injection. Both fluorescence imaging and quantitative measurement showed the highest tumor accumulation of DOX at 24 hrs after injecting of iRGD-modified polymers. Improvement of vascular integrity and reduction of vascular mimicries were found after Endostar injection, and raised tumor accumulation of boron as well.

Conclusion

The developed nanoparticle is an inspiring candidate for the safe clinical application for BNCT.

Assessment of long-term risks of secondary cancer in paediatric patients with brain tumours after boron neutron capture therapy

This study firstly explored the risks of secondary cancer in healthy organs of Chinese paediatric patients with brain tumours after boron neutron capture therapy (BNCT). Three neutron beam irradiation geometries (i.e. right lateral, top to bottom, posterior to anterior) were adopted in treating patients with brain tumours under the clinical environment of BNCT. The concerned organs in this study were those with high cancer morbidity in China (e.g. lung, liver and stomach). The equivalent doses for these organs were calculated using Monte Carlo and anthropomorphic paediatric phantoms with Chinese physiological features. The risk of secondary cancer, characterised by the lifetime attributable risk (LAR) factor given in the BEIR VII report, was compared among the three irradiation geometries. The results showed that the LAR was lower with the PA irradiation geometry than with the two other irradiation geometries when the 2 cm diameter tumour was at a depth of 6 cm on the right side of the brain. Under the PA irradiation geometry, the LAR in the organs increased with increasing tumour volume and depth because of the long irradiation time. As the patients aged from 10-15 years old, the LAR decreased, which was related to the increased patient height and shortened life expectancy. Female patients had a relatively higher risk of secondary cancer than male patients in this study, which could be due to the thinner body thickness and the weaker protective effect on the internal organs of the female patients. In conclusion, the risks of secondary cancer in organs were related to irradiation geometries, gender, and age, indicating that the risk of secondary cancer is a personalised parameter that needs to be evaluated before administering BNCT, especially in patients with large or deep tumours.

Analysis on the emission and potential application of Cherenkov radiation in boron neutron capture therapy: A Monte Carlo simulation study

This paper was aimed to explore the physics of Cherenkov radiation and its potential application in boron neutron capture therapy (BNCT). The Monte Carlo toolkit Geant4 was used to simulate the interaction between the epithermal neutron beam and the phantom containing boron-10. Results showed that Cherenkov photons can only be generated from secondary charged particles of gamma rays in BNCT, in which the 2.223 MeV prompt gamma rays are the main contributor. The number of Cherenkov photons per unit mass generated in the measurement region decreases linearly with the increase of boron concentration in both water and tissue phantom. The work presented the fundamental basis for applications of Cherenkov radiation in BNCT.

Clinical classification criteria for radicular pain caused by lumbar disc herniation: the radicular pain caused by disc herniation (RAPIDH) criteria

BACKGROUND CONTEXT

Classification criteria are recommended for diseases that lack specific biomarkers to improve homogeneity in clinical research studies. Because imaging evidence of lumbar disc herniations (LDHs) may not be associated with symptoms, clinical classification criteria based on patient symptoms and physical examination findings are required.

PURPOSE

This study aimed to produce clinical classification criteria to identify patients with radicular pain caused by LDH.

STUDY DESIGN

The study design was a two-stage process. Phase 1 included a Delphi process and Phase 2 included a cohort study.

PATIENT SAMPLE

The patient sample included outpatients recruited from spine clinics in five countries.

OUTCOME MEASURES

The outcome measures were items from history and physical examination.

MATERIALS AND METHODS

In Phase 1, 17 spine experts participated in a Delphi process to select symptoms and signs suggesting radicular pain caused by LDH. In Phase 2, 19 different clinical experts identified patients they confidently classified as presenting with (1) radicular pain caused by LDH, (2) neurogenic claudication (NC) caused by lumbar spinal stenosis, or (3) non-specific low back pain (NSLBP) with referred leg pain. Patients completed survey items and specialists documented examination signs. A score to predict radicular pain caused by LDH was developed based on the coefficients of the multivariate model. An unrestricted grant of less than US$15,000 was received from MSD: It was used to support the conception of the Delphi, data management, and statistical analysis. No fees were allocated to participating spine specialists.

RESULTS

Phase 1 generated a final list of 74 potential symptoms and signs. In Phase 2, 209 patients with pain caused by LDH (89), NC (63), or NSLBP (57) were included. Items predicting radicular pain caused by LDH (p<.05) were monoradicular leg pain distribution, patient-reported unilateral leg pain, positive straight leg raise test <60° (or femoral stretch test), unilateral motor weakness, and asymmetric ankle reflex. The score had an AUC of 0.91. An easy-to-use weighted set of criteria with similar psychometric characteristics is proposed (specificity 90.4%, sensitivity 70.6%).

CONCLUSIONS

Classification criteria for identifying patients with radicular pain caused by LDH are proposed. Their use could improve the homogeneity of patients enrolled in clinical research studies.

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

PURPOSE

Boron 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.

METHODS

A 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.

RESULTS

Significant 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.

CONCLUSIONS

Treatment 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.

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.

Present status of Accelerator-Based BNCT

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 (7)Li(p,n)(7)Be and (9)Be(p,n)(9)B and exothermic (9)Be(d,n)(10)B 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. (9)Be(p,n)(9)B needs at least 4-5 MeV bombarding energy to have a sufficient yield, while (9)Be(d,n)(10)B 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

(7)Li(p,n)(7)Be 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. (9)Be(d,n)(10)B at 1.4 MeV, with a thin target has been shown to be a realistic option for the treatment of deep-seated lesions.

Development of a dual phantom technique for measuring the fast neutron component of dose in boron neutron capture therapy

PURPOSE

Research and development of various accelerator-based irradiation systems for boron neutron capture therapy (BNCT) is underway throughout the world. Many of these systems are nearing or have started clinical trials. Before the start of treatment with BNCT, the relative biological effectiveness (RBE) for the fast neutrons (over 10 keV) incident to the irradiation field must be estimated. Measurements of RBE are typically performed by biological experiments with a phantom. Although the dose deposition due to secondary gamma rays is dominant, the relative contributions of thermal neutrons (below 0.5 eV) and fast neutrons are virtually equivalent under typical irradiation conditions in a water and/or acrylic phantom. Uniform contributions to the dose deposited from thermal and fast neutrons are based in part on relatively inaccurate dose information for fast neutrons. This study sought to improve the accuracy in the dose estimation for fast neutrons by using two phantoms made of different materials in which the dose components can be separated according to differences in the interaction cross sections. The development of a "dual phantom technique" for measuring the fast neutron component of dose is reported.

METHODS

One phantom was filled with pure water. The other phantom was filled with a water solution of lithium hydroxide (LiOH) capitalizing on the absorbing characteristics of lithium-6 (Li-6) for thermal neutrons. Monte Carlo simulations were used to determine the ideal mixing ratio of Li-6 in LiOH solution. Changes in the depth dose distributions for each respective dose component along the central beam axis were used to assess the LiOH concentration at the 0, 0.001, 0.01, 0.1, 1, and 10 wt. % levels. Simulations were also performed with the phantom filled with 10 wt. % 6LiOH solution for 95%-enriched Li-6. A phantom was constructed containing 10 wt. % 6LiOH solution based on the simulation results. Experimental characterization of the depth dose distributions of the neutron and gamma-ray components along the central axis was performed at Heavy Water Neutron Irradiation Facility installed at Kyoto University Reactor using activation foils and thermoluminescent dosimeters, respectively.

RESULTS

Simulation results demonstrated that the absorbing effect for thermal neutrons occurred when the LiOH concentration was over 1%. The most effective Li-6 concentration was determined to be enriched 6LiOH with a solubility approaching its upper limit. Experiments confirmed that the thermal neutron flux and secondary gamma-ray dose rate decreased substantially; however, the fast neutron flux and primary gamma-ray dose rate were hardly affected in the 10%-6LiOH phantom. It was confirmed that the dose contribution of fast neutrons is improved from approximately 10% in the pure water phantom to approximately 50% in the 10%-6LiOH phantom.

CONCLUSIONS

The dual phantom technique using the combination of a pure water phantom and a 10%-6LiOH phantom developed in this work provides an effective method for dose estimation of the fast neutron component in BNCT. Improvement in the accuracy achieved with the proposed technique results in improved RBE estimation for biological experiments and clinical practice.

Verification of nuclear data for the Tsukuba plan, a newly developed treatment planning system for boron neutron capture therapy

Various verifications were performed to apply JENDL-4.0 as nuclear data for a newly developed treatment planning system with a homogeneous or precise human-like phantom. The nitrogen dose calculated by JENDL-4.0 differed slightly from that calculated by ENDF/B-VII.0. However, the total weighted dose-based dose volume histogram in the boron neutron capture therapy (BNCT) treatment for brain tumors calculated by JENDL-4.0 was in good agreement with the results of the ENDF/B-VII.0 calculation. Therefore, calculation with JENDL-4.0 can be applied to the BNCT dose calculation.