Sulfur vacancy-rich bismuth sulfide nanowire derived from CAU-17 for radioactive iodine capture in complex environments: Performance and intrinsic mechanisms.

Effective capture and immobilization of volatile radioiodine from the off-gas of post-treatment plants is crucial for nuclear safety and public health, considering its long half-life, high toxicity, and environmental mobility. Herein, sulfur vacancy-rich Vs-Bi2S3@C nanocomposites were systematically synthesized via a one-step solvothermal vulcanization of CAU-17 precursor. Batch adsorption experiments demonstrated that the as-synthesized materials exhibited superior iodine adsorption capacity (1505.8 mg g-1 at 200 °C), fast equilibrium time (60 min), and high chemisorption ratio (91.7%), which might benefit from the nanowire structure and abundant sulfur vacancies of Bi2S3. Furthermore, Vs-Bi2S3@C composites exhibited excellent iodine capture performance in complex environments (high temperatures, high humidity and radiation exposure). Mechanistic investigations revealed that the I2 capture by fabricated materials primarily involved the chemical adsorption between Bi2S3 and I2 to form BiI3, and the interaction of I2 with electrons provided by sulfur vacancies to form polyiodide anions (I3-). The post-adsorbed iodine samples were successfully immobilized into commercial glass fractions in a stable form (BixOyI), exhibiting a normalized iodine leaching rate of 3.81 × 10-5 g m-2 d-1. Overall, our work offers a novel strategy for the design of adsorbent materials tailed for efficient capture and immobilization of volatile radioiodine.

G-quadruplex DNA-based colorimetric biosensor for the ultrasensitive visual detection of strontium ions using MnO2 nanorods as oxidase mimetics.

Strontium-90 (90Sr) is a major radioactive component that has attracted great attention, but its detection remains challenging since there are no specific energy rays indicative of its presence. Herein, a biosensor that is capable of rapidly detecting Sr2+ ions is demonstrated. Simple colorimetric method for sensitive detection of Sr2+ with the help of single-stranded DNA was developed by preparing MnO2 nanorods as oxidase mimic catalysis 3,3',5,5'-tetramethylbenzidine (TMB). Under weakly acidic conditions, MnO2 exhibited a strong oxidase-mimicking activity to oxidize colorless TMB into blue oxidation products (oxTMB) with discernible absorbance signals. Nevertheless, the introduction of a guanine-rich DNA aptamer inhibited MnO2-mediated TMB oxidation and reduced oxTMB formation, resulting in blue fading and diminished absorbance. Upon the addition of strontium ions to the system, the aptamers formed a stable G-quadruplex structure with strontium ions, thereby restoring the oxidase-mimicking activity of MnO2. Under the best experimental conditions, the absorbance exhibits a linear relationship with the Sr2+ concentration within the range 0.01-200 µM, with a limit of detection of 0.0028 µM. When the concentration of Sr2+ from 10-8 to 10-6 mol L-1, a distinct color change gradient could be observed in paper-based sensor. We successfully applied this approach to determine Sr2+ in natural water samples, obtaining recoveries ranging from 97.6 to 103% with a relative standard deviation of less than 5%. By providing technical solutions for detection, our work contributed to the effective monitoring of transportation of radioactive Sr in the environment.

Study of Alternative Imaging Methods for In Vivo Boron Neutron Capture Therapy.

Boron Neutron Capture Therapy (BNCT) is an innovative and highly selective treatment against cancer. Nowadays, in vivo boron dosimetry is an important method to carry out such therapy in clinical environments. In this work, different imaging methods were tested for dosimetry and tumor monitoring in BNCT based on a Compton camera detector. A dedicated dataset was generated through Monte Carlo tools to study the imaging capabilities. We first applied the Maximum Likelihood Expectation Maximization (MLEM) iterative method to study dosimetry tomography. As well, two methods based on morphological filtering and deep learning techniques with Convolutional Neural Networks (CNN), respectively, were studied for tumor monitoring. Furthermore, clinical aspects such as the dependence on the boron concentration ratio in image reconstruction and the stretching effect along the detector position axis were analyzed. A simulated spherical gamma source was studied in several conditions (different detector distances and boron concentration ratios) using MLEM. This approach proved the possibility of monitoring the boron dose. Tumor monitoring using the CNN method shows promising results that could be enhanced by increasing the training dataset.

Synthesis and characterization of Ag@Cu-based MOFs as efficient adsorbents for iodine anions removal from aqueous solutions.

Due to the critical importance of capturing radioiodine from aquatic environments for human health and ecosystems, developing highly efficient adsorbent materials with rapid kinetics for capturing iodide ions in aqueous solutions is urgently needed. Although extensive research has been conducted on iodine adsorption in gas and organic phases, limited research has been dedicated to adsorption in aqueous solutions. An effective technique for removing iodide was proposed using Ag@Cu-based MOFs synthesized by incorporating Ag into calcined HKUST-1 with varying mass ratios of Ag/Cu-C. Extensive characterization using SEM, XRD, XPS, and nitrogen adsorption-desorption analysis confirmed successful incorporation of Ag in Cu-C. Batch adsorption experiments were conducted, demonstrating that the 5% Ag@Cu-C material exhibited a high adsorption capacity of 247.1 mg g-1 at pH 3. Mechanism investigations revealed that Cu0 and dissolved oxygen in water generate Cu2O and H2O2, while Ag and a small amount of CuO generate Ag2O and Cu2O. Furthermore, iodide ions in the solution are captured by Cu+ and Ag+ adsorption sites. These findings highlighted the potential of Ag@Cu-based MOFs as highly effective adsorbents for iodine anions removal in radioactive wastewater.

Boron concentration prediction from Compton camera image for boron neutron capture therapy based on generative adversarial network.

Prompt gamma monitoring for the prediction of boron concentration is valuable for the dose calculation of boron neutron capture therapy (BNCT). This work proposes to use generative adversarial network (GAN) to predict the boron distribution based on Compton camera (CC) imaging quickly and provide a scientific basis for its application in BNCT. The BNCT and Compton imaging process was simulated, then the image reconstructed from the simulation and the contour of skin from CT are used as input, and the distribution of boron concentration from PET data is set as the output to train the network. The structural similarity, peak signal-to-noise ratio, and root mean square error of the images generated by the trained network are improved significantly, and the ratio of the boron concentration between the tumor area and the normal tissue is improved from 1.55 to 3.85, which is much closer to the true value of 3.52. The trained network can optimize the original image within 0.83 s, which is much faster than iterative optimization. The proposed method could help to ease the current online monitoring problem of boron concentration on a computational level, thereby promoting the clinical development of BNCT technology.

Proton range monitoring based on picosecond detection using a Cherenkov radiation detector: A Monte Carlo study.

In this study, we analyzed the performance of a PbF2 crystal-based detector at proton range monitoring with Monte Carlo simulations. The correlations between the depth-dose and Cherenkov profiles showed that the changes in the peak position in the Cherenkov profiles corresponded to the changes in the corresponding depth-dose profiles. Moreover, the deviations between the changes in the peak positions in the two curves were generally less than 2 mm. The results also showed that the actual proton range could be obtained using flight time information. When the proton energy was 160 MeV, the peak position detected in the Cherenkov profile detected was 14.83 cm with a flight time of 5.3-5.4 ns (starting from the time when protons were emitted), and the actual proton range in polymethyl-methacrylate was 15 cm. Therefore, the accuracy of the proton range measurements could be improved and the absolute range obtained by using the fast and time-sensitive characteristics of the proposed Cherenkov radiator.

Cu-Zn bimetal ZIFs derived nanowhisker zero-valent copper decorated ZnO nanocomposites induced oxygen activation for high-efficiency iodide elimination.

Studies on the elimination of iodide anions (I-) by Cu-based adsorbents have been conducted for decades, however its unsatisfactory adsorption performance and its non-reusability are still the main obstacles for large-scale practical applications. Here, an efficient technique was proposed for the elimination of iodide using nanowhisker zero-valent copper (nwZVC) decorated ZnO nanocomposites obtained by two steps pyrolysis of Cu-Zn bimetal ZIFs precursors. The as-synthesized materials were extensively characterized and the results clearly revealed that nanoscale ZVC were well-dispersed in the ZnO matrix, and the morphology and the amount of nanoscale ZVC could be tuned by adjusting the molar ratio of Cu/Zn in ZIF precursors. The following batch adsorption experiments demonstrated that the resultant materials exhibited high adsorption capacity of 270.8 mg g-1 under condition of adequate oxygen, as well as high selectivity, strong acidity resistance and an excellent reusability. The mechanism investigations revealed that the elimination of I- by as-fabricated materials involved adsorption process coupled with oxidation, and the existence of nwZVC was responsible for this since nwZVC could activate molecular oxygen to generate H2O2 accompanied by the release of Cu+, thus leading to I- adsorbed by the released Cu+ and oxidized by the H2O2.

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.

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.

A Monte Carlo study of pinhole collimated Cerenkov luminescence imaging integrated with radionuclide treatment.

Cerenkov luminescence imaging (CLI) is an emerging optical imaging technique, which has been widely investigated for biological imaging. In this study, we proposed to integrate the CLI technique with the radionuclide treatment as a "see-and-treat" approach, and evaluated the performance of the pinhole collimator-based CLI technique. The detection of Cerenkov luminescence during radionuclide therapy was simulated using the Monte Carlo technique for breast cancer treatment as an example. Our results show that with the pinhole collimator-based configuration, the location, size and shape of the tumors can be clearly visualized on the Cerenkov luminescence images of the breast phantom. In addition, the CLI of multiple tumors can reflect the relative density of radioactivity among tumors, indicating that the intensity of Cerenkov luminescence is independent of the size and shape of a tumor. The current study has demonstrated the high-quality performance of the pinhole collimator-based CLI in breast tumor imaging for the "see-and-treat" multi-modality treatment.

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.

Investigation of the dose perturbation effect for therapeutic beams with the presence of a 1.5 T transverse magnetic field in magnetic resonance imaging-guided radiotherapy.

BACKGROUND: Magnetic resonance imaging (MRI)-guided radiotherapy is a promising image-guided cancer radiotherapy method. For MRI-guided radiotherapy, the proper energy of a therapeutic beam is important for beam-designing processes, and the magnetic-induced dose perturbation would be mainly influenced, especially the perturbation surrounding the tissue-air or air-tissue interfaces. Thus, it was necessary to investigate the impact of beam energy from photon, proton, and carbon ion beams on the magnetic-induced dose perturbations. MATERIALS AND METHODS: Using a phantom of a water-air-water structure, the dose distributions were calculated with or without the presence of a 1.5 T uniform magnetic field through GEANT4. Based on the calculated doses, magnetic-induced dose perturbations were then obtained. For investigating the effects of beam energies on magnetic-induced dose perturbations, low-, middle-, and high-beam energies were adopted for each beam type. RESULTS AND DISCUSSION: For photon beams, the dose perturbations were increased as the beam energies increased. At the up water-air interface, the maximum perturbations exceeded 50%. Near the edge of the radiation field, perturbations of 5%-20% were achieved. For proton and carbon ion beams, their Bragg peaks were shifted from original positions, and the shifting distances were increased with the increased beam energies. However, no evident magnetic-induced dose perturbations were noted at the up water-air interface and bottom air-water interface for all the beam energies. To some extent, this study provided references for assessing the effects of beam energies on magnetic-induced dose perturbations, especially the perturbations around the air cavities inside cancer patients. CONCLUSION: In MRI-guided cancer radiotherapy, the dose perturbation effects for therapeutic beams are relatively obvious, and the beam energies of therapeutic beams have large impacts on the magnetic-induced dose perturbations with the presence of a 1.5 T transverse magnetic field.

Measurement of dose in radionuclide therapy by using Cerenkov radiation.

This work aims to determine the relationship between Cerenkov photon emission and radiation dose from internal radionuclide irradiation. Water and thyroid phantoms were used to simulate the distribution of Cerenkov photon emission and dose deposition through Monte Carlo method. The relationship between Cerenkov photon emission and dose deposition was quantitatively analyzed. A neck phantom was also used to verify Cerenkov photon detection for thyroid radionuclide therapy. Results show that Cerenkov photon emission and dose deposition exhibit the same distribution pattern in water phantom, and this relative distribution relationship also existed in the thyroid phantom. Moreover, Cerenkov photon emission exhibits a specific quantitative relation to dose deposition. For thyroid radionuclide therapy, only a part of Cerenkov photon produced by thyroid could penetrate the body for detection; therefore, the use of Cerenkov radiation for measurement of radionuclide therapy dose may be more suitable for superficial tumors. This study demonstrated that Cerenkov radiation has the potential to be used for measuring radiation dose for radionuclide therapy.

Modulation of lateral positions of Bragg peaks via magnetic fields inside cancer patients: Toward magnetic field modulated proton therapy.

PURPOSE: This work investigated whether the Bragg peak (BP) positions of proton beams can be modulated to produce uniform doses and cover a tumor under the magnetic fields inside cancer patients, and whether magnetic field modulated proton therapy (MMPT) is effective in vital organ protection. METHODS: The authors initially constructed an ideal water phantom comprising a central tumor surrounded by cuboid organ regions using GEANT4. Second, we designed the proton beams passing through the gap between two adjacent organ regions during beam configuration. Third, we simulated the beam transports under magnetic fields inside the phantom through GEANT4. Then, the beams were discarded, which did not stop in the tumor. Fourth, the authors modulated the intensities of the remaining beams to produce uniform tumor doses. Subsequently, the calculated MMPT doses were compared with those of traditional methods, such as single, opposing, orthogonal, and box fields. Moreover, the authors repeated the above research procedures for abdominal anatomies comprising tumors at the pancreatic tail and liver to evaluate whether MMPT is effective for the human anatomy. RESULTS: For the water phantom, the vital organ doses were approximately 50%, 30%, 30%, and 15% for the single, opposing, orthogonal, and box fields, respectively. As the vital organ doses decreased, the organ volume receiving proton irradiations for the opposing, orthogonal, and box fields increased by two, two, and four times compared with that for the single field. The vital organ volume receiving proton irradiations were controlled to a fairly low level through MMPT, whereas the BP positions of the proton beams were properly modulated through the magnetic fields inside the phantom. The tumor was sufficiently covered by a 95% dose line, and the maximum tumor doses were smaller than 110%. For the pancreatic tumor case, the proton beams were curved and bypassed the kidney to generate uniform doses inside the tumor through MMPT. In the liver tumor case, the liver volume receiving proton irradiations was reduced by approximately 40% through MMPT compared with traditional methods. CONCLUSIONS: The BP positions can be intentionally modulated to produce uniform tumor doses under the magnetic fields inside cancer patients. In some special cases, the vital organs surrounding the tumor can almost be exempted from proton irradiations without sacrificing tumor dose coverage through MMPT. For the tumors inside parallel organs, the parallel organ volume receiving proton irradiations was largely reduced through MMPT. The results of this study can serve as beneficial implications for future proton therapy studies with reduced vital organ damage and complications.

Optimization of the Compton camera for measuring prompt gamma rays in boron neutron capture therapy.

Optimization of the Compton camera for measuring prompt gamma rays (0.478MeV) emitted during boron neutron capture therapy (BNCT) was performed with Geant4. The parameters of the Compton camera were determined as follows: 3cm thick - 10cm wide scatter detector (Silicon), 10cm thick - 10cm wide absorber detector (Germanium), and 1cm distance between the scatter and absorber detectors. For a typical brain tumor treatment, the overall detection efficiency of the optimized Compton camera was approximately 0.1425% using the Snyder's head phantom with a sphere tumor (4cm diameter and ~1cm depth).

Influence of Neutron Sources and 10B Concentration on Boron Neutron Capture Therapy for Shallow and Deeper Non-small Cell Lung Cancer.

Boron Neutron Capture Therapy (BNCT) is a radiotherapy that combines biological targeting and high Linear Energy Transfer (LET). It is considered a potential therapeutic approach for non-small cell lung cancer (NSCLC). It could avoid the inaccurate treatment caused by the lung motion during radiotherapy, because the dose deposition mainly depends on the boron localization and neutron source. Thus, B concentration and neutron sources are both principal factors of BNCT, and they play significant roles in the curative effect of BNCT for different cases. The purpose was to explore the feasibility of BNCT treatment for NSCLC with either of two neutron sources (the epithermal reactor at the Massachusetts Institute of Technology named "MIT source" and the accelerator neutron source designed in Argentina named "MEC source") and various boron concentrations. Shallow and deeper lung tumors were defined in the Chinese hybrid radiation phantom, and the Monte Carlo method was used to calculate the dose to tumors and healthy organs. The MEC source was more appropriate to treat the shallow tumor (depth of 6 cm) with a shorter treatment time. However, the MIT source was more suitable for deep lung tumor (depth of 9 cm) treatment, as the MEC source is more likely to exceed the skin dose limit. Thus, a neutron source consisting of more fast neutrons is not necessarily suitable for deep treatment of lung tumors. Theoretical distribution of B in tumors and organs at risk (especially skin) was obtained to meet the treatable requirement of BNCT, which may provide the references to identify the feasibility of BNCT for the treatment of lung cancer using these two neutron sources in future clinical applications.

GEANT4 calculations of neutron dose in radiation protection using a homogeneous phantom and a Chinese hybrid male phantom.

The purpose of this study is to verify the feasibility of applying GEANT4 (version 10.01) in neutron dose calculations in radiation protection by comparing the calculation results with MCNP5. The depth dose distributions are investigated in a homogeneous phantom, and the fluence-to-dose conversion coefficients are calculated for different organs in the Chinese hybrid male phantom for neutrons with energy ranging from 1 × 10(-9) to 10 MeV. By comparing the simulation results between GEANT4 and MCNP5, it is shown that using the high-precision (HP) neutron physics list, GEANT4 produces the closest simulation results to MCNP5. However, differences could be observed when the neutron energy is lower than 1 × 10(-6) MeV. Activating the thermal scattering with an S matrix correction in GEANT4 with HP and MCNP5 in thermal energy range can reduce the difference between these two codes.

A Monte Carlo-based radiation safety assessment for astronauts in an environment with confined magnetic field shielding.

The active shielding technique has great potential for radiation protection in space exploration because it has the advantage of a significant mass saving compared with the passive shielding technique. This paper demonstrates a Monte Carlo-based approach to evaluating the shielding effectiveness of the active shielding technique using confined magnetic fields (CMFs). The International Commission on Radiological Protection reference anthropomorphic phantom, as well as the toroidal CMF, was modeled using the Monte Carlo toolkit Geant4. The penetrating primary particle fluence, organ-specific dose equivalent, and male effective dose were calculated for particles in galactic cosmic radiation (GCR) and solar particle events (SPEs). Results show that the SPE protons can be easily shielded against, even almost completely deflected, by the toroidal magnetic field. GCR particles can also be more effectively shielded against by increasing the magnetic field strength. Our results also show that the introduction of a structural Al wall in the CMF did not provide additional shielding for GCR; in fact it can weaken the total shielding effect of the CMF. This study demonstrated the feasibility of accurately determining the radiation field inside the environment and evaluating the organ dose equivalents for astronauts under active shielding using the CMF.

Calculations of S values and effective dose for the radioiodine carrier and surrounding individuals based on Chinese hybrid reference phantoms using the Monte Carlo technique.

The S values for the thyroid as the radioiodine source organ to other target organs were investigated using Chinese hybrid reference phantoms and the Monte Carlo code MCNP5. Two radioiodine isotopes (125)I and (131)I uniformly distributed in the thyroid were investigated separately. We compared our S values for (131)I in Chinese phantoms with previous studies using other types of phantoms: Oak Ridge National Laboratory (ORNL) stylized phantoms, International Commission on Radiological Protection (ICRP) voxel phantoms, and University of Florida (UF) phantoms. Our results are much closer to the UF phantoms. For each specific target organ, the S value for (131)I is larger than for (125)I in both male and female phantoms. In addition, the S values and effective dose to surrounding face-to-face exposed individuals, including different genders and ages (10- and 15-year-old juniors, and adults) from an adult male radioiodine carrier were also investigated. The target organ S values and effective dose for surrounding individuals obey the inverse square law with the distance between source and target phantoms. The obtained effective dose data in Chinese phantoms are comparable to the results in a previous study using the UF phantoms. The data generated in this study can serve as the reference to make recommendations for radiation protection of the Chinese patients or nuclear workers.