Neutron flux evaluation algorithm with a combination of Monte Carlo and removal-diffusion calculation methods for boron neutron capture therapy

BACKGROUND

In Japan, the clinical treatment of boron neutron capture therapy (BNCT) has been applied to unresectable, locally advanced, and recurrent head and neck carcinomas using an accelerator-based neutron source since June of 2020. Considering the increase in the number of patients receiving BNCT, efficiency of the treatment planning procedure is becoming increasingly important. Therefore, novel and rapid dose calculation algorithms must be developed. We developed a novel algorithm for calculating neutron flux, which comprises of a combination of a Monte Carlo (MC) method and a method based on the removal-diffusion (RD) theory (RD calculation method) for the purpose of dose calculation of BNCT.

PURPOSE

We present the details of our novel algorithm and the verification results of the calculation accuracy based on the MC calculation result.

METHODS

In this study, the "MC-RD" calculation method was developed, wherein the RD calculation method was used to calculate the thermalization process of neutrons and the MC method was used to calculate the moderation process. The RD parameters were determined by MC calculations in advance. The MC-RD calculation accuracy was verified by comparing the results of the MC-RD and MC calculations with respect to the neutron flux distributions in each of the cubic and head phantoms filled with water.

RESULTS

Comparing the MC-RD calculation results with those of MC calculations, it was found that the MC-RD calculation accurately reproduced the thermal neutron flux distribution inside the phantom, with the exception of the region near the surface of the phantom.

CONCLUSIONS

The MC-RD calculation method is useful for the evaluation of the neutron flux distribution for the purpose of BNCT dose calculation, except for the region near the surface.

Application of stoichiometric CT number calibration method for dose calculation of tissue heterogeneous volumes in boron neutron capture therapy

BACKGROUND

Monte Carlo simulation code is commonly used for the dose calculation of boron neutron capture therapy. In the past, dose calculation was performed assuming a homogeneous mass density and elemental composition inside the tissue, regardless of the patient's age or sex. Studies have shown that the mass density varies with patient to patient, particularly for those that have undergone surgery or radiotherapy. A method to convert computed tomography numbers into mass density and elemental weights of tissues has been developed and applied in the dose calculation process using Monte Carlo codes. A recent study has shown the variation in the computed tomography number between different scanners for low- and high-density materials.

PURPOSE

The aim of this study is to investigate the effect of the elemental composition inside each calculation voxel on the dose calculation and the application of the stoichiometric CT number calibration method for boron neutron capture therapy planning.

METHODS

Monte Carlo simulation package Particle and Heavy Ion Transport code System was used for the dose calculation. Firstly, a homogeneous cubic phantom with the material set to ICRU soft tissue (four component), muscle, fat, and brain was modelled and the NeuCure BNCT system accelerator-based neutron source was used. The central axis depth dose distribution was simulated and compared between the four materials. Secondly, a treatment plan of the brain and the head and neck region was simulated using a dummy patient dataset. Three models were generated; (1) a model where only the fundamental materials were considered (simple model), a model where each voxel was assigned a mass density and elemental weight using (2) the Nakao20 model, and (3) the Schneider00 model. The irradiation conditions were kept the same between the different models (irradiation time and irradiation field size) and the near maximum (D1%) and mean dose to the organs at risk were calculated and compared.

RESULTS

A maximum percentage difference of approximately 5% was observed between the different materials for the homogeneous phantom. With the dummy patient plan, a large dose difference in the bone (greater than 12%) and region near the low-density material (mucosal membrane, 7%-11%) was found between the different models.

CONCLUSIONS

A stoichiometric CT number calibration method using the newly developed Nakao20 model was applied to BNCT dose calculation. The results indicate the importance of calibrating the CT number to elemental composition for each individual CT scanner for the purpose of BNCT dose calculation along with the consideration of heterogeneity of the material composition inside the defined region of interest.

Translational research of boron neutron capture therapy for spinal cord gliomas using rat model

Boron neutron capture therapy (BNCT) is a type of targeted particle radiation therapy with potential applications at the cellular level. Spinal cord gliomas (SCGs) present a substantial challenge owing to their poor prognosis and the lack of effective postoperative treatments. This study evaluated the efficacy of BNCT in a rat SCGs model employing the Basso, Beattie, and Bresnahan (BBB) scale to assess postoperative locomotor activity. We confirmed the presence of adequate in vitro boron concentrations in F98 rat glioma and 9L rat gliosarcoma cells exposed to boronophenylalanine (BPA) and in vivo tumor boron concentration 2.5 h after intravenous BPA administration. In vivo neutron irradiation significantly enhanced survival in the BNCT group when compared with that in the untreated group, with a minimal BBB scale reduction in all sham-operated groups. These findings highlight the potential of BNCT as a promising treatment option for SCGs.

[The imaging presentations of the fallopian canal cerebrospinal fluid leaking]

Objective: To summarize the imaging presentations of the fallopian canal cerebrospinal fluid leaking (FCCFL). Methods: The high resolution CT (HRCT)and MRI materials of 4 patients (4 ears) with FCCFL confirmed by surgery between August 2016 to November 2023 were retrospectively analyzed. Among these, there were 2 males and 2 females, their ages ranged from 6 to 69 years. Results: All of the FCCFL were unilateral, including 2 on the left and 2 on the right.Clinically, the patients with FCCFL suffered from clear nasal fluid flow, ear tightness, and hearing loss. On CT, all of the affected ears were depicted markedly dilatation of the proximal portion of fallopian canal(FC), the labyrinthine segment and geniculate fossa were involved in 4 cases, and involvement of tympanic segment in 1 case at the same time. The geniculate fossa in the affected side were significantly enlarged, protruding upwards into the tympanic cavity, with one case simultaneously involving the cochlea. On MRI, the hyposignal on T1WI and hypersignal on T2WI or water sequence like cerebrospinal fluid (CSF) were shown in the enlargement FC, without diffusion restriction, and non-enhancing with administration Gadolinium contrast.CSF-like signal effusion was shown in all of the affected tympanum, of which, the CSF-like signal effusion was demonstrated in the area along the superficial petrosal nerve, the right pterygopalatine fossa and the parapharyngeal space. The adjacent intracranial meninges were presented thickening in 3 cases. Conclusion: The imaging appearances of FCCFL present some characteristics:on HRCT, the proximal portions of the affected FC depicts markedly enlargement,especially the geniculate fossa.While they present CSF-like signal, no diffusion restriction, and no enhancement administration, Gadolinium contrast on MRI, accompanying the CSF-like signal effusion in the affected tympanum.

Out-of-field dosimetry using a validated PHITS model and computational phantom in clinical BNCT

BACKGROUND

The out-of-field radiation dose for boron neutron capture therapy (BNCT), which results from both neutrons and γ-rays, has not been extensively evaluated. To safely perform BNCT, the neutron and γ-ray distributions inside the treatment room and the whole-body dose should be evaluated during commissioning. Although, certain previous studies have evaluated the whole-body dose in the clinical research phase, no institution providing BNCT covered by health insurance has yet validated the neutron distribution inside the room and the whole-body dose.

PURPOSE

To validate the Monte Carlo model of the BNCT irradiation room extended for the whole-body region and evaluate organ-at-risk (OAR) doses using the validated model with a human-body phantom.

METHODS

First, thermal neutron distribution inside the entire treatment room was measured by placing Au samples on the walls of the treatment room. Second, neutron and gamma-ray dose-rate distributions inside a human-body water phantom were measured. Both lying and sitting positions were considered. Bare Au, Au covered by Cd (Au+Cd), In, Al, and thermoluminescent dosimeters were arranged at 11 points corresponding to locations of the OARs inside the phantom. After the irradiation, γ-ray peaks emitted from the samples were measured by a high-purity germanium detector. The measured counts were converted to the reaction rate per unit charge of the sample. These measurements were compared with results of simulations performed with the Particle and Heavy Ion Transport code System (PHITS). A male adult mesh-type reference computational phantom was used to evaluate OAR doses in the whole-body region. The relative biological effectiveness (RBE)-weighted doses and dose-volume histograms (DVHs) for each OAR were evaluated. The median dose (D50% ) and near-maximum dose (D2% ) were evaluated for 14 OARs in a 1-h-irradiation process. The evaluated RBE-weighted doses were converted to equivalent doses in 2 Gy fractions.

RESULTS

Experimental results within 60 cm from the irradiation center agreed with simulation results within the error bars except at ±20, 30 cm, and those over 70 cm corresponded within one digit. The experimental results of reaction rates or γ-ray dose rate for lying and sitting positions agreed well with the simulation results within the error bars at 8, 4, 11, 7 and 7, 4, 7, 6, 5, 6 out of 11 points, respectively, for Au, Au+Cd, In, Al, and TLD. Among the detectors, the discrepancies in reaction rates between experiment and simulation were most common for Au+Cd, but were observed randomly for measurement points (brain, lung, etc.). The experimental results of γ-ray dose rates were systematically lower than simulation results at abdomen and waist regions for both positions. Extending the PHITS model to the whole-body region resulted in higher doses for all OARs, especially 0.13 Gy-eq increase for D50% of the left salivary gland.

CONCLUSION

The PHITS model for clinical BNCT for the whole-body region was validated, and the OAR doses were then evaluated. Clinicians and medical physicists should know that the out-of-field radiation increases the OAR dose in the whole-body region.

Feasibility study of optical imaging of the boron-dose distribution by a liquid scintillator in a clinical boron neutron capture therapy field

BACKGROUND

Evaluation of the boron dose is essential for boron neutron capture therapy (BNCT). Nevertheless, a direct evaluation method for the boron-dose distribution has not yet been established in the clinical BNCT field. To date, even in quality assurance (QA) measurements, the boron dose has been indirectly evaluated from the thermal neutron flux measured using the activation method with gold foil or wire and an assumed boron concentration in the QA procedure. Recently, we successfully conducted optical imaging of the boron-dose distribution using a cooled charge-coupled device (CCD) camera and a boron-added liquid scintillator at the E-3 port facility of the Kyoto University Research Reactor (KUR), which supplies an almost pure thermal neutron beam with very low gamma-ray contamination. However, in a clinical accelerator-based BNCT facility, there is a concern that the boron-dose distribution may not be accurately extracted because the unwanted luminescence intensity, which is irrelevant to the boron dose is expected to increase owing to the contamination of fast neutrons and gamma rays.

PURPOSE

The purpose of this research was to study the validity of a newly proposed method using a boron-added liquid scintillator and a cooled CCD camera to directly observe the boron-dose distribution in a clinical accelerator-based BNCT field.

METHOD

A liquid scintillator phantom with 10 B was prepared by filling a small quartz glass container with a commercial liquid scintillator and boron-containing material (trimethyl borate); its natural boron concentration was 1 wt%. Luminescence images of the boron-neutron capture reaction were obtained in a water tank at several different depths using a CCD camera. The contribution of background luminescence, mainly due to gamma rays, was removed by subtracting the luminescence images obtained using another sole liquid scintillator phantom (natural boron concentration of 0 wt%) at each corresponding depth, and a depth profile of the boron dose with several discrete points was obtained. The obtained depth profile was compared with that of calculated boron dose, and those of thermal neutron flux which were experimentally measured or calculated using a Monte Carlo code.

RESULTS

The depth profile evaluated from the subtracted images indicated reasonable agreement with the calculated boron-dose profile and thermal neutron flux profiles, except for the shallow region. This discrepancy is thought to be due to the contribution of light reflected from the tank wall. The simulation results also demonstrated that the thermal neutron flux would be severely perturbed by the 10 B-containing phantom if a relatively larger container was used to evaluate a wide range of boron-dose distributions in a single shot. This indicates a trade-off between the luminescence intensity of the 10 B-added phantom and its perturbation effect on the thermal neutron flux.

CONCLUSIONS

Although a partial discrepancy was observed, the validity of the newly proposed boron-dose evaluation method using liquid-scintillator phantoms with and without 10 B was experimentally confirmed in the neutron field of an accelerator-based clinical BNCT facility. However, this study has some limitations, including the trade-off problem stated above. Therefore, further studies are required to address these limitations.

Proposal of recommended experimental protocols for in vitro and in vivo evaluation methods of boron agents for neutron capture therapy

Recently, boron neutron capture therapy (BNCT) has been attracting attention as a minimally invasive cancer treatment. In 2020, the accelerator-based BNCT with L-BPA (Borofalan) as its D-sorbitol complex (Steboronine®) for head and neck cancers was approved by Pharmaceutical and Medical Devices Agency for the first time in the world. As accelerator-based neutron generation techniques are being developed in various countries, the development of novel tumor-selective boron agents is becoming increasingly important and desired. The Japanese Society of Neutron Capture Therapy believes it is necessary to propose standard evaluation protocols at each stage in the development of boron agents for BNCT. This review summarizes recommended experimental protocols for in vitro and in vivo evaluation methods of boron agents for BNCT based on our experience with L-BPA approval.

Experimentally determined relative biological effectiveness of cyclotron-based epithermal neutrons designed for clinical BNCT: in vitro study

A neutron beam for boron neutron capture therapy (BNCT) of deep-seated tumours is designed to maintain a high flux of epithermal neutrons, while keeping the thermal and fast neutron component as low as possible. These neutrons (thermal and fast) have a high relative biological effectiveness in comparison with high energy photon beams used for conventional X-ray radiotherapy. In the past, neutrons for the purpose of BNCT were generated using nuclear reactors. However, there are various challenges that arise when installing a reactor in a hospital environment. From 2006, the Kyoto University Research Reactor Institute, in collaboration with Sumitomo Heavy Industries, began the development of an accelerator-based neutron source for clinical BNCT in a bid to overcome the shortcomings of a nuclear reactor-based neutron source. Following installation and beam performance testing, in vitro studies were performed to assess the biological effect of the neutron beam. Four different cell lines were prepared and irradiated using the accelerator-based neutron source. Following neutron and gamma ray irradiation, the survival curve for each cell line was calculated. The biological end point to determine the relative biological effectiveness (RBE) was set to 10% cell survival, and the D10 for each cell line was determined. The RBE of the accelerator-based neutron beam was evaluated to be 2.62.

Evaluation of the Effectiveness of Boron Neutron Capture Therapy with Iodophenyl-Conjugated closo-Dodecaborate on a Rat Brain Tumor Model

High-grade gliomas present a significant challenge in neuro-oncology because of their aggressive nature and resistance to current therapies. Boron neutron capture therapy (BNCT) is a potential treatment method; however, the boron used by the carrier compounds-such as 4-borono-L-phenylalanine (L-BPA)-have limitations. This study evaluated the use of boron-conjugated 4-iodophenylbutanamide (BC-IP), a novel boron compound in BNCT, for the treatment of glioma. Using in vitro drug exposure experiments and in vivo studies, we compared BC-IP and BPA, with a focus on boron uptake and retention characteristics. The results showed that although BC-IP had a lower boron uptake than BPA, it exhibited superior retention. Furthermore, despite lower boron accumulation in tumors, BNCT mediated by BC-IP showed significant survival improvement in glioma-bearing rats compared to controls (not treated animals and neutrons only). These results suggest that BC-IP, with its unique properties, may be an alternative boron carrier for BNCT. Further research is required to optimize this potential treatment modality, which could significantly contribute to advancing the treatment of high-grade gliomas.

Optimizing Boron Neutron Capture Therapy (BNCT) to Treat Cancer: An Updated Review on the Latest Developments on Boron Compounds and Strategies

Boron neutron capture therapy (BNCT) is a tumor-selective particle radiotherapy. It combines preferential boron accumulation in tumors and neutron irradiation. The recent initiation of BNCT clinical trials employing hospital-based accelerators rather than nuclear reactors as the neutron source will conceivably pave the way for new and more numerous clinical trials, leading up to much-needed randomized trials. In this context, it would be interesting to consider the implementation of new boron compounds and strategies that will significantly optimize BNCT. With this aim in mind, we analyzed, in this review, those articles published between 2020 and 2023 reporting new boron compounds and strategies that were proved therapeutically useful in in vitro and/or in vivo radiobiological studies, a critical step for translation to a clinical setting. We also explored new pathologies that could potentially be treated with BNCT and newly developed theranostic boron agents. All these radiobiological advances intend to solve those limitations and questions that arise during patient treatment in the clinical field, with BNCT and other therapies. In this sense, active communication between clinicians, radiobiologists, and all disciplines will improve BNCT for cancer patients, in a cost- and time-effective way.

Efficacy of spesolimab for the treatment of generalized pustular psoriasis flares across pre-specified patient subgroups in the Effisayil 1 study

Effisayil 1 was a multicentre, randomized, double-blind, placebo-controlled study of the anti-interleukin (IL)-36 receptor monoclonal antibody, spesolimab, in patients presenting with a generalized pustular psoriasis (GPP) flare. Previously published data from this study revealed that within 1 week, rapid pustular and skin clearance were observed in patients receiving spesolimab versus placebo. In this pre-specified subgroup analysis, the efficacy of spesolimab was evaluated according to patient demographic and clinical characteristics at baseline in patients receiving spesolimab (n = 35) or placebo (n = 18) on Day 1. Efficacy was by assessed by achievement of primary endpoint (Generalized Pustular Psoriasis Physician Global Assessment [GPPGA] pustulation subscore of 0 at Week 1) and key secondary endpoint (GPPGA total score of 0 or 1 at Week 1). Safety was assessed at Week 1. Spesolimab was found to be efficacious and had a consistent and favourable safety profile in patients presenting with a GPP flare, regardless of patient demographics and clinical characteristics at baseline.

Development of optimization method for uniform dose distribution on superficial tumor in an accelerator-based boron neutron capture therapy system

To treat superficial tumors using accelerator-based boron neutron capture therapy (ABBNCT), a technique was investigated, based on which, a single-neutron modulator was placed inside a collimator and was irradiated with thermal neutrons. In large tumors, the dose was reduced at their edges. The objective was to generate a uniform and therapeutic intensity dose distribution. In this study, we developed a method for optimizing the shape of the intensity modulator and irradiation time ratio to generate a uniform dose distribution to treat superficial tumors of various shapes. A computational tool was developed, which performed Monte Carlo simulations using 424 different source combinations. We determined the shape of the intensity modulator with the highest minimum tumor dose. The homogeneity index (HI), which evaluates uniformity, was also derived. To evaluate the efficacy of this method, the dose distribution of a tumor with a diameter of 100 mm and thickness of 10 mm was evaluated. Furthermore, irradiation experiments were conducted using an ABBNCT system. The thermal neutron flux distribution outcomes that have considerable impacts on the tumor's dose confirmed a good agreement between experiments and calculations. Moreover, the minimum tumor dose and HI improved by 20 and 36%, respectively, compared with the irradiation case wherein a single-neutron modulator was used. The proposed method improves the minimum tumor volume and uniformity. The results demonstrate the method's efficacy in ABBNCT for the treatment of superficial tumors.

A Novel MR Imaging Sequence of 3D-ZOOMit Real Inversion-Recovery Imaging Improves Endolymphatic Hydrops Detection in Patients with Ménière Disease

BACKGROUND AND PURPOSE

The detection rate of premortem MR imaging endolymphatic hydrops is lower than that of postmortem endolymphatic hydrops in Ménière disease, indicating that current MR imaging techniques may underestimate endolymphatic hydrops. Therefore, we prospectively investigated whether a novel high-resolution MR imaging technique, the 3D zoomed imaging technique with parallel transmission real inversion-recovery (3D-ZOOMit real IR), would improve the detection of endolymphatic hydrops compared with conventional 3D TSE inversion-recovery with real reconstruction.

MATERIALS AND METHODS

Fifty patients with definite unilateral Ménière disease were enrolled and underwent 3D-ZOOMit real IR and 3D TSE inversion-recovery with real reconstruction 6 hours after IV gadolinium injection. The endo- and perilymph spaces were scored separately. The contrast-to-noise ratio, SNR, and signal intensity ratio of the 2 sequences were respectively calculated and compared. The presence of endolymphatic hydrops was evaluated.

RESULTS

The endolymphatic space in the cochlea and vestibule was better visualized with 3D-ZOOMit real IR than with conventional 3D TSE inversion-recovery with real reconstruction (P < .001). There were differences between the 2 sequences in the evaluation of no cochlear hydrops and cochlear hydrops (both, P < .017). All contrast-to-noise ratio, SNR, and signal intensity ratio values of 3D-ZOOMit real IR images were statistically higher than those of conventional 3D TSE inversion-recovery with real reconstruction (all, P < .001).

CONCLUSIONS

The 3D-ZOOMit real IR sequences are superior to conventional 3D TSE inversion-recovery with real reconstruction sequences in visualizing the endolymphatic space, detecting endolymphatic hydrops, and discovering contrast permeability.

Development and evaluation of dose calculation algorithm with a combination of Monte Carlo and point-kernel methods for boron neutron capture therapy

We developed a 'hybrid algorithm' that combines the Monte Carlo (MC) and point-kernel methods for fast dose calculation in boron neutron capture therapy. The objectives of this study were to experimentally verify the hybrid algorithm and to verify the calculation accuracy and time of a 'complementary approach' adopting both the hybrid algorithm and the full-energy MC method. In the latter verification, the results were compared with those obtained using the full-energy MC method alone. In the hybrid algorithm, the moderation process of neutrons is simulated using only the MC method, and the thermalization process is modeled as a kernel. The thermal neutron fluxes calculated using only this algorithm were compared with those measured in a cubic phantom. In addition, a complementary approach was used for dose calculation in a geometry simulating the head region, and its computation time and accuracy were verified. The experimental verification indicated that the thermal neutron fluxes calculated using only the hybrid algorithm reproduced the measured values at depths exceeding a few centimeters, whereas they overestimated those at shallower depths. Compared with the calculation using only the full-energy MC method, the complementary approach reduced the computation time by approximately half, maintaining nearly same accuracy. When focusing on the calculation only using the hybrid algorithm only for the boron dose attributed to the reaction of thermal neutrons, the computation time was expected to reduce by 95% compared with the calculation using only the full-energy MC method. In conclusion, modeling the thermalization process as a kernel was effective for reducing the computation time.

Accelerator based epithermal neutron source for clinical boron neutron capture therapy

The world’s first accelerator based epithermal neutron source for clinical boron neutron capture therapy (BNCT) was designed, developed, and commissioned between 2008 and 2010 by Sumitomo Heavy Industries in collaboration with Kyoto University at the Kyoto University Institute for Integrated Radiation and Nuclear Science. The accelerator system is cyclotron-based and accelerates a proton up to an energy of approximately 30 MeV. The proton strikes a beryllium target, which produces fast neutrons that traverse a beam shaping assembly composed of a combination of lead, iron, aluminum, and calcium fluoride to reduce the neutron energy down to the epithermal range (∼10 keV) suitable for BNCT. The system is designed to produce an epithermal neutron flux of up to 1.4 × 10 9 n · cm − 2 · s − 1 (exiting from the moderator of a 12 cm diameter collimator) with a proton current of 1 mA. In 2017, the same type of accelerator was installed at the Kansai BNCT Medical Center and in March 2020 the system received medical device approval in Japan (Sumitomo Heavy Industries, NeuCure® BNCT system). Soon after, BNCT for unresectable, locally advanced, and recurrent carcinoma of the head and neck region was approved by the Japanese government for reimbursement covered by the national health insurance system.

Intensity-modulated irradiation for superficial tumors by overlapping irradiation fields using intensity modulators in accelerator-based BNCT

The distribution of the thermal neutron flux has a significant impact on the treatment efficacy. We developed an irradiation method of overlapping irradiation fields using intensity modulators for the treatment of superficial tumors with the aim of expanding the indications for accelerator-based boron neutron capture therapy (BNCT). The shape of the intensity modulator was determined and Monte Carlo simulations were carried out to determine the uniformity of the resulting thermal neutron flux distribution. The intensity modulators were then fabricated and irradiation tests were conducted, which resulted in the formation of a uniform thermal neutron flux distribution. Finally, an evaluation of the tumor dose distribution showed that when two irradiation fields overlapped, the minimum tumor dose was 27.4 Gy-eq, which was higher than the tumor control dose of 20 Gy-eq. Furthermore, it was found that the uniformity of the treatment was improved 47% as compared to the treatment that uses a single irradiation field. This clearly demonstrates the effectiveness of this technique and the possibility of expanding the indications to superficially located tumors.

Exploration of the threshold SUV for diagnosis of malignancy using 18F-FBPA PET/CT

Background

The goal of the study was to evaluate the diagnostic ability of 18F-FBPA PET/CT for malignant tumors. Findings from 18F-FBPA and 18F-FDG PET/CT were compared with pathological diagnoses in patients with malignant tumors or benign lesions.

Methods

A total of 82 patients (45 males, 37 females; median age, 63 years; age range, 20–89 years) with various types of malignant tumors or benign lesions, such as inflammation and granulomas, were examined by 18F-FDG and 18F-FBPA PET/CT. Tumor uptake of FDG or FBPA was quantified using the maximum standardized uptake value (SUVmax). The final diagnosis was confirmed by cytopathology or histopathological findings of the specimen after biopsy or surgery. A ROC curve was constructed from the SUVmax values of each PET image, and the area under the curve (AUC) and cutoff values were calculated.

Results

The SUVmax for 18F-FDG PET/CT did not differ significantly for malignant tumors and benign lesions (10.9 ± 6.3 vs. 9.1 ± 2.7 P = 0.62), whereas SUVmax for 18F-FBPA PET/CT was significantly higher for malignant tumors (5.1 ± 3.0 vs. 2.9 ± 0.6, P < 0.001). The best SUVmax cutoffs for distinguishing malignant tumors from benign lesions were 11.16 for 18F-FDG PET/CT (sensitivity 0.909, specificity 0.390) and 3.24 for 18F-FBPA PET/CT (sensitivity 0.818, specificity 0.753). ROC analysis showed significantly different AUC values for 18F-FDG and 18F-FBPA PET/CT (0.547 vs. 0.834, p < 0.001).

Conclusion

18F-FBPA PET/CT showed superior diagnostic ability over 18F-FDG PET/CT in differential diagnosis of malignant tumors and benign lesions. The results of this study suggest that 18F-FBPA PET/CT diagnosis may reduce false-positive 18F-FDG PET/CT diagnoses.

ET-4 BASIC RESEARCH OF BORON NEUTRON CAPTURE THERAPY USING A NOVEL BORON COMPOUND TARGETED TO INTEGRIN

Background

Boron neutron capture therapy (BNCT) is a particle radiation modality capable of selectively destroying tumor cells. The most commonly used boron compound for BNCT is boronphenylalanine (BPA). BPA is taken up into the tumor cell via the L-type aminoacid transporter (LAT-1). However, there are some BPA-refractory situations. Therefore, a novel boron compound is expected to improve the therapeutic performance of BNCT. We focused on integrinαvβ3, which is overexpressed in malignant gliomas as in many cancer cells, and have developed cRGD-MID-AC, a conjugate of cyclic RGD (cRGD), which selectively inhibited integrinαvβ3, and MID-AC, which we have already reported as effective on BNCT as BPA as a boron compound in F98 rat glioma models. We evaluated the efficacy of BNCT using this novel compound.Methods: F98 glioma cells were exposed to BPA, cRGD-MID-AC, and cRGD-MID for cellular uptake and neutron irradiation experiment. Intracellular boron concentrations and compound biological effectiveness (CBE) for each boron compound was calculated. After intravenous administration (i.v.) of cRGD-MID-AC or BPA, the biodistribution of boron compounds was measured and neutron irradiation experiment were performed in F98 rat glioma models.

Results

Intracellular boron concentrations of BPA and cRGD-MID-AC were increased gradually at all exposed time, and CBE for cRGD-MID-AC was comparable to that for BPA. In cRGD-MID-AC, the boron concentration in the tumor was the highest at 8 h after i.v. and tended to be retained longer at 24h. In vivo neutron irradiation experiment, long-term survival was observed only in the group irradiated 8 h after cRGD-MID-AC i.v.. These experiments suggest that cRGD-MID-AC has sufficient cell-killing effect and may be more effective in vivo.

Conclusion

cRGD-MID-AC has a tumor accumulation mechanism different from that of BPA, and could be an effective boron carrier in BNCT for malignant gliomas.

RT-6 POTENTIAL AND PROSPECTS OF BORON NEUTRON CAPTURE THERAPY USING A COMBINATION OF MULTIPLE BORON AGENTS

Boron neutron capture therapy (BNCT) is a particle therapy that can target tumors at the cellular level. BNCT has been developed for the treatment of malignant gliomas with widely infiltrated tumors, but as the indication for BNCT was expanded to include the whole body, the focus shifted to borophalan-10B (BPA), which is based on the essential amino acid phenylalanine, as a candidate agent. We started BNCT for brain tumors in 2002 with a protocol combining two compounds (BPA, BSH) that had been clinically used, but later, with the development of an accelerator-based system, we conducted a clinical study of a single agent of BPA with a modified administration protocol in a nuclear reactor. In this report, we analyze the clinical studies of BNCT for recurrent malignant glioma using the reactor as a neutron source, and discuss the possibility of BNCT using multiple drugs in combination. The median survival with BSH+BPA was 11.0 months (n=29) overall, and the MST with BPA alone was 11.1 months (n=24), with similar results for BPA alone. The blood boron levels at the time of irradiation were 46.3 and 27.3 μg/ml, respectively, which were higher with the addition of BSH. The irradiation doses converted to X-rays (Gy) equivalent were calculated to be 69 and 76 Gy-Eq for the maximum tumor, 37 and 40 Gy-Eq for the minimum, and 10.9 and 10.5 Gy-Eq for the normal brain, respectively. The biological effectiveness ratios for tumor and normal tissue from neutron capture reactions with boron compounds and tissue boron concentrations were factored into these calculations, and since BPA and BSH have different target systems (BPA in the infiltration zone and BSH in the contrast zone, respectively), we believe that their combined use may improve therapeutic efficacy and attenuate adverse events.

[The correlation between reflux esophagitis and Helicobacter pylori infection based on natural population]

Objective: Reflux esophagitis (RE) may be negatively correlated with Helicobacter pylori (H. pylori) infection, but the conclusion and relevant mechanism is still controversial. This study proposed to explore the correlation between RE and H. pylori infection based on natural population. Methods: From July 2013 to December 2014, 3 940 residents aged 40-69 years were recruited in Linqu County of Shandong Province and Hua County of Henan Province by the whole sampling method. All the subjects underwent gastroscopy, and gastric mucosa biopsy specimens were collected for pathological diagnosis and Warthin-Starry (WS) staining to identify H. pylori infection. Venous blood samples of some subjects were collected for H. pylori immunoglobulin G (H. pylori-IgG) detection. Also, demographic and sociological data were collected. Chi-square test and logistic regression were used to analyze the correlation between RE and H. pylori infection. Results: A total of 359 cases of RE were detected. Excluding RE and other upper gastrointestinal organic diseases, 3 382 cases were considered as controls. Chi-square test showed that WS staining positive rate in RE group was significantly lower than that in control group (P=0.023), but there was no significant difference in the positive rate of H. pylori-IgG between the two groups (P=0.281). There were significant differences between RE group and control group in gender composition, age, body mass index (BMI), smoking, alcohol consumption, education level and mucosal active inflammation. Multivariate regression analysis showed that RE was negatively correlated with gastric mucosa active inflammation [OR=0.754 (95%CI 0.600-0.949), P=0.016], and positively correlated with male [OR=4.231 (95%CI 3.263-5.486), P<0.001], age ≥60 years, BMI≥24 kg/m² [OR=1.540 (95%CI 1.220-1.945), P<0.001]. Compared to those aged 40-49 years and 50-59 years, the odds ratio (OR) of RE in these aged ≥60 years were 1.566 (95%CI 1.144-2.143, P=0.005) and 1.405 (95%CI 1.093-1.805, P=0.008). Conclusion: RE is more closely related to H. pylori present infection. Multivariate analysis showed that RE is negatively correlated with active inflammation of gastric mucosa caused by H. pylori infection, and positively correlated with male, overweight and aged ≥60 years.

Design of a filtration system to improve the dose distribution of an accelerator-based neutron capture therapy system

PURPOSE

The aim of this study is to design and evaluate a neutron filtration system to improve the dose distribution of an accelerator-based neutron capture therapy system.

METHODS

An LiF-sintered plate composed of 99%-enriched ⁶ Li was utilized to filter out low-energy neutrons to increase the average neutron energy at the beam exit. A 5-mm thick filter to fit inside a 12-cm diameter circular collimator was manufactured, and experimental measurements were performed to measure the thermal neutron flux and gamma-ray dose rate inside a water phantom. The experimental measurements were compared with the Monte Carlo simulation, particle, and heavy ion transport code system. Following the experimental verification, three filter designs were modeled, and the thermal neutron flux and the biologically weighted dose distribution inside a phantom were simulated. Following the phantom simulation, a dummy patient CT dataset was used to simulate a boron neutron capture therapy (BNCT) irradiation of the brain. A mock tumor located at 4, 6, 8 cm along the central axis and 4-cm off-axis was set, and the dose distribution was simulated for a maximum total biologically weighted brain dose of 12.5 Gy with a beam entering from the vertex.

RESULTS

All three filters improved the beam penetration of the accelerator-based neutron source. Filter design C was found to be the most suitable filter, increasing the advantage depth from 9.1 to 9.9 cm. Compared with the unfiltered beam, the mean weighted dose in the tumor located at a depth of 8 cm along the beam axis was increased by ∼25%, and 34% for the tumor located at a depth of 8 cm and off-axis by 4 cm.

CONCLUSION

A neutron filtration system for an accelerator-based BNCT system was investigated using Monte Carlo simulation. The proposed filter design significantly improved the dose distribution for the treatment of deep targets in the brain.

Improvement in the neutron beam collimation for application in boron neutron capture therapy of the head and neck region

In June 2020, the Japanese government approved boron neutron capture therapy for the treatment of head and neck cancer. The treatment is usually performed in a single fraction, with the neutron irradiation time being approximately 30–60 min. As neutrons scatter in air and loses its intensity, it is preferable to bring the patient as close to the beam port as possible to shorten the irradiation time. However, this can be a challenge, especially for patients with head and neck cancer, as the shoulders are an obstacle to a clean positioning. In this study, a novel neutron collimation system for an accelerator based neutron source was designed to allow for a more comfortable treatment, without compromising the irradiation time. Experimental measurements confirmed the simulation results and showed the new collimator can reduce the irradiation time by approximately 60% (under the same condition where the distance between the source and the patient surface was kept the same). The dose delivered to the surrounding healthy tissue was reduced with the new collimator, showing a 25% decrease in the D₅₀ of the mucosal membrane. Overall, the use of the newly designed collimator will allow for a more comfortable treatment of the head and neck region, reduce the treatment time, and reduce the dose delivered to the surrounding healthy tissue.

[The changes of blood-labyrinth barrier in idiopathic sudden sensorineural hearing loss and the relationship with clinical features and prognosis]

Objective: To investigate the clinical features and prognosis in patients with idiopathic sudden sensorineural hearing loss (ISSNHL) with blood-labyrinth barrier breakdown (BLB-B). Methods: Clinical data of patients with unilateral ISSNHL hospitalized from December 2017 to December 2018 were retrospectively analyzed. According to the results of 3D-FLAIR MRI and enhanced MRI scanning, these patients were divided into two groups, i.e., normal and abnormal inner ear groups. The patients in abnormal inner ear group were further divided into two subgroups: BLB-B and BLB-B with exudation. The differences and correlations among the groups in clinical characteristics, in terms of gender, age, deafness side, basic diseases, dizziness/vertigo, vestibular function, hearing loss degree, as well as classification of hearing curve, and prognosis were analyzed by statistical software SPSS 23.0. Results: Data were collected from 150 cases, in which 68 were male and 82 were female, aged (46.2±14.6) years, including 67 cases with normal inner ears and 83 cases with abnormal inner ears (13 cases with BLB-B; 70 cases with BLB-B and exudation). The dizziness/vertigo incidence, side ratio, hearing loss degree, classification of hearing curve, vestibular dysfunction (vestibular double temperature test, HIT and VAT) and therapeutic effect were different between normal and abnormal inner ear groups (P<0.05). The dizziness/vertigo incidence, side ratio, hearing loss degree, classification of hearing curve, vestibular dysfunction (vestibular double temperature test, o/cVEMP, HIT and VAT) and therapeutic effect were different among normal inner ear, BLB-B and BLB-B with exudation groups (P<0.05). Pairwise comparison between groups revealed that vestibular dysfunction (vestibular double temperature test, o/cVEMP, HIT and VAT) and therapeutic effect were different between normal inner ear and BLB-B groups (P<0.05); The dizziness/vertigo incidence, side ratio, hearing loss degree, classification of hearing curve, vestibular dysfunction (vestibular double temperature test, o/cVEMP, HIT and VAT) and therapeutic effect were different between normal inner ear and BLB-B with exudation groups (P<0.05). There was no significant different between BLB-B and BLB-B with exudation groups. Conclusion: BLB-B displayed by 3D-FLAIR MRI manifestation in ISSNHL patients indicates more serious cochlear and vestibular dysfunction, and worse therapeutic effect.

Comprehensive evaluation of dosimetric impact against position errors in accelerator-based BNCT under different treatment parameter settings

Background

Patients who undergo accelerator‐based (AB) boron neutron capture therapy (BNCT) for head and neck cancer in the sitting position are generally uncomfortably immobilized, and patient motion during this treatment may be greater than that in other radiotherapy techniques. Furthermore, the treatment time of BNCT is relatively long (up to approximately 1 h), which increases the possibility of patient movement during treatment. As most BNCT irradiations are performed in a single fraction, the dosimetric error due to patient motion is of greater consequence and needs to be evaluated and accounted for. Several treatment parameters are required for BNCT dose calculation.

Purpose

To investigate the dosimetric impacts (DIs) against position errors using a simple cylindrical phantom for an AB‐BNCT system under different treatment parameter settings.

Methods

The treatment plans were created in RayStation and the dose calculation was performed using the NeuCure® dose engine. A cylindrical phantom (16 cm diameter × 20 cm height) made of soft tissue was modeled. Dummy tumors in the form of a 3‐cm‐diameter sphere were arranged at depths of 2.5 and 6.5 cm (denoted by T_2.5 and T_6.5, respectively). Reference plans were created by setting the following parameters: collimator size = 10, 12, or 15 cm in diameter, collimator‐to‐surface distance (CSD) = 4.0 or 8.0 cm, tumor‐to‐blood ratio (T/B ratio) using ¹⁸F‐fluoro‐borono‐phenylalanine = 2.5 or 5.0, and ¹⁰B concentration in blood = 20, 25, or 30 ppm. The prescribed dose was D_95% ≥ 20 Gy‐eq for both T_2.5 and T_6.5. Based on the reference plans, phantom‐shifted plans were created in 26 directions [all combinations of left–right (LR), anterior–posterior (AP), and superior–inferior (SI) directions) and three distances (1.0, 2.0, and 3.0 cm). The DIs were evaluated at D_80% of the tumors. The shift direction dependency of the DI in the LR, AP, and SI directions was evaluated by conducting a multiple regression analysis (MRA) and other analyses where required.

Results

The coefficients of the MRA of the DIs for LR, AP, and SI shifts were −0.08, 2.16, and −0.04 (p‐values = 0.084, <0.01, and 0.334) for T_2.5 and −0.05, 2.08, and 0.15 (p‐values = 0.526, <0.01, and 0.065) for T_6.5, respectively. The analysis of variance showed that DIs due to the AP shift were significantly greater for smaller collimator sizes on T_2.5 and smaller CSD on T_6.5. Dose reduction due to SI or LR (lateral) shifts was significantly greater for smaller collimator sizes on both T_2.5 and T_6.5 and smaller CSD on T_2.5, according to the Student's t‐test. There were no significant differences in the DIs against both the AP shift and the lateral shift between the different T/B ratios and ¹⁰B concentrations.

Conclusion

The DIs were largely affected by the shift in the AP direction and were influenced by the different treatment parameters.

[Correlation analysis of 3D-FLAIR MRI characteristics of the inner ear and vestibular function in the patients with vestibular neuritis]

Objective: The characteristics of 3D-FLAIR MRI images of the inner ear of patients with vestibular neuritis were preliminarily studied to explore the possible pathogenesis of vestibular neuritis, and the correlation analysis was conducted in combination with vestibular function to provide a basis for accurate diagnosis of vestibular neuritis. Methods: A total of 36 patients with vestibular neuritis (VN) from December 2019 to October 2020 were collected from the Vertigo Department of Shandong Provincial ENT Hospital, Cheeloo College of Medicine, Shandong University. There were 36 cases (18 females, 18 males) with unilateral acute vestibular neuritis, 17 cases of left ear and 19 cases of right ear. According to the results of 3D-FLAIR MRI in the inner ears, the patients were divided into the enhanced group and the non-enhanced group (the health side served as the normal control group). The results of vestibular function examination in the two groups were compared. SPSS19.0 software was used for statistical processing to analyze the relationship between the vestibular function and the characteristics of 3D-FLAIR imaging in the inner ears. Results: Abnormal enhancement of 3D-FLAIR was found in 31 cases (86.1%) of the 36 cases, including 14 cases of both vestibular nerve and vestibular terminal organ enhancement, eight cases of superior vestibular nerve enhancement alone, seven cases of vestibular terminal organ enhancement alone, and two cases of cochlear enhancement alone. Observation of abnormal reinforcement of vestibular nerve showed: twenty-one cases of superior vestibular nerve reinforcement, one case of superior and inferior vestibular nerve reinforcement. No abnormalities were found in 3D-FLAIR of inner ear in 5 cases. According to the analysis of vestibular function results, there were 19 cases (52.8%) with total vestibular involvement, sixteen cases (44.4%) with superior vestibular involvement alone, and one case (2.8%) with inferior vestibular involvement alone. Comparison of vestibular function between the five cases (non-enhancement group) and the 31 cases (enhanced group) in the 3D-FLAIR group of the inner ears showed that the CP values of caloric tests in the enhanced group were higher (60.81±3.49 vs 34.12±7.37), with statistically significant difference (t=-2.898, P<0.01). Conclusion: In patients with vestibular neuritis, 3D-FLAIR MRI scan of the inner ear provides visual imaging evidence for clinical practice, considering that the lesion site of vestibular neuritis is not only in the vestibular nerve, but also in the vestibular end organ. Patients with 3D-FLAIR enhanced in the inner ear may have more significant vestibular function damage.

[Comparison of hip offset and rotation center reconstruction between robot-assisted and manual total hip arthroplasty]

Objective: To compare the differences of hip offset and rotation center reconstruction between robot-assisted and manual total hip arthroplasty (THA). Methods: Patients underwent robot-assisted and manual THA from May to September of 2020 in the First Affiliated Hospital of Chongqing Medical University were enrolled in this study. The patients included 27 patients (28 hips) in robot-assisted THA (rTHA) group and 29 patients (31 hips) in manual THA (mTHA) group. In rTHA group, there were 16 males and 11 females, with a mean age of (59±13) years. In mTHA group, there were 18 males and 11 females, with a mean age of (63±14) years. Basic information, including gender, age, body mass index (BMI), diagnosis and functional scoring etc, were recorded. In rTHA group, Mako robot system was used for preoperative planning, intraoperative real-time location and navigation. In mTHA group, traditional preoperative template design and surgical procedure were carried out. Operation time and functional scoring were compared postoperatively. Femoral offset, acetabular offset, global offset, rotation center changes in vertical and horizontal directions were measured on pelvis X-ray and analyzed. The correlation between intraoperative feedback of global offset change in robot system and postoperative measured global offset were analyzed. Results: Operation time in rTHA group was (80±10) min, which was statistically longer than that in mTHA group ((58±18) min, P<0.001). With 6 months' follow-up, the Harris scoring in rTHA group was 94.9±2.8, which was statistically higher than that in mTHA group (93.1±2.8, P=0.017), however there was no statistic difference in WOMAC scoring between rTHA and mTHA group (7.0±3.8 vs 7.1±2.4, P=0.840). Absolute global offset change within 5 mm, 5-10 mm and lager than 10 mm were 71.4%(20/28), 28.6%(8/28) and 0 in rTHA group, which were 45.2%(14/31), 29.0%(9/31) and 25.8%(8/31) in mTHA group (all P<0.05). A positive relation was found between intraoperative feedback of global offset change in robot system and postoperative measured global offset in rTHA group (r=0.77, P<0.001). It was found that rotation center changes concentrated in outer upper quadrant in both groups, and rotation center change in rTHA group concentrated mainly in the area less than 10 mm, however, rotation center change in mTHA group was more dispersive compared with rTHA group. Conclusion: rTHA may accurately reconstruct hip offset and rotation center, intraoperation feedback of global offset change may be an effective reference.

The Use of Episodic Memory Tests for Screening in Clinical Trials for Early Alzheimer's Disease: A Comparison of the Free and Cued Selective Reminding Test (FCSRT) and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)

BACKGROUND

Screening procedures for early Alzheimer's disease (AD) trials seek to efficiently identify participants who fulfill clinical and biomarker criteria for AD and enrich for those most likely to experience significant clinical progression during the study. Episodic memory performance is often assessed in screening, but the utility of different memory tests for optimizing screening efficiency and/or rates of clinical progression remains uncertain.

OBJECTIVES

Cross-study comparisons of the effects of inclusion criteria based on performance on the Free and Cued Selective Reminding Test (FCSRT) or the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) on screen-failure rates for episodic memory and β-amyloid (Aβ) positivity (by CSF or PET) and on subsequent rates of clinical disease progression in randomized participants across three clinical trials in early (prodromal-to-mild) AD.

DESIGN

Secondary analyses of cross-sectional and longitudinal clinical trial data.

SETTING

Multi-center international clinical trials.

PARTICIPANTS

Individuals with prodromal-to-mild AD screened and/or randomized in clinical trials for crenezumab (CREAD, CREAD2) or semorinemab (Tauriel). Cross-sectional analyses of screening data for episodic memory impairment included participants from CREAD2 (n=2897) and Tauriel (n=887) and for Aβ positivity included participants from CREAD (n=1138), CREAD2 (n=1119), and Tauriel (n=483). Longitudinal analyses of rates of clinical progression included participants from CREAD (n=779), CREAD2 (n=773), and Tauriel (n=331).

MEASUREMENTS

Cross-sectional analyses examined eligibility rates per cutoffs defined for the FCSRT (CREAD, CREAD2) or RBANS (Tauriel) and per Aβ positivity using CSF and/or PET biomarkers. Longitudinal analyses examined rates of clinical progression on the Clinical Dementia Rating-Sum of Boxes (CDR-SB), the 13-item version of the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog13), and Alzheimer's Disease Cooperative Study-Activities of Daily Living Scale (ADCS-ADL).

RESULTS

Lower rates of study eligibility per episodic memory criteria were seen with the FCSRT (CREAD2) relative to the RBANS (Tauriel), but similar rates of eligibility per Aβ positivity criteria were seen amongst participants with episodic memory impairment per the cutoffs used on either assessment. Similar rates of clinical decline over 18 months on the CDR-SB, ADAS-Cog13, and ADCS-ADL were observed in study populations enriched using the FCSRT (CREAD, CREAD2) or the RBANS (Tauriel).

CONCLUSIONS

Cutoffs for episodic memory impairment on the FCSRT used in the CREAD and CREAD2 studies are more stringent than those on the RBANS used in the Tauriel study, resulting in lower rates of eligibility. However, given that study enrichment with either test yields similar rates of Aβ positivity and clinical progression, considerations beyond these factors may drive the decision of which assessment to use for screening in early AD clinical trials.

Optical imaging of lithium-containing zinc sulfate plate in water during irradiation of neutrons from boron neutron capture therapy (BNCT) system

PURPOSE

Optical imaging of ionizing radiation is a possible method for dose distribution measurements. However, it is not clear whether the imaging method is also applicable to neutrons. To clarify this, we performed the imaging of neutrons in water from boron neutron capture therapy (BNCT) systems. Such systems require efficient distribution measurements of neutrons for quality assessment (QA) of the beams.

METHOD

A water-filled phantom was irradiated from the side with an epithermal neutron beam, in which a lithium-containing zinc sulfate (Li-ZnS(Ag)) plate was set in the beam direction, and during this irradiation the scintillation of the plate was imaged using a cooled CCD camera. In the imaging, Li-6 in the Li-ZnS(Ag) plate captures neutrons and converts them to alpha particles (He-4) and tritium (H-3), while ZnS(Ag) in the Li-ZnS(Ag) plate produces scintillation light in the plate. We also conducted Monte Carlo simulation and compared its results with the experimental results.

RESULTS

The image of the emitted light from the Li-ZnS(Ag) plate was clearly obtained with an imaging time of 0.5 s. The depth and lateral profiles of the measured image using the Li-ZnS(Ag) plate showed the same shapes as the neutron distributions measured with gold foil, within a difference of 8%. The destructive effect of neutrons on the CCD camera increased ∼3 times, but the unit was still working after the measurement.

CONCLUSION

The optical imaging of neutrons in water is possible, and it has the potential to be a new method for efficient QA as well as for research on neutrons. This article is protected by copyright. All rights reserved.

Evaluation of a treatment planning system developed for clinical boron neutron capture therapy and validation against an independent Monte Carlo dose calculation system

Boron neutron capture therapy (BNCT) for the treatment of unresectable, locally advanced, and recurrent carcinoma of the head and neck cancer has been approved by the Japanese government for reimbursement under the national health insurance as of June 2020. A new treatment planning system for clinical BNCT has been developed by Sumitomo Heavy Industries, Ltd. (Sumitomo), NeuCure® Dose Engine_. To safely implement this system for clinical use, the simulated neutron flux and gamma ray dose rate inside a water phantom was compared against experimental measurements. Furthermore, to validate and verify the new planning system, the dose distribution inside an anthropomorphic head phantom was compared against a BNCT treatment planning system SERA and an in-house developed Monte Carlo dose calculation program. The simulated results closely matched the experimental results, within 5% for the thermal neutron flux and 10% for the gamma ray dose rate. The dose distribution inside the head phantom closely matched with SERA and the in-house developed dose calculation program, within 3% for the tumour and a difference of 0.3 Gy_w for the brain.

Development of an irradiation method for superficial tumours using a hydrogel bolus in an accelerator-based BNCT

The aim of this study is the development of an irradiation method for the treatment of superficial tumours using a hydrogel bolus to produce thermal neutrons in accelerator-based Boron Neutron Capture Therapy (BNCT).To evaluate the neutron moderating ability of a hydrogel bolus, a water phantom with a hydrogel bolus was irradiated with an epithermal neutron beam from a cyclotron-based epithermal neutron source. Phantom simulating irradiation to the plantar position was manufactured using three-dimensional printing technology to perform an irradiation test of a hydrogel bolus. Thermal neutron fluxes on the surface of a phantom were evaluated and the results were compared with the Monte Carlo-based Simulation Environment for Radiotherapy Applications (SERA) treatment planning software. It was confirmed that a hydrogel bolus had the same neutron moderating ability as water, and the calculation results from SERA aligned with the measured values within approximately 5%. Furthermore, it was confirmed that the thermal neutron flux decreased at the edge of the irradiation field. It was possible to uniformly irradiate thermal neutrons by increasing the bolus thickness at the edge of the irradiation field, thereby successfully determining uniform dose distribution. An irradiation method for superficial tumours using a hydrogel bolus in the accelerator-based BNCT was established.

TB-6 Experimental evaluation of the therapeutic potential of boron neutron capture therapy in primary central nervous system lymphoma

Background: High-dose methotrexate and whole brain radiation therapy (WBRT) is the recommended treatment for primary central nervous system lymphoma (PCNSL). Although the initial treatment is successful, the recurrence rate is high and the prognosis is poor. Boron neutron capture therapy (BNCT) is a nuclear reaction-based tumor cell-selective particle irradiation that occurs when non-radioactive boron-10 is irradiated with neutrons to produce α particles (10B [n, α] 7Li). In this study, we conducted a basic research to explore the possibility of BNCT as a treatment option for PCNSL. Methods: Cellular uptake of boron using human lymphoma cell-lines after exposure to boronophenylalanine (BPA) were evaluated. The cytotoxicity of lymphoma cells by photon irradiation or neutron irradiation with BPA were also evaluated. The lymphoma cells were implanted into the mouse brain and the bio-distribution of boron after administration of BPA were measured. In neutron irradiation studies, the therapeutic effect of BNCT on mouse CNSL models were evaluated in terms of survival time. Results: The boron concentration in lymphoma cells after BPA exposure was sufficiently high, and lymphoma cells showed cytotoxicity by photon irradiation, and also by BNCT. In in vivo bio-distribution study, lymphoma cells showed enough uptake of BPA with well contrasted to the brain. In the neutron irradiation experiment, the BNCT group showed a significant prolongation in their survival time compared to the control group. Conclusions: In our study, BNCT showed its effectiveness for PCNSL in a mouse brain tumor model. PCNSL is a radio-sensitive tumor with a extremely good response rate, but it also has a high recurrence rate / a high rate of adverse events, so there is no effective treatment for recurrence after treatment. Our translational study showed that BNCT is possibly have an important role against PCNSL during the therapy lines as a new treatment option for PCNSL patients.

Efficacy of Boron Neutron Capture Therapy in Primary Central Nervous System Lymphoma: In Vitro and In Vivo Evaluation

Background: Boron neutron capture therapy (BNCT) is a nuclear reaction-based tumor cell-selective particle irradiation method. High-dose methotrexate and whole-brain radiation therapy (WBRT) are the recommended treatments for primary central nervous system lymphoma (PCNSL). This tumor responds well to initial treatment but relapses even after successful treatment, and the prognosis is poor as there is no safe and effective treatment for relapse. In this study, we aimed to conduct basic research to explore the possibility of using BNCT as a treatment for PCNSL. Methods: The boron concentration in human lymphoma cells was measured. Subsequently, neutron irradiation experiments on lymphoma cells were conducted. A mouse central nervous system (CNS) lymphoma model was created to evaluate the biodistribution of boron after the administration of borono-phenylalanine as a capture agent. In the neutron irradiation study of a mouse PCNSL model, the therapeutic effect of BNCT on PCNSL was evaluated in terms of survival. Results: The boron uptake capability of human lymphoma cells was sufficiently high both in vitro and in vivo. In the neutron irradiation study, the BNCT group showed a higher cell killing effect and prolonged survival compared with the control group. Conclusions: A new therapeutic approach for PCNSL is urgently required, and BNCT may be a promising treatment for PCNSL. The results of this study, including those of neutron irradiation, suggest success in the conduct of future clinical trials to explore the possibility of BNCT as a new treatment option for PCNSL.

Smoking and incidence of insomnia: a systematic review and meta-analysis of cohort studies

OBJECTIVE

This study investigated the impact of smoking on the incidence of insomnia.

STUDY DESIGN

Systematic review and meta-analysis of cohort studies.

METHODS

PubMed, EMBASE, Web of Science, Cochrane Library, and OVID were searched through March 2020. Cohort studies reporting the effect of smoking on the incidence of insomnia were included. We quantitatively analyzed the basic framework and study characteristics and then pooled estimate effects with 95% confidence intervals (CIs) of outcomes of each included study using fixed-effects meta-analyses.

RESULTS

This systematic review included six cohort studies involving 12,445 participants. Quantitatively summarized results suggested that smoking could significantly increase the incidence of insomnia (odds ratio [OR]: 1.07, 95% CI: 1.02, 1.13). Regular smoking was significantly associated with the incidence of insomnia (OR = 1.07, 95% CI: 1.01, 1.13). As for occasional smokers and ex-smokers, the pooled analysis did not indicate a significant association (occasional smoker: OR = 2.09, 95% CI: 0.44, 9.95; ex-smoker; OR = 1.02, 95% CI: 0.67, 1.54). Subgroup analysis by age, gender ratio, and region showed a statistically significant relationship between smoking and the incidence of insomnia in specific groups.

CONCLUSIONS

Integrated longitudinal observational evidence identified smoking as a significant risk factor of insomnia. Considering the limited amount of available studies, more high-quality and prospective cohort studies of large sample sizes are needed to explore details of this association.

Photoneutron-induced damage reduction for cardiac implantable electronic devices using neutron-shielding sheets in high-energy X-ray radiotherapy: A phantom study

PURPOSE

To evaluate damage reduction in cardiac implantable electronic devices (CIEDs) caused by photoneutrons in high-energy X-ray radiotherapy using a neutron-shielding sheet (NSS).

METHODS

The NSS consists of a bolus with a thickness of 1 or 2 cm (Bls1 or Bls2) as a moderator and several absorbers (20%, 50%, or 80% B₄C silicone sheet [B₄C20, B₄C50, or B₄C80] or a 40% LiF silicone sheet [LiF40]). First, a linear accelerator (LINAC) with a water-equivalent phantom was modeled in the simulation and measured experimentally. Several NSSs were placed on the phantom, a Eu:LiCaAlF₆ scintillator was placed between the phantom and the NSS, and X-rays were irradiated. The relative counts (Cr = counts when placing the NSS or Bls2) were compared between the experiment and simulation. Second, CIED damage was evaluated in the simulation. The relative damage (Dr = damage when placing or not placing the NSS) was compared among all the NSSs. In addition, the γ-ray and leaking X-ray dose from B₄C was measured using a dosimetric film. After determining the optimal NSS combination, Dr value analysis was performed by changing the length of one side and the thickness.

RESULTS

The Cr values of the simulation and experiment agreed within a 30% percentage difference, except for Bare or LiF40-only. The Dr value was reduced by 43% when Bls2 + B₄C80 was applied. The photon dose was less than 5 cGy/1500 MU. The Dr values were smaller for the smaller lengths of one side of B₄C80 and decreased as the M-layer thickness increased.

CONCLUSIONS

The CIED damage induced by photoneutrons generated by a LINAC was effectively reduced by applying the optimal NSS.

T1rho mapping of cartilage and menisci in patients with hyperuricaemia at 3 T: a preliminary study

AIM

To compare and assess T_1rho values of the femorotibial cartilage compartments and subregional menisci in patients with hyperuricaemia at 3 T.

MATERIALS AND METHODS

Thirty-two patients were enrolled in the study and were subdivided into two subgroups: 15 healthy controls (three women, 12 men; mean age = 45.3 ± 10.9 years, age range 25-72 years) and 17 patients with asymptomatic hyperuricaemia (two women, 15 men; mean age = 44.4 ± 12.7 years, age range 26-77 years). All patients were evaluated using 3 T magnetic resonance imaging (MRI) using an eight-channel phased-array knee coil (transmit-receive). Wilcoxon's rank sum test and analysis of covariance (ANCOVA) were conducted to determine whether there were any statistically significant differences in the T_1rho values of the femorotibial cartilage compartments and subregional menisci between the two subgroups.

RESULTS

Lateral tibial cartilage (45.8 ± 2.9 ms) in the healthy subgroup had significantly lower (p<0.05) T_1rho values than those of all subcompartments of the femorotibial cartilage in the hyperuricaemia subgroup. The lateral femoral cartilage (LF) in hyperuricaemia (54.6 ± 3.9 ms) subgroup had significantly higher (p<0.05) T_1rho values than those of all subcompartments of the femorotibial cartilage except the LF in the healthy subgroup. Significantly higher (p<0.05) T_1rho values existed in the LF of the healthy (54.6 ± 4.7 ms) subgroup in comparison with those of all subcompartments of femorotibial cartilage except the LF in hyperuricaemia subgroup.

CONCLUSIONS

T_1rho values in certain compartments of the femorotibial cartilage in patients with hyperuricaemia are elevated compared to those in healthy patients presumably due to reduced proteoglycan content, to which particular attention should be paid when diagnosing and treating the patients with hyperuricaemia in a clinical setting.

Participation in sport and physical activity in adults with intellectual disabilities

BACKGROUND

People with intellectual disability face a number of barriers to participation in physical activity. This paper aimed to determine rates of sport and physical activity participation in an Australian sample of adults with intellectual disability, compared with rates of participation in the general Australian population. A secondary aim was to investigate factors that may contribute to participation of adults with intellectual disability.

METHOD

Participants were part of the Australian Child to Adult Development (ACAD) study, consisting of a community sample with intellectual disability (n = 305), groups of adults with autism (n = 94), Down syndrome (n = 64), fragile X syndrome (n = 52), Williams syndrome (n = 45), and Prader-Willi syndrome (n = 30). Participation in sport/physical activity was reported over the past 3 months. Rates of participation were reported for adults with intellectual disability and compared with rates in a general Australian population sample. The relationship between participation in physical activity and age, degree of intellectual disability, physical mobility, living situation, socio-economic disadvantage, and behaviour and emotional problems were also conducted.

RESULTS

Participants in the ACAD community sample with intellectual disability participated in sport/physical activity at lower rates than the general Australian population (42% compared with 71%). Having no physical mobility impairment was significantly associated with higher rates of participation. Those with Down syndrome participated in sport/physical activity at higher rates than the community sample with intellectual disability, while no difference in sport/physical activity participation was observed in the groups with autism or other syndromes.

CONCLUSION

Australian adults with intellectual disability participate in sport and physical activity at lower rates than the general population. Having a physical mobility impairment was associated with lower rates of participation. However, people living in supported accommodation were more likely to participate than those in other living situations. Having Down syndrome was associated with a higher participation rate than the community sample.

The Therapeutic Effects of Dodecaborate Containing Boronophenylalanine for Boron Neutron Capture Therapy in a Rat Brain Tumor Model

Simple Summary

We have developed a new boron compound for application in boron neutron capture therapy (BNCT) named boronophenylalanine–amide alkyl dodecaborate (BADB). It is characterized by a larger amount of ¹⁰B per molecule, linking boronphenylalanine (BPA) and dodecaborate, and we conducted various experiments on its efficacy. Its high accumulation at the cellular level made it a promising novel drug, but it did not sufficiently accumulate in brain tumor tissue when intravenously administered. However, in neutron irradiation experiments, the drug showed remarkably high compound biological effectiveness and significantly prolonged the survival time in rat brain tumor models. We confirmed the antitumor efficacy of BADB in BNCT and its additional efficacy when administered in combination with BPA. Though this drug showed poor results when administered as a single agent, it was superior to BPA alone when administered in combination with BPA, making it a drug that we have been waiting for in our clinical practice.

Abstract

Background: The development of effective boron compounds is a major area of research in the study of boron neutron capture therapy (BNCT). We created a novel boron compound, boronophenylalanine–amide alkyl dodecaborate (BADB), for application in BNCT and focused on elucidating how it affected a rat brain tumor model. Methods: The boron concentration of F98 rat glioma cells following exposure to boronophenylalanine (BPA) (which is currently being utilized clinically) and BADB was evaluated, and the biodistributions in F98 glioma-bearing rats were assessed. In neutron irradiation studies, the in vitro cytotoxicity of each boron compound and the in vivo corresponding therapeutic effect were evaluated in terms of survival time. Results: The survival fractions of the groups irradiated with BPA and BADB were not significantly different. BADB administered for 6 h after the termination of convection-enhanced delivery ensured the highest boron concentration in the tumor (45.8 μg B/g). The median survival time in the BADB in combination with BPA group showed a more significant prolongation of survival than that of the BPA group. Conclusion: BADB is a novel boron compound for BNCT that triggers a prolonged survival effect in patients receiving BNCT.