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New radiophotoluminescence (RPL) phosphate glass containing 6Li was successfully made from the powder of NaPO3, Al(PO3)3, LiOH, HPO3 and AgCl. The ternary diagram of NaPO3–Al(PO3)3–LiPO3 has clarified the region where satisfactory RPL characteristics of the glass are kept up. The synthesised phosphate glass indicated good RPL characteristics on the condition that the content of LiPO3 was below 10 wt%. Gamma-ray irradiation experiments showed that the newly synthesised phosphate glass had satisfactory linearity and wide dynamic range in dose measurement and low variation in sensitivity. It was confirmed from thermal neutron irradiation experiments that a pair of the newly synthesised phosphate glass containing enriched 6Li and 7Li, or nLi and enriched 7Li could be effectively used for the evaluation of thermal neutron dosimetry. [ABSTRACT FROM PUBLISHER]

A confocal laser microscope system was developed for the measurement of radiophotoluminescence (RPL) photons emitted from a minute alpha-ray-irradiated area in an RPL glass dosemeter. The system was composed mainly of an inverted-type microscope, an ultraviolet laser, an XY movable stage and photon-counting circuits. The photon-counting circuits were effective in the reduction of the background noise level in the measurement of RPL photons. The performance of this microscope system was examined by the observation of standard RPL glass samples irradiated using 241Am alpha rays. The spatial resolution of this system was ∼3 μm, and with regard to the sensitivity of this system, a hit of more than four to five alpha rays in unit area produced enough amount of RPL photons to construct the image. [ABSTRACT FROM PUBLISHER]

An electron cyclotron resonance (ECR) plasma source for broad ion-beam processing has been upgraded by a cylindrically comb-shaped magnetic-field configuration and 11–13 GHz frequency microwaves. A pair of comb-shaped magnets surrounds a large-bore discharge chamber. The magnetic field well confines plasmas with suppressing diffusion toward the axial direction of the cylindrical chamber. The magnetic field is constructed with a multipole and two quasiring permanent magnets. The plasma density clearly increases as compared with that in a simple multipole magnetic-field configuration. The frequency of microwaves output from the traveling-wave tube amplifier can be easily changed with an input signal source. The plasma density for 13 GHz is higher than that for 11 GHz. The maximum plasma density has reached approximately 1018 m-3 at a microwave power of only 350 W and a pressure of 1.0 Pa. The enhancement of plasma generation by second-harmonic resonance and microwave modes has been investigated. The plasma density and the electron temperature are raised around the second-harmonic resonance zone. And then, the ion saturation current is periodically increased with varying the position of the plate tuner. The distance between the peaks is nearly equal to half of the free-space wavelength of microwave. The efficiency of ECR has been improved by using the comb-shaped magnetic field and raising microwave frequency, and then the high-density plasma source has been accomplished at low microwave power. [ABSTRACT FROM AUTHOR]

A new electron cyclotron resonance (ECR) plasma source has been developed for broad ion-beam processing. A Ku-band traveling-wave tube amplifier (11–13 GHz) is adopted to generate high-density plasma under low-pressure conditions. An eight-pole magnetic field is selected to improve good uniformity and plasma confinement. The ECR zone for 11 GHz microwaves, i.e., 0.393 T, is formed within 6.5 mm of the inner wall of a chamber. The ECR plasma is generated by low microwave power (∼200 W). The radial profile of plasma density and electron temperature is measured with a Langmuir probe. The plasma density is approximately 3×1017 m-3 at the microwave power of 200 W. The uniformity of the density is within ±12.6% over 140 mm in diameter. [ABSTRACT FROM AUTHOR]

The purpose of this study is to develop a portable monitor that can measure the energy spectrum and dose of gamma-rays simultaneously in real time for the benefit of medical staff who must work in clinical radiation environments. For this purpose, we have developed a prototype monitor using a CsI (Tl) scintillator combined with a multi-pixel photon counter (MPPC). For real-time measurement, we employed an improved sequential Bayesian estimation (k-α method) to convert the measured pulse height spectrum into an energy spectrum. Then we confirmed that reconstruction of the energy spectrum and dose estimation could simultaneously be carried out in real time by the k-α method in a radiation field composed of mixed standard gamma-ray sources. In this study, we carried out measurements in a background gamma-ray field to confirm applicability of the prototype monitor to the weakest type of radiation field. In addition, we conducted measurements in front of a nuclear fuel storage room (∼2 μSv/h) in the authors' laboratory to evaluate practicality of the monitor for measuring fields with a complex energy spectrum. As a result, it was found that the dose could be estimated in about 20 s after start of measurements even in the background field. For the energy spectrum, it was instantly reconstructed within 60 s in front of the fuel storage room. On the other hand, it could successfully be estimated within 10 min in the background gamma-ray field. Currently, the convergence of the energy spectrum is determined visually from time dependent change of the spectrum and dose. As a next step, we will attempt to develop a more quantitative procedure for determining the convergence. • ・We have developed a monitor system that can measure energy spectrum and dose of gamma-ray at the same time in real time in medical application spots. • ・The device consists of CsI (Tl) crystal and Multi-Pixel Photon Counter (MPPC). • ・The real-time measurement was realized by the sequential Bayesian estimation. • ・The practicability of the device was confirmed by measurement in front of the fuel storage room and in background gamma-ray field. [ABSTRACT FROM AUTHOR]

Purpose: The effect of chronic low dose-rate radiation exposure on cancers was investigated by analyzing the data of mice experiments conducted at the Institute for Environmental Sciences (IES). This analysis focuses on the differences between malignant lymphomas and solid cancers., Materials and Methods: The analysis is conducted based on the mathematical model introduced in our previous work. The model is expanded to analyze malignant lymphomas and solid cancers separately. Using the expanded model, the effect of chronic low dose-rate radiation on malignant lymphomas and solid cancers are discussed based on their occurrences, progressions, and mortalities., Results: Non-irradiated control group and 20 mGy/day × 400 days irradiated groups are analyzed. The analysis showed that radiation exposure shortened mean life expectancy for both malignant lymphomas and solid cancers (shorter by 89.6 days for malignant lymphomas and 149.3 days for solid cancers). For malignant lymphomas, both the occurrence and the progression are affected by radiation exposure. The mean age at which malignant lymphoma developed in mice was shortened by 32.7 days and the mean progression period was shortened by 57.3 days. The occurrence of solid cancer is also affected by radiation exposure, wherein the mean age at which solid cancer develops was shortened by 147.9 days. However, no significant change in progression period of solid cancers was seen in the analysis., Conclusions: The analysis showed that the occurrence and mean lifespan are affected in both malignant lymphomas and solid cancers. The shortening of the progression period is only seen in malignant lymphoma, no significant change was observed in solid cancers.

Purpose: In this paper, we described our mathematical model for radiation-induced life shortening in detail and applied the model to the experimental data on mice to investigate the effect of radiation on cancer-related life-shortening., Materials and Methods: Our mathematical model incorporates the following components: (i) occurrence of cancer, (ii) progression of cancer over time, and (iii) death from cancer. We evaluated the progression of cancer over time by analyzing the cancer incidence data and cumulative mortalities data obtained from mice experiments conducted at the Institute for Environmental Sciences (IES)., Results: We analyzed non-irradiated control and 20 mGy/day × 400 days irradiated groups. In the analysis, all malignant neoplasms were lumped together and referred to as 'cancer'. Our analysis showed that the reduction in lifespan (104 days in median) was the result of the early onset of cancer (68 days in median) and the shortening of the cancer progression period (48 days in median)., Conclusions: We described in detail our mathematical model for radiation-induced life-shortening attributed to cancer. We analyzed the mice data obtained from the experiment conducted at the IES using our model. We decomposed radiation-induced life-shortening into the early onset of cancer and the shortening of the cancer progression period.

The blood-brain barrier (BBB) is likely to be intact during the early stages of brain metastatic melanoma development, and thereby inhibits sufficient drug delivery into the metastatic lesions. Our laboratory has been developing a system for boron drug delivery to brain cells via cerebrospinal fluid (CSF) as a viable pathway to circumvent the BBB in boron neutron capture therapy (BNCT). BNCT is a cell-selective cancer treatment based on the use of boron-containing drugs and neutron irradiation. Selective tumor targeting by boron with minimal normal tissue toxicity is required for effective BNCT. Boronophenylalanine (BPA) is widely used as a boron drug for BNCT. In our previous study, we demonstrated that application of the CSF administration method results in high BPA accumulation in the brain tumor even with a low dose of BPA. In this study, we evaluate BPA biodistribution in the brain following application of the CSF method in brain-tumor-model rats (melanoma) utilizing matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI). We observed increased BPA penetration to the tumor tissue, where the color contrast on mass images indicates the border of BPA accumulation between tumor and normal cells. Our approach could be useful as drug delivery to different types of brain tumor, including brain metastases of melanoma.

Boron neutron capture therapy (BNCT) is a non-invasive type of radiation therapy developed for humans and translated to veterinary medicine. However, clinical trials on BNCT for patients with brain tumors are on-going. To improve the therapeutic efficacy of BNCT for brain tumors, we developed a boron delivery system that involves the cerebrospinal fluid (CSF), in contrast to the conventional method that involves intravenous (IV) administration. This study aimed to investigate the time-concentration profile of boron in the CSF as well as the uptake rate of boron by the brain cells after administering L-p‑boronophenylalanine (BPA) into the lateral ventricle of normal rats. Brain cell uptake rates were compared between the CSF-based and IV administration methods. The CSF-based and IV administration methods achieved comparable brain cell uptake levels; however, the former method involved lower BPA doses than the latter method. These findings suggest that the CSF method may reduce the economic and physical burdens associated with this treatment in brain tumor patients. Future studies should validate these findings in rat models of brain tumors., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The authors performed a combined analysis using the data obtained from continuous low dose rate irradiation experiments on mice conducted at the Institute for Environmental Sciences, namely, cancer incidence data and lifespan data. They estimated the length of cancer progression period, which is difficult to assess experimentally. The combined analysis showed that the mean cancer progression period is 173 d in the control group and 103 d in the irradiated group., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Recently, exploitation of cerebrospinal fluid (CSF) circulation has become increasingly recognized as a feasible strategy to solve the challenges involved in drug delivery for treating brain tumors. Boron neutron capture therapy (BNCT) also faces challenges associated with the development of an efficient delivery system for boron, especially to brain tumors. Our laboratory has been developing a system for boron delivery to brain cells using CSF, which we call the "boron CSF administration method". In our previous study, we found that boron was efficiently delivered to the brain cells of normal rats in the form of small amounts of L-p-boronophenylalanine (BPA) using the CSF administration method. In the study described here, we carried out experiments with brain tumor model rats to demonstrate the usefulness of the CSF administration method for BNCT. We first investigated the boron concentration of the brain cells every 60 min after BPA administration into the lateral ventricle of normal rats. Second, we measured and compared the boron concentration in the melanoma model rats after administering boron via either the CSF administration method or the intravenous (IV) administration method, with estimation of the T/N ratio. Our results revealed that boron injected by the CSF administration method was excreted quickly from normal cells, resulting in a high T/N ratio compared to that of IV administration. In addition, the CSF administration method resulted in high boron accumulation in tumor cells. In conclusion, we found that using our developed CSF administration method results in more selective delivery of boron to the brain tumor compared with the IV administration method.

Boron Neutron Capture Therapy (BNCT) is a promising cancer therapy, which has recently been in practical use in Japan especially using an accelerator. In BNCT real-time measurement of local boron dose is required. In the present study, a novel design of a SPECT system for BNCT (BNCT-SPECT) has been carried out to realize estimation of the local boron dose, i.e., treatment effect of BNCT. Necessary performance which BNCT community requires includes accuracy of 5% and spatial resolution of 5 mm, which are regarded to be difficult to realize. A possible design was investigated to meet the requirements. The design results we achieved are as follows: As for the elemental detection device, GAGG (3.5 × 3.5 × 30 mm 3 ) was selected, and for the collimator, the collimator hole diameter was 3.5 mm, the collimator hole pitch was 4 mm and the collimator length was 26 cm. For the obtained performance with the design, the accuracy was 4.4% and the spatial resolution was 5.1 mm. Currently prior to production of the real system, a prototype of BNCT-SPECT is being developed to acquire real projection data to confirm the performance and examine our own image reconstruction method with the obtained projection data., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Based on the activation method using 71 Ga(n,γ) 72 Ga reaction, a cubic neutron flux intensity detector for epi-thermal neutrons was designed for boron neutron capture therapy (BNCT), and experimentally tested with a prototype detector in a neutron field produced at OKTAVIAN facility of Osaka University, Japan. The experimental test results and related analysis indicated that the performance of the detector was confirmed to be acceptable in the neutron field of BNCT. Practically, the neutron flux intensity mainly covering from 0.5 eV to 10 keV can be measured within 3% by the present detector., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

A novel optically stimulated luminescence (OSL) detector containing isotopically enriched boron was developed for thermal neutron dosimetry. Alumina containing isotopically enriched boron (Al2O3:B) was synthesised by the sol-gel method. The Al2O3:B was annealed up to ~1800 K. For X-ray diffractometer (XRD) analysis, the diffraction pattern of the Al2O3:B had reflex peaks corresponding to α-Al2O3. The sensitivity of Al2O3:B to photons was slightly 2% of that of a commercial Al2O3:C. The Al2O3:B detector had satisfactory linearity in X-ray dose measurement. A thermal neutron field was constructed using a 241Am-Be neutron source and graphite blocks. A pair of Al2O3:10B and Al2O3:11B detectors were set in the thermal neutron field. The response of Al2O3:10B was larger than that of Al2O3:11B owing to the 10B(n,α)7Li reactions. The sensitivity of Al2O3:10B to thermal neutrons was estimated to be two orders less than the photon sensitivity. Therefore, the pair of Al2O3:10B and Al2O3:11B detectors were useful for thermal neutron dosimetry., (© The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The neutron flux monitors from 10keV to 1MeV designed for boron neutron capture therapy (BNCT) were experimentally tested with prototype monitors in an appropriate neutron field produced at the intense deuterium-tritium neutron source facility OKTAVIAN of Osaka University, Japan. The experimental test results and related analysis indicated that the performance of the monitors was good and the neutron fluxes from 10keV to 1MeV of practical BNCT neutron sources can be measured within 10% by the monitors., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Our research group is now investigating a BNCT-SPECT system with cadmium tellurite (CdTe) detectors, which can obtain a three-dimensional image of the BNCT treatment effect by measuring the 478keV gamma-rays emitted from an excited state of the 7 Li nucleus generated by the 10 B(n,α) reaction. The BNCT-SPECT system is composed of a collimator and an array-type CdTe detector. In this study, we produced an array detector with two CdTe elements to test the basic detection property for anti-coincidence events. Our investigation confirmed that the detector offers an improved S/N ratio by the anti-coincidence detection. We also proposed an estimation method using the MCNP5 to analyze coincidence events in the detector., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The performance of an epithermal neutron (0.5eV

Proton-lithium (p-Li) reaction is being examined worldwide as a candidate nuclear production reaction for accelerator based neutron source (ABNS) for BNCT. In this reaction, the emitted neutron energy is not so high, below 1 MeV, and especially in backward angles the energy is as low as about 100 keV. The intensity measurement was thus known to be difficult so far. In the present study, a simple method was investigated to monitor the absolute neutron intensity of the p-Li neutron source by employing the foil activation method based on isomer production reactions in order to cover around several hundreds keV. As a result of numerical examination, it was found that (107)Ag, (115)In and (189)Os would be feasible. Their features found out are summarized as follows: (107)Ag: The most convenient foil, since the half life is short. (115)In: The accuracy is the best at 0°, though it cannot be used for backward angles. And (189)Os: Suitable nuclide which can be used in backward angles, though the gamma-ray energy is a little too low. These would be used for p-Li source monitoring depending on measuring purposes in real BNCT scenes., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

To identify individual cells exposed to a X-ray microbeam in a cell population, we developed a biocompatible microchamber-array chip using UV lithography of photopolymer SU-8. The center-to-center distance between microchambers is 50 mum including a wall of 15 mum height. Using the microchamber-array chip, we performed tracking of individual exposed cells. Sample cells loaded in a microchamber array were selectively irradiated with the X-ray microbeam under microscopic observation. All the irradiated cells were indexed by the array arrangement of the microchambers. For about 24 h of post-irradiation incubation, the irradiated cells were identified successfully by time-lapse observation. In addition, the induction of radiation effects was observed in identified cells using immunofluorescence.

Origins of peak broadening in a histogram of measured adhesive forces were studied. The adhesive forces were measured in water by pulsed-force-mode atomic force microscopy. One sample was prepared by a microcontact printing method on a sputtered gold film with fine grains, on which CH(3)- and COOH-terminated regions were produced. Gold surfaces of other samples were chemically modified homogeneously by a self-assembling method in solution. Their surfaces were, however, topographically different, i.e. (i) an Au(111)-terrace-rich gold film prepared by vacuum vapor deposition at high temperature and (ii) sputtered gold films on cover glass with different grain sizes obtained by different deposition time. These sample surfaces and the probe tip surface were all CH(3)-terminated by self-assembled monolayers with CH(3)(CH(2))(19)SH. The main origin of peak broadening in the histogram was the topographic effect. Namely, the change in the grain sizes and the change in multiplicity of contacts between the tip and convexities of the grains resulted in the distribution of the observed adhesive forces.