National Institutes for Quantum and Radiological Science and Technology
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Diffusion Tensor Image Analysis Along the Perivascular Space in Former Professional Athletes with Repetitive Mild Traumatic Brain Injury History
No full textRationale and objectives: The long-term changes in the glymphatic system of former professional athletes exposed to repetitive mild traumatic brain injuries remain poorly understood. This study aimed to use diffusion tensor image analysis along the perivascular space (DTI-ALPS) to evaluate the glymphatic system activity and correlate the ALPS index with neuropsychiatric symptoms in former professional athletes.
Materials and methods: 30 former professional athletes and 24 age- and sex-matched controls underwent DTI with 3 T magnetic resonance imaging, and neuropsychiatric tests were performed in the athlete group.
Results: The ALPS index (mean, right, and left) in the athlete group was compared to that in controls, and correlations with clinical variables were analyzed. The mean, right, and left ALPS indices in the athlete group were significantly lower than those of the control group (mean: 1.49±0.12 vs. 1.61±0.16, cohen's d=0.847, p<0.01; right: 1.51±0.12 vs. 1.61±0.16, cohen's d=0.722, p=0.01; and left: 1.47±0.15 vs. 1.60±0.20, cohen's d=0.765, p<0.01). The mean and right ALPS indices were positively correlated with the Wisconsin Card Sorting Test performance in the athlete group (mean: r=0.41, p=0.04; right: r=0.43, p=0.03; not significant after Bonferroni correction).
Conclusion: A lower ALPS index in former professional athletes may be associated with impairments in cognitive function, reflected in glymphatic dysfunction.journal articl
Electronic structure of B2Ir2O7 probed by resonant inelastic x-ray scattering at the oxygen K edge: Metallicity, hybridization, and electronic correlations
No full textThe electronic structure of metallic Bi2Ir2O7 has been investigated by a combination of soft x-ray absorption spectroscopy, x-ray emission spectroscopy (XES), and resonant inelastic x-ray scattering (RIXS) in the vicinity of the oxygen K edge. The O K-edge RIXS spectra are found to resemble the O K-edge XES spectra with resonating features but with an absence of any Raman modes, revealing the highly itinerant nature of this compound. The O K-edge response is compared with scalar relativistic band structure calculations within the local density approximation, which captures the main spectral characteristics. The RIXS spectra either display a localized or delocalized Ir 5d response, depending on whether the photon energy is tuned to the pre-edge or above. Our results uncover a significant coupling of O K-edge RIXS via the O 2p?Ir 5d hybridization to the partial density of states of the Ir 5d states. An alternative explanation of the Ir 5d?O 2p hybridization spectral structure in the optical region of the RIXS spectra is given in terms of Ir dd excitations. Our findings allow us to infer that the relative electronic correlations in the metallic Bi2Ir2O7 compound with sizable spin-orbit coupling are 0.06???/???0.22 and thus are in the moderate-to-weak regime.We found that the Jeff model, developed to understand the existence of insulating states in various iridate perovskites, is not applicable to Bi2Ir2O7, casting doubts on its applicability to pyrochlore iridates with moderate to weak electronic correlations. We argue that the strong O 2p?Ir 5d?Bi 6s/6p hybridization is responsible for the highly itinerant nature of this material. Our results establish the capability of O K-edge RIXS to identify the electronic ground state of 5d spin-orbit transition metal compounds and to qualitatively assess their degree of localization.journal articl
Exploiting network optimization stability for enhanced PET image denoising using deep image prior
No full textObjective. Positron emission tomography (PET) is affected by statistical noise due to constraints on tracer dose and scan duration, impacting both diagnostic performance and quantitative accuracy. While deep learning-based PET denoising methods have been used to improve image quality, they may introduce over-smoothing, which can obscure critical structural details and compromise quantitative accuracy. We propose a method for making a deep learning solution more reliable and apply it to the conditional deep image prior (DIP). Approach. We introduce the idea of stability information in the optimization process of conditional DIP, enabling the identification of unstable regions within the network's optimization trajectory. Our method incorporates a stability map, which is derived from multiple intermediate outputs of a moderate neural network at different optimization steps. The final denoised PET image is then obtained by computing a linear combination of the DIP output and the original reconstructed PET image, weighted by the stability map. Main results. We employed eight high-resolution brain PET datasets for comparison. Our method effectively reduces background noise while preserving small structure details in brain [18F]FDG PET images. Comparative analysis demonstrated that our approach outperformed existing methods in terms of peak-to-valley ratio and background noise suppression across various low-dose levels. Additionally, region-of-interest analysis confirmed that the proposed method maintains quantitative accuracy without introducing under- or over-estimation. Furthermore, we applied our method to full-dose PET data to assess its impact on image quality. The results revealed that the proposed method significantly reduced background noise while preserving the peak-to-valley ratio at a level comparable to that of unfiltered full-dose PET images. Significance. The proposed method introduces a robust approach to deep learning-based PET denoising, enhancing its reliability and preserving quantitative accuracy. Furthermore, this strategy can potentially advance performance in high-sensitivity PET scanners and surpass the limit of image quality inherent to PET scanners.journal articl
OpenPETによる重粒子腺がん治療イメージング
No full text高い線量集中制をもつ重粒子線がん治療は、正常組織への影響を抑えつつ腫瘍を効果的に制御できる。重粒子線を生体に照射すると、副次的に陽電子抄出核種が生成される。そのため、実際の治療ビームに関する情報を得るには、解放空間を有するOpenPETを用いた照射中のイメージングが有効であり、治療ビームの飛程や治療効果を照射直後にその場で評価できると期待される。われわれは、2008年の初期提案以降、OpenPETの研究開発を継続しており、HIMAC[（Heavy Ion Mwdical Accelerator in Chiba）の物理実験室での照射イメージング実験を経て、2023年より頭頸部がん患者を対象とした臨床試験を開始した。本編では、これまでのOpenPET装置の開発と、現在進行中の臨床試験について概説する。journal articl
Development of a polarized proton solid target for measuring the spin correlation coefficient of deuteron?proton scattering and analysis of radiation damage
No full textThe polarized proton solid target was developed for the spin correlation coefficient measurement toward
three-nucleon force research. The electromagnet of the polarized proton target was newly designed for
dynamic nuclear polarization based on photo-exited triplet electron spins (triplet-DNP) using a single crystal of
naphthalene (C10H8) doped with deuterated pentacene (C22D14). The polarized target system can be operated
in 0.3 T and at 100 K and has a large aperture of 60? to the azimuthal angles of ?? = 0?, 90?, 180?, and 270? for
the scattered particles. The trajectory simulation for the scattered deuterons and recoiled protons in a deuteronproton
(????) elastic scattering indicates that the measurement of the spin correlation coefficient between
??c.m. = 69.6??150.7? in the center-of-mass system at ????? = 100 MeV can be applicable. Proton?proton scattering
experiment at 200 MeV was performed to determine the target polarization and to investigate radiation damage
due to beam irradiations. From a scattering asymmetry, the proton polarization is determined to ??????
? 0.3 but is
strongly depolarized by the radiation damage. The radiation damage is analyzed quantitatively by decomposing
into target heating and radical generation. The former is dominant up to 106 count per second and the latter
becomes a major contribution at the higher beam intensities. Finally, the performance of the spin correlation
coefficient measurement at the ???? elastic scattering is discussed. Combined with the polarized deuteron ion
source at RIKEN, the expected statistical accuracy is comparable to the previous studies at IUCF.journal articl
ITER TFコイル製作における超伝導導体と巻線部調達の技術的インターフェース問題の解決
No full textThe National Institutes for Quantum Science and Technology （QST） is responsible for manufacturing 33 TF conductors and 9 TF coil winding packs （WP）. QST has been conducting these manufacturing processes. However, technical issues related to the interface between the TF conductor and WP arose due to differences in standards and quality culture among countries. These issues included PT indication on the welding line of the conductor jacket and high carbide concentration during heat treatment. QST could overcome these issues with the cooperation of manufacturers, domestic agencies, and the ITER organization. In addition, QST revealed the pressure drop characteristics of the conductor in the transverse and longitudinal directions, these data will prove valuable in future ITER operations. Based on this experience in TF conductor and WP manufacturing, a proposal for an optimized scheme for developing DEMO coils is described.journal articl
Development of an ultrasensitive small animal PET with 4-layer DOI detectors for sub-second dynamic rodent imaging
No full textObjective: Dynamic PET imaging is important for preclinical research since it can visualize the functional information of rodent models as a function of time. However, the temporal resolution of small animal PET imaging has been limited to a scale of seconds due to low sensitivity, and it is not sufficient to capture cardiac or brain function accurately. Here, we present an ultrasensitive small-animal PET scanner with total-body coverage for sub-second dynamic imaging of a rat.
Methods: The ultrasensitive small animal PET scanner has a 155 mm inner diameter and 325.6 mm axial coverage. The PET scanner has 6 rings, each of which has 10 depth-of-interaction detectors. Each depth-of-interaction detector consists of a 4-layer Zr-doped gadolinium oxyorthosilicate crystal array (2.85 mm pitch, 30 mm total thickness) and 8×8 multi-anode photomultiplier tubes. The physical PET performance was evaluated based on the National Electrical Manufacturers Association NU4 protocol. Sub-second dynamic rat imaging was performed with 18F-FDG tracer.
Main Results: The peak absolute sensitivity was 20.2% and spatial resolution was 2.6 mm at the center of the field of view with an energy window of 400-600 keV. Total-body images of a rat were obtained with a single bed position. The cardiac function of a rat was visualized with 0.25 s temporal resolution, which was hardly possible with conventional small animal PET scanners.
Significance: The developed ultrasensitive animal PET enabled sub-second dynamic PET imaging in rodent models with total-body coverage. In conclusion, the ultrasensitive small animal PET scanner can serve as a useful molecular imaging tool for preclinical research with its long axial coverage sub-second temporal resolution.journal articl
Metal-Free Raman Sensing Platforms of Organic Nanowire Arrays Produced by High Energy Charged Particles
No full textAn organic nanowire fabrication technique, i.e., single-particle-triggered linear polymerization, which yields nanowires consisting of a wide range of organic molecules with perfectly controlled sizes, is developed via chemical reactions induced by a high-energy charged particle. A freestanding purely organic nanowire array (ONA) structure is fabricated to maximize the surface area with the designed surface affinity for analyte molecules. The ONA is demonstrated as an effective sensing platform for Raman spectroscopy with a high enough sensitivity against a series of analytes including rhodamine, crystal violet, methylene blue, neutral red, methyl orange, as well as oligopeptides. The designed electron transfer reactions between the analytes and nanowires provide Raman signal enhancement factors of up to 108 with the detection limit of the analytes as 10?9 M for the rhodamine, indicating the viability of these ONAs as a novel class of metal-free Raman sensing probes.journal articl
Rolling two-dimensional covalent organic framework (COF) sheets into one-dimensional electronic and proton-conductive nanotubes
No full textMimicking the interconvertible carbon allotropes of 2-dimensional (2D) graphene and 1-dimensional (1D) carbon nanotubes (CNTs), herein we report the in situ transformation of 2D π-conjugated covalent organic frameworks (COFs) sheet into 1D nanotubular structures via self-assembly the sheets at solvent interfaces. The facile “roll-sheets” self-assembly resulted in coaxial nanotubes with uniform cross-sectional diameter, which was realized for diazapyrene-based COFs but not for the corresponding pyrene COF, although both possess similar chemical structures. Upon replacing the carbon atoms at 2,7-positions of pyrene with nitrogen, contrasting optical and electronic properties were realized, reflecting the rolled structure of the conjugated 2D sheets. The nanotubes exhibited concerted electronic- and proton-conducting nature with stable conducting pathways at ambient conditions. The nitrogen centers act simultaneously as the site for charge carrier doping and proton acceptors, as evidenced by the high photo- and electrical conductivity, as well as the record proton conductivity (σ = 1.98 S cm?1) results. The present diazapyrene-based 1D nanotubular COF serves as a unique materials platform with electronic conduction in the wall and proton conduction in the core, respectively.journal articl
Completion of Manufacturing and Testing of 8 ITER Gyrotrons with its Auxiliary Systems
No full textITER用ジャイロトロン8本の製作及び性能確認試験が完了したのでその結果について、これまでの開発の歴史も踏まえて報告する。8本のジャイロトロンの性能試験の結果、8本共にITER機構が要求する、周波数170GHz、マイクロ波出力1MW、運転時間300秒を達成した。8本の性能のバラツキは出力±25kW、周波数±25MHzと大きな性能差は見られなかったことを報告する。QSTフュージョンエネルギーワークショップconference presentatio