arXiv subjects

Takahiro Moriya

Publications and source records attributed to Takahiro Moriya.

3 recordsLinked to original sources

arXiv2026

108 ps coincidence time resolution through optimized scintillators, photodetectors, readout electronics, and DOI-based timing correction in orthogonally stacked detector configurations

Objective. Existing commercial time-of-flight positron emission tomography (TOF-PET) systems yield a coincidence time resolution (CTR) of ~200 ps or less full width at half maximum (FWHM). Recently, there has been a challenge to achieve a CTR of 100 ps FWHM at the system level. However, current silicon photomultipliers (SiPMs) and 20-mm-thick scintillators in conventional single-ended readout scheme is difficult to achieve 100 ps CTR; the photon transport time spread (PTS) within the scintillator crystal is a major barrier. Differences in the interaction position result in variations in PTS on the order of several tens of ps, thereby degrading the CTR. A shorter scintillator can improve CTR; however, this can degrade detection efficiency. Approach. To overcome this trade-off between the CTR and detection efficiency, we previously proposed xDetector, an orthogonally stacked configuration along the longitudinal axis of scintillator crystals. We investigated the CTR potential of the xDetector by improving the scintillator, photodetector, and readout electronics, and by applying CTR correction based on a three-dimensional interaction within the scintillator. Main results. Based on error propagation, the CTR of the paired xDetector was calculated as 113.5 $\pm$ 2.7 ps FWHM. Furthermore, the CTR of the xDetector was measured at four positions along the longitudinal axis by manually sliding the xDetector, and the corrected achieved CTR was 108.6 $\pm$ 1.9 ps FWHM. Moreover, compared with the conventional single detector using a 20.0 mm scintillator, CTR improved by an average of 10.3%. Significance. The xDetector offers potential as a PET detector concept to achieve a CTR of 100 ps FWHM. Such timing performance is expected to improve TOF-PET image quality and quantitative accuracy, contributing to more reliable disease detection and diagnosis than current PET detectors.

physics.med-ph↗

arXiv2025

Scintillator-integrated microchannel plate photomultiplier tubes for ultrafast timing over keV-GeV energy scales

Precise measurement of radiation has long played a vital role in a wide range of research and industrial fields, from fundamental physics beyond the Standard Model to medical imaging such as time-of-flight positron emission tomography. Developing radiation detectors that achieve high timing precision-on the order of a few tens of picoseconds-and energy measurement capabilities remains indispensable yet challenging. In this study, we developed two types of scintillator-integrated microchannel plate photomultiplier tubes (SCI-IMPs), one incorporating barium fluoride, and the other bismuth germanate, to enable simultaneous high-precision timing and energy measurements. To evaluate their performance over a wide energy range from keV- to GeV-scale, electron-positron annihilation gamma rays and cosmic ray muons were used. For energy measurements, both detectors achieved an energy resolution of approximately 35% at 511 keV. For timing measurements using 511 keV, coincidence time resolutions (CTRs) of approximately 50 ps full width at half maximum (FWHM) were obtained for both detectors. In contrast, for cosmic ray muon experiments where cosmic ray muon energy is typically on the order of GeV, CTRs were measured to be 25.1 and 16.8 ps FWHM for barium fluoride- and bismuth germanate-based detectors, respectively. The versatile scintillator-integration technique established in this study can broaden the applicability of the newly developed SCI-IMPs. In particular, these results demonstrate that the developed detectors push the boundaries of timing performance while retaining energy measurement and hold promise for future applications in fundamental physics experiments and medical imaging.

physics.ins-det↗

arXiv2024

Simplified Shielded MEG-MRI Multimodal System with Scalar-mode Optically Pumped Magnetometers as MEG Sensors

Magnetoencephalography (MEG) conventionally operates within high-performance magnetic shields due to the extremely weak magnetic field signals from the measured objects and the narrow dynamic range of the magnetic sensors employed for detection. This limitation results in elevated equipment costs and restricted usage. Additionally, the information obtained from MEG is functional images, and to analyze from which part of the brain the signals are coming, it is necessary to capture morphological images separately. When MEG and morphological imaging devices are separate, despite their individual high measurement accuracies, discrepancies in positional information may arise. In response, we have developed a low-field magnetic resonance imaging system that incorporates scalar-mode optically pumped magnetometers with a wide dynamic range and exceptionally high measurement sensitivity as sensors for MEG. Operating at low magnetic fields eliminates the need for superconducting coils in magnetic resonance imaging and the high-performance magnetic shields essential for MEG, promising a substantial cost reduction compared to traditional approaches. We achieved a noise level of about $16\,\rm{pT/Hz}^{1/2}$ with a single channel magnetometer, and reached a noise level of $367\,\rm{fT/cm/Hz}^{1/2}$ through differential measurements. The system successfully conducted MR imaging on a phantom, demonstrating the potential of MEG and MRI fusion.

physics.med-ph↗