Yosuke Ito

• Ph. D
• Junior Associate Professor at Kyoto University

Low-field or ultra-low-field magnetic resonance imaging (LF-/ULF-MRI) does not require expensive superconducting coils. Therefore, LF-/ULF-MRI systems that use normally conducting magnets allow the static magnetic field to be switched on and off. As this feature allows various devices to be installed inside the LF-/ULF-MRI system, LF-/ULF-MRI is su...

Recently, optically pumped magnetometers (OPMs), which use the spin polarization of alkali metal atoms to measure magnetic fields, have attracted much attention. However, in order to realize high‐sensitivity biomagnetic field measurements using OPMs, it is necessary to reduce environmental magnetic noise and system noise. In this study, we investig...

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...

The purpose of this investigating R&D committee on magnetic sensor with machine learning is to grasp the research and development trends in the basic technology of magnetic sensor with machine learning. Since 2020 we held 12 regular meeting and co-sponsored 5 joint technical meeting on "Magnetics". With 30 committee members and invited 10 guest spe...

Recently, optically pumped magnetometers (OPMs), which use the spin polarization of alkali metal atoms to measure magnetic fields, have attracted much attention. However, in order to realize high-sensitivity biomagnetic-field measurements using OPMs, it is necessary to reduce environmental magnetic noise and system noise. In this study, we investig...

In recent years, measuring biomagnetic fields in the Earth's field by differential measurements of scalar-mode OPMs have been actively attempted. In this study, the sensitivity of the scalar-mode OPMs under the geomagnetic environment in the laboratory was studied by numerical simulation. Although the noise level of the scalar-mode OPM in the labor...

Functional magnetic resonance imaging (fMRI) conventionally relies on hemodynamics response induced some seconds after neural activation. Therefore, the temporal limitations of fMRI is the main challenge and we focused on the spin-lock sequence, which identifies neural magnetic field using magnetic resonance between the spin-lock pulse and the meas...

In this study, we carried out computer simulations to apply the SSS method to flat multi-channel OPMs with auxiliary sensors and examined the suppression effect of environmental magnetic noise. We assumed that auxiliary sensors are added so that the environmental magnetic noise can be effectively suppressed, and assessed the appropriate position of...

Spin-lock preparation was studied to detect tiny oscillatory magnetic fields such as a neural magnetic field without the blood oxygen level-dependent effect. This approach is a direct measurement and independent of static magnetic field strength. Accordingly, it is anticipated as a feasible functional magnetic resonance imaging (fMRI) in low and ul...

Several noninvasive techniques for the direct measurement of the neuronal activity using magnetic resonance imaging (MRI) have recently been reported. As a promising candidate, we focus on a spin-lock MRI sequence (i.e., stimulus-induced rotary saturation (SIRS)) directly measuring a tiny oscillating magnetic field. Previous phantom studies on SIRS...

We demonstrated the feasibility of the spin-lock preparation sequence using low-field magnetic resonance (MR) imaging that prevents interference from blood-oxygenation-level-dependent effects. We focused on two spin-lock preparations: spin-lock Mz (SL-Mz) and stimulus-induced rotary saturation (SIRS) and analyzed the magnetization dynamics during t...

Recently, the main issue in neuroscience has been the imaging of the functional connectivity in the brain. No modality that can measure functional connectivity directly, however, has been developed yet. Here, we show the novel MRI sequence, called the partial spinlock sequence toward direct measurements of functional connectivity. This study invest...

Optically pumped magnetometers (OPMs) that are equipped with hybrid cells of K and Rb have been studied for improving their sensitivity and biomagnetic field measurements. The densities of the two alkali metal atoms and their density ratio are especially important for hybrid OPMs. In this study, we fabricated five hybrid cells using different K and...

Optically pumped magnetometers (OPMs) that are equipped with hybrid cells of K and Rb have been studied for improving their sensitivity and biomagnetic field measurements. The densities of the two alkali metal atoms and their density ratio are especially important for hybrid OPMs. In this study, we fabricated five hybrid cells using different K and...

We studied stimulus-induced rotary-saturation preparation (which enables measurement of oscillating magnetic fields using MRI) and derived an analytical solution of the Bloch equation to understand magnetization dynamics mathematically and comprehensively and to conduct simulations without sequential-calculation techniques such as the Runge-Kutta m...

Multi-channel measurements with fine spatial resolution will make magnetoencephalograms (MEGs) possible with small animals using optically pumped magnetometers (OPMs). Therefore, we fabricated a 20-channel probe-beam detector that uses a K-Rb hybrid OPM to increase the spatial resolution. First, we investigated the sensitivity of the detector using...

Recently, optically pumped atomic magnetometers (OPAMs) replacing SQUID-based magnetometers have attracted a considerable attention. To apply the OPAMs to biomagnetic field measurements, simultaneous multilocation measurements are required. To fulfill the specific requirement, we have developed a hybrid cell, which contains potassium and rubidium a...

Superconducting quantum interference devices are widely used in basic and clinical biomagnetic measurements such as low-field magnetic resonance imaging and magnetoencephalography primarily because they exhibit high sensitivity at low frequencies and have a wide bandwidth. The main disadvantage of these devices is that they require cryogenic coolan...

Highly sensitive magnetic sensors for biomagnetic measurements are often used in gradiometers to suppress the magnetic noise from the environment. We propose a differential measurement method in optically pumped atomic magnetometers, where the frequency responses from the two magnetometers are balanced separately and the signals are subtracted. A m...

An optically pumped K–Rb hybrid atomic magnetometer can be a useful tool for biomagnetic measurements due to the high spatial homogeneity of its sensor property inside a cell. However, because the property varies depending on the densities of potassium and rubidium atoms, optimization of the densities is essential. In this study, by using the Bloch...

In the field of biomagnetic measurement, optically-pumped atomic magnetometers (OPAMs) have attracted significant attention. With the improvement of signal response and the reduction of sensor noise, the sensitivity of OPAMs is limited mainly by environmental magnetic noise. To reduce this magnetic noise, we developed the optical gradiometer, in wh...

In the field of biomagnetic measurements, optically pumped atomic magnetometers (OPAMs) are expected to be alternative sensors to magnetometers based on superconducting quantum interference devices (SQUIDs). In addition, miniaturized OPAMs are required for practical use. To address this issue, we developed a compact module of a high-sensitivity OPA...

We have developed a K-Rb hybrid optically pumped atomic magnetometer (OPAM) for biomagnetic measurements. With this hybrid OPAM, we used a linear photodiode array and a charge-coupled device (CCD) sensor to instantaneously measure 1-D and 2-D magnetic field distributions generated by a test coil, respectively. The measured distributions were compar...

The goal of this study is to determine optimal conditions of optically pumped atomic magnetometers using a hybrid cell of potassium and rubidium atoms. We theoretically investigated the properties of the magnetometers and considered the optimal density ratio of potassium and rubidium atoms. We found that the experimental results agreed well with th...

We measured the spatial homogeneity of spin polarization, which is directly related to the sensitivity and magnetic linewidth of an optically pumped atomic magnetometer with a hybrid cell of K and Rb atoms. This was done by changing the position of the probe beam. Furthermore, for comparison, we also measured the sensitivity and magnetic linewidth...

We have developed an optically pumped atomic magnetometer using a hybrid cell of K and Rb. The hybrid optical pumping technique can apply dense alkali-metal vapor to the sensor head and leads to high signal intensity. We use dense Rb vapor as probed atoms, and achieve a sensitivity of approximately 100 fTrms/Hz1/2 around 10 Hz. In this case, the se...

Measuring biomagnetic fields, such as magnetocardiograms (MCGs), is important for investigating biological functions. To address to this need, we developed an optically pumped atomic magnetometer. In this study, human MCGs were acquired using a potassium atomic magnetometer without any modulating systems. The sensitivity of the magnetometer is comp...

In this paper, we describe the detection of rotating magnetic fields using optically pumped atomic magnetometers (OPAMs) for measuring magnetic resonance (MR) signals. From the results of rotating- and alternating-magnetic-field measurements, we found that to detect a rotating magnetic field with high sensitivity, the rotation direction of the magn...

We carried out plasma enhanced chemical vapor deposition using a plasma jet at atmospheric pressure for one-dimensional deposition of SiO2 films and ZnO compounds, and measured the film quality by Fourier transform infrared spectroscopy. In the case of SiO2, the deposition rate was about 400 nm/s and the breakdown voltage was 5×105 V/cm. On the oth...

An optically pumped atomic magnetometer using a hybrid cell of potassium and rubidium atoms was demonstrated to yield high sensitivity to magnetic fields. We operated the magnetometer with the four possible combinations of optically pumped and optically probed atoms and found that the combination of optically pumped potassium and optically probed r...

We have investigated the discharge mechanisms in a helium plasma jet with a coaxial dielectric barrier discharge (DBD) configuration, which can generate low-temperature plasma plume mainly by positive corona streamer propagation. In this study, we focused on the relationships between the coaxial DBD inside a glass tube and the positive streamer pro...

In order to investigate the effect of accumulated charge on a substrate surface in the deposition of a SiO2 film with an atmospheric-pressure plasma jet, we have measured the discharge current flowing into a copper substrate, which was placed 20 mm from the exit of the plasma jet and connected to a variable capacitor in series. We found that the di...

Plasma enhanced chemical vapor deposition using a non-thermal plasma jet was applied to deposition of ZnO films. Using vaporized bis(octane-2,4-dionato)zinc flow crossed by the plasma jet, the deposition rate was as high as several tens of nm/s. From the results of infrared spectra, the films deposited at the substrate temperature Tsub = 100 °C con...

We have diagnosed the electron density in nitrogen plasma generated in a device composed of coaxial-hollow microdielectric-barrier discharges using a millimetre-wave transmission method. At atmospheric pressure the generated plasma occupied almost the entire hollow-electrode space, and the electron density was estimated as 1012–1013 cm−3. This valu...

The deposition rates of oxide films such as SiO 2 and ZnO by using non-thermal plasma jet at atmospheric pressure has been investigated. We could obtain high deposition rates of both of two materials. It was found that the deposition rate was affected by the ca-pacitance of the substrate and the deposited films so that the accumulated charge on the...

The behavior of N2+ ions in a low-frequency driven atmospheric pressure He plasma jet effused into ambient air was analyzed from laser induced fluorescence (LIF) spectroscopy measurements. The gas temperature derived from the rotational distribution was kept near room temperature and the drift velocity of N2+ ions estimated from the line shape was...

We present an experimental study of plasma enhanced chemical vapor deposition (PECVD) of SiO2 films from tetraethoxysilane (TEOS) using a plasma jet based on capillary dielectric barrier discharge (CDBD) at atmospheric pressure. We tried three different configurations: (a) coaxial type, (b) a crossed type with a vertical plasma jet and a tilted TEO...

Propagation of electromagnetic waves in several types of microplasmas has been examined experimentally in a frequency range 10 75 GHz. Firstly, the fundamental characteristics of the propagation were investigated using a planar geometry of microplasma assembly, and the electron density was derived by a comparison of the transmittance with the theor...

Kyoto University (京都大学) 0048 新制・課程博士 博士(工学) 甲第15383号 工博第3262号 新制/工/1491 27861 2010-03-23 京都大学大学院工学研究科電子工学専攻 (主査)教授 髙岡 義寛, 教授 北野 正雄, 教授 藤田 静雄 学位規則第4条第1項該当