A new measurement method called current-induced magnetic modulation spectroscopy (CIMMS), which measures the electrical impedance in a contactless manner using a high-frequency current and an induced magnetic field, has been proposed. CIMMS is to apply high-frequency minute current to a living body, measure the induced magnetic field with a magnetic sensor to obtain impedance, and measure changes such as respiration, pulse, and inflammation/collapse of lung fields. CIMMS has many advantages such as be able to measure even with clothes on, however, it cannot be realized without a magnetic sensor with high frequency and high sensitivity. Therefore, we focused on optically pumped atomic magnetometer (OPAM) as magnetic sensor used for CIMMS. OPAM has the potential to achieve ultra-high sensitivity and broadband. However, it requires a large and complicated system such as a strict magnetic shield and vibration isolation. Therefore, we developed that small and movable OPAM system that operates under unshielded condition. We also report that we achieved sensitivity of <7.2pT/Hz1/2 at 35~225kHz by using a phase locked loop
We have succeeded in coating an aluminum oxide thin film of inorganic-organic hybrid on the inner wall of the cell of an optically pumped atomic magnetometer using spin polarization of alkali metal atoms by a unique room temperature molecular layer deposition method. The relaxation time of polarized spin was investigated by using the pump probe method, and it was revealed that the relaxation time of spin polarization can be significantly improved and the relaxation prevention effect can be remarkably exhibited as compared with the case without coating.
In recent years, MRI using a rare gas has attracted attention. Rare gas MRI can perform imaging of lungs with few protons and can also evaluate gas dynamics and hemodynamics. Attempts have been made to enhance the signal intensity by hyperpolarizing nuclear spins to obtain NMR signals from the gas. This hyperpolarization technology is also expected to be effective when combined with low-field MRI including permanent magnet type. In this study, a xenon (129Xe) hyperpolarization system using a 795nm laser was constructed and evaluated using a 0.3T NMR system. As a result, it was shown that the NMR signal intensity from 129Xe can be enhanced 1.5 times with a polarization of 30 minutes.
We developed molecular layer deposition method of atomically thin hybrid polymer film for the first time by developing atomic layer deposition method with sequential surface chemical reactions in order to minimize the effect of the dipole-dipole interaction between the electron spin of alkali metal atoms and the nuclear spin of the atoms in the glass of the cell. We controlled film thickness of polymer thin film precisely and finally aimed at improving the sensitivity of the optically pumped atomic magnetometer. In the presentation, we report on the relaxation time of spin polarization by atomically thin hybrid polymer film with laser pump-probe method.
In recent years, hyperpolarized noble gas MRI attracts attention. Spin-exchange optical pumping (SEOP) is often used for hyperpolarizing nuclear spin of noble gas. Although there are many reports on rare gas hyperpolarization devices using SEOP, most of them use high power CW lasers exceeding 10 W. Large output laser has high risk of exposure, high cost and high energy consumption. However, in SEOP, only a very small amount coincident with D1 line works and almost all other power is abandoned. Therefore, in this study, we development that Xe hyperpolarizing system using narrow linewidth Ti:Sapphire laser and demonstrated that this system can pump with lower pawer by tuning wavelength to D1 line. As a result, we show that system using narrow linewidth laser can get equally or lager signal augment ratio by 1/45 times lower irradiation power than conventional system.
Hyperpolarized (HP) noble gas has attracted attention in NMR / MRI. In an ultra-low magnetic field, the effectiveness of signal enhancement by HP noble gas should be required because reduction of the signal intensity is serious. One method of generating HP noble gas is spin exchange optical pumping which uses selective excitation of electrons of alkali metal vapor and spin transfer to nuclear spin by collision to noble gas. Although SEOP does not require extreme cooling or strong magnetic field, generally it required large-scale equipment including high power light source to generate HP noble gas with high efficiency. In this study, we construct a simply generation system of HP xenon-129 by SEOP with an ultralow magnetic field (up to 1 mT) and small-scale light source (about 1W). In addition, we measure in situ NMR signal at the same time, and then examine efficient conditions for SEOP in ultra-low magnetic fields.
KEYWORDS: Magnetic resonance imaging, Xenon, Magnetism, Optical pumping, Gas lasers, Gases, Functional imaging, Tomography, Chemical oxygen iodine lasers, Chemical species, Rubidium, Control systems, Inspection
Nuclear magnetic resonance imaging (MRI) is widely used as tomographic image inspection in clinical. MRI has many advantages such as obtaining tomographic images by non-exposure. However, it requires a strong magnetic field (0.4 to 3 T in general), so it also has disadvantages such as large size and high cost. If we use extremely low magnetic field as low as the earth B-field for MRI may be useful. In this study, we demonstrated the increase of nuclear magnetic resonance signals by spin hyperpolarization by spin exchange optical pumping for xenon in an extremely low magnetic field.
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