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2. Human MCG measurements with an ultrasensitive optically-pumped atomic magnetometer

Author

KAMADA, Keigo, ITO, Yosuke, and KOBAYASHI, Tetsuo

Subjects
原子磁気センサ, 心磁図, 生体磁気計測
Abstract

脳磁図(MEG)や心磁図(MCG)等の生体磁気信号計測は, 生体機能の解明や疾患等の診断に用いられる非侵襲的計測・イメージングモダリティの中でも重要な役割を担っている.我々は生体磁気信号計測を目標として超高感度光ポンピング原子磁気センサシステムを開発している.本研究では, ヒトのMCGを計測する上で十分な感度を有したカリウム原子磁気センサを構築しMCG計測を行った.計測信号に対しては, 原子磁気センサの周波数応答を考慮した波形の復元を行った.得られたMCGの空間分布の結果は, 従来のSQUID磁束計により計測された結果とも一致しており, 光ポンピング原子磁気センサによる生体磁気信号計測の信頼性と実現可能性が示された., Measurement of biomagnetic fields such as magnetoencephalograms (MEGs) and magnetocardiograms (MCGs) is one of the important non-invasive imaging modalities to investigate biological functions and to diagnose disease. We have developed an ultrasensitive optically-pumped atomic magnetometer for biomagnetic measurements. In this study, human MCGs were measured with a potassium atomic magnetometer. The sensitivity of the atomic magnetometer was definitively sufficient for recording of the human MCGs. The measured signals were recovered by considering the frequency characteristics of the atomic magnetometer. The activity of the human heart estimated with the MCG maps showed good agreements with those measured with SQUID magnetometers. These results demonstrated reliability and feasibility of biomagnetic measurements with optically-pumped atomic magnetometers., 本文データは学協会の許諾に基づきCiNiiから複製したものである

Published
2011

10. Effect of Spatial Homogeneity of Spin Polarization on Magnetic Field Response of an Optically Pumped Atomic Magnetometer Using a Hybrid Cell of K and Rb Atoms

Author

20589189, 40175336, Ito, Yosuke, Ohnishi, Hiroyuki, Kamada, Keigo, Kobayashi, Tetsuo, 20589189, 40175336, Ito, Yosuke, Ohnishi, Hiroyuki, Kamada, Keigo, and Kobayashi, Tetsuo

Abstract

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 of atomic magnetometers with single K and single Rb cells, and found that optically thick atoms were spin polarized homogeneously with the hybrid cell. Optically thin alkali metal vapor can be spin polarized homogeneously, and the spin polarization transfers to an optically thick alkali metal vapor. An atomic magnetometer with the hybrid cell was found to be more effective in realizing simultaneous signal measurements at different locations with the uniform sensitivity and magnetic linewidth.

Published
2012

11. Development of an optically pumped atomic magnetometer using a K-Rb hybrid cell and its application to magnetocardiography

Author

Ito, Yosuke, Ohnishi, Hiroyuki, Kamada, Keigo, Kobayashi, Tetsuo, Ito, Yosuke, Ohnishi, Hiroyuki, Kamada, Keigo, and Kobayashi, Tetsuo

Abstract

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/Hz[1/2] around 10 Hz. In this case, the sensitivity is limited by the system noise, and the magnetic linewidth is narrower than that for direct Rb optical pumping. We demonstrated magnetocardiography using the magnetometer and obtained clear human magnetocardiograms.

Published
2012

12. Development of an optically pumped atomic magnetometer using a K-Rb hybrid cell and its application to magnetocardiography

Author

20589189, 40175336, Ito, Yosuke, Ohnishi, Hiroyuki, Kamada, Keigo, Kobayashi, Tetsuo, 20589189, 40175336, Ito, Yosuke, Ohnishi, Hiroyuki, Kamada, Keigo, and Kobayashi, Tetsuo

Abstract

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/Hz[1/2] around 10 Hz. In this case, the sensitivity is limited by the system noise, and the magnetic linewidth is narrower than that for direct Rb optical pumping. We demonstrated magnetocardiography using the magnetometer and obtained clear human magnetocardiograms.

Published
2012

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Author

KAMADA, Keigo, ITO, Yosuke, KOBAYASHI, Tetsuo, 20589189, 40175336, KAMADA, Keigo, ITO, Yosuke, KOBAYASHI, Tetsuo, 20589189, and 40175336

Abstract

Measurement of biomagnetic fields such as magnetoencephalograms (MEGs) and magnetocardiograms (MCGs) is one of the important non-invasive imaging modalities to investigate biological functions and to diagnose disease. We have developed an ultrasensitive optically-pumped atomic magnetometer for biomagnetic measurements. In this study, human MCGs were measured with a potassium atomic magnetometer. The sensitivity of the atomic magnetometer was definitively sufficient for recording of the human MCGs. The measured signals were recovered by considering the frequency characteristics of the atomic magnetometer. The activity of the human heart estimated with the MCG maps showed good agreements with those measured with SQUID magnetometers. These results demonstrated reliability and feasibility of biomagnetic measurements with optically-pumped atomic magnetometers.

Published
2011

20. Rate-equation approach to optimal density ratio of K-Rb hybrid cells for optically pumped atomic magnetometers.

Author

Ito Y, Ohnishi H, Kamada K, and Kobayashi T

Subjects
Algorithms, Humans, Magnetics, Magnetocardiography, Magnetoencephalography, Quantum Theory, Electric Power Supplies, Potassium chemistry, Rubidium chemistry
Abstract

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 the theoretical estimations and the density ratio of potassium and rubidium atoms should be around 200 to achieve the highest sensitivity.

Published
2013
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