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Kurashima K, Kataoka M, Nakano T, Fujiwara K, Kato S, Nakamura T, Yuzawa M, Masuda M, Ichimura K, Okatake S, Moriyasu Y, Sugiyama K, Oogane M, Ando Y, Kumagai S, Matsuzaki H, Mochizuki H. Development of Magnetocardiograph without Magnetically Shielded Room Using High-Detectivity TMR Sensors. SENSORS (BASEL, SWITZERLAND) 2023; 23:646. [PMID: 36679442 PMCID: PMC9866167 DOI: 10.3390/s23020646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 12/23/2022] [Accepted: 12/29/2022] [Indexed: 06/17/2023]
Abstract
A magnetocardiograph that enables the clear observation of heart magnetic field mappings without magnetically shielded rooms at room temperatures has been successfully manufactured. Compared to widespread electrocardiographs, magnetocardiographs commonly have a higher spatial resolution, which is expected to lead to early diagnoses of ischemic heart disease and high diagnostic accuracy of ventricular arrhythmia, which involves the risk of sudden death. However, as the conventional superconducting quantum interference device (SQUID) magnetocardiographs require large magnetically shielded rooms and huge running costs to cool the SQUID sensors, magnetocardiography is still unfamiliar technology. Here, in order to achieve the heart field detectivity of 1.0 pT without magnetically shielded rooms and enough magnetocardiography accuracy, we aimed to improve the detectivity of tunneling magnetoresistance (TMR) sensors and to decrease the environmental and sensor noises with a mathematical algorithm. The magnetic detectivity of the TMR sensors was confirmed to be 14.1 pTrms on average in the frequency band between 0.2 and 100 Hz in uncooled states, thanks to the original multilayer structure and the innovative pattern of free layers. By constructing a sensor array using 288 TMR sensors and applying the mathematical magnetic shield technology of signal space separation (SSS), we confirmed that SSS reduces the environmental magnetic noise by -73 dB, which overtakes the general triple magnetically shielded rooms. Moreover, applying digital processing that combined the signal average of heart magnetic fields for one minute and the projection operation, we succeeded in reducing the sensor noise by about -23 dB. The heart magnetic field resolution measured on a subject in a laboratory in an office building was 0.99 pTrms and obtained magnetocardiograms and current arrow maps as clear as the SQUID magnetocardiograph does in the QRS and ST segments. Upon utilizing its superior spatial resolution, this magnetocardiograph has the potential to be an important tool for the early diagnosis of ischemic heart disease and the risk management of sudden death triggered by ventricular arrhythmia.
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Affiliation(s)
- Koshi Kurashima
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Makoto Kataoka
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Takafumi Nakano
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba-yama, Aoba-ku, Sendai 980-8579, Miyagi, Japan
| | - Kosuke Fujiwara
- Spin Sensing Factory Corporation, Research Center for Rare Metal and Green Innovation, 403 468-1 Aramaki Aza-Aoba, Aoba-ku, Sendai 980-0845, Miyagi, Japan
| | - Seiichi Kato
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Takenobu Nakamura
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Masaki Yuzawa
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Masanori Masuda
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Kakeru Ichimura
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Shigeki Okatake
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Yoshitaka Moriyasu
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
| | - Kazuhiro Sugiyama
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba-yama, Aoba-ku, Sendai 980-8579, Miyagi, Japan
| | - Mikihiko Oogane
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba-yama, Aoba-ku, Sendai 980-8579, Miyagi, Japan
| | - Yasuo Ando
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba-yama, Aoba-ku, Sendai 980-8579, Miyagi, Japan
| | - Seiji Kumagai
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba-yama, Aoba-ku, Sendai 980-8579, Miyagi, Japan
- Spin Sensing Factory Corporation, Research Center for Rare Metal and Green Innovation, 403 468-1 Aramaki Aza-Aoba, Aoba-ku, Sendai 980-0845, Miyagi, Japan
| | - Hitoshi Matsuzaki
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba-yama, Aoba-ku, Sendai 980-8579, Miyagi, Japan
- Spin Sensing Factory Corporation, Research Center for Rare Metal and Green Innovation, 403 468-1 Aramaki Aza-Aoba, Aoba-ku, Sendai 980-0845, Miyagi, Japan
| | - Hidenori Mochizuki
- Device & Process Application Development Unit, Research & Development Center, Asahi Kasei Microdevices Corporation, Atsugi AXT Maintower 20F, 3050 Okata, Atsugi 243-0021, Kanagawa, Japan
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Distribution of Magnetic Flux Density under Stress and Its Application in Nondestructive Testing. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12157612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Carbon steels are commonly used in railroad, shipment, building, and bridge construction. They provide excellent ductility and toughness when exposed to external stresses. They are able to resist stresses and strains effectively, and guarantee safe operation of the devices through nondestructive testing (NDT). The magnetic metal memory (MMM) can be used as an NDT method to measure the residual stress. The ability of carbon steel to produce a magnetic memory effect under stress is explored here, and enables the magnetic flux density to be analyzed. The relationship between stress and magnetic flux density has not been fully presented until now. The purpose of this paper is to assess the relationship between stress distribution and the magnetic flux density measured by the experiment. For this, an experimental method for examining a carbon steel plate (SA 106), based on the four-point loading test, was used. The effect of stresses resulting from the applied loads on the response of the experimented SA 106 specimen was examined. A three directional tunnel magnetoresistance (TMR) measurement system was used to collect the triaxial magnetic flux density distribution in the SA 106 specimen. In addition, finite element method (FEM) analyses were performed, and provided information on the direction and distribution of the stress over the studied SA 106 specimen. Indeed, a correlation was derived by comparing the stress analysis by FEM and the measured triaxial magnetic flux density.
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