Magnetocardiogram measured by fundamental mode orthogonal fluxgate array

Karo, Hikaru; Sasada, I.

doi:10.1063/1.4918958

Cited by 43 publications

(16 citation statements)

References 10 publications

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“…Recently, performance of room-temperature (RT) magnetic flux sensors such as magnetoresistance (MR)-device-based sensors, magnetoimpedance (MI) sensors, or fluxgates have been improved and begun to be applied to detect biomagnetic fields that are extremely small and detected only using superconducting quantum interference device (SQUID) flux sensors [2]- [6]. The magnetic field resolution of the RT sensors is still inferior to the SQUID sensors.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

2021

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Recently, the room-temperature (RT) magnetic flux sensors are becoming used for biomagnetic measurements. The RT sensors have a large advantage that they can be placed closer to the magnetic sources and obtain larger signals, unlike the superconducting quantum interference device (SQUID) flux sensors. However, when an RT sensor is placed closer to the sources, the dimension of the sensitivity region cannot be negligible, and the directional dependence of sensitivity should be considered to estimate the theoretical magnetic signals for magnetic source analysis. We proposed a method to evaluate the directional dependence of the sensitivity of the RT sensors in response to adjacent magnetic sources using the array of coils arranged along a circular arc. Consequently, it was revealed that a specific magnetoresistance device-based flux sensor with a certain spatial extent had the directional dependence of sensitivity with a bell-shaped profile. We also proposed the multiple sensitivity points model for the bell-shaped profile and estimated the sensitivity distribution over the sensitivity region, which is expected to be effective in improving the accuracy of the magnetic source analysis using an RT sensor array.

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Section: Introductionmentioning

confidence: 99%

Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

2021

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“…Recently, room temperature (RT) magnetic sensors with an improved resolution such as fluxgate or magnetoresistance (MR) devices have been employed for the detection of weak biomagnetic fields. Magnetocardiography (MCG) performed using RT magnetic sensors has been reported [2], [3]. RT magnetic sensors have a significant advantage over the SQUID magnetic sensors in terms of flexibility in sensor arrangement.…”

Section: Introductionmentioning

confidence: 99%

Calibration of Room Temperature Magnetic Sensor Array for Biomagnetic Measurement

et al. 2019

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Biomagnetic field measurement is a promising tool for the investigation of electrical activities in a living body. Room temperature (RT) magnetic sensors with an improved resolution such as magnetoresistance (MR) devices have been recently employed for the detection of weak magnetic fields, which were earlier detected solely using superconducting interference device magnetic sensors. The position, orientation, and sensitivity of each magnetic sensor in a sensor array must be precisely determined for accurate magnetic source analysis. We proposed a calibration method using an array of multiple coils, which is applicable to an RT magnetic sensor array. To demonstrate the validity of the proposed calibration method, we applied it to an MR devicebased magnetocardiography (MCG) system equipped with an L-shaped planar sensor array, which was newly developed for the simultaneous observation of both anterior and lateral sides of the body. The deviation of the sensor parameters from the designed values was estimated via calibration. The result of the marker coil localization test indicated that the calibration considerably improved the accuracy of the magnetic source analysis. Finally, we demonstrated a preliminary MCG measurement using the calibrated magnetic sensor array.

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“…In recent years, several high-sensitivity magnetic sensors that can operate at room temperature have been developed. Among these sensors, a uxgate magnetometer [2,3], a tunnel magneto-resistance (TMR) sensor [4], and a magneto-impedance (MI) sensor [5] can measure a magnetocardiogram. Reference 2, 3 and 4 described the development of 32-channel, 36-channel and single-channel MCG measurement systems, respectively, and demonstrated MCG measurement using an MSR.…”

Section: Introductionmentioning

confidence: 99%

Study of Spatial Filter for Magnetocardiography Measurements without a Magnetically Shielded Room

Ogata

Tanaka

Hata

et al. 2019

ABE

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Magnetocardiography (MCG) is an effective modality for clinical application and health monitoring due to non-contact measurement and mapping of heart activity at high spatial resolution. A superconducting quantum interference device (SQUID) magnetometer is usually used for measuring MCG signals. However, a SQUID magnetometer has high running cost due to the liquid helium. Moreover, measuring MCG signals inside a magnetically shielded room (MSR) can be costly. Therefore, we developed a 64-channel magneto-impedance (MI) sensor system that does not require an MSR. However, the MCG measurement has very high noise level without an MSR. In this paper, we discuss the signal processing techniques of various noise reduction methods to decrease very loud noises. In particular, we investigated three spatial lter conditions that decrease correlated noises among the 64-channel signals to achieve a high peak value of MCG signals. By using a spatial lter that uses the average of the circumference channels and gradient, the distortion of MCG signals can be reduced. The average reduction in amplitude of the R wave as a result of using a spatial lter was 4.5 pT. Furthermore, the signal to noise ratio (SNR) of the P wave was 29.1 dB, while that of the R wave was 42.3 dB, and clear MCG signals were obtained when using the spatial lter that uses the average of the circumference channels and the gradient. Finally, we successfully measured the MCG signals without an MSR.

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Magnetocardiogram measured by fundamental mode orthogonal fluxgate array

Cited by 43 publications

References 10 publications

Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

Calibration of Room Temperature Magnetic Sensor Array for Biomagnetic Measurement

Study of Spatial Filter for Magnetocardiography Measurements without a Magnetically Shielded Room

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