Magnetics Business & Technology - September/October 2020 - 11

FEATURE ARTICLE
TDK has developed compact and highly sensitive biomagnetic
sensors through development of applications with magnetoresistive (MR) element technology utilizing spintronics technology that
was cultivated through the manufacture of hard disc drive heads.
This has made it possible to sense weak biomagnetic fields which
could only be measured by using a SQUID (Superconducting
Quantum Interference Device) flux meter up to now. Through collaborative research with the graduate school of the Tokyo Medical
and Dental University, TDK developed its biomagnetic measurement system using a multi-channel sensor array.

sent the differences in the direction of the lines of magnetic force.
The red area shows the direction in which the line of magnetic
force is ballooning. The blue area shows the direction in which the
line of magnetic force is drawing inwards. R waves of the electrocardiogram accompany the contraction of the ventricles.

"We are the first in the world to successfully carry out measurement and visualization of the cardiac magnetic fields using MR
sensors," says the company. "Unlike the SQUID flux meter, which
is an expensive and bulky system that also requires a
cooling device using liquid helium (Dewar), this system, which uses MR sensors, is capable of measurement with high sensitivity even at room temperature.
It is also compact and has excellent operability and
portability. As a result, it is expected to have applications not only in the field of medical diagnosis such as
magnetocardiography, but also in the fields of health
care and sports science."

For more info, see www.tdk-ventures.com and www.tdk.com.

Judging from the magnetic field distribution, direction of the line of
magnetic force, and the right hand screw rule, it can be estimated
that the action potential of the heart at this time is flowing in the
direction shown by the green arrow.

Important features include its detailed magnetic
resolution which is close to the SQUID domain with a
system cost of about one-tenth of a SQUID flux meter.
TDK is also developing a sensor with a magnetic
resolution of just a few pico-Teslas that can be used to
measure the magnetic fields of the brain.

CONNECTING MAGNETISM
TO INDUSTRY 4.0

Example of measurement and visualization of cardiac
magnetic field distribution using a 64ch MR magnetic sensor array
The image above shows an example of measurement
and visualization of cardiac magnetic field distribution using TDK's 64ch MR magnetic sensor arrays.
The blue waveform is an electrocardiogram (ECG),
the green waveform is a magnetocardiogram (MCG),
and the picture is the magnetic field distribution of the
heart superimposed on the X-ray image of the chest.
The black dots are sensor channels and the waveform
of the magnetocardiogram is the time waveform of
magnetic field intensity obtained from sensor channels indicated by yellow dots. The peak of one of the
waveforms faces the opposite direction of the other
one because of the difference in direction of the lines
of magnetic force.

MAGNETIZING SYSTEMS AND QUALITY CONTROL
FOR ELECTRIC MOTORS IN AUTOMOTIVE
AND POWERTRAIN APPLICATIONS

MAGNETIZING SYSTEMS
FOR INDUSTRY

MEASURING SYSTEMS
FOR LABS & RESEARCH

Nerviano, Milan, Italy (HQ) +39 0331 589 785
Lake Orion, Michigan, USA +1 248 340 7040
Shanghai, CHINA +86 21 5401 9806
www.laboratorio.elettroﬁsico.com

The white curved lines in the photo, which are similar
to the isobar lines of a weather map, connect points
with magnetic field intensity equal to around the heart
at the time of measurement supporting R waves of the
electrocardiogram. The red area and blue area repre-

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September/October 2020 * Magnetics Business & Technology

http://www.tdk-ventures.com https://www.tdk.com/corp/en/index.htm http://www.laboratorio.elettrofisico.com http://www.MagneticsMag.com

Magnetics Business & Technology - September/October 2020

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