Magnetocardiography With Optically Pumped Magnetometers: Three Research Papers

Short answer: Magnetocardiography (MCG) records the weak magnetic field produced by the heart. Three published research papers, from 2017, 2019 and 2024, report recording heart signals with optically pumped magnetometers (OPMs) of different designs. These are laboratory and proof-of-concept studies. Nothing here is medical advice or a claim about clinical use.

What is being measured?

Each heartbeat produces a tiny magnetic field outside the body. Optically pumped magnetometers sense magnetic fields through the spin of atoms in a vapour cell, read out with light. The three papers below test different OPM designs on the same task, recording the familiar P wave, QRS complex and T wave of the cardiac cycle.

What did the 2017 helium paper report?

The paper "Magnetocardiography measurements with 4He vector optically pumped magnetometers at room temperature", published in 2017, calls itself a proof of concept study. Its abstract says it demonstrates for the first time the possibility of recording MCG signals with 4He vector OPMs run in a gradiometer mode. The sensors rely on the parametric resonance of helium in zero magnetic field, work at room temperature and give a tri-axis vector measurement.

The authors report a measured sensitivity of around 210 fT per root hertz in the 2 to 300 Hz band. They recorded MCG signals from a phantom and from two healthy subjects. They report that the OPM data matched reference electrocardiogram recordings in heart rate, in the shape of the main patterns of the cardiac cycle and in QRS width.

What did the 2024 Heliyon paper report?

The Heliyon paper, "Vector magnetocardiography using compact optically-pumped magnetometers", published in April 2024, describes a spin-exchange-relaxation-free (SERF) magnetometer measuring 14 mm by 25 mm by 90 mm. Its abstract reports a sensitivity of 25 fT per root hertz. Two sensors are arranged orthogonally to form one vector channel, and the system has seven channels. Scanning gives 7 by 9 vector MCG mapping.

The authors report that the P, QRS and T peaks can be distinguished clearly, and they present a vector scatter plot to show the directional information. The abstract also says vector MCG gives more spatial information than the conventional approach of taking only the component perpendicular to the chest.

What about the 2019 Applied Physics Letters paper?

The paper "Magnetocardiography with a 16-channel fiber-coupled single-cell Rb optically pumped magnetometer" appeared in Applied Physics Letters in 2019. We could not read its abstract text. From the title alone, it uses a single Rb vapour cell with 16 channels coupled by fibre. We claim nothing beyond that.

What do the papers have in common?

They use different atoms and layouts: helium in 2017, rubidium in 2019 and a SERF design in 2024. All of them show heart signals from OPMs. Two of the three abstracts we read describe small studies, with the 2017 work on two healthy subjects and a phantom. We do not describe any of this as a medical device or a diagnostic method.

How to read this

Sensitivity values such as 210 fT and 25 fT per root hertz are the authors' reported figures for their own setups, and the two numbers describe different sensors, so they are not a ranking. Peer review does not guarantee clinical relevance, and the abstracts we read make no clinical claims that we repeat here.

FAQ

What is magnetocardiography?

It is the recording of the heart's magnetic field. The 2017 paper compares its OPM recordings with electrocardiogram traces.

Why use optically pumped magnetometers?

The 2024 abstract says OPMs can provide functionality for bio-magnetic field detection and mapping. The helium sensors in the 2017 paper work at room temperature.

What does vector MCG add?

According to the 2024 abstract, it gives more spatial information than taking only the component perpendicular to the chest.

Is this ready for clinics?

We make no such claim. The papers described are research studies.

Which paper was not fully readable?

The 2019 Applied Physics Letters abstract could not be read, so we rely only on its title.