Magnetocardiography measurements with⁴He vector optically pumped magnetometers at room temperature

Abstract

In this paper, we present a proof of concept study which demonstrates for the first time the possibility to record magnetocardiography (MCG) signals with 4 He vector optically-pumped magnetometers (OPM) operated in a gradiometer mode. Resulting from a compromise between sensitivity, size and operability in a clinical environment, the developed magnetometers are based on the parametric resonance of helium in zero magnetic field. Sensors are operated at room-temperature and provide a tri-axis vector measurement of the magnetic field. Measured sensitivity is around 210 fT/√Hz in the bandwidth [2 Hz; 300 Hz]. MCG signals from a phantom and two healthy subjects are successfully recorded. Human MCG data obtained with the OPMs are compared to reference electrocardiogram (ECG) recordings: similar heart rates, shapes of the main patterns of the cardiac cycle (P/T waves, QRS complex) and QRS widths are obtained with both techniques.

Cavity-enhanced microwave readout of a solid-state spin sensor

“…In addition, unlike alternative optical readout techniques, MW cavity readout does not introduce deleterious overhead time in the measurement process. Finally, the technique promises favorable scaling; the measurement SNR increases linearly with the number (N) of defects interrogated, allowing for readout at the spin-projection limit for sufficiently large N. Room-temperature magnetometry with sensitivity approaching the spin-projection limit would enable an increase in the utility of solid-state quantum sensors, for example in magnetocardiography 51 and magnetoencephalography 52 devices. Although demonstrated here using NV − centers in diamond, MW cavity readout can be performed on other solid-state crystals and paramagnetic spins, and is not exclusive to the small minority demonstrating optical fluorescence with significant spin-state dependence.…”

Unshielded magnetocardiography: Repeatability and reproducibility of automatically estimated ventricular repolarization parameters in 204 healthy subjects

“…Still, the need of liquid helium and related costs of cryogenic instrumentations may be a limitation. However, recent development of reliable optical magnetometers working at room temperature is foreseen as an important cornerstone for the construction of innovative portable biomagnetic devices, usable in emergency room, at patient's bedside (Morales et al., ; Shah, ) or even for dynamic monitoring (Lau et al., ). Other novel technologies, such as magnetometry with nitrogen‐vacancy defects in diamond are under investigation with advanced testing for biomagnetic measurements (Barry et al., ).…”

“…Multichannel magnetocardiographic mapping (MCG) is a noninvasive/noncontact and radiation‐free method detecting the cardiac magnetic field (CMF), through high‐sensitivity magnetometers such as the direct current superconducting quantum interference devices (DC‐SQUIDs) (Fenici, Brisinda, & Meloni, ; Fenici, Brisinda, Sorbo, & Venuti, ; Leder et al., ; Sosnytska, ; Tavarozzi, Comani, Del Gratta, Di Luzio et al., ) or, more recently, optical ones (Lau, Petkovic, & Haueisen, ; Morales et al., ). Compared to the electrocardiogram (ECG), MCG provides additional information, being CMF less affected by tissue conductivities, and is more sensitive to tangential currents, and capable to detect vortex currents too (Brockmeier et al., ; Fenici Brisinda, & Meloni ).…”

Magnetocardiography on an isolated animal heart with a room-temperature optically pumped magnetometer

“…In the present work, the magnetometer is operated at close to zero field (just as SERF magnetometers are) and has a maximum response at DC as this is optimal for detection of the MCG. Note also that recently MCG from an adult person was detected with a room-temperature OPM based on 4 He 16 .…”