Magnetic field imaging (MFI) is a contact free cardiac imaging method, which detects the electromagnetic signals of the heartbeat using a magnetic sensor array. The magnetic field of the human heart contains information that cannot be determined from typical measurements of its electrical field, collected through conventional electrocardiograms (ECG). Specifically, visualization of the magnetic field of the heart in the form of an MFI map can help infer the risk of sudden cardiac death. MFI for cardiac imaging has developed into the technique known as magnetocardiography (MCG) and requires extremely sensitive detectors to create accurate images of the electromagnetic cardiac output. To date the standard for MCG are magnetometers which record a signal based on the use of superconducting quantum interference devices (SQUIDs). SQUIDs are exquisitely sensitive magnetometers used to measure subtle changes in magnetic fields based on superconducting loops. However, maintenance and handling of SQUID based instruments for clinical use is sophisticated and expensive because they require helium cooling. Recently a novel class of devices for measuring weak magnetic fields in the clinic was developed, the optically pumped cesium vapor magnetometer (OPM). OPMs were first used in geological applications, but have been developed to the level of sensitivity necessary to detect the human heart’s magnetic field. OPMs are advantageous because they can have similar sensitivity to SQUIDs for MFI, but can be used at room temperature. However, the bandwidth of OPM based systems has been limited, hindering their use in cardiac MFI.
In the recent work by Lembke et al
. a 57-channel OPM based system for cardiac MFI was designed at the University of Jena. The OPM based system enables simultaneous measurement of the human heart in all channels and was designed to be integrated into a clinical system previously utilizing SQUIDs for MFI. In the work presented herein, the authors demonstrate the results of the first clinical measurements with this novel system, performed in a weakly aluminum shielded room. This is the first demonstration of MFI-measurements in a clinical setup using OPMs instead of SQUIDs to collect diagnostically relevant data. This study establishes that diagnostically useful data can be collected from a multi-channel OPM, which covers the entire patient chest, similarly to MFI systems based on SQUID detection technology. The multi-channel OPM system demonstrated sufficient sensitivity and bandwidth to be used in the clinical setting for MFI in a healthy test person measured at room temperature.
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