Ionic activities in the heart cells generates electrical potentials on the body surface, which are detected by electrocardiography (ECG). These electrical activities also generate very weak magnetic fields, which at a magnitude of between 10-11 Tesla and 10-14 Tesla. Such magnetic signals are extremely weak as compared to the earth’s natural magnetic field of approximately 10-4 Tesla. Magnetocardiography (MCG) is a non-invasive technique to record and display these local, weak magnetic field signals by the use of very sensitive magnetic detectors, commonly known as SQUID (Superconducting QUantum Interference Device) magnetometers.
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These multichannel sensors effectively cancel the environmental magnetic and electro-magnetic noises in order to create a map of cardiac magnetic activities. Digital signal processing is then applied to enhance the ration between signal and noise. The diagnosis of heart diseases, especially coronary artery disease, can then be made reliably by the doctors based on the parameters from the magnetic field or current maps.
The first primitive MCG system was being developed in early 1960s. Many improved models have been adopted worldwide for clinical diagnosis. The latest refined model (The MCG system, CS MAGII, Biomagnetik Park GmbH) has been implanted in hospitals in Germany since 2011. The first MCG centre in Asia is set up in Hong Kong, adapting the same technology from Germany.