Magnetic field measurements of the human heart at room temperature
The 'magnetically best shielded room on earth' has the size of an apartment block and is located on the site of the Physikalisch-Technische Bundesanstalt (PTB), Institute Berlin. Magnetic fields such as that of the earth are kept out here as effective as nowhere else. Such ideal conditions allow to measure the tiny magnetic fields of, e.g., the human heart. This was the motivation for the American National Institute of Standards and Technology (NIST) to ask PTB to jointly test a newly developed optical magnetic field sensor. It is based on a physical principle very different from SQUIDs, which are usually applied for biomagnetic field measurements. The optical sensor does not need advanced cooling and has the size of a lump of sugar. A high-quality measurement of the human heart signal was demonstrated using this optical sensor. The sensor's suitability was thus proven for biomagnetic measurements in the picotesla range. In...