The beating heart produces magnetic fields with a distinctive signature. Tiny variations in that signature could reveal the presence of cardiac disease. Magnetometers that can measure such small fluctuations have been in use for some time, employed for tasks such as geophysical exploration and detecting buried objects. Unfortunately, the high cost of these large-scale systems, and the specialist skills needed to operate them, precludes their use in a medical environment. What's more, examining a patient with such a device would require their containment within a magnetic shield.

The Leeds team is working to develop a magnetomer that overcomes these limitations – with the ultimate aim of creating a low-cost, easy-to-use device that can be taken to a patient in a hospital bed. According to group leader Ben Varcoe, a professor in experimental quantum information, the key advance was separating the device into two sections.

The magnetic field detector – a rubidium vapour gas cell – is housed within several layers of magnetic shielding that reduce the Earth's field about a billion-fold. The sensor head, meanwhile, is external to this shielding and contained within a handheld probe.

"The reason this is such a breakthrough for us was that initially we thought that the cell needed to act as both the detector and the sensor head," Varcoe told medicalphysicsweb. "Once we realized that the probe could be remote from the gas cell, then most of the bulk of the device was moved away from the sensor into a [separate] container."

The sensor head comprises a series of pick-up coils with opposite windings (a differential magnetometer), a design that has inherent noise cancellation properties. The sensor records cardiac signals over a few heartbeats and transmits them into the heavily shielded environment. The atomic cell is then probed by a laser to determine the measured magnetic fields. Another advantage of the probe is that it doesn't need to be in direct contact with the patient; it will work several millimetres away, enabling scanning through clothes.

Both the gas cell and coil design are established techniques, in atomic and medical physics, respectively. Varcoe says that it's the combination of the two that was key to the device miniaturization. "The breakthrough was enabled by Melody Blackman, a graduate student with a medical physics background, who took the atomic physics experiment and made it into a real medical device," he explained.

The novel magnetometer is said to be particularly suitable for foetal heart measurement – enabling direct detection of the foetal heartbeat. Other potential applications include detecting ischaemia and guiding surgical treatment for arrhythmia. The instrument could also be adapted for examining brain function, to study magnetic fields originating from epilepsy, for example, and determining the brain's response to various stimuli.

The Leeds team is now working to develop a miniaturized version of the original magnetometer for widespread medical use, under the guidance of Blackman. Following clinical trials, the device could be ready for routine diagnostic applications in around three years.