What Is a Squid Magnetometer?

A superconducting quantum interference device (SQUID) magnetometer is an instrument for detecting and measuring the magnetic fields generated by electric current. The magnetometer converts the magnetic fluctuations back into an electronic signal and relays the signal to a monitoring device which produces a topographical map of the magnetic impulses. The sensitivity of a SQUID magnetometer allows it to be used as a medicinal diagnostic tool.

The SQUID magnetometer usually consists of a highly conductive coil attached to the sensor and probe. In medical applications, these components are typically contained within a cryogenic chamber called a Dewar. The apparatus is cooled by liquid helium or nitrogen. The temperature in this chamber may be as low as -459 degrees Fahrenheit (-273 degrees Celsius). The probe exits the chamber and attaches to a flux loop, which transfers the signal to a monitor.

Magnetoencephalography uses SQUID magnetometers to map neuron function. A device specially designed for encephalography resembles a helmet containing 300 encapsulated sensors. In addition to placing the helmet while the patient is in a sitting position, technicians usually apply several skin sensors that indicate the position of the head. Patients may also be required to lie on a table with the head encapsulated by the helmet.

This noninvasive form of diagnostic medicine can measure activity within millimeter-sized areas or larger of the brain. SQUID magnetometers generally capture magnetic signals in mere milliseconds, producing a high-resolution image depicted as peaks. Neurologists use SQUID magnetometers for diagnosing epilepsy or Alzheimer’s. When used in conjunction with a magnetic resonance imaging (MRI) machine, physicians can transpose magnetic field signals over specific areas of the brain.

Physicians can assess depolarization and repolarization of heart muscle using magnetocardiography. The SQUID magnetometer used for cardiology resembles a large movable cylinder containing sensors. Technicians position the device over the patient, like a portable x-ray machine. By measuring the magnetic fields produced by the electric signals that are emitted by the heart, cardiologists can diagnose and treat potentially life-threatening dysrhythmias. Physicians can implement this method of cardiography in a catheter lab.

The biomedical applications of a SQUID magnetometer include many areas of the body. Obstetricians use magnetocardiography to assess fetal heart conditions. This highly sophisticated technology also assists physicians in diagnosing gastroenterological disorders. The equipment is typically contained within a shielded room that prevents interference from electronic devices or other sources of magnetic fields.