Magnetic Resonance Imaging (MRI) is a medical imaging technique used to examine the anatomy and physiological processes of the body. To form the images, MRIs utilize strong magnetic fields, magnetic field gradients, and radio waves. The MRI environment has high levels of magnetic induction density, typically in the range of 1.5 T to 3 T, systems with 9.4 T to 21 T also exist in the market. In such an environment, conventional temperature sensors like thermocouples, RTD’s or any metal sensing elements are not designed to function. The metal sensing elements distort the field distribution and thereby affect the output image quality.

FOS are widely used in the many MRI applications and we will explore them below :

Superconductor Magnet
MRI field is generated by the superconductor magnet which consists of many coils and windings through which electricity passes, leading to the creation of a magnetic field. The below schematic shows the placement of the coils in a typical MRI machine. As mentioned earlier, the magnetic density is in the order 1.5 T to 3T and in some systems stronger fields in the 9.4 T to 21 T exist.
MRI Coils
A coil consists of one or more loops of conductive fiber looped around the core. These coils are used to create the magnetic field as well as detect a changing magnetic field by voltage induced in the wire. These coils need precise temperature monitoring because an overheating of them can cause a change in the quality of the images produced. Due to the coils being a part of the hardware for the MRI, big temperature sensors are not ideal. FOS probes are ultrathin with diameters from 100 to 500 µm. They can be easily integrated into existing devices with no or minimum modification.
Patient Temperature Monitoring
MRI examinations take place in a narrow cylindrical tube for about 10-15 mins, which sometime may induce panic attacks or claustrophobia.