Dynamic field fluctuations that are present during MR image acquisitions lead to reduced image quality and image artifacts. There is a wide variety of sources for these fluctuations that impact the field over different timescales. Short term field fluctuations, from microseconds to seconds, occur as a result of eddy currents from encoding gradients, patient motion interacting with the main field of the scanner, mechanical vibration, and other sources. Long term fluctuations, with characteristic times from seconds to minutes to hours can result from gradient heating, with characteristic mechanical resonances changing in response to epoxy stiffness in the coil itself. Longer term changes can also be caused by main field drift due to energy imparted in the system by the pulsing gradient field.

In vivo field monitoring directly measures non-idealities in the encoding field arising from both long- and short-term fluctuations. Image data can then be corrected for these fluctuations, restoring image fidelity and SNR.

What would it mean for your imaging if you could improve image SNR? Field monitoring can compliment existing sequences and readout trajectories and can be used to enable new sequences and readouts, some of which have intrinsically better signal properties than traditional acquisition strategies.