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Field Monitoring

MR experiments rely on a homogeneous and stable static magnetic field, superimposed by dynamic field gradients, which change in magnitude over time depending on the applied pulse sequence. In reality, the magnetic field at any point deviates from the desired value. The subject introduces static changes in the magnetic field, due to the fact that it consists of matter of various magnetic properties, and dynamic changes caused by movement due to breathing, etc. Field gradients, on the other hand, suffer from various technical limitations such as the limited slew rate of the amplifiers. To better understand and correct these effects requires a good knowledge of the magnetic field in the volume of interest. This information can be used in a multitude of ways, including post-processing correction of MRI data, real-time shimming, feedback into the pulse sequence and correction of field changes due to subject motion. At the same time, measuring the magnetic field provides a means for examining and optimising pulse sequences. A typical system consists of probes made from a droplet of sample liquid in a capillary surrounded by a micro-coil. We are developing this system for our 9.4T scanner inspired by the ideas presented by De Zanche et al. This will provide our institute with a highly sensitive magnetic resonance based field sensing device.


Additional Information

Contact Person

Wieland A. Worthoff, PhD