Department of Radiology - Medical Physics

Magnetic Resonance Imaging (MRI) is sensitive to the presence of undesired non-linear magnetic fields during image encoding which creates geometric distortions, signal voids or image artefacts if the image reconstruction is not adapted to take the non-linearities into account. This is the case when considering off-resonance maps induced by the imaged object, patient motion creating dynamic field changes or because the applied encoding (gradient) fields do not match the expected fields. Numerous techniques have been developed to correct for magnetic field inhomogeneities. However, these methods always use MR imaging techniques and are often specific for MRI sequences. In order to estimate the dynamic magnetic field changes independently of the used MR sequence, independent hardware needs to be used. One possibility is to monitor the magnetic field changes using a field camera consisting of an array of small Nuclear Magnetic Resonance (NMR) probes, which is referred to as Magnetic Field Monitoring (MFM). Field cameras were built and integrated to human MR scanners (Siemens Magnetom Tim TRIO). Research topics are for example

• Trajectory calibration for Single‐shot imaging with higher‐dimensional encoding
• Encoding (gradient) coil characterization
• Physiological field changes

This research is performed in collaboration with the MR Technology group of the Institute for Biomedical Enginerring, ETH Zürich.