A Third-Order Field Camera with Microsecond Resolution for MR System Diagnostics

Christoph Barmet¹, Bertram J. Wilm¹, Matteo Pavan¹, Klaas P. Pruessmann¹

A magnetic field-camera, based on 16 NMR probes, with microsecond temporal resolution is presented. It allows for simultaneous dynamic magnetic field measurements of all field components up to 3rd spatial order. Contrary to conventional field-cameras, it captures the full BW of the gradient fields. Three situations were studied on a 3T scanner: the response to abrupt gradient changes, drifts and eddy currents during an fMRI scan and the subsequent magnet cooling. This field-camera is a valuable tool for MR systems engineering and diagnostics: the assessment of gradient coils and amplifiers, fast pre-emphasis calibration, testing and tuning of higher-order shim systems.