B0 Field Monitoring by Air-Matched Phantoms

Frederik Testud¹, Maxim Zaitsev¹

Fast magnetic resonance imaging sequences such as GRE EPI are sensitive to spatial and temporal changes of B₀ arising from susceptibility effects, temperature changes of the shims and motion of the object. This leads to time variant common image artefacts such as distortions and intensity losses. A field map is typically acquired at the beginning of the scan whereas neither temporal nor spatial changes of B₀ are monitored during the experiment. As a possible remedy, we propose to use phantoms susceptibility-matched to air which are used to monitor the B₀ evolution and determine the changes of the shim coefficients.