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Abstract #0645

Steady-State B1 Mapping of Dynamically Changing RF Fields

Shaihan J. Malik1, Francesco Padormo1, Joseph V. Hajnal1

1Robert Steiner MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, London, United Kingdom

Actual flip angle imaging (AFI) is a fast B1 mapping method consisting of a steady-state spoiled gradient echo imaging sequence with TR periods of alternating duration. Temporal variation of B1 field is known to occur due to, for example, physiological motion and it would be desirable to measure these variations or to avoid artifacts resulting from them. We have studied the behaviour of the AFI sequences steady-state in response to oscillatory B1 field amplitudes, using both simulation and experiment, and show that under certain conditions such modulations can be faithfully measured using AFI.