Robust large field-of-view water selective imaging at 3T with parallel transmission

Introduction: Spectral fat suppressed or water selective imaging (e.g. using 1331 binomial pulses) for large fields-of-view is difficult to achieve, particularly at higher field because of problems in achieving a high-quality shim of the static B0 field. Off resonance effects cause the water and fat resonances to be position dependent, causing water only selection/fat suppression to fail in some regions of the image, most frequently at the edge of the field of view. The recent development of parallel transmission (PTx) has provided greater control over the radio-frequency (B1) field; and while this can be used to influence the homogeneity of flip angle (e.g. RF shimming [1]), we demonstrate that it can also be used to mitigate off resonance problems and so make water selective imaging more robust at 3T.