Improved fat suppression of the breast using discretized frequency shimming

Purpose Robust fat suppression is essential in bilateral breast MRI at 7 Tesla. The lack of good fat suppression can result in errors when calculating the enhancement curve from dynamic contrast‐enhanced acquisitions. In this work we propose discretized frequency shimming to improve the quality of fat suppression by exploiting the capabilities of a parallel transmit setup. Methods With discretized frequency shimming, different resonance frequencies are used for the different transmitters of the radiofrequency coil. This can be particularly useful for frequency‐selective radiofrequency pulses, such as water excitation. The potential of this method has been investigated by simulations on seven acquired B0 maps. Prospective experiments on phantoms and four healthy volunteers were performed to illustrate the performance of discretized frequency shimming. Results Simulations show a decrease in off‐resonance excitation for all subjects when discretized frequency shimming is used. This decrease is highly subject‐dependent, but can result in up to 30% better fat suppression, as observed in phantom and volunteer experiments. Conclusions Discretized frequency shimming improves fat suppression in bilateral breast MRI at 7 Tesla. Magn Reson Med 79:593–599, 2018. © 2017 International Society for Magnetic Resonance in Medicine.