Scott B. King1, Chen-Yi Liu2, Vyacheslav Volotovskyy1, Christopher P. Bidinosti2, Krzysztof Jasinski3, Mike J. Smith1, Jonathan C. Sharp4, Boguslaw Tomanek4
1Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, Manitoba, Canada; 2Department of Physics, University of Winnipeg, Winnipeg, Manitoba, Canada; 3Department of Magnetic Resonance Imaging, Polish Academy of Sciences, H. Niewodniczanski Institute of Nuclear Physics, Krakow, Poland; 4Institute for Biodiagnostics (West), National Research Council of Canada, Calgary, Alberta, Canada
Due to RF wave behavior and sample interaction at high B0 fields, B1+ shimming aiming at uniform excitation is important for improved SNR and image uniformity, while avoiding complicated 2D spatially selective RF methods. Using a single transmit channel at 3T we have demonstrated that an asymmetric variable pitch spiral birdcage with one end domed can be an effective method of B1+ shimming, enabling a more uniform B1+ field distribution. New RF-only MRI methods could benefit from such uniform B1+ phase gradients. Furthermore, these optimized current distributions may provide insight into building blocks for Tx-array element designs.