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.