Target-Pattern-Informed Variable-Density Trajectory Design for Low-SAR Pulse Design in Parallel Transmission

Rainer Schneider¹, ², Matthias Gebhardt¹, Jens Haueisen², Josef Pfeuffer¹

A lot of work has been done towards SAR-constrained optimization in pTX. However, in clinical use these methods can be too computationally intensive for highly parameterized spatially selective pulses. We propose a target-pattern-driven variable-density k-space trajectory (TD) metric, which inherently offers significant RF hardware efficiency and a beneficial impact on local and global SAR performance. To evaluate potential benefits of the TD approach, an elaborate simulation study for an 8ch 3T whole-body multi-channel TX array was conducted. The TD method was applied to a 3D-selective stack-of-spirals trajectory and compared to equal and fixed variable-density designs for varying TX acceleration factors.