A Low Inductance Nonlinear Gradient Array Design to Mitigate PNS and Reduce Voltage for Extension to Ultrasonic Whole-Body Fast and Silent MRI

Motivation: A nonlinear gradient has the potential to facilitate whole-body ultrasonic silent encoding at 20 kHz while avoiding PNS. Yet, high voltage concerns at 20 kHz switching limits the maximum number of windings possible in a nonlinear gradient design. Goal(s): To demonstrate encoding with a nonlinear gradient field produced by a gradient-array design. Approach: We designed a prototype nonlinear gradient-array and imaged a phantom at 20 kHz. Data was reconstructed using a PSF-based method. Results: The gradient-array enabled a nonlinear gradient shape to be generated with lower inductance than is possible with a single series circuit, reducing the induced voltage. Impact: Whole-body silent MRI is necessary to improve patient comfort. Here, we show a nonlinear gradient-array is a viable option to avoid PNS while achieving ultrasonic switching rates. This suggests whole-body fast and silent MRI is possible with a gradient-array design.