Safe Diffusion Lobes for Diminished Gradient Vibration

Motivation: Gradient coil vibrations are a source of loud acoustics, persistent field distortions, potential system damage, and in some cases signal dropout in diffusion MRI. Vibrations are particularly strong at mechanical resonant frequencies. Goal(s): To design “safe” time-optimal diffusion gradients which avoid mechanical resonant frequencies. Approach: A convex optimization problem is formed which seeks to maximize b-value for a given duration while constraining the discrete cosine transform of the diffusion lobe. A bisection search is applied to duration to find the shortest feasible solution with the target b-value. Results: Safe diffusion lobes greatly diminished coil vibration and minimized oscillations in the gradient fields. Impact: Safe diffusion lobes were shown to avoid specified gradient mechanical resonant frequencies reducing vibrations and persistent k-space oscillations. These waveforms have clinical and research potential to improve auditory comfort, prevent DWI signal dropout and image artifacts, and prevent system damage.