Reassessment of Peripheral Nerve Stimulation thresholds for the Impulse model-optimized asymmetric head gradient coil

Motivation: Peripheral Nerve Stimulation (PNS) remains a physiologic limitation to boosting spatiotemporal resolution with more powerful gradient coils. Goal(s): We investigated discrepancies in previous threshold measurements and model predictions from the PNS experienced by volunteers scanned with the Impulse gradient coil on the NexGen MAGNETOM Terra 7T scanner. Approach: Thresholds were measured in the NexGen 7T scanner and compared to earlier measurements performed at the factory and model predictions. Results: Discrepancies may be attributed to unknown variability in subject anatomy resulting in wide subject variation of thresholds, differences in the age distributions of cohorts, or unconfirmed z-positions of the subjects in the gradient coil. Impact: As we explore unprecedented gradient performance at 7T, new observations of Impulse gradient PNS thresholds are reported to avoid unnecessary subject discomfort, demonstrate variables affecting gradient coil PNS testing, and offer opportunity to improve gradient coil modeling of PNS.