Comparison at 7T of the Impulse head gradient and whole-body SC72 gradient transfer functions.

Motivation: Ultra-high field MRI requires high performance and accurate gradients to push forward the spatio-temporal resolution, especially for fMRI scans. Goal(s): Compare two commercial gradient coils (whole-body SC72 and head-only Impulse) available on 7T scanners. Approach: Characterization of the gradient transfer function (GTF) and measurement of field perturbations following a spoiler gradient using a field camera. Results: The Impulse gradient coil revealed a smooth GTF profile while the SC72 gradient coil exhibited strong resonances. Field oscillations following a spoiler gradient were greatly reduced with the Impulse gradient. Disconnecting the 3rd order shim coils on the SC72 gradient coil improved the quality of its response. Impact: The GTF of the head-only Impulse gradient coil yields interesting prospects. It remains to be determined whether the apparent benefits versus the SC72 are due to the absence of third order shim coils.