Title

Peripheral Nerve Stimulation Measures in aComposite Gradient System

Document Type

Article

Publication Date

2015

Journal

Concepts in Magnetic Resonance - Part B: Magnetic Resonance Engineering

Volume

44B

Issue

3

First Page

66

Last Page

74

URL with Digital Object Identifier

10.1002/cmr.b.21269

Abstract

Purpose: This work compared peripheral nerve stimulation (PNS) thresh-olds for the MRI scanner body gradients (BODY), a head/neck insert gradient (INSERT),and the combination of both gradient sets used simultaneously (COMPOSITE).Methods:For BODY, INSERT and COMPOSITE gradients, PNS thresholds were determined byexposing subject volunteers to stepped increases in gradient strength. For COMPOSITEmode, the INSERT was applied at equal (experiment 1) or double (experiment 2) theBODY gradient strength. Results: The locations and thresholds of peripheral nerve stimu-lation depended on the gradient system configuration, gradient axis, and gradientstrength. Stimulation in the body occurred when using the BODYY-gradient axis eithersingly (110 T/m/s) or in COMPOSITE mode (315 T/m/s experiment 2) and adding theinsert gradient had negligible effect on stimulation. Stimulation in the head/sinus areagenerally occurred when using the INSERTX-gradient either singly (213 T/m/s) or inCOMPOSITE mode (320 T/m/s) and adding the body gradient had negligible effect onstimulation. In the COMPOSITE mode, both the location of stimulation and the limitinggradient strength matched location and strength of the limiting component gradient.Conclusion: Stimulation, to a first-order approximation, is independent for the two gradi-ent systems. In COMPOSITE mode, PNS can be dominated by either of the individualgradient components, indicating that the contribution of each component can beincreased until the threshold limit of each component gradient is reached. COMPOSITEgradients provide increased gradient performance with PNS thresholds higher than eithercomponent gradient system operating alone

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