# Mitigation of peripheral nerve stimulation (PNS) in MRI

> **NIH NIH R01** · MASSACHUSETTS GENERAL HOSPITAL · 2020 · $626,069

## Abstract

7. Project Summary/Abstract
 Peripheral nerve stimulation (PNS) in MRI results from electric fields induced by the switching of
gradient coil, which may result in stimulation of the largest nerves in the body (large diameter nerves
are easier to excite than small ones). The use of current generation of Gmax=80 mT/m, Smax=200
T/m/s whole-body MRI gradients is largely constrained by PNS rather than amplifier power,
mechanical issues or heat removal and specialty coils such as the Gmax=300 mT/m, Smax=200 T/m/s
“MGH Connectome” coil can only be fully used within a fraction of its operational parameter space.
Impacting these PNS limitations will allow faster imaging, higher resolution and reduced distortions in
many sequences routinely used for research and in the clinic for head/neck as well as body imaging,
such as EPI, DWI, bSSFP, RARE and PROPELLER. Head-only (HO) gradient inserts have higher
thresholds but their latest generation are also PNS limited. Additionally, most neuroimaging research
studies and nearly all clinical studies use whole-body (WB) gradient systems.
 In this program, we develop a gradient design tool with explicit PNS constraints and
validate the PNS benefits by experimental tests of optimized WB and HO designs. The state-of-
the-art boundary element (BEM)-stream function (SF) approach for designing the winding patterns of
gradient coils optimizes the magnetic field subject to electrical, mechanical and thermal constraints,
but ignores the primary limiting factor; PNS. Although design rules-of-thumb exist, PNS is not directly
incorporated in the design step. Instead, PNS is assessed after construction of a coil prototype on
volunteers. This is a costly and slow approach that allows only minimal PNS mitigation iteration. In
this proposal, we build on our work modeling magneto-stimulation in full-body peripheral nerve
models which takes into account: i) the coil wire pattern, ii) the detailed shaping of the induced
electric fields by the tissue boundaries, iii) the dependence of the stimulation effect on the relative
orientation between electric field and nerves, iv) the non-linear nerve dynamics and their differing
properties depending on class (motor, somatosensory or autonomic) and branching distance from the
CNS. Our preliminary results indicate that we can increase PNS thresholds by 2X for WB and 1.7X
for HO designs. The cost is a moderate increase of the linearity error (5%) and inductance (32%, only
required for WB designs). This shows that winding patterns intrinsically contain degrees-of-freedom
that can support substantial PNS improvements if one has the tools to uncover them during the
design phase. We therefore incorporate our PNS analysis into an industry-standard BEM-SF design
optimization framework and validate our results by building and testing the best coil designs in a PNS
threshold study of healthy volunteers.

## Key facts

- **NIH application ID:** 9969967
- **Project number:** 1R01EB028250-01A1
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** Bastien Guerin
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $626,069
- **Award type:** 1
- **Project period:** 2020-05-01 → 2024-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9969967

## Citation

> US National Institutes of Health, RePORTER application 9969967, Mitigation of peripheral nerve stimulation (PNS) in MRI (1R01EB028250-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9969967. Licensed CC0.

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