FENCE: Flexible Electric Noise reduCtion Endo-shield for the Suppression of Electromagnetic Interference in Low-Field MRI

TL;DR

FENCE introduces a flexible, retrofittable PCB shield inside RF coils to effectively reduce electromagnetic interference in low-field MRI, improving image quality without significantly compromising coil performance.

Contribution

The paper presents FENCE, a novel, adaptable EMI shielding method using internal PCB shields that can be added to existing RF coils for better noise suppression.

Findings

FENCE significantly reduces EMI levels in MRI images.

FENCE causes only a minor reduction (~9-18%) in coil Q factor.

Simulations accurately predicted FENCE's shielding performance.

Abstract

Electromagnetic interference (EMI) is a significant challenge for low-field MRI systems operating without conventional Faraday-shielded rooms. Traditional EMI mitigation approaches include external shields, subject grounding via electrodes, or active noise cancellation requiring synchronized receive channels. These methods either limit portability, introduce patient discomfort, or demand advanced hardware. In this work, we start from the hypothesis that EMI primarily couples capacitively from the body to the RF coil. We investigated two methods of blocking capacitive coupling while preserving inductive MRI signal detection: First, we employed capacitive segmentation of the RF coil and studied its effect on EMI coupling. Second, we present FENCE (Flexible Electromagnetic Noise reduCtion Endo-shield), a novel approach blocking capacitive coupling using flexible PCB shields placed inside the RF coil. FENCE can be retrofitted to existing RF coils. Finite element (FE) simulations were used to estimate the expected shielding performance and the impact on RF coil losses prior to practical implementation. Testing in various realistic scenarios then demonstrated that the combination of FENCE with segmented solenoid coils is effective against both environmental noise sources and controlled EMI. In phantom experiments, FENCE significantly improved imaging performance and reduced EMI levels to near-baseline levels with 9% reduction in coil quality factor (Q factor), showing good agreement with the predictions from the FE simulations. In-vivo head imaging confirmed these results across diverse electromagnetic environments significantly improving imaging performance while showing an ~18% decrease in Q factor. FENCE provides a simple method for EMI mitigation in low-field MRI, enhancing image quality while maintaining system portability and accessibility.