Subject grounding to reduce electromagnetic interference for MRI scanners operating in unshielded environments

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Physics

Background:

• Portable low-field MRI offers point-of-care imaging advantages.
• Electromagnetic interference (EMI) degrades image quality in unshielded environments.
• Effective EMI mitigation is crucial for diagnostic utility.

Purpose of the Study:

• To evaluate subject grounding as a method to reduce EMI in portable low-field MRI.
• To compare different grounding strategies for their effectiveness.
• To assess the impact on image quality and signal-to-noise ratio (SNR).

Main Methods:

• Experiments used 47 mT and 72 mT MRI scanners with turbo spin echo sequences.
• Subject grounding was achieved via conductive sleeves or ECG electrodes.
• EMI was tested under ambient, single-frequency, and broadband conditions.

Main Results:

• Subject grounding significantly reduced EMI in both hand and brain imaging.
• Conductive sleeves reduced hand imaging noise by up to 85x.
• Grounding with RF shields reduced brain imaging noise to 1.2x baseline, even with added EMI.

Conclusions:

• Subject grounding is a simple, effective, and reproducible EMI mitigation strategy for low-field MRI.
• It is particularly beneficial for hand imaging and complements RF shielding for brain imaging.
• This method is robust across various EMI conditions and scanner types.