External Dynamic InTerference Estimation and Removal (EDITER) for low field MRI

Abstract

Purpose Point‐of‐care MRI requires operation outside of Faraday shielded rooms normally used to block image‐degrading electromagnetic interference (EMI). To address this, we introduce the EDITER method (External Dynamic InTerference Estimation and Removal), an external sensor‐based method to retrospectively remove image artifacts from time‐varying external interference sources. Theory and Methods The method acquires data from multiple EMI detectors (tuned receive coils as well as untuned electrodes placed on the body) simultaneously with the primary MR coil during and between image data acquisition. We calculate impulse response functions dynamically that map the data from the detectors to the time varying artifacts then remove the transformed detected EMI from the MR data. Performance of the EDITER algorithm was assessed in phantom and in vivo imaging experiments in an 80 mT portable brain MRI in a controlled EMI environment and with an open 47.5 mT MRI scanner in an uncontrolled EMI setting. Results In the controlled setting, the effectiveness of the EDITER technique was demonstrated for specific types of introduced EMI sources with up to a 97% reduction of structured EMI and up to 76% reduction of broadband EMI in phantom experiments. In the uncontrolled EMI experiments, we demonstrate EMI reductions of up to 99% using an electrode and pick‐up coil in vivo. We demonstrate up to a nine‐fold improvement in image SNR with the method. Conclusion The EDITER technique is a flexible and robust method to improve image quality in portable MRI systems with minimal passive shielding and could reduce the reliance of MRI on shielded rooms and allow for truly portable MRI.

iMPI – portable human-sized Magnetic Particle Imaging Scanner for real-time endovascular Interventions

“…However, external background noise from active hardware components causes distinct SNR reduction, especially in a clinical catheterization laboratory. As known from low-eld MRI devices, which often are operating without shielding techniques [40], there are several approaches available for active suppression of electromagnetic interference (EMI) retrospectively using additional sensors picking up the environmental background noise, e.g., EDITER [41]. First implementations are also available for MPI for active suppression of EMI, e.g., the excitation frequencies [42].…”

On‐site construction of a point‐of‐care low‐field MRI system in Africa

“…Compared with other systems in the literature, the only feature not installed currently is the particular form of shielding, except for a grounded copper sheet that lined the inside of the bore to prevent coupling between the RF and gradient coils. Many different types have been suggested in the literature, including a simple aluminum Faraday box 7 or flexible conducting cloth, 11,14,24 or the use of external sensors followed by signal processing to remove electromagnetic interference. 24,25…”

“…Many different types have been suggested in the literature, including a simple aluminum Faraday box 7 or flexible conducting cloth, 11,14,24 or the use of external sensors followed by signal processing to remove electromagnetic interference. 24,25…”

Low‐field MRI: A report on the 2022 ISMRM workshop

“…34 She described "downsizing" using anatomy-specific scanners, reducing system weight, modifying spatial encoding strategies, safety considerations, eliminating cryogen usage and power requirements, and mitigating electromagnetic interference. 28,46 Session 7 described image contrast at low field. José Marques provided a detailed overview of how physical properties and contrast mechanisms vary across field strengths from 0T to 7T.…”

“…Clarissa Cooley discussed the hardware requirements for portable MRI 34 . She described “downsizing” using anatomy‐specific scanners, reducing system weight, modifying spatial encoding strategies, safety considerations, eliminating cryogen usage and power requirements, and mitigating electromagnetic interference 28,46 …”