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

• Main Authors: Cauley, S.F (Author), Cooley, C.Z (Author), Grissom, W.A (Author), Sappo, C.R (Author), Srinivas, S.A (Author), Stockmann, J.P (Author), Vaughn, C.E (Author), Wald, L.L (Author)
• Format: Article
• Language: English
• Published: John Wiley and Sons Inc 2022
• Subjects: accessible MRI; active RF shielding; adult; algorithm; Algorithms; Article; artifact; Artifacts; clinical effectiveness; controlled study; Data acquisition; Electrodes; Electromagnetic pulse; Electromagnetic shielding; External Dynamic InTerference Estimation and Removal; External dynamics; External interference; female; human; image artifact; Image data acquisition; Image enhancement; image quality; imaging algorithm; imaging phantom; Impulse response; Impulse response functions; in vivo study; information processing; Interference estimation; low field MRI; Magnetic resonance imaging; Magnetic Resonance Imaging; male; nuclear magnetic resonance imaging; Passive shielding; Phantom experiment; Phantoms; Phantoms, Imaging; portable MRI; Retrospective Studies; retrospective study; Scanning; Theory and methods; young adult
• Online Access: View Fulltext in Publisher

 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. © 2021 International Society for Magnetic Resonance in Medicine