Non-remote reference noise cancellation - using reference data in the presence of surface-NMR signals

Müller‐Petke, Mike

doi:10.1016/j.jappgeo.2020.104040

Cited by 12 publications

(2 citation statements)

References 21 publications

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“…Active and post processing cancellation approaches to EMI mitigation that are more flexible and are less intrusive to the subject have been developed for Magnetotellurics, [20][21][22] transient electromagnetics, 23 SQUID MRI, 24 surface NMR instrumentation, [25][26][27][28][29][30][31][32] ECG, 33 EEG 34 and MRI. [35][36][37][38][39][40][41][42][43] Large "figure 8"-shaped surface coils have also been used to cancel EMI actively 26,31 for surface NMR groundwater surveys, but this method is not easily translated to in vivo brain imaging.…”

Section: Introductionmentioning

confidence: 99%

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

Srinivas

Cauley

Stockmann

et al. 2021

Magnetic Resonance in Med

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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.

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Section: Introductionmentioning

confidence: 99%

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

Srinivas

Cauley

Stockmann

et al. 2021

Magnetic Resonance in Med

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“…The standard surface NMR experiment repeats the measurement multiple times for different excitation pulses. The subsequent signal processing workflow typically includes most or all of these steps: detection and culling of impulsive noise, that is, despiking , modelling and subtraction of powerline harmonic noise (Larsen et al 2014;Larsen & Behroozmand 2016), remote reference noise cancellation (Müller-Petke & Spectral analysis of surface NMR data 287 Müller-Petke 2020), stacking (Jiang et al 2011), digital filtering and synchronous envelope detection (Legchenko & Valla 1998;Müller-Petke et al 2016). Ideally, the signal processing results in high signal-to-noise ratio data from which the NMR signal amplitude, relaxation time and phase can be determined (Roy & Lubczynski 2014).…”

Section: Introductionmentioning

confidence: 99%

OUP accepted manuscript

2021

Geophysical Journal International

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Due to its direct sensitivity to groundwater, surface nuclear magnetic resonance (NMR) is an intriguing, non-invasive geophysical technique. However, the surface NMR signal is inherently weak. In turn, the signal-to-noise ratio is often poor, and many signal processing steps must be used to improve it. One of the last processing steps is the extraction of the complex envelope of the NMR signal. This is normally done with synchronous detection, but a different method, spectral analysis was recently suggested, and it has shown promising results. Spectral analysis differs from synchronous detection, as it is a non-causal filtering method with a much narrower detection bandwidth and corresponding improved noise rejection. Until now, spectral analysis has not been applied to data sets acquired with commercially available equipment. We investigate the applicability and performance of spectral analysis on two data sets acquired with the two instruments on the market. The investigation is done with synthetic signals embedded in noise-only data and with field data. Our analysis reveals that spectral analysis is applicable for both instruments and leads to high-quality NMR envelopes. With a synthetic mono-exponential NMR signal embedded in noise-only data, we find that spectral analysis is better able to retrieve all NMR parameters. With field data, we find that the relative uncertainty on gated data is improved by a factor of 2-4 in one data set and a factor of 4-9 in a second data set. We invert both data sets, and show that spectral analysis leads to better-resolved models with lower model uncertainty.

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Portable Brain Scanner Technology for Use in Emergency Medicine

Wald¹,

Cooley²

2022

Magnetic Resonance Microscopy

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Non-remote reference noise cancellation - using reference data in the presence of surface-NMR signals

Cited by 12 publications

References 21 publications

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

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

OUP accepted manuscript

Portable Brain Scanner Technology for Use in Emergency Medicine

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