Real-time MR artifacts filtering during continuous EEG/fMRI acquisition

G. Garreffa, M. Carnì, G. Gualniera, G. B. Ricci, L. Bozzao, D. De Carli, P. Morasso, P. Pantano, C. Colonnese, V. Roma, B. Maraviglia

Research output: Contribution to journalArticlepeer-review

Abstract

The purpose of this study was the development of a real-time filtering procedure of MRI artifacts in order to monitor the EEG activity during continuous EEG/fMRI acquisition. The development of a combined EEG and fMRI technique has increased in the past few years. Preliminary "spike- triggered" applications have been possible because in this method, EEG knowledge was only necessary to identify a trigger signal to start a delayed fMRI acquisition. In this way, the two methods were used together but in an interleaved manner. In real simultaneous applications, like event-related fMRI study, artifacts induced by MRI events on EEG traces represent a substantial obstacle for a right analysis. Up until now, the methods proposed to solve this problem are mainly based on procedures to remove post-processing artifacts without the possibility to control electrophysiological behavior of the patient during fMRI scan. Moreover, these methods are not characterized by a strong "prior knowledge" of the artifact, which is an imperative condition to avoid any loss of information on the physiological signals recovered after filtering. In this work, we present a new method to perform simultaneous EEG/fMRI study with real-time artifacts filtering characterized by a procedure based on a preliminary analytical study of EPI sequence parameters-related EEG-artifact shapes. Standard EEG equipment was modified in order to work properly during ultra-fast MRI acquisitions. Changes included: high-performance acquisition device; electrodes/cap/wires/cables materials and geometric design; shielding box for EEG signal receiver; optical fiber link; and software. The effects of the RF pulse and time-varying magnetic fields were minimized by using a correct head cap wires-locked environment montage and then removed during EEG/fMRI acquisition with a subtraction algorithm that takes in account the most significant EPI sequence parameters. The on-line method also allows a further post-processing utilization.

Original languageEnglish
Pages (from-to)1175-1189
Number of pages15
JournalMagnetic Resonance Imaging
Volume21
Issue number10
DOIs
Publication statusPublished - Dec 2003

Keywords

  • Electroencephalograph (EEG)
  • Functional MRI
  • Real-time filtering

ASJC Scopus subject areas

  • Biophysics
  • Clinical Biochemistry
  • Structural Biology
  • Radiology Nuclear Medicine and imaging
  • Condensed Matter Physics

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