1. Real-time MR artifacts filtering during continuous EEG/fMRI acquisition
- Author
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Marco Carnì, Giovanni Ricci, Pietro Morasso, Bruno Maraviglia, Patrizia Pantano, G. Gualniera, Luigi Bozzao, D. De Carli, Girolamo Garreffa, V. Roma, and Claudio Colonnese
- Subjects
Computer science ,Biomedical Engineering ,Biophysics ,Electroencephalography ,EEG-fMRI ,Signal ,Electroencephalograph (EEG) ,Software ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Computer vision ,Functional MRI ,Artifact (error) ,Signal processing ,medicine.diagnostic_test ,Echo-Planar Imaging ,business.industry ,Subtraction ,Real-time filtering ,Signal Processing, Computer-Assisted ,Magnetic Resonance Imaging ,Functional MRI, Electroencephalograph (EEG), Real-time filtering ,Eeg activity ,Artificial intelligence ,Artifacts ,business ,electroencephalograph (eeg) ,functional mri ,real-time filtering ,Algorithms - 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.
- Published
- 2003