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Further steps toward direct magnetic resonance (MR) imaging detection of neural action currents: Optimization of MR sensitivity to transient and weak currents in a conductor
Author(s) -
Pell Gaby S.,
Abbott David F.,
Fleming Steven W.,
Prichard James W.,
Jackson Graeme D.
Publication year - 2006
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.20857
Subject(s) - sensitivity (control systems) , signal (programming language) , current (fluid) , transient (computer programming) , nuclear magnetic resonance , physics , pulse (music) , position (finance) , magnetic resonance imaging , optics , detector , computer science , electronic engineering , medicine , finance , radiology , engineering , economics , thermodynamics , programming language , operating system
The characteristics of an MRI technique that could be used for direct detection of neuronal activity are investigated. It was shown that magnitude imaging using echo planar imaging can detect transient local currents. The sensitivity of this method was thoroughly investigated. A partial k ‐space EPI acquisition with homodyne reconstruction was found to increase the signal change. A unique sensitivity to the position of the current pulse within the imaging sequence was demonstrated with the greatest signal change occurring when the current pulse coincides with the acquisition of the center lines of k ‐space. The signal change was shown to be highly sensitive to the spatial position of the current conductor relative to the voxel. Furthermore, with the use of optimization of spatial and temporal placement of the current pulse, the level of signal change obtained at this lower limit of current detectability was considerably magnified. It was possible to detect a current of 1.7 μA applied for 20 ms with an imaging time of 1.8 min. The level of sensitivity observed in our study brings us closer to that theoretically required for the detection of action currents in nerves. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.