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Toward direct mapping of neuronal activity: MRI detection of ultraweak, transient magnetic field changes
Author(s) -
Bodurka Jerzy,
Bandettini Peter A.
Publication year - 2002
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.10159
Subject(s) - nuclear magnetic resonance , magnetic field , pulse sequence , transient (computer programming) , pulse (music) , spin echo , imaging phantom , physics , magnetic resonance imaging , chemistry , optics , computer science , medicine , quantum mechanics , detector , radiology , operating system
A novel method based on selective detection of rapidly changing Δ B 0 magnetic fields and suppression of slowly changing Δ B 0 fields is presented. The ultimate goal of this work is to present a method that may allow detection of transient and subtle changes in B 0 in cortical tissue associated with electrical currents produced by neuronal activity. The method involves the detection of NMR phase changes that occur during a single‐shot spin‐echo (SE) echo‐planar sequence (EPI) echo time. SE EPI effectively rephases all changes in B 0 that occur on a time scale longer than the echo time (TE) and amplifies all Δ B 0 changes that occur during TE/2. The method was tested on a phantom that contains wires in which current can be modulated. The sensitivity and flexibility of the technique was demonstrated by modulation of the temporal position and duration of the stimuli‐evoked transient magnetic field relative to the 180 RF pulse in the imaging sequence—requiring precise stimulus timing. Currently, with this method magnetic field changes as small as 2 × 10 −10 T (200 pT) and lasting for 40 msec can be detected. Implications for direct mapping of brain neuronal activity with MRI are discussed. Magn Reson Med 47:1052–1058, 2002. Published 2002 Wiley‐Liss, Inc.