Is there a change in water proton density associated with functional magnetic resonance imaging?
Jochimsen, Thies H;
Norris, David G;
Möller, Harald E;
(2005)
Is there a change in water proton density associated with functional magnetic resonance imaging?
Magnetic resonance in medicine : official journal of the Society of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, 53 (2).
pp. 470-473.
ISSN 0740-3194
DOI: https://doi.org/10.1002/mrm.20351
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In a recent series of studies (see, for example, Stroman et al. Magn Reson Imag 2001; 19:827-831), an increase of water proton density has been suggested to correlate with neuronal activity. Owing to the significant implications of such a mechanism for other functional experiments, the functional signal changes in humans at very short echo times were re-examined by spin-echo EPI at 3 T. The results do not confirm the previous hypothesis of a significant increase in extravascular proton density at TE = 0. Instead, an alternative explanation of the effect is offered: The use of a low threshold to identify activated voxels may generate an artificial offset in functional contrast due to the inclusion of false-positives in the analysis.