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Extravascular proton‐density changes as a non‐BOLD component of contrast in fMRI of the human spinal cord
Author(s) -
Stroman P.W.,
Krause V.,
Malisza K.L.,
Frankenstein U.N.,
Tomanek B.
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.10178
Subject(s) - spinal cord , nuclear magnetic resonance , echo time , contrast (vision) , signal (programming language) , magnetic resonance imaging , chemistry , neuroscience , physics , linear relationship , proton , medicine , psychology , radiology , mathematics , computer science , statistics , quantum mechanics , optics , programming language
The fractional signal intensity change (ΔS/S) observed during activation in T 2 ‐weighted fMRI of the spinal cord has previously been shown to depend linearly on the echo time (TE) but to have a positive value of roughly 2.5% extrapolated to zero TE. In this study we investigated the origin of this finding by measuring the ΔS/S in spinal fMRI with very short TEs. Our results demonstrate that the ΔS/S does not approach zero, but has a value as high as 3.3% at TE = 11 ms. At TEs > 33 ms we observed the linear relationship between ΔS/S and TE as in previous studies. These data demonstrate that there is a non‐BOLD contribution to signal changes observed in spinal fMRI. We hypothesize that this contribution is a local proton density increase due to increased water exudation from capillaries with increased blood flow during neuronal activation, and term this effect “signal enhancement by extravascular protons” (SEEP). Magn Reson Med 48:122–127, 2002. © 2002 Wiley‐Liss, Inc.