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Long component time constant of 23 Na T * 2 relaxation in healthy human brain
Author(s) -
Bartha Robert,
Me Ravi S.
Publication year - 2004
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.20144
Subject(s) - white matter , nuclear magnetic resonance , human brain , relaxation (psychology) , nuclear medicine , brain tissue , cortex (anatomy) , chemistry , physics , magnetic resonance imaging , medicine , anatomy , neuroscience , biology , psychiatry , radiology
Signal intensity in 23 Na images is altered in pathologic conditions such as ischemia and may provide information regarding tissue viability complementary to MR diffusion and perfusion imaging. However, the multicomponent transverse relaxation of 23 Na (spin 3/2) complicates the determination of tissue sodium concentration from 23 Na images with nonzero echo‐time. The purpose of this study was to measure the long component time constant of tissue sodium T * 2relaxation in the healthy human brain at 4 T. Multiecho gradient‐echo 23 Na images (10 echo‐times ranging from 3.8–68.7 ms) were acquired in five healthy human volunteers. T * 2was quantified on a pixel‐by‐pixel basis using a nonnegative least squares fitting routine using 100 equally spaced bins between 0.5–99.5 ms and parametric maps were produced representing components between 0.5–3, 3.1–50, 50.1–98, and 98.1–99.5 ms. The long T * 2component of tissue sodium (average ± standard deviation) varied between cortex (occipital = 22.0 ± 2.4 ms), white matter (parietal = 18.2 ± 1.9 ms), and subcortical gray matter (thalamus = 16.9 ± 2.4 ms). These results demonstrate considerable regional variability and establish a foundation for future characterization of 23 Na T * 2in conditions such as cerebral ischemia and cancer. Magn Reson Med 52:407–410, 2004. © 2004 Wiley‐Liss, Inc.