Long component time constant of 23Na T relaxation in healthy human brain

✍ Scribed by Robert Bartha; Ravi S. Menon

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 155 KB
• Volume: 52
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.20144

✦ Synopsis

Abstract

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 relaxation 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 was 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 component 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 in conditions such as cerebral ischemia and cancer. Magn Reson Med 52:407–410, 2004. © 2004 Wiley‐Liss, Inc.