Sodium long-component T mapping in human brain at 7 Tesla

✍ Scribed by Lazar Fleysher; Niels Oesingmann; Bernd Stoeckel; Robert I. Grossman; Matilde Inglese

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 728 KB
• Volume: 62
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.22133

✦ Synopsis

Abstract

Sodium (^23^Na) MRI may provide unique information about the cellular and metabolic integrity of the brain. The quantification of tissue sodium concentration from ^23^Na images with nonzero echo time (TE) requires knowledge of tissue‐specific parameters that influence the single‐quantum sodium signal such as transverse (T~2~) relaxation times. We report the sodium (^23^Na) long component of the effective transverse relaxation time T values obtained at 7 T in several brain regions from six healthy volunteers. A two‐point protocol based on a gradient‐echo sequence optimized for the least error per given imaging time was used (TE~1~ = 12 ms; TE~2~ = 37 ms; averaged N~1~ = 5; N~2~ = 15 times; pulse repetition time = 130 ms). The results reveal that long T component of tissue sodium (mean ± standard deviation) varied between cerebrospinal fluid (54 ± 4 ms) and gray (28 ± 2 ms) and white (29 ± 2 ms) matter structures. The results also show that the long T component increases as a function of the main static field B~0~, indicating that correlation time of sodium ion motion is smaller than the time‐scale defined by the Larmor frequency. These results are a prerequisite for the quantification of tissue sodium concentration from ^23^Na MRI scans with nonzero echo time, will contribute to the design of future measurements (such as triple‐quantum imaging), and themselves may be of clinical utility. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.