Sodium MRI in human heart: A review

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Abstract

This paper offers a critical review of the properties, methods and potential clinical application of sodium (23Na) MRI in human heart. Because the tissue sodium concentration (TSC) in heart is about ~40μmol/g wet weight, and the 23Na gyromagnetic ratio and sensitivity are respectively about one-quarter and one-11th of that of hydrogen (1H), the signal-to-noise ratio of 23Na MRI in the heart is about one-6000th of that of conventional cardiac 1H MRI. In addition, as a quadrupolar nucleus, 23Na exhibits ultra-short and multi-component relaxation behavior (T1 ~ 30ms; T2 ~ 0.5-4ms and 12-20ms), which requires fast, specialized, ultra-short echo-time MRI sequences, especially for quantifying TSC. Cardiac 23Na MRI studies from 1.5 to 7T measure a volume-weighted sum of intra- and extra-cellular components present at cytosolic concentrations of 10-15mM and 135-150mM in healthy tissue, respectively, at a spatial resolution of about 0.1-1ml in 10min or so. Currently, intra- and extra-cellular sodium cannot be unambiguously resolved without the use of potentially toxic shift reagents. Nevertheless, increases in TSC attributable to an influx of intra-cellular sodium and/or increased extra-cellular volume have been demonstrated in human myocardial infarction consistent with prior animal studies, and arguably might also be seen in future studies of ischemia and cardiomyopathies - especially those involving defects in sodium transport. While technical implementation remains a hurdle, a central question for clinical use is whether cardiac 23Na MRI can deliver useful information unobtainable by other more convenient methods, including 1H MRI.

Original languageEnglish (US)
Pages (from-to)187-196
Number of pages10
JournalNMR in Biomedicine
Volume29
Issue number2
DOIs
StatePublished - Feb 1 2016

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Keywords

  • Heart
  • MRI
  • Myocardial infarction
  • Quantification
  • Sodium
  • T
  • T
  • Total sodium content
  • Ultra-short echo time

ASJC Scopus subject areas

  • Spectroscopy
  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging

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