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Sodium MRI in human heart: a review
Author(s) -
Bottomley Paul A.
Publication year - 2016
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3265
Subject(s) - sodium , nuclear magnetic resonance , chemistry , magnetic resonance imaging , relaxation (psychology) , human heart , isotopes of sodium , medicine , cardiology , physics , radiology , organic chemistry
This paper offers a critical review of the properties, methods and potential clinical application of sodium ( 23 Na) MRI in human heart. Because the tissue sodium concentration (TSC) in heart is about ~40 µmol/g wet weight, and the 23 Na gyromagnetic ratio and sensitivity are respectively about one‐quarter and one‐11th of that of hydrogen ( 1 H), the signal‐to‐noise ratio of 23 Na MRI in the heart is about one‐6000th of that of conventional cardiac 1 H MRI. In addition, as a quadrupolar nucleus, 23 Na exhibits ultra‐short and multi‐component relaxation behavior ( T 1 ~ 30 ms; T 2 ~ 0.5–4 ms and 12–20 ms), which requires fast, specialized, ultra‐short echo‐time MRI sequences, especially for quantifying TSC. Cardiac 23 Na MRI studies from 1.5 to 7 T measure a volume‐weighted sum of intra‐ and extra‐cellular components present at cytosolic concentrations of 10–15 mM and 135–150 mM in healthy tissue, respectively, at a spatial resolution of about 0.1–1 ml in 10 min 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 23 Na MRI can deliver useful information unobtainable by other more convenient methods, including 1 H MRI. Copyright © 2015 John Wiley & Sons, Ltd.