Sodium MRI in human heart: a review.
Sodium MRI in human heart: a review.
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人心中的钠MRI：评论。
DOI：
10.1002/nbm.3265
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发表时间：
2016-02
影响因子：
2.9
通讯作者：
Bottomley PA
中科院分区：
文献类型：
--
作者：
Bottomley PA
This paper offers a critical review of the properties, methods and potential clinical application of sodium (23Na) magnetic resonance imaging (MRI) in human heart. Because the tissue sodium concentration (TSC) in heart is about ~40µmol/g wet wt, and the 23Na gyromagnetic ratio and sensitivity are respectively about 1/4th and 1/11th that of hydrogen (1H), the signal-to-noise ratio of 23Na MRI in heart is about 1/6000th 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), that requires fast, specialized, ultra-short echo-time MRI sequences, especially for quantifying TSC. Cardiac 23Na MRI studies from 1.5–7 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. Presently, 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. The properties, methods and clinical potential of sodium MRI in human heart are reviewed. The myocardial sodium concentration is about ~40µmol/g.wet.wt., and its signal-to-noise ratio is about 1/6000th of conventional proton MRI. Sodium’s short multi-component relaxation behavior necessitates fast, ultra-short-echo MRI sequences, especially for quantification. Presently, intra- and extra-cellular sodium cannot be unambiguously resolved, but increased sodium primarily attributable to sodium influx, is demonstrated in human myocardial infarction. The added value of cardiac 23Na MRI vs. existing methods remains key.
