Efficient quantitation of 23NA concentrations including fast and slow T2 components in the human heart using UTE-CSI and the blood pool as a reference

Matthew Robson, Damian Tyler, Joseph Selvanayagam, Jane Francis, Stefan Neubauer

Research output: Contribution to journalMeeting Abstractpeer-review

Abstract

Introduction: Sodium concentrations in the human heart increase during ischemia due to failure of the Na-K pump, which results in increases in intra-cellular sodium (23Na). This has been demonstrated extensively in animal models ([1]), and has also been demonstrated in humans ([2]). Here we describe technical developments that further advance this field. 23Na exists as a 3/2-spin nucleus its quadrapolar moment results in it having bi-exponential relaxation under typical biological conditions. The relative concentration of these two relaxation components, and T2's of each of these components may indicate the environment of the nucleus. The sum of these two components yields the total sodium concentration.

Purpose: Develop an approach to:
1. Measure the rates of fast and slow relaxation
2. Quantify the amount of sodium in terms of the mM concentrations for each relaxation component.

Theory: Use of the ultra-short TE Chemical Shift Imaging acquisition method allows us to acquire images with a TE as short as 70us, and to acquire the free-induction decay so as to capture both the short and long T2 components efficiently ([3]). After reconstruction we can fit the two relaxation components to evaluate the relative amounts and relaxation rates of the two signal components. To provide quantitation we use the blood pool as a reference. The left ventricular blood pool is a good choice for a reference as it has a known Na concentration 135 mM/l–145 mM/l, which can tested, has a similar T2 to the myocardial tissue, contains a high level of Na, and finally is located close to the tissue of interest and hence will be similarly affected by the transmit RF fields.

Methods: All work was performed on a Siemens Sonata 1.5T system with multinuclear capabilities and a 23Na coil (Rapid-Biomedical). UTE-CSI was used in a cardiac gated fashion using the Ernst angle and a repetition time of 20 ms. Five male volunteers were imaged supine. The 23Na acquisition required around 25 minutes (dependent on heart rate), total exam time was around 40 minutes. Fiducial markers and proton images were used to determine the exact coordinates of the RF coil for each run enabling correction of the receive field profile.

Results: An example image of the long T2 component is shown in Fig. 1.
Original languageEnglish
Article number111
Number of pages1
JournalJournal of Cardiovascular Magnetic Resonance
Volume8
Issue number1
DOIs
Publication statusPublished - 2006
Externally publishedYes

Bibliographical note

Friday, January 20, 2006, 10:30 AM–12:00 PM, Best Oral Abstracts: Clinical

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