Acute changes in extracellular volume fraction in skeletal muscle monitored by²³Na NMR spectroscopy

Abstract

In this article, we induced acute changes in extracellular volume fraction in skeletal muscle tissue and compared the sensitivity of a standard 1H T2 imaging method with different 23Na‐NMR spectroscopy parameters within acquisition times compatible with clinical investigations. First, we analyzed the effect of a short ischemia on the sodium distribution in the skeletal muscle. Then, the lower leg of 21 healthy volunteers was scanned under different vascular filling conditions (vascular draining, filling, and normal condition) expected to modify exclusively the extracellular volume. The first experiment showed no change in the total sodium content during a 15 min ischemia, but the intracellular weighted 23Na signal slowly decreased. For the second part, significant variations of total sodium content, sodium distribution, and T1 and T2∗ of 23Na signal were observed between different vascular filling conditions. The measured sodium distribution correlates significantly with sodium T1 and with the short and long T2∗ fractions. In contrast, significant changes in the proton T2w signal were observed only in three muscles. Altogether, the mean T2w signal intensity of all muscles as well as their mean T2 did not vary significantly with the extracellular volume changes. In conclusion, at the expense of giving up spatial resolution, the proposed 23Na spectroscopic method proved to be more sensitive than standard 1H T2 approach to monitor acute extracellular compartment changes within muscle tissue.

Much Ado about N…atrium: modelling tissue sodium as a highly sensitive marker of subclinical and localized oedema

“…red lines; Figure 1) rather than concentration is much closer to what MRI actually does when recording signals from single atoms. Recent evidence of higher sensitivity of 23 Na-based analysis over standard 1 H T 2 MRI approaches to monitor acute ischaemic extracellular compartment changes within skeletal muscle in humans [15] supports our contentions.…”

“…Moreover, the concept of a ‘final solution’ applies to chemical analysis of ashed [2,4] and/or digested [13] tissues, but also to any other technique that does not allow (accurate) spatial differentiation of intracellular and extracellular compartments. This is the case for MRI voxels in clinical practice: apart from some approaches currently limited to research [15,16], 23 Na-MRI only offers ‘total’ 23 Na signal thus far. Indeed, measurement of absolute changes (i.e.…”

Fast in vivo 23Na imaging and T2* mapping using accelerated 2D-FID magnetic resonance spectroscopic imaging at 3 T: Proof of concept and reliability study

“…The estimated mean muscle relaxation times (T 15 The average muscle absolute concentration (after T 2 * correction) was 28.6 ± 3.3 mM, which is also in agreement with reported biopsy results. 7 In terms of T 2 * spatial distribution, the slow fraction is larger and slower in areas with large blood vessel, which makes sense.…”

“…The intact skeletal muscles T 2 * values have been measured previously using a non-localized FID method. 8,15 Such relaxometry methods estimate the averaged value from a large scanned area, which may include different tissues in addition to the muscles. Moreover, because of this partial volume effect, the estimated value may not be enough to perform a voxel-wise relaxation correction.…”

Donnan dominated ion homeostasis and the longevity of ischemic Na+-loaded dystrophic skeletal muscle

“…Ion homeostatic impairment of V m regulation presents clinically as myogenic contractility (Ishpekova et al 1999;Nojszewska et al 2017). Muscle tissue edema (versus SMF edema) in DMD has been confusing but concurrent 23 Na-MRI and proton-MRI (to gauge fiber-H 2 O) (Weber et al 2011;Gerhalter et al 2017Gerhalter et al ,2019 is providing greater clarity. Quantifying muscle ischemia has been problematic, but that is changing (Zhang et al 2020; Deitz et al 2020)).…”