Abstract
Sodium (23Na) is the most abundant cation present in the human body and is involved in a large number of vital body functions. In the last few years, the interest in Sodium Magnetic Resonance Imaging (23Na MRI) has considerably increased for its relevance in physiological and physiopathological aspects. Indeed, sodium MRI offers the possibility to extend the anatomical imaging information by providing additional and complementary information on physiology and cellular metabolism with the heteronuclear Magnetic Resonance Spectroscopy (MRS). Constraints are the rapidly decaying of sodium signal, the sensitivity lack due to the low sodium concentration versus 1H-MRI induce scan times not clinically acceptable and it also constitutes a challenge for sodium MRI. With the available magnetic fields for clinical MRI scanners (1.5 T, 3 T, 7 T), and the hardware capabilities such as strong gradient strengths with high slew rates and new dedicated radiofrequency (RF) sodium coils, it is possible to reach reasonable measurement times (~10–15 min) with a resolution of a few millimeters, where it has already been applied in vivo in many human organs such as the brain, cartilage, kidneys, heart, as well as in muscle and the breast. In this work, we review the different geometries and setup of sodium coils described in the available literature for different in vivo applications in human organs with clinical MR scanners, by providing details of the design, modeling and construction of the coils.
Highlights
In recent years, the scientific interest in sodium (23Na) magnetic resonance imaging (MRI) and spectroscopy (MRS) has experienced a significant increase.While hydrogen (1H) MRI is an established non-invasive diagnostic technique for investigating the morpho-functional status of a tissue, Magnetic Resonance Spectroscopy (MRS) of both hydrogen and nuclei other than hydrogen can derive complementary biochemical information on tissue physiology and viability, as well as on cellular metabolism.Among the heteronuclei that can be investigated by magnetic resonance approaches, sodium has a prominent role because of its pathophysiological relevance.Sodium is the most abundant cation in the human body, where it is involved in maintaining the homeostasis of the organism and in other vital body functions
Lakshmanan [37] built an array of eight triangular loops with a height of 17.8 cm (H/F) and base of 17.8 cm on the elliptical cylinder which fitted closely to the human head to maximize loading, with r ratio of ~2.5
The sodium signal-to-noise ratio (SNR) performance was slightly better than the SNR performance of the commercial coil despite some SNR decrease in the neck region. This combination of high sodium sensitivity and full hydrogen imaging capability makes an important contribution towards clinically used sodium MRI due to a more optimized and faster workflow
Summary
The scientific interest in sodium (23Na) magnetic resonance imaging (MRI) and spectroscopy (MRS) has experienced a significant increase. Tissue sodium concentration is increasingly recognized as a sodium MRI-derived biomarker for the investigation of cell function and viability. In this regard, methods for the differentiation of intra- and extracellular sodium have been proposed [11,12,13]. With the increasing magnetic field strength of modern MRI scanners (1.5 T, 3 T, 7 T), the improved hardware capabilities such as strong gradient strengths with high slew rates, and new dedicated RF sodium coils, it is possible to reach reasonable measurement times (~10 min–15 min) with a resolution of a few millimeters.
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