Biophysical Journal 14: 653-659 (1974)
© 1974 the Biophysical Society

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Nuclear Magnetic Resonance of Tissue ²³Na

II. Theoretical Line Shape

ABSTRACT

The theoretical line-shape function of the nuclear magnetic resonance (NMR) signal of ²³Na in biological tissue (and other unoriented systems) was obtained under the following conditions: (I) there occur two states of ²³Na in the system, (II) the exchange of ²³Na between the two states is rapid (but not too rapid), (III) in the absence of exchange, the ²³Na in one state is characterized by a single transverse relaxation time T₂ and a single Larmor frequency, and (IV) in the absence of exchange, the ²³Na in the other state possesses (a) two different values of T₂ and/or (b) more than one Larmor frequencies in the first order perturbation effect. The theoretical signal obtained consists of two Lorentzian components, which are centered at the same frequency, but characterized by different T₂. Only the narrower component, comprising 40% of the total intensity, is visible, when the fast T₂ is sufficiently short. The theoretical line-shape function of ²³Na signal was also calculated for oriented systems in which the above conditions are fulfilled.