| 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. |
