Analytical approach to the MR signal.

In this work, an analytical evaluation of the MR signal is presented using the principle of reciprocity for any transmit and receive probe(s) with general geometrical structure(s). It is shown that the excitation of the spins cannot be explained using the principle of reciprocity in its standard form due to the asymmetry in the permeability tensor of the transverse magnetization. In the reception problem, the standard form of the principle of reciprocity is then utilized to calculate the NMR signal. As expected, the analysis shows that the strength of the NMR signal is a function of the receive coil's (fictitious) circularly polarized component of the field that poses an opposite sense of rotation to that corresponding with the excitation field, produced by the same coil, if it were to be used for excitation. Copyright (c) 2005 Wiley-Liss, Inc.