Selective excitation in N.M.R. and considerations for its application in three-dimensional imaging
Since its inception, nuclear magnetic resonance has proved to be a fruitful area of research, and one of the most recent advances is in its application to the imaging of structure within objects. The original technique used, known as projection-reconstruction, is rather sensitive to errors in the magnetic fields and on its own is not practicable for full 3-d imaging, so interest has turned to a number of alternative methods. The technique investigated here, selective excitation, achieves imaging by the use of excitation sequences which can restrict the signal response to chosen regions of a spin sample. In order to make use of the Fellgett advantage, the ideal situation in this case would seem to be to confine excitation to a column of spins from which various properties can then be 'read out' by application of a lengthwise gradient.