Practical aspects of ghosting in resistive nuclear magnetic resonance imaging systems

The concept of 'ghosting' in NMR images is discussed and it is demonstrated that, among other things, any external modulation of the NMR signal can produce such effects. A simple theoretical model, based on elementary Fourier modulation theory is presented for saturation recovery imaging sequences. Both amplitude (AM) and frequency (FM) modulations are considered. The predictions of the theory with regard to the positions and amplitudes of the ghosts produced by such modulations are outlined. Appropriate AM and FM conditions are generated experimentally on a 0.1 T resistive NMR system and measurements on the concomitant ghost images verify the theoretical predictions. Some practical implications of the phenomenon, with particular relevance to resistive magnet systems, are highlighted.