Having studied the different components, we can now move on to examine the characteristics of hydrogen nuclei, as employed in NMR in chemistry. For imaging it is necessary to add spatial data to the signal to allocate a position to the different signals.
To do so, we start by selecting the slice plane, within which the horizontal and vertical directions will then be defined. The term « encoding » is used, as the spatial data obtained are not the classic co-ordinates (x, y, z), but are observed through a specific spatial filter. The RF signals received are then processed to reverse the filter effect and reconstruct the image
Decoding of spatial information, included in the NMR signal as modifications of frequency and phase, is performed by an inverse Fourier Transform.