As it was discussed in Chapter 6.3.2., frequency encoding, i.e. the application of a gradient during data collection, is not a compulsory element of an MR sequence. It is a very efficient way of data collection, but it can be replaced by phase encoding. Even if a gradient is not applied at all during readout, and all dimensions of space are read out by phase encoding, the signal still will not be static. In this case practically an NMR experiment is carried out as well besides imaging. The modulation of the signal is caused by the precession frequency that is slightly different in the different chemical environments. Therefore, an image of the chemical composition of the sample can be obtained as well.
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