Animation 8.1 (In and Out of Phase)

This animation supports Figures 8.19 and 8.20. Fat and water process at different frequencies at the same field strength. This is called chemical shift. It is analogous to the hour and minute hands of a watch that also travel at different frequencies around the watch face. It is clear to see from this animation that because fat and water have different frequencies, they are in phase with the each other at certain times and out of phase with each other at other times. Fat and water are only in phase if their magnetic moments are at the same place at the same time. If we select a TE so that fat and water are out of phase with each other, then in voxels in which fat and water at present, there is no signal. However, if the TE is selected to match when fat and water are in phase with each other, then there is signal in voxels is where fat and water coexist.