Figure 1. .

Principles of Dixon imaging. If the image is acquired when the water and fat have the same phase (a), the signals from water (W) and fat (F) constructively interfere, and the total signal S = W + F. If the image is acquired when water and fat are in opposed phase (b), W and F destructively interfere and S = W− F. (c) Shows data from a single voxel in normal bone marrow (which contains both water and fat), using a gradient echo-based Dixon acquisition with very closely spaced echo times. This data explicitly shows the signal oscillation over time as the fat and water signals dephase, come back into phase,and then dephase again. There is also a progressive reduction in the height of the IP peaks with increasing  echo timeowing to signal decay (in this case with the time constant T₂*).