Fig 3. Illustration of the physical principles of in-phase/opposed-phase imaging.

A, At echo time (TE) of 4.6 ms, both the fat and water protons are in phase, and signal intensity is received from voxels containing both tissue types.

B, At TE of 2.4 ms, the protons on water and fat molecules are 180° opposed, and the signal intensity from one cancels the signal intensity from the other. Voxels that contain both tissue types have a reduction in signal intensity.