Multipoint dixon technique for water and fat proton and susceptibility imaging

Extensions to a previously described three-point Dixon magnetic resonance imaging technique are presented that use alternative water/fat phase-encoding strategies. The technique is generalized to phase encoding of (-theta, O, theta) or (O, theta, 2 theta) radians, and the signal-to-noise ratio (S/N) performance is evaluated. It was found that a theta of 2 pi/3 radians has optimal S/N but that a theta of pi radians is a good compromise and that phase encoding of (O, pi, 2 pi) radians offer an advantage over the previous method, which used (-pi, O, pi) increments, in that a T2' (intravoxel susceptibility dephasing) image may be obtained in addition to the usual water, fat, and Bo images. A new four-point method with phase encoding of (O, pi, 2 pi, 3 pi) radians that can also provide a measure of the spectral width of the fat resonance is suggested. The disadvantages of the method are the extra imaging time and low S/N efficiency.