Separation of fat and water in fast spin-echo MR imaging with the three-point dixon technique

A method for suppressing fat in fast spin‐echo imaging with the three‐point Dixon technique is described. The method differs from the three‐point Dixon method used in conventional spin‐echo imaging in that the readout gradient instead of a radio‐frequency pulse is shifted. This method preserves the Carr‐Purcell‐Meiboom‐Gill nature of the fast spin‐echo sequence and hence is less sensitive to magnetic field inhomogeneities and resonance frequency mistiming. As in the original three‐point Dixon technique used in conventional spin‐echo imaging, three acquisitions are required to estimate the field inhomogeneity and completely separate fat and water. The extra time required is not excessive considering that the fast spin‐echo method is frequently applied with multiple signal acquisition. Also, this technique achieves an expected signal‐to‐noise ratio comparable to 2.67 signal acquisitions, which is approximately 94% of the signal‐to‐noise ratio obtained with three signal acquisitions. The method is demonstrated with applications to phantoms and a human volunteer.