Chemical shift-based true water and fat images: regional phase correction of modified spin-echo MR images.

The process of separating water and fat signal in magnetic resonance images with the Dixon pulse sequence is hindered by phase errors in the water-fat opposed image. These errors arise from static field inhomogeneities, varying magnetic susceptibilities of different body tissues, and other causes. Phase correction performed with data from phantom imaging can compensate for static field inhomogeneities but not for the other effects. A regional phase-correction algorithm is presented that removes non-chemical-shift phase effects and produces true water and fat images. The technique has been applied with good results to 21 patients and healthy volunteers. The images include ones of the abdomen, knees, hips, spine, and head. This method of regional phase correction is an efficacious way of producing separate water and fat images with the Dixon pulse sequence.