WATER-FAT IMAGING WITH DIRECT PHASE-ENCODING

A new method is introduced for water-fat imaging. With three acquisiti ons, a general direct phase encoding (DPE) of the chemical shift infor mation is achieved. Pixels containing both water and fat are solved di rectly. Pixels with only a single component are resolved with local an d global orientation filters, which use phase information from neighbo ring pixels. The fact that a single component is more likely to be wat er than fat in living tissues is also useful. A second pass solution y ields water and fat images with superior signal-to-noise ratio. Unlike other methods, DPE does not rely on the error-prone phase unwrapping; also, it easily handles disconnected tissues. Because the magnetizati on vectors of water and fat are sampled not only at parallel or antipa rallel, they can be not only separated but also identified respectivel y, which is desirable for routine clinical work. DPE has been implemen ted on several imagers at various field strengths and has been demonst rated in a large number of clinical cases to be useful and robust in v arious parts of the body.