Accelerated water-fat imaging using restricted subspace field map estimation and compressed sensing.

Water-fat separation techniques play an important role in a variety of clinical and research applications. In particular, multiecho separation methods remain a topic of great interest due to their ability to resolve water and fat images in the presence of B(0)-field inhomogeneity. However, these methods are inherently slow as they require multiple measurements. An accelerated technique with reduced k-space sampling is desirable to decrease the scan time. This work presents a new method for water-fat separation from accelerated multiecho acquisitions. The proposed approach does not require the region-growing or region-merging schemes that are typically used for field map estimation. Instead, the water, fat, and field map signals are estimated directly from the undersampled k-space measurements. In this work, up to 2.5×-acceleration is demonstrated in a water-fat phantom, ankle, knee, and liver.