Improving non-contrast-enhanced steady-state free precession angiography with compressed sensing.

Flow-independent angiography offers the ability to produce vessel images without contrast agents. Angiograms are acquired with magnetization-prepared three-dimensional balanced steady-state free precession sequences, where the phase encodes are interleaved and the preparation is repeated before each interleaf. The frequent repetition of the preparation significantly decreases the scan efficiency. The number of excitations can instead be reduced with compressed sensing by exploiting the compressibility of the angiograms. Hence, the phase encodes can be undersampled to save scan time without significantly degrading image quality. These savings can be allotted for preparing the magnetization more often, or alternatively, improving resolution. The enhanced resolution and contrast achieved with the proposed method are demonstrated with lower leg angiograms. Depiction of the vasculature is significantly improved with the increased resolution in the phase-encode plane and higher blood-to-background contrast. (c) 2009 Wiley-Liss, Inc.