Three-dimensional hybrid-encoded MRI using compressed sensing

Compressed sensing (CS) has been successfully applied to accelerate conventional magnetic resonance imaging (MRI) with Fourier encoding. However in Fourier encoding, the low spatial frequency always has to be fully sampled such that the high frequency is insufficiently sampled at high accelerations, leading to serious loss of resolution. Non-Fourier encoding has been studied in the context of compressed sensing for 2-D imaging, but with limited improvement. In this paper, we propose a novel 3-D acquisition method using hybrid encoding. The method exploits random encoding with a circulant structure along the phase encoding direction, while keeping conventional Fourier encoding along the readout and slice encoding directions. A 2-D random undersampling pattern is used for accelerating the scans. Both simulation and experimental results demonstrate that the proposed method preserves much better resolution than the conventional 3-D Fourier encoding when the same acceleration factors are used.