PSF-choice: a novel MRI method for shaping point-spread functions in phase-encoding dimensions.

An imaging method to obtain arbitrary point-spread functions (PSFs) in phase-encoding dimensions is described. This method, called PSF-Choice, is particularly relevant for applications, such as spectroscopic imaging, in which only a very few phase encodes are acquired and ringing artifact can be a serious problem. PSF-Choice uses partial 2D RF excitations to produce aliased excitations that are encoded using standard phase-encoding gradients. Theoretically, the PSF of the reconstructed result depends only on the RF excitation profile. Simulations demonstrate that a Gaussian-like PSF can be achieved, eliminating the side lobes that are associated with ringing artifact. It is further shown that neither the spatial resolution (as represented by the width of the PSF) nor the signal-to-noise ratio (SNR) of the method is adversely affected when compared to standard phase encoding. In the sense that the same number of encodes are required as with standard phase encoding, temporal resolution is also maintained. Phantom experiments demonstrate the initial feasibility of the method to eliminate ringing artifact.