An algorithm is described for reducing ghost artifacts in echo planar imaging (EPI) using phase corrections derived from images reconstructed using only even or odd k-space lines. The N/2 ghost, that arises principally from time-reversal of alternate k-space lines, was significantly reduced by this algorithm without the need for a calibration scan. In images obtained in eight subjects undergoing EPI for auditory functional MRI (fMRI) experiments, N/2 ghost intensity was reduced from 10.3% +/- 2.1% (range: 7.9-14.1%) to 4.5% +/- 0.2% (range: 4.1-4.9%) of parent image intensity, corresponding to a percent reduction in ghost intensity of 54% +/- 9% (range: 43-65%), and the algorithm restored this intensity to the parent image. It provided a significant improvement in image appearance, and increased the correlation coefficients related to neural activation in functional MRI studies. The algorithm provided reduction of artifacts from all polynomial orders of spatial phase errors in both spatial directions. The algorithm did not eliminate N/2 ghost intensity contributed by field inhomogeneities, susceptibility, or chemical shift.

We demonstrated a new CaHfO3-NaNbO3 solid solution system that allows stable antiferroelectric (AFE) (P) phase to exist under ambient conditions. Based on crystal chemistry viewpoint of relative change of the Goldschmidt tolerance factor (t) and polarizability, two new solid solutions were fabricated using the perovskite end member CaHfO3. It was found that the CaHfO3 effectively stabilized the antiferroelectric (AFE) P phase in NaNbO3. In this article, electrical properties and transmission electron microscopy experiments were conducted to verify the stabilization and enhancement of antiferroelectric behavior over the various solid solutions, where both structural signature of ¼{010} superlattice diffraction reflections and electrical characteristic of double polarization-electric (P-E) hysteresis were observed.

We previously reported various solid solution systems that demonstrated the stabilized antiferroelectric (P) phases in NaNbO 3 through lowering the tolerance factor. However, all those reported modifications were achieved by adding A 2+ B 4+ O 3 type solid solutions. A lead-free antiferroelectric (AFE) solid solution xBiScO 3-(1-x)NaNbO 3 was rationalized by adopting the tolerance factor design rule. Specifically, adding BiScO 3 was found to effectively stabilize the AFE phase without changing the crystal symmetry of NaNbO 3. Microstructure and electron zone axis diffraction patterns from transmission electron microscopy revealed the stabilized AFE (P) phase in this solid solution. Besides, the electric-fieldinduced polarization with a double-hysteresis loop was observed. The present results pointed out that the strategy could also be applied while adding A 3+ B 3+ O 3 type solid solutions. In addition, it expanded the compositional design that can be applied to antiferroelectric materials.