Fig3.

Phase-cycled bSSFP with 7-fold total acceleration. Conventional GRAPPA broke down at such high acceleration factor, and had 19.0% error with severe aliasing artifacts and noise amplification. JVC-GRAPPA was able to mitigate some of these artifacts, but still yielded a large error of 10.7%. Combination of 6-fold uniform and 7/8 partial Fourier sampling provided the same 7-fold net acceleration. In this setting, virtual coil concept was not applicable in Joint GRAPPA. Its combination with POCS reconstruction led to 9.2% RMSE and some signal underestimation in k-space (white arrow). J-LORAKS was able to outperform all methods with 8.0% error, and was more successful in completing the partially sampled k-space without the need for an additional POCS step.