Nicole Seiberlich1, Philipp Ehses2, Jeffrey L. Duerk, 1,3, Robert Gilkeson1, Mark A. Griswold1,3
1Radiology, Case Western Reserve University, Cleveland, OH, United States; 2Experimentelle Physik V, Universitaet Wuerzburg, Wuerzburg, Germany; 3Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
While standard radial GRAPPA can be used to reconstruct images with low undersampling factors, its primary assumption (that segments of the radial lines can be approximated as Cartesian) breaks down at high acceleration factors. A new through-time calibration method has recently been proposed; this method yields high image quality, but requires large numbers of calibration frames. The method proposed here uses through-k-space segments as well as repetitions through time to reduce the number of calibration frames needed while maintaining image quality. This hybrid radial GRAPPA calibration method is demonstrated for real-time, ungated cardiac acquisitions with frame rates of 43 ms.