Gradient waveform pre‐emphasis based on the gradient system transfer function

• Published in: Magnetic resonance in medicine 2018-10, Vol.80 (4), p.1521-1532
• Main Authors: Stich, Manuel, Wech, Tobias, Slawig, Anne, Ringler, Ralf, Dewdney, Andrew, Greiser, Andreas, Ruyters, Gudrun, Bley, Thorsten A., Köstler, Herbert
• Format: Article
• Language: English
• Subjects: Algorithms; Brain - diagnostic imaging; Field cameras; GIRF; gradient impulse response; gradient system transfer function; gradient waveform pre‐emphasis; GSTF; Head - diagnostic imaging; Humans; Image acquisition; Image contrast; Image processing; Image Processing, Computer-Assisted - methods; Image reconstruction; In vivo methods and tests; linear and time‐invariant system; Magnetic Resonance Imaging - methods; Models, Biological; Phantoms, Imaging; Signal Processing, Computer-Assisted; Trajectories; Transfer functions
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.27147

Purpose The gradient system transfer function (GSTF) has been used to describe the distorted k‐space trajectory for image reconstruction. The purpose of this work was to use the GSTF to determine the pre‐emphasis for an undistorted gradient output and intended k‐space trajectory. Methods The GSTF of the MR system was determined using only standard MR hardware without special equipment such as field probes or a field camera. The GSTF was used for trajectory prediction in image reconstruction and for a gradient waveform pre‐emphasis. As test sequences, a gradient‐echo sequence with phase‐encoding gradient modulation and a gradient‐echo sequence with a spiral read‐out trajectory were implemented and subsequently applied on a structural phantom and in vivo head measurements. Results Image artifacts were successfully suppressed by applying the GSTF‐based pre‐emphasis. Equivalent results are achieved with images acquired using GSTF‐based post‐correction of the trajectory as a part of image reconstruction. In contrast, the pre‐emphasis approach allows reconstruction using the initially intended trajectory. Conclusion The artifact suppression shown for two sequences demonstrates that the GSTF can serve for a novel pre‐emphasis. A pre‐emphasis based on the GSTF information can be applied to any arbitrary sequence type.