K-Space Trajectory Correction in Spiral-In/Out Bssfp Imaging

Xue Feng¹, Sameul William Fielden¹, Hao Tan¹, Craig H. Meyer^1,2

Spiral-in/out bSSFP differs from spiral-out bSSFP in that it has a symmetric spiral-in gradient in front of a spiral-out gradient. This yields TE=TR/2 and leads to ing of the 0th and 1st gradient moments via symmetry, which saves time compared to a flow-compensated spiral rewinder. However, eddy currents and other gradient imperfections of the gradient system affect the fidelity of the k-space trajectory and cause blurring and distortion in reconstructed images. In this abstract we compare cardiac spiral-in/out bSSFP images reconstructed using a k-space trajectory calculated using a single gradient delay model to those reconstructed using a model that incorporates gradient delays and eddy currents calibrated for each physical axis. We compare each of these to measured trajectories. In addition, we measured B0 eddy currents and analyzed their effect in spiral-in/out bSSFP imaging. Using estimated trajectory corrects most of the infidelity in k-space trajectory and improves the image quality. B0 eddy currents, however, have little effect on the reconstructed images.