Reversed half-echo stack-of-stars TrueFISP (TrueSTAR)

Abstract

Purpose: To introduce a reversed half-echo readout scheme for artifact-free two-dimensional (2D) radial and three-dimensional (3D) stack-of-stars TrueFISP imaging, termed TrueSTAR. Methods: TrueSTAR imaging (echo time [TE]/repetition time [TR] = 0.94/1.62 ms for 2D, TE/TR = 0.85/1.21 ms for 3D) was evaluated in phantoms and for in vivo chest imaging at 1.5T and was compared with contemporary center-out (TE/TR = 0.66/1.62 ms for 2D, TE/TR = 0.36/1.21 ms for 3D) and symmetric (TE/TR = 0.93/1.86 ms for 2D, TE/TR = 0.85/1.70 ms for 3D) radial acquisition schemes in terms of image quality and severity of artifacts. Results: Images obtained using a center-out sampling scheme were blurred as a result of trajectory inconsistencies in the k-space center, whereas in vivo acquisitions with symmetric sampling were prone to banding artifacts from the increased TR, compared with center-out and TrueSTAR acquisitions. In contrast, TrueSTAR imaging inherits both benefits, namely, a short TR from the half-echo readout, resulting in reduced banding artifacts, and a high trajectory fidelity in the k-space center from center-in trajectories, yielding an improved signal homogeneity. In addition, near artifact-free 3D TrueSTAR chest imaging (TE/TR = 0.88/1.27 ms) is demonstrated at 3T. Conclusion: TrueSTAR makes use of a generic radial sampling scheme that mitigates residual MR system imperfections, offering artifact-free chest imaging at 1.5T. Magn Reson Med 76:583–590, 2016. © 2015 Wiley Periodicals, Inc.