Improved Radial Spoiled Gradient Echo Imaging with Randomized RF Phases and Gradient Moments

Introduction Radiofrequency (RF) spoiling is the most established spoiling method for gradient echo imaging. It is based on a quadratic variation of RF (and receiver) phase angles in successive TRs, coupled with a constant gradient moment at the end of each TR period to create a range of resonance offset angles within each imaging voxel (1). However, it was recognized that RF spoiling yields non-ideal steady state signal intensities, particularly at larger flip angles and T1/TR ratios, leading to significant quantification errors (2-3). For example, a recent variable flip angle gradient echo imaging study reported systematic T1 measurement errors of 20-50% due to non-ideal RF spoiling as implemented by three major MR scanner manufacturers (3). In this work, a novel spoiling scheme is proposed, based on applying random gradient moments and RF phases to achieve ideal average signal intensity, in conjunction with the radial acquisition scheme to suppress artifacts caused by TR-to-TR signal fluctuations. The proposed method achieves ideal spoiling within a wide range of flip angles (0-90) and repetition times (5-3000 ms). Simulation and phantom experiments demonstrate the superior performance of the proposed random spoiling scheme over conventional RF spoiling.