Suppression of Oscillation and Ghosting in RF-Spoiled Gradient-Echo-Based Dynamic Imaging

This study aims to address the suppression of oscillation and ghosting appearing in RF-spoiled gradient-echo-based dynamic imaging, which is caused by the pseudo-steady state (PSS) of magnetization.

We extended the concept of the previous RF phase-cycle-adapted averaging method to RF-spoiled gradient-echo-based cine (or 2D line-scan) imaging by introducing an appropriate intertrial RF phase-cycle shift while maintaining flexibility in the number of phase-encoding lines. The proposed method was validated through theoretical analysis based on the PSS magnetization, 2D Bloch simulations, phantom and human brain imaging on a 3 T clinical scanner. Furthermore, its performance was evaluated using spectral analysis and tSNR maps.

In both phantom and human brain images, the proposed method effectively suppressed ghosting artifacts and oscillatory components at specific frequencies. Averaging over multiple trials, whose number is determined by the number of phase increment (ψ) rotations required for the PSS magnetization to return to its initial phase, fully eliminated the ghosts and oscillatory components, and even when the number of trials was reduced, it significantly mitigated them. The proposed method provided robust performance in both phantom and human brain images, with improved signal quality as shown in tSNR maps.

In this work, we theoretically investigated the PSS behavior of magnetization in RF-spoiled gradient-echo-based cine imaging and demonstrated a method to effectively suppress oscillation and ghosting appearing in RF-spoiled gradient-echo-based cine images. This study is expected to provide a valuable tool for various applications of ultrahigh temporal resolution MRI, including fMRI, utilizing cine imaging.